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Pulmonary fibrosis involves various types of immune cells and soluble mediators, including TGF-β and IL-35, a recently identified heterodimeric cytokine that belongs to the IL-12 cytokine family. However, the effect of regulatory IL-35 may play an important role in fibrotic diseases. The aim of this paper is to explore the immunoregulatory role of IL-35 in the development of fibrosis in interstitial lung disease (ILD). To gain a better understanding of this issue, the concentrations of IL-35 and different profibrotic cytokines in fibrotic (F-ILD) and non-fibrotic (NF-ILD) patients by ELISA were compared to that of intracellular IL-35 and IL-17 on CD4+ T cells stimulated in the presence of BAL or with different ratios of recombinant IL-35 (rIL-35) and TGF-β (rTGF-β), which were evaluated by flow cytometry. We observed that BAL concentration of IL-35 was lower in F patients (p 0.001) and was negatively correlated with concentrations of TGF-β (p 0.001) and IL-17 (p 0.001). In supplemented cell cultures, BAL from NF but not F patients enhanced the percentage of IL-35 + CD4+ T (p 0.001) cells and decreased the percentage of IL-17 + CD4+ T cells (p 0.001). The percentage of IL-35 + CD4+ T cells correlated positively with BAL concentration of IL-35 (p = 0.02), but correlated negatively with BAL concentrations of IL-17 (p = 0.007) and TGF-β (p = 0.01). After adjusting the concentrations of recombinant cytokines to establish a TGF-β: IL-35 ratio of 1:4, an enhanced percentage of IL-35 + CD4+ T cells (p 0.001) but a decreased percentage of IL-17 + CD4+ T cells (p 0.001) was observed. After adding recombinant IL-35 to the BAL from F patients until a 1:4 ratio of TGF-β: IL-35 was reached, a significantly increased percentage of IL-35 + CD4+ T cells (p 0.001) and a decreased percentage of IL-17 + CD4+ T cells (p = 0.003) was found. These results suggest that IL-35 may induce an anti-fibrotic response, regulating the effect of TGF-β and the inflammatory response on CD4+ T cells. In addition, the TGF-β: IL-35 ratio in BAL has been shown to be a potential biomarker to predict the outcome of F patients with ILD.

Myeloid-derived suppressor cells (MDSC) are important to the tumour microenvironment as they actively suppress the immune system and promote tumour progression and metastasis. These cells block T-cell activation in the tumour microenvironment, preventing anti-tumour immune activity. The ability of a treatment to alter the suppressive function of these cells and promote an immune response is essential to enhancing overall therapeutic efficacy. Interleukin-12 (IL-12) has the potential not only to promote anti-tumour immune responses but also to block the activity of cells capable of immune suppression. This paper identifies a novel role for IL-12 as a modulator of MDSC activity, with implications for IL-12 as a therapeutic agent. Treatment with IL-12 was found to alter the suppressive function of MDSC by fundamentally altering the cells. Interleukin-12-treated MDSC exhibited up-regulation of surface markers indicative of mature cells as well as decreases in nitric oxide synthase and interferon-γ mRNA both in vitro and in vivo. Treatment with IL-12 was also found to have significant therapeutic benefit by decreasing the percentage of MDSC in the tumour microenvironment and increasing the percentage of active CD8(+) T cells. Treatment with IL-12 resulted in an increase in overall survival accompanied by a reduction in metastasis. The findings in this paper identify IL-12 as a modulator of immune suppression with significant potential as a therapeutic agent for metastatic breast cancer.

Those immunologists old enough to remember doing experiments at a time when music by the Beatles might have been playing in the background, data were plotted with pencils and graph paper, and gene cloners were the bacteriologists somewhere down the corridor, will remember that T cells were either OKT4 or OKT8, the latter population confusingly termed ‘suppressor/cytotoxic’.1 Those for whom all the above terms are mysterious should find an ageing laboratory head to ask. Nowadays, OKT8 cells are termed CD8, and mechanisms by which they can regulate or suppress other responses have been characterized in a number of examples.2,3 One mechanism by which this can occur is through the release of cytokines that condition dendritic cells (DC), leading to immune deviation of DC-stimulated responses. A number of recent papers, including the work from Noble and colleagues in this volume, characterize the ability of various T-cell populations to modulate DC function in this way.4–8 DC are pivotal antigen-presenting cells (APC) in the immune system, because of their unique ability to induce primary immune responses.9 There exists a complex, bi-directional interaction between the DC and the T cell that determines the nature of the response that the activated T cell will subsequently mount. Viewed as a conventional interaction between an APC and a CD4 T cell, polarization of the T cell to a T helper type 1 (Th1) or Th2 phenotype may be determined by several factors, including the nature, dose and binding affinity of the antigenic peptide, structural features of the T-cell receptor (TCR), and the expression of co-stimulatory molecules.10 Furthermore, the nature of the DC may itself confer inherent skewing to a Th1 or Th2 outcome. Two publications during 1999 defined DC subpopulations, in mice and humans, respectively, that conferred Th1/Th2 skewing on the subsequent responses.11,12 Rissoan and colleagues, working with human DC, showed that peripheral-blood-monocyte-derived, interleukin-4 (IL-4)/granulocyte–macrophage colony-stimulating-factor-expanded immature myeloid DC (DC1) preferentially induce a strong interferon-γ (IFN-γ) response from co-cultured, allogeneic CD45RO− CD4 T cells.11 Conversely, the DC2 population, derived from plasmacytoid cells preferentially induce IL-4, IL-5 and IL-10 from T cells. While the precise developmental relationship between the subsets of DC that have been characterized in mice and humans is not yet clear, similar observations were made by Moser's group working in a murine model.12 CD8α+ or CD8α− DC were pulsed with keyhole limpet haemocyanin and used to prime mice in vivo. Priming with the former population led to a polarized Th1 response and priming with the latter population gave a Th2 response. In the context of a dynamic immune system with APC presenting diverse antigens to T cells, it may be inappropriate to hard-wire the T-cell cytokine response in a fixed way to the identity of the presenting DC. Indeed, it now appears that there is a high degree of flexibility and even reversibility with respect to modulation of DC function by local cytokines or stimulation with pathogens.13,14 If DC require cytokine priming to activate T cells, but T cells are the main source of immune cytokines, how can the arming process ever proceed? The answer of course is that in the physiological context, this cytokine milieu for DC maturation and polarization can be triggered as a direct result of DC exposure to infectious agents, that is, through innate immunity.14,15 Binding of bacterial lipopolysaccharide to toll-like receptor (TLR)-4 on DC leads to activation for Th1 responses.15 DC can also be polarized to stimulate Th1 responses by Bordetella pertussis toxin, while different strains of Candida albicans can license for either Th1 or Th2 activation (Fig. 1).16,17 In general, the licensing of DC for Th1 activation is associated with the stimulation of tumour necrosis factor-α and/or IL-12 from the DC. In studies using cholera toxin, heat-killed yeast and zymosan granules, all of which have been shown to promote the activation of Th2 responses by DC, this can ensue from the induction of IL-10, inhibiting the release of Th1-promoting cytokines, although it is not invariably accompanied by IL-10 release.14,18 Figure 1 Mediators and cell types known to license dendritic cells for T helper type 1 (Th1) and Th2 activation. Recently another facet has been added to this model with the realization that the licensing of DC for activation of T cells may be achieved not just through innate recognition of infectious agents but through the release of cytokines from T cells. That is, T cells activate or differentiate DC permitting appropriate presentation to T cells. This presupposes that there are populations of T cells with the ability to mount a rapid cytokine response at the very initiation of presentation. A number of recent papers address the nature of these T cells and the impact of their DC programming. Indeed, even in the context of activation by bacterial products such as lipopolysaccharide, DC can lose the ability to produce IL-12 on subsequent CD40 ligation by naive cells unless supplied with T-cell-derived IFN-γ.19 One solution to the problem of a rapid T-cell response to arm DC for Th1 responses comes from the observation that immature, human, myeloid DC express very low levels of human leucocyte antigen class II, but abundant CD1 molecules which can be recognized by the γδ receptors of Vδ1 cells.5 This maturation process involves the production of both tumour necrosis factor-α and IL-12. In another example, using lymphochoriomeningitis virus TCR transgenic T cells, naive CD8 T cells were able to support DC maturation.4 A related model used alloreactive, naive CD40L-negative CD8 cells that were able to respond to class I/peptide with an extremely rapid, DC-polarizing IFN-γ response.6 The experiments reported by Noble and colleagues in this issue add to this story and reiterate the DC regulatory role of CD8 cells.8 The groups of Noble and Kemeny have proposed that CD8 cells can regulate immunoglobulin E (IgE) responses; the present findings offer a clear mechanism for this through the CD8-mediated modulation of DC function for immune deviation from a Th2 to a Th1 phenotype.5 In an earlier paper using CD8 cells from the OT-I TCR transgenic line specific for ovalbumin it had been shown that CD8 T cells had the ability to inhibit the IgE response to antigen. This was not dependent on a direct effect of T-cell-derived IFN-γ on Th1/Th2 skewing, but on the ability of CD8 cells (but not CD4) cells to induce IL-12 release from DC.5 In the present paper, this principle is extended to the analysis of the graft-versus-host reaction, which also encompasses hyper-IgE reactivity. The experimental model is the transfer of parental strain splenocytes into (BALB/c × C57BL/6)F1 recipients. The control of Th1/Th2 responses and IgE class switching by CD8 cells is confirmed in this model since the removal of CD8 cells from the donor population causes a dramatic increase in IgE production. There is also an increase in the IgG1 anti-DNA autoantibody response. Again, the effect of the CD8 population appears to be independent of their own IFN-γ release but dependent on their ability to elicit a rapid IL-12/IL-18 response in the DC. A better understanding of these events should open up another front on which we can hope to manipulate the Th1/Th2 polarization that contributes to inappropriate immune reactivity in autoimmunity and asthma. The knowledge that both innate recognition of pathogens by DC and specific activation of CD8 T cells can create the conditions for reprogramming of DC function and subsequent CD4 T-cell immune deviation offers a possible solution to the conundrum of the diverse array of infectious agents that can be causally related to the onset of autoimmunity. In the meantime, there is much work to be done on the detailed characterization of the very early events at the top of this cascade. We need to know which are the populations of CD8 cells that mediate this DC arming in vivo, precisely which cytokines are involved and what form of activation and signalling are required. Indeed, we lack even a clear model for what could be the nature of the DC maturational differences that would preferentially skew responses to Th1 or Th2. For those too deferential to confront their ageing laboratory head, OKT4 and OKT8 were the early antibodies for human CD4 and CD8 cells and the Beatles were a pop group.

Summary Mass vaccination of the global population against SARS‐CoV‐2 will, we hope, turn the tide against this devastating pandemic. To complement vaccinations, better tools are needed to enable viral infections and immunological protection to be monitored. Accurate tools provide sound data for informed decision‐making at many levels, from personal to governmental. The measurement of viral RNA is currently routinely used to detect active infections, but only gives a positive result during infection and is unable to reveal historic infections. Tests involving a detection of SARS‐CoV‐2‐specific antibodies can reveal prior exposures to virus and can measure anti‐viral immune responses induced after natural infection or after vaccination. They may eventually also be used to predict an individual's likelihood of becoming re‐infected. Here, we report on the development of a sensitive ELISA technique to detect multiple isotypes of antibodies against the spike glycoprotein, in samples of both serum and saliva. This paper provides an important step towards understanding the immune response to SARS‐CoV‐2 and may therefore eventually help us to effectively control it.

The first decade of the 21st Century has been proving an exciting one for the field of Immunology as indeed it has been for this journal. Our ability to both manipulate the molecules and cells of the immune system and to image the consequences of these changes is yielding answers at a phenomenal rate. Since this journal started in 1958, it has been involved in reporting many key developments in Immunology, notably including the first proposal of a suppressive/regulatory T-cell population1 (Gershon and Kondo, 1970). In the past seven years, under the editorship of Mike Kemeny, the journal has gone from strength to strength. The impact factor has risen from 2·29 in 2000 to 3·51 in 2005 at a time when many comparable immunology journals have seen impact factors decline due to the sheer amount of published material in the field from the many new journals. Despite the greatly increased number of competing titles, the ranking of Immunology among journals in the field has risen from 43 to 31 over this period. The journal has a truly international outlook, attracting large numbers of submissions from the USA, Europe, Asia, Australia and South America. For those who don't know me, I am Head of the Human Disease Immunogenetics Groups at the Department of Infectious Diseases and Immunity, Imperial College, Hammersmith Hospital, London. The Group has a long-standing interest in molecular immunology approaches to the analysis of HLA class II gene products and CD4 T cells in disease, encompassing both ‘humanised’ transgenic disease models and human studies. Diseases of interest span both autoimmunity and infectious disease. Prior to joining Imperial College I was a senior scientist with the Medical Research Council for a number of years and before that was at Imperial Cancer Research Fund (now Cancer Research UK). In taking over from Mike as Editor, I will continue to promote the reputation of the journal as a key niche for reporting important, basic, immunological findings. Immunology research finds itself expanding, perhaps more than at any time since the impact on the field of molecular biology in the early 1980s, with the use of new and emergent technologies. We wish to encourage researchers investigating immunological questions via approaches such as in silico modelling, protein crystallography, proteomics, genomics, plasmon resonance and molecular, cellular or whole-animal imaging to submit their manuscripts for publication. We will continue to publish review articles in key areas of basic immunology by leading figures in the field and have a number of exciting contributions in the pipeline. Ongoing changes in the handling of manuscripts and access to papers will, we believe, make this an increasingly appealing place to submit. Immunology has upgraded to a new version of the Manuscript Central electronic manuscript handling system (http://www.mc.manuscriptcentral.com/imm) resulting in even more efficient and rapid manuscript turnover. We are constantly looking at ways to improve the efficiency with which manuscripts are allocated to reviewers, reports are received back, and initial decisions sent out. The average time to OnlineEarly publication is now 52 days. A new author initiative will enable authors to track online the production status of their accepted article. Using Author Services, authors have the ability to track the progress of their manuscript from receipt at the publishers through the production process to publication online and in print. Registered authors benefit from free access to the full text of their papers as well as a discount on Blackwell publications. If you have an enquiry or wish to propose a Review article for the journal please contact the Editorial Office via: gro.ygolonummi@nibot.s. We look forward to receiving your manuscripts.

Summary MHC class I-related gene protein (MR1) is a non-polymorphic MHC class IB antigen-presenting molecule that is the restricting molecule for mucosal-associated invariant T (MAIT) cells, a prominent population of innate-like antibacterial T cells. The MAIT cell–MR1 axis represents a new paradigm in antigen presentation, with the MR1 ligand derived from vitamin B compounds or their metabolic precursors. Many bacteria and some fungi produce the activating ligand for MR1. In evolution, MR1 is highly conserved in most, but not all, mammals. In humans and rodents it is expressed in a broad range of cell types, both haematopoietic and non-haematopoietic, although cell surface expression has been difficult to detect. Although MR1 trafficking shares features with both the MHC class I and MHC class II pathways, it is distinct. Several strands of evidence suggest that the intracellular location where MR1 is loaded differs for soluble ligand and for ligand derived from intact bacteria. The regulation of MR1 surface expression may also vary between different cell types. This paper will review what is currently known about the expression and trafficking of MR1 and propose a model for the loading and trafficking of MR1.

Summary The antigenic reactivity of constituents of Schistosoma mansoni and peanut (Arachis hypogaea) was investigated to determine whether identical antigenic epitopes possessed by both organisms provided a possible explanation for the negative correlation between chronic schistosome infection and atopy to allergens. Aqueous extracts of peanuts were probed in Western immunoblots with rabbit IgG antibodies raised against the egg, cercarial and adult worm stages of S. mansoni. Several molecules in the peanut extract were antigenically reactive with antibodies from the various rabbit anti-schistosome sera. A pair of cross-reactive peanut molecules at ~30 000–33 000 molecular weight was purified and both proteins were identified by mass spectrometric analysis as the peanut allergen Ara h 1. Anti-S. mansoni soluble egg antigen antibodies that were eluted off the peanut molecules reacted with two S. mansoni egg antigens identified by mass spectrometry as IPSE/α-1 and κ-5. Alignments of the amino acid sequences of Ara h 1 and either IPSE/α-1 or κ-5 revealed a low level of peptide sequence identity. Incubation of nitrocellulose paper carrying electrophoresed peanut molecules, six constituents of other allergic plants and S. mansoni egg antigens in a mild solution of sodium metaperiodate before probing with antibodies, inhibited most of the cross-reactivities. The results are consistent with the antigenic cross-reactive epitopes of S. mansoni egg antigens, peanut and other allergic plants being cross-reactive carbohydrate determinants (CCDs). These findings are novel and an explanation based on ‘blocking antibodies’ could provide an insight for the inverse relationship observed between schistosome infection and allergies.

Summary The nuclear factor-κB (NF-κB) family of transcription factors play an essential role for the regulation of inflammatory responses, immune function and malignant transformation. Aberrant activity of this signalling pathway may lead to inflammation, autoimmune diseases and oncogenesis. Over the last two decades great progress has been made in the understanding of NF-κB activation and how the response is counteracted for maintaining tissue homeostasis. Therapeutic targeting of this pathway has largely remained ineffective due to the widespread role of this vital pathway and the lack of specificity of the therapies currently available. Besides regulatory proteins and microRNAs, long non-coding RNA (lncRNA) is emerging as another critical layer of the intricate modulatory architecture for the control of the NF-κB signalling circuit. In this paper we focus on recent progress concerning lncRNA-mediated modulation of the NF-κB pathway, and evaluate the potential therapeutic uses and challenges of using lncRNAs that regulate NF-κB activity.

B cells have an important pathogenic role in the development of type 1 diabetes in the non‐obese diabetic (NOD) mouse. We have previously reported that NOD mice display an increased percentage of TACI high‐expressing B cells compared with C57BL/6 mice and this trait is linked to chromosomes 1 and 8. In this paper the genetic association of the transmembrane activator, calcium modulator and cyclophilin ligand interactor (TACI) trait was confirmed using double congenic NOD.B6C1/Idd22 mice. TACI ligation by a proliferation‐inducing ligand (APRIL) has been shown to influence plasma cell differentiation, immunoglobulin production and isotype switch. Hence, the functional consequence of the up‐regulation of TACI on NOD B cells was analysed both in vitro and in vivo. NOD B cells stimulated with APRIL showed an enhanced plasma cell differentiation and class switch to IgG and IgA compared with B cells from C57BL/6 mice. Moreover, flow cytometry analyses revealed that germinal centre B cells in NOD failed to down‐regulate TACI. Availability of the TACI ligand B‐cell activating factor (BAFF) has been shown to be a limiting factor in the germinal centre reaction. In line with this, upon immunization with 4‐hydroxy‐3‐nitrophenylacetyl hapten‐conjugated hen egg lysozyme, NOD mice produced higher titres of low‐affinity antibodies compared with C57BL/6 mice. This observation was supported by the detection of increased levels of BAFF in NOD germinal centres after immunization compared with C57BL/6 by immunofluorescence. Our results support the hypothesis that increased TACI expression on NOD B cells contributes to the pathogenesis of type 1 diabetes in the NOD mouse.

The study of cellular and molecular immunology is almost completely dependent on monoclonal antibody technology. Despite the relatively long history of monoclonal antibodies, there is still huge potential for developing novel and transformative uses for this technology. In this issue of Immunology, we present two such papers, one focussing on anti-complement (C5) antibodies, the other on anti-CD6-specific antibodies. Both manuscripts describe novel ways that monoclonal antibodies may be used for scientific and potentially for therapeutic benefit.

In a companion article to this study,(1) the successful programming of a JAWSII dendritic cell (DC) line's antigen uptake and processing was demonstrated based on pre-treatment of DCs with a specific 'cocktail' of select chemokines. Chemokine pre-treatment modulated cytokine production before and after DC maturation [by lipopolysaccharide (LPS)]. After DC maturation, it induced an antigen uptake and processing capacity at levels 36% and 82% higher than in immature DCs, respectively. Such programming proffers a potential new approach to enhance vaccine efficiency. Unfortunately, simply enhancing antigen uptake does not guarantee the desired activation and proliferation of lymphocytes, e.g. CD4(+) T cells. In this study, phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs were examined in long-term co-culture with antigen-specific CD4(+) T cells to quantify how chemokine pre-treatment may impact the adaptive immune response. When a model antigen, ovalbumin (OVA), was added after intentional LPS maturation of chemokine-treated DCs, OVA-biased CD4(+) T-cell proliferation was initiated from ~ 100% more undivided naive T cells as compared to DCs treated only with LPS. Secretion of the cytokines interferon-γ, interleukin-1β, interleukin-2 and interleukin-10 in the CD4(+) T cell : DC co-culture (with or without chemokine pre-treatment) were essentially the same. Chemokine programming of DCs with a 7 : 3 ratio of CCL3 : CCL19 followed by LPS treatment maintained partial immature phenotypes of DCs, as indicated by surface marker (CD80 and CD86) expression over time. Results here and in our companion paper suggest that chemokine programming of DCs may provide a novel immunotherapy strategy to obviate the natural endocytosis limit of DC antigen uptake, thus potentially increasing DC-based vaccine efficiency.

This paper describes an experimental model of neuroinflammation based on the production of interleukin-6 (IL-6) by neural glial cells infected with Theiler's murine encephalomyelitis virus (TMEV). Production of IL-6 mRNA in mock-infected and TMEV-infected SJL/J murine astrocytes was examined using the Affymetrix murine genome U74v2 DNA microarray. The IL-6 mRNA from infected cells showed an eightfold increase in hybridization to a sequence encoding IL-6 located on chromosome number 5. Quantitative real-time reverse transcription PCR (qPCR) was used to study the regulation of IL-6 expression. The presence of IL-6 in the supernatants of TMEV-infected astrocyte cultures was quantified by ELISA and found to be weaker than in cultures of infected macrophages. The IL-6 was induced by whole TMEV virions, but not by Ad.βGal adenovirus, purified TMEV capsid proteins, or UV-inactivated virus. Two recombinant inflammatory cytokines, IL-1α and tumour necrosis factor-α were also found to be potent inducers of IL-6. The secreted IL-6 was biologically active because it fully supported B9 hybridoma proliferation in a [3H]thymidine incorporation bioassay. The cerebrospinal fluid of infected mice contained IL-6 during the acute encephalitis phase, peaking at days 2–4 post-infection. Finally, this in vitro neuroinflammation model was fully inhibited, as demonstrated by ELISA and qPCR, by five selective oestrogen receptor modulators.

Removal of apoptotic cells from inflammatory sites by macrophages is an important step in the resolution of inflammation. However, the effect of inflammatory modulators on phagocytic clearance of apoptotic cells remains to be clarified. In this paper, we demonstrate that lipopolysaccharide (LPS), a potent inflammatory agent, inhibits the phagocytosis of apoptotic neutrophils by mouse peritoneal macrophages. This inhibition can be attributed to both LPS-mediated induction of tumour necrosis factor (TNF-α) and suppression of growth arrest-specific gene 6 (Gas6) in macrophages. We found that LPS-induced TNF-α production inhibited phagocytic ability of macrophages in an autocrine manner. In contrast, Gas6 expression in macrophages was blocked by LPS, which also contributes to the inhibition of macrophage phagocytosis by LPS. Our data suggest that phagocytic clearance of apoptotic neutrophils by macrophages can be regulated by local pro- and anti-inflammatory factors in two opposite states.

Peripheral blood CD4(+) CD45RO(+) T cells activated in vitro are able to induce expression of tumour necrosis factor-α (TNF-α) in monocytes via a contact-dependent mechanism. Activation is achieved either with interleukin-2 (IL-2)/IL-6/TNF-α over an 8-day period or cross-linking CD3 using anti-CD3 antibody for 48 hr. In this paper, we show that the p38 mitogen-activated protein kinase (MAPK) signalling pathway played different roles in the generation of effector function in these two types of activated T cells. In anti-CD3 activated T cells, p38 MAPK is a negative regulator for anti-CD3 induced cell proliferation and has no significant effect on the acquisition of either the effector function (induction of monocyte-derived TNF-α) or production of T-cell cytokines. In contrast, the p38 MAPK signalling pathway is required for the acquisition of cytokine-induced effector function and promotes cell proliferation and cytokine production.

Pemphigus vulgaris (PV) is considered to be an autoimmune disease affecting skin and mucous membranes. Traditionally, PV autoantibodies are thought to recognize antigens located in the intercellular substance (ICS) of keratinocytes; antigens represented mainly by the desmosomal cadherin desmoglein 3 (Dsg3). Accordingly, titres of anti-ICS and anti-Dsg3 immunoglobulin G (IgG) are considered to be major laboratory criteria when making a diagnosis of PV. In this paper, we demonstrated for the first time that PV IgG bind antigen(s) expressed on the surface of peripheral blood mononuclear cells (PBMC), as revealed by immunofluorescence studies. This novel autoantigen is immunoprecipitated by PV IgG as a 130 000 molecular weight protein. However, Western blot analysis of the immunocomplexes failed to show reactivity with anti-Dsg3 monoclonal and polyclonal antibodies. Taken together, our data provide strong evidence that PV autoimmunity targets a 130 000 antigen other than Dsg3 on PBMC. This shifting from epidermis to blood cells may open new perspectives for a better understanding of pemphigus autoimmunity and more rational approaches to its treatment.

It has been known for 15 years that the chicken epidermis contains ATPase+ and major histocompatibility complex class II-positive (MHCII+) dendritic cells. These cells were designated as Langerhans cells but neither their detailed phenotype nor their function was further investigated. In the present paper we demonstrate a complete overlapping of ATPase, CD45 and vimentin staining in all dendritic cells of the chicken epidermis. The CD45+ ATPase+ vimentin+ dendritic cells could be divided into three subpopulations: an MHCII+ CD3- KUL01+ and 68.1+ (monocyte-macrophage subpopulation markers) subpopulation, an MHCII- CD3- KUL01- and 68.1- subpopulation and an MHCII- CD3+ KUL01- and 68.1- subpopulation. The first population could be designated as chicken Langerhans cells. The last population represents CD4- CD8- T-cell receptor-alphabeta- and -gammadelta- natural killer cells with cytoplasmic CD3 positivity. The epidermal dendritic cells have a low proliferation rate as assessed by bromodeoxyuridine incorporation. Both in vivo and in vitro experiments showed that dendritic cells could be mobilized from the epidermis. Hapten treatment of epidermis resulted in the decrease of the frequency of epidermal dendritic cells and hapten-loaded dendritic cells appeared in the dermis or in in vitro culture of isolated epidermis. Hapten-positive cells were also found in the so-called dermal lymphoid nodules. We suggest that these dermal nodules are responsible for some regional immunological functions similar to the mammalian lymph nodes.

Summary B cells and dendritic cells, lacking functional Wiskott–Aldrich syndrome protein (WASP), have aberrant formation of membrane protrusions. We hypothesized that protrusions may play a role in antigen presentation, and consequently, that impaired antigen presentation may be an underlying factor of the immune deficiency in patients with Wiskott–Aldrich syndrome. In this paper, we investigated the antigen presentation capacity of B cells and dendritic cells from WASP knockout mice, using soluble and particulate antigen, to CD4+ T cells from T-cell receptor transgenic DO11.10 mice. As antigen we used soluble ovalbumin (OVA), a peptide thereof (amino acids 323–339) or bacteria expressing OVA. We found that WASP-deficient B cells and dendritic cells efficiently processed and presented soluble OVA protein as well as its peptide in vitro, inducing proliferation and cytokine production from CD4+ T cells. Antigen presentation of soluble protein was efficient also in vivo, because immunization of WASP-deficient mice with OVA elicited proliferation of transferred, fluorescent-labelled, CD4+ T cells. Although we could detect uptake of bacteria in dendritic cells, processing and presentation of bacterial-expressed OVA was impaired in WASP-deficient dendritic cells. In conclusion, our data suggest that WASP is not needed for processing and presentation of soluble antigen, but that efficient presentation of particulate antigen require WASP.

Tumour necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine produced by several cell types, including T cells upon antigen stimulation. Its production is crucial for the development of an early defence against many pathogens, but its beneficial effects are dependent on the strength and duration of its expression. In this paper we present evidence indicating that serum increases translational efficiency of TNF-alpha in human peripheral blood mononuclear cells stimulated with superantigen. The increase in translation of TNF-alpha due to serum could be inhibited by the phosphatidylinositol (PI) 3-K inhibitors, wortmannin and LY294002, suggesting that PI 3-K is involved in the translational control of TNF-alpha by serum. Similarly to primary T cells, stimulation of Jurkat T cells with superantigen led to TNF-alpha secretion and this was up-regulated by serum. Transfection of Jurkat cells with a constitutively active form of PI 3-Kalpha increased the production of TNF-alpha in cells stimulated with superantigen. Additionally, we used the specific inhibitors targeting ERK kinase and p38 mitogen-activated protein kinase (MAPK), potentially downstream of PI 3-kinase, PD98059 and SB203580. Differently from with PI 3-K inhibitors, the accumulation of TNF-alpha mRNA was inhibited by PD98059 or SB203580. These results suggest that, in T cells, activation of PI 3-K is an important step in controlling TNF-alpha protein synthesis in response to growth factors.

Secondary lymphoid tissue consists of two major populations of cells: lymphoid cells and stromal cells. It is generally accepted that these two cell populations influence each other however, factors mediating these processes are poorly understood. In this paper we characterize one of the possible means of communication between stroma and lymphocytes namely through hepatocyte growth factor/c-met receptor interactions. Hepatocyte growth factor (HGF) is a pleiotropic factor that is mainly produced by mesenchymal cells and acts on cells of epithelial origin which express the HGF receptor c-met. Here we demonstrate that biologically active HGF is constitutively produced by fibroblast-like stromal cells from human lymphoid tissues. HGF secretion from stromal cells was increased by direct contact with activated T cells. This increase was abrogated when activated T cells were separated physically from stromal cells. Using neutralizing antibody or cytokine inhibitors we provide evidence that enhancement of HGF production was due to additive effects of T-cell membrane-associated interleukin-1 (IL-1) and CD40 ligand. Finally, we also show that B lymphocytes activated with CD40L/anti-mu or phorbol 12-myristate 13-acetate (PMA) express c-met receptor. Co-culture of activated B cells with stromal cells from spleen leads to enhanced production of immunoglobulins. This can be partially inhibited by introduction of anti-HGF neutralizing antibodies to the culture system. Substitution of stromal cells with recombinant HGF did not produce enhancement of immunoglobulin secretion. On the other hand stimulation of c-met receptor with HGF leads to enhanced integrin-mediated adhesion of activated B cells to vascular cell adhesion molecule (VCAM-1) and fibronectin. On the basis of the above experiments we conclude that HGF production by fibroblast-like stromal cells can be modulated by activated T cells, thus providing signals for the regulation of adhesion of c-met expressing B cells to extracellular matrix proteins. In this way HGF may indirectly influence immunoglobulin secretion by B cells.

An immunodominant epitope of human immunodeficiency virus-1 (HIV-1) gp160 recognized by Dd class I major histocompatibility complex (MHC) molecule-restricted, CD8+ cytotoxic T lymphocytes (CTL) was originally identified as a peptide composed of 15 amino acids (P18IIIB: RIQRGPGRAFVTIGK). However, further study has indicated that a 10-mer peptide, I-10 (RGPGRAFVTI), within P18IIIB is the minimal-sized epitope and the trimming step(s) of two carboxyl terminal amino acids (GK) is essential to produce I-10 from P18IIIB. In the processing, angiotensin-1-converting enzyme (ACE), found in sera, plays a central role in generating I-10. Target cells could be sensitized with I-10 under conditions where ACE activity in the sera was abrogated. In contrast, in the case of P18IIIB, requiring further processing to delete the C-terminus of two amino acids in order to act, sensitization of target cells was completely abrogated under the conditions. Pretreatment of target cells with brefeldin A (BFA), preventing the presentation of endogenous antigens from the class I MHC molecule pathway, did not inhibit the presentation of P18IIIB. Moreover, glutaraldehyde-fixed cells, which can not process native protein, though they could present the exogenously added peptides, were also sensitized by P18IIIB. These results clearly demonstrate that the fine processing to produce I-10 occurred in the extracellular milieu. Furthermore, our result suggests that the longer P18IIIB can bind to the class I molecules on the cell surface, and then be trimmed by ACE while it is bound. The mechanisms behind the extracellular processing outlined in this paper will offer important information for designing peptide-based vaccines to elicit MHC molecule-restricted effectors.

Summary As is well known in the case of Langerhans cells, dendritic cells (DCs) play a crucial role in the initiation of immunity to simple chemicals such as noted in the contact hypersensitivity. Because DCs are scattered in non-lymphoid organs as immature cells, they must be activated to initiate primary antigen-specific immune reactions. Therefore, we hypothesized that some simple chemicals must affect the function of DCs. In this paper, we first demonstrated that human monocyte-derived DCs responded to such simple chemicals as 2,4-dinitrochlorobenzene (DNCB), 2,4,6-trinitrochlorobenzene (TNCB), 2,4-dinitrofluorobenzene (DNFB), NiCl2, MnCl2, CoCl2, SnCl2, and CdSO4 by augmenting their expression of CD86 or human leucocyte antigen-DR (HLA-DR), down-regulating c-Fms expression or increasing their production of tumour necrosis factor-α (TNF-α). In addition, the DCs stimulated with the chemicals demonstrated increased allogeneic T-cell stimulatory function. Next, we found that, among these chemicals, only NiCl2 and CoCl2 induced apoptosis in them. Finally, we examined the effects of these chemicals on CD86 expression by three different macrophage subsets and DCs induced from the cultures of human peripheral blood monocytes in the presence of macrophage colony-stimulating factor (M-CSF), M-CSF + interleukin-4 (IL-4), granulocyte–macrophage colony-stimulating factor (GM-CSF), and GM-CSF + IL-4, respectively. Among them, only DCs dramatically augmented their expression of CD86. These observations have revealed unique characteristics of DCs, which convert chemical stimuli to augmentation of their antigen presenting function, although their responses to different chemicals were not necessarily uniform in the phenotypic changes, cytokine production or in the induction of apoptosis.

We previously demonstrated that the majority (>/= 90%) of porcine ileal Peyer's patch (IPP) follicular cells are immature B cells destined to die by apoptosis, when incubated at 37 degrees. In this paper we approached the mechanisms responsible for positive selection of porcine IPP follicular immature B-cell selection, by screening for various cell types, cytokines and polyclonal and monoclonal antibodies for promoting the survival of IPP B cells. Of these reagents, only CD3 cross-linked purified T cells from mesenteric lymph nodes were able to rescue IPP follicular B cells from apoptosis, although polyclonal anti-IPP lymphocyte antibodies delayed apoptosis. This survival effect could be reproduced simply by incubating IPP follicular B cells with soluble and cell membrane-expressed CD154, an observation consistent with the demonstrated presence of CD40 and CD154 on porcine IPP follicular B cells and activated T cells, respectively. The IPP follicular B cells rescued in this manner expressed a more mature surface marker phenotype. Immunohistology and fluorescence-activated cell sorter analysis demonstrated that subpopulations of IPP follicular T cells (less than 0.5%) express CD154. Thus, perhaps unexpectedly, CD154 on T cells may play a role in the positive selection of immature B cells in the porcine IPP. The origin and control of the activated T cells identified within the porcine IPP remains to be investigated.

Unlike other immunoglobulin G (IgG) subclasses, IgG4 antibodies in plasma have been reported to be functionally monovalent. In this paper we show that the apparent monovalency of circulating IgG4 is caused by asymmetry of plasma IgG4. A large fraction of plasma IgG4 molecules have two different antigen-binding sites, resulting in bispecificity. Sera from patients with IgG4 antibodies to both house dust mite and grass pollen induced cross-linking of Sepharose-bound grass pollen antigen to radiolabelled house dust mite allergen Der p I. This bispecific binding activity was not observed in sera with IgG4 antibodies to either grass pollen or house dust mite exclusively. Depletion of IgG4 antibodies resulted in disappearance of the bispecific activity. By size exclusion chromatography we excluded the possibility that bispecific activity was caused by aggregation of IgG4 antibodies. These results indicate that circulating (polyclonal) IgG4 antibodies have two different antigen-binding sites and therefore are functionally monovalent antibodies.

Cells of the B-cell lineage play an essential part in the immune response, not only as the producers of antigen-specific antibodies, but also as antigen-presenting cells. Unlike T cells, however, the establishment of long-term normal B-cell lines has proved to be exceedingly difficult. In this paper we demonstrate that cell membrane-expressed CD154 (CD40 ligand) is able to support the continual growth of porcine mesenteric lymph node B-cell cultures for more than 4 months without the addition of exogenous cytokines, such as interleukin-4 (IL-4). Addition of IL-4, but not interferon-gamma (IFN-gamma) or IL-13, to these cultures enhanced proliferation, as, to a lesser extent, did addition of IL-2. Interestingly, however, whilst IFN-gamma-supplemented cultures largely consisted of immunoglobulin M (IgM)-positive cells, cultures with IL-13 or IL-4 contained a significantly increased proportion of IgG-positive cells.

We previously showed that the mixed haplotype Abetaz/Aalphad major histocompatibility complex (MHC) class II molecules function as restricting element for autoreactive T-cell clones derived from autoimmune prone (NZBxNZW)F1 (B/WF1) mice. Subsequent analysis revealed that some of these Abetaz/Aalphad-restricted autoreactive T-cell clones were pathogenic upon transfer to pre-autoimmune B/WF1 mice. In this paper, we analysed the peptide-binding motif of Abetaz/Aalphad class II molecules. Amino acid-sequencing analysis of peptides eluted from purified Abetaz/Aalphad molecules revealed several sequences, including one that corresponds to murine l-plastin 588-601. Synthetic 18-mer l-plastin 588-605 peptide (SMARKIGARVYALPEDLV, as described by the amino acid single letter code) was demonstrated to bind to Abetaz/Aalphad MHC class II molecules on transfectant B lymphoma cells (TAbetaz). A competitive binding inhibition assay using truncation peptides revealed the core sequence for binding resides in 591Arg to 601Pro. Binding inhibition assay using substitution peptides, each having substitution to the other 19 residues at positions from 590Ala to 601Pro, revealed four major anchor sites 592Lys (p1), 594Gly (p3), 595Ala (p4), 597Val (p6) and one minor anchor site 600Leu (p9). Positively charged residues are not allowed at p3 and negatively charged residues are not allowed at p4 and p6. Relatively large hydrophobic residues (Leu, Ile) are not tolerated at p3 and p4. Met and Trp are not tolerated at p6. Based on these findings, the characteristics of peptides recognized by autoreactive T cells in B/WF1 mice are discussed.

In a previous report, we investigated inflammatory responses induced by injecting Listeria monocytogenes into one testis of a mouse. We demonstrated that the contralateral testis also developed an orchitis despite the absence of bacteria, indicating that the inflammation on the uninfected, contralateral side was of autoimmune character. In both infected and autoimmune testes, gammadelta and alphabeta T cells infiltrated during the inflammation. In this paper, we present the data of a comparison of the character of gammadelta T cells of the infected and autoimmune testes. In both testes, gammadelta T cells appeared to be activated, as assessed by high CD44 and low l-selectin expression. Analysis of T-cell receptor (TCR) usage in both inflammation types revealed the same gammadelta TCR repertoire. Finally, the semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that gammadelta T cells in both types of inflammation were capable of producing interleukin-2 (IL-2), IL-4, interferon-gamma (IFN-gamma), IL-10 and transforming growth factor-beta (TGF-beta). These results imply that gammadelta T cells present in infected-induced and autoimmunity-induced inflammation have the same characteristics and could work as immunoregulatory cells.

As part of our current efforts to develop assays and reagents to study the immune system of marine mammals, and in view of the effort currently made to develop monoclonal antibodies to cell surface proteins of lymphocyte subsets in different species, the present paper reports on the characterization of a monoclonal antibody against the homologue of CD45R on cetacean lymphocytes. The specificity of this antibody has been characterized on the basis of immunoprecipitation of the antigen it recognized, immunoperoxidase staining on cetacean lymph node and thymus sections, as well as one and two-colour flow cytometric analysis of cetacean peripheral blood mononuclear cells and single-cell suspensions of thymus, lymph node and spleen. Anticetacean CD45R (F21.H) immunoprecipitated proteins of 180, 200 and 220 x 10(3) MW, with the 180 x 10(3) MW from being predominantly expressed on T cells and the 220 x 10(3) MW form expressed predominantly on B cells and thymocytes F21.H labelled all B cells and a proportion of T cells on single-cell suspensions of spleen cells. CD45R- killer whale peripheral blood lymphocytes expressed a higher density of CD2 than CD45R+, a characteristic of memory T cells. Killer whale T lymphocytes also lost the expression of CD45R upon activation with concanavalin A (Con A) and phytohaemagglutinin (PHA). This is the first report of a monoclonal antibody to CD45R in cetaceans, and this antibody is foreseen as a possible valuable diagnostic and research tool to assess immune functions of captive and wild cetaceans as part of the evaluation of their health status.

This paper describes the results of immuno-histochemical staining for chicken mannan-binding lectin (MBL) in formalin-fixed tissue sections from non-infected chickens, and from chickens infected with infectious laryngotracheitis virus (ILTV) or infectious bursal disease virus (IBDV). In the non-infected chickens, MBL was detected in the cytoplasm of a few hepatocytes and in the germinal centres of the caecal tonsils, whereas sections of kidney, heart muscle, spleen, cerebrum, thymus, adrenal gland, bursa of Fabricius, bone marrow and trachea were without staining. In the ILTV-infected chickens, an intense staining reaction for MBL was detected in the cytoplasm of all hepatocytes and on the surface of, and inside, ILTV-infected cells. Also in the IBDV-infected chickens, an intense staining reaction for MBL was detected in the cytoplasm of all hepatocytes. No staining was seen in the follicles of the bursa of Fabricius, but MBL was present in non-identified cells in the interstitium, and in the cytoplasm of macrophage-like cells, located peripheral to the ellipsoid of the spleen. These findings indicate the liver as the primary site of MBL synthesis, and points to up-regulation as a result of the viral infections. The location outside the liver could indicate a role of MBL in the immune defence.

We have previously reported that T lymphocytes proliferating in vitro to the hapten trinitrochlorobenzene (TNCB) exhibit a very restricted V beta gene usage and response to TNCB is limited to T-cell receptors (TCR) composed of V beta 8.2 in combination with V alpha 3.2, V alpha 8 and V alpha 10. This paper investigates the role played by T lymphocytes expressing the V beta 8.2 gene segment in the contact sensitivity (CS) reaction to TNCB in the intact mouse and in its passive transfer into naive recipient mice. Mice injected with monoclonal antibodies to V beta 8 are unable to develop CS upon immunization with TNCB and 4-day TNCB-immune lymph node cells from mice that had been depleted in vivo or in vitro of V beta 8+ T lymphocytes fail to transfer CS. However, when separated V beta 8+ and V beta 8- cells were used for passive transfer, it was found that V beta 8+ T lymphocytes failed to transfer CS when given alone to recipient mice and a V beta 8- population was absolutely required. Further analysis revealed that within the V beta 8- population, T lymphocytes expressing the gamma delta TCR were fundamental to allow transfer of the CS reaction. These gamma delta cells were found to be antigen non-specific, genetically unrestricted and to rearrange the V gamma 3 gene segment. This indicates that transfer of the CS reaction requires cross-talk between V beta 8+ and gamma delta+ T lymphocytes, thus confirming our previous results obtained using TNCB-specific T-cell lines. Time-course experiments showed that V beta 8+ lymphocytes taken 4-24 days after immunization with TNCB were able to proliferate and produce interleukin-2 (IL-2) in response to the specific antigen in vitro. Similar time-course experiments were then undertaken using the passive transfer of the CS reaction system. The results obtained confirm that TNCB-specific V beta 8+ T lymphocytes are present in the lymph nodes of immunized mice from day 4 to day 24, and reveal that gamma delta+ T lymphocytes are active for a very short period of time, i.e. days 4 and 5 after immunization. In fact, TNCB-specific V beta 8+ cells are able to transfer CS when taken 4-24 days after immunization, providing the accompanying V beta 8- or gamma delta+ T lymphocyte are obtained 4 days after immunization. In contrast, injection of V beta 8+ T lymphocytes together with V beta 8- or gamma delta+ T lymphocytes that had been taken 2 or 6 days after immunization, failed to transfer significant CS into recipient mice. Taken together, our results confirm that cross-talk between V beta 8+ and gamma delta+ T lymphocytes is necessary for full development of the CS reaction and may explain why the CS reaction in the intact mouse lasts up to 21 days after immunization while the ability of immune lymph node cells to transfer CS is limited to days 4 and 5 after immunization.

We have previously reported an experimental autoimmune model induced by the local infection of Listeria monocytogenes. The unilateral inoculation of virulent Listeria into a testis of a normal mouse induced a delayed-type hypersensitivity response against testicular antigen and caused autoimmune orchitis in the contralateral testis. The orchitis was transferred to naive mice by T cells from the intratesticularly infected mice. In this paper, we demonstrated that avirulent Listeria, which lacks the expression of listeriolysin O, failed to induce any anti-testicular responses or contralateral orchitis even when it was inoculated at a high dose into the testis. Furthermore, the intraperitoneal inoculation of virulent Listeria with testicular antigen induced the anti-testicular responses and orchitis although intraperitoneal inoculation of testicular antigen with avirulent Listeria failed to induce them. The difference between virulent and avirulent Listeria in the induction of anti-testicular responses was supposed to be dependent on the difference in macrophage activation by the two bacterial strains because, first, the anti-testicular responses were elicited in normal mice when macrophages from virulent Listeria-infected mice were intraperitoneally transferred with testicular antigen although no viable bacteria were detected from the macrophages, and secondly, in contrast, the intraperitoneal co-inoculation of macrophages from avirulent Listeria-infected mice and testicular antigen failed to elicit any anti-testicular responses. Finally, we found that the virulent Listeria-induced macrophages expressed a higher level of CD80 (B7-1) and CD86 (B7-2) molecules than did the avirulent Listeria-induced macrophages and naive peritoneal macrophages. These results thus suggest that virulent Listeria activates macrophages to induce autoreactive T cells while avirulent Listeria does not. The up-regulation of B7 molecules by virulent Listeria infection is a candidate of the mechanism for the activation of autoreactive T cells.

A number of subunit-based vaccine candidates have recently begun to erode the exclusive position of Mycobacterium bovis bacillus Calmette-Guérin (BCG), which gives unpredictable and highly variable protection against tuberculosis. In this paper we investigated the protective capacity of the 19,000 MW and 38,000 MW glyco-lipoproteins of M. tuberculosis expressed by recombinant vaccinia viruses in a mouse Mycobacterium tuberculosis infection model. Both proteins were expressed at high levels by recombinant vaccinia-infected cells. In addition, two inoculations of C57B1/6 mice with either recombinant vaccinia virus significantly reduced the bacterial counts in the lungs of M. tuberculosis H37Rv-infected mice, when compared with the group infected with control virus. This is the first report of protection against tuberculous infection using recombinant vaccinia viruses with results that suggest that secreted glyco-lipoproteins in conjunction with the vaccinia vector represent suitable candidates for further vaccine-related studies.

In our recent studies, an inhibitor of vacuolar-type H(+)-ATPase, concanamycin A (CMA) has been shown to neutralize acidic pH in vacuolar organelles, including lytic granules, and to decrease the perforin content markedly. In the present paper, we have further investigated the role of acidification in perforin storage by using CMA. In CD8+ cytotoxic T-lymphocyte (CTL) clones, the amount of perforin decreased rapidly at 30-90 min but no more decrease occurred at 90-120 min after the addition of CMA. Since exposure to actinomycin D, cycloheximide, or brefeldin A failed to reduce the perforin content, the perforin decrease in CMA-treated cells seems to be largely due to a reduction in the perforin already stored in lytic granules, rather than to the inhibition of the de novo synthesis or the intracellular glycoprotein transport of perforin. Diisopropylfluorophosphoridate (DFP) markedly antagonized the decrease in the perforin content in CMA-treated cells, while other protease inhibitors, i.e. antipain, E-64, leupeptin, pepstatin A and phenylmethylsulphonyl fluoride, did not. Nevertheless, DFP hardly reversed the abrogation of the killing activity by CMA. Indeed, the lytic granules prepared from DFP plus CMA-treated cells showed only a marginal level of haemolytic activity. In cell-free experiments using perforin-enriched granule fractions, acidic pH completely blocked the perforin activity. Under the acidic conditions, perforin was more resistant to an inactivation by calcium when exposed to calcium prior to the haemolysis test. Thus, these data suggest that perforin is primarily inactivated, possibly in a calcium-dependent manner, and is subsequently hydrolysed by DFP-sensitive proteases in the lytic granules at neutral pH. We conclude that acidic pH plays an essential role to maintain the integrity of perforin within the lytic granules.

This paper describes the immunoregulatory effects of interleukin-10 (IL-10) on synovial cells in vitro. Synovial cells were cultured with IL-10 in the presence or absence of various cytokines. Following incubation, the costimulatory molecule expression on synovial cells and cytokine production in culture supernatants were analysed by an indirect immunofluorescence method and enzyme-linked immunosorbent assay, respectively. We also examined the effect of IL-10 on the function of synovial cells as antigen-presenting cells (APC). Synovial cells spontaneously express several kinds of costimulatory molecule and produce various kinds of cytokines. Stimulation of synovial cells with interferon-gamma (IFN-gamma), IL-1 beta, or 12-O-tetradecanoyl phorbol 13-acetate (TPA) markedly enhanced the expression of costimulatory molecules and cytokine production of these cells. Both spontaneous and up-regulated costimulatory molecule expression and cytokine production were significantly suppressed by the addition of IL-10. Autologous T-cell proliferation was stimulated by purified protein derivative (PPD) in IFN-gamma-treated synovial cells and treatment of these synovial cells with IL-10 also suppressed T-cell proliferation. Our results suggest that IL-10 has an inhibitory effect on synovial cells and is an important immunoregulatory component of the cytokine network in rheumatoid arthritis.

Invariant chain (Ii) plays an important role in major histocompatibility complex (MHC) class II antigen processing and presentation and is constitutively synthesized in B lymphocytes, in macrophages, dendritic cells and in some epithelial cells. It has been shown that interferon-gamma, tumour necrosis factor-alpha and interleukin-4 co-regulate Ii and MHC class II expression in various cell types. We describe here a novel regulation of Ii expression in macrophages. Treatment of the premature monocytic cell lines WEHI 265.1, M1 and WEHI-3B with recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) strongly enhances Ii expression while class II expression is not induced. In contrast, GM-CSF did not enhance Ii in mature macrophage cell lines. The increase of Ii expression in WEHI 265.1 cells takes several days. This long induction time, and a difference in activity between GM-CSF-conditioned medium and GM-CSF, together suggest that GM-CSF stimulates WEHI 265.1 cells to secrete a factor that modulates Ii expression. These results may imply a class II-independent function of Ii, which we discuss in this paper.

We have examined the emigration of chicken thymocytes after intrathymic fluorescein isothiocyanate (FITC) labelling in situ. In this paper we show that in young birds about 0.7% and 0.4% of thymocytes emigrate from the thymus to the blood and the spleen, respectively, per day. This suggests that, as in mammals, most thymocytes die within the thymus. At 3 weeks of age gamma delta and alpha beta T cells leave the thymus in comparable levels to their appearance in the blood. The phenotype of recent emigrants in peripheral tissues is similar to that of mature T cells. Interestingly, recent emigrants contain relatively much higher numbers of CD4+ and fewer CD8+ cells than is observed in peripheral tissues in a steady-state situation.

Heat-shock proteins (hsp) represent a highly conserved family of proteins, normally localized in the cytoplasm and nucleus, whose expression is induced in situations involving cell stress. This paper reports the unusual translocation of hsp to the cell membrane of T cells undergoing apoptosis. We observed that glucocorticosteroid-induced thymocyte death is associated to the surface expression of hsp 60 and hsp 70 in a discrete fraction of apoptotic cells. hsp surface expression is closely related to a thymic subset of immature CD3low/- T cells. The expression of surface hsp 60 appears early after treatment with dexamethasone (3 hr) whereas the membrane expression of hsp 70 follows different kinetics and peaks later. Morphological analysis of the hsp+ apoptotic cells suggest that this subset represents late-stage apoptotic cells at their minimal volume before fragmentation into apoptotic bodies. Membrane expression of hsp is also associated with apoptosis in peripheral blood mononuclear cells from AIDS patients cultured in vitro. Altogether, we show that a discrete fraction of cells undergoing apoptosis expresses membrane hsp 60 and hsp 70, supporting the hypothesis that apoptosis causes a radical alteration in the expression of cell surface molecules. Surface hsp expressed during apoptosis may constitute a novel immune-context able to generate packages of self- and exogenous antigens, originating from degradation of altered cells.

Peripheral lung tissue contains large numbers of T cells, strategically located for immune surveillance at the blood-air interface. Given the intensity of antigenic exposure at this site, it is clear that local T-cell activation events require strict control, in order to maintain tissue homeostasis. How this control is achieved in this unique tissue microenvironment is unknown, and the present study sought to elucidate the process via detailed analysis of the surface phenotypic characteristics of freshly isolated lung T cells. We report below that these cells display typical characteristic of 'postactivation', notably elevated basal Ca2+ concentrations, down-modulated T-cell receptors, expression of Ia and 'late' activation antigens and concomitant CD4/CD8. However, levels of interleukin-2 receptor and CD2 expression were below those expected of 'activated' T-cell populations, and virtually all of the cells were found to be in the G0/G1 phases of the cell cycle. These properties bear a remarkable similarity to those of T cells activated in the presence of endogenous tissue (alveolar) macrophages from the lung (see accompanying paper). We hypothesize that they reflect the in vivo operation of an endogenous macrophage-mediated T-cell anergy-induction process, the function of which is to limit the local clonal expansion of T cells in peripheral lung tissue after in situ activation.

The paper by Barrett et al. in this issue1 describes a canine model of atopic asthma where parental allergic status directly influences the disease manifestation in the offspring. Newborns of the sensitized breeder pairs were significantly more responsive to ragweed exposure through inhalation than the control offspring of non-sensitized naive parents. Other elevated disease parameters included ragweed-specific immunoglobulin E (IgE), eosinophil counts in the bronchoalveolar lavage fluid and pulmonary resistance after ragweed inhalation. Despite the fact that, at present, these results are primarily descriptive, this dog model opens the possibility to investigate, in a controlled setting, the mechanisms of vertical transmission of allergy predisposition. Moreover, it may allow us to answer several open questions that are not possible to address in human clinical studies and are currently highly contentious. It has been known that allergic parents are more likely to have allergic children. Whereas, nature, i.e. the genetic predisposition, clearly plays a role, it appears that perinatal nurture by allergic mothers may put children at even higher risk of becoming allergic. A clinical study demonstrated an almost five-fold higher probability of infants of atopic mothers developing atopic dermatitis in comparison with children of atopic fathers.2 However, it is not clear which factors (allergens, IgE, cytokines, immune cells) play a predominant role in the transfer of the atopic bias from mother to child, or whether this transfer occurs pre- or postnatally, i.e. via the placenta or mother's milk, respectively. If the intrauterine influences are preponderant, little can be done to separate the fetus from the undesired exposure and thus prevent the allergy in the newborn. Nevertheless, at least hypothetically, allergic mothers may limit the intrauterine transfer of patho-aetiological factors by avoiding allergen contact. This theory, however, is contested by clinical observations.3 The second possible route for transmission of the pro-allergic maternal influences is by breast-feeding. Except for modern humans, mother's milk is the only dietary option for the newborn mammal. In addition to its nutritional value milk also supplements the innate and acquired host defences of the not yet fully immunocompetent newborn. This is achieved by antibodies, cytokines, chemokines and leucocytes, including T and B cells, present in milk and in especially high quantities in colostrum. These factors, which under normal circumstances protect the newborn, may be involved in sensitization and vertical transmission of atopy predisposition from mother to child. The latter possibility makes breast-feeding by atopic individuals especially controversial. Comprehensive review of over three decades of clinical observations concluded that extended breast-feeding protects from atopy.4 However, several modern reports challenge this notion. One showed that long-term exclusive breast-feeding lowers the rates of recurrent wheeze in the first years of life only, but increases the risk of asthma and recurrent wheeze in 6–13-year-old atopic children of asthmatic mothers.5 Another recent study demonstrated that breast-feeding failed to protect children at high risk from developing eczema.6 Moreover, a third cohort study of more than 1000 children provided evidence that breast-feeding for 4 weeks or longer doubled the risk of asthma in mid-childhood, irrespective of whether the mothers were atopic or not.7 The distinct features of the population groups studied, including socioeconomic and ethnic factors, as well as the different disease manifestations and parameters recorded, may explain the disparity of conclusions. The requirement for straightforward recommendations for atopic mothers as to whether to breast-feed or not, necessitates further experimental work to resolve the current controversy and settle the polemic debate.7–10 Well-controlled mechanistic experimental models, such as the canine model established by Barrett et al.,1 may provide invaluable clues as to the molecular mechanisms of vertical transfer of allergy predisposition via the mother's milk, and the relative contribution of the potential patho-aetiological factors present in it. On one hand, mother's milk is a cocktail of a wide range of immunomodulating factors, including antibodies, cytokines, chemokines and immune cells. On the other hand, it mirrors the mother's environment, exemplified by the presence in it of allergic and toxic exogenous substances. Dietary allergens are also present in mother's milk, with their peak milk concentrations expected 4–6 h after their ingestion.11 This would suggest that atopic mothers that breast-feed should be encouraged to avoid food allergens, e.g. cows' milk, egg, or soy. However, this notion is contested by a clinical study3 that failed to show any beneficial effect of allergen avoidance. Actually, exposure to allergens in the mother's milk may even be beneficial because of the induction of oral tolerance in newborns. In a canine model of atopy, dogs sensitized early in life parenterally with ovalbumin (OVA) developed high OVA-specific serum IgE levels and clinical symptoms of atopy.12 Oral administration of OVA in milk suppressed these allergic responses to OVA.13 Thus, it appears that orally administered food allergens, in conjunction with the milk milieu, may not be as harmful as initially thought, but may actually act as tolerogenic principles. What other factors may be contributing to the potential transfer of atopy through the milk? Immunoglobulins, particularly IgA, the most abundant immunoglobulin class in milk, are responsible for the protective passive immunity transferred to the newborn and also may have immunomodulatory effects. Comparison of milk from mothers of allergic and healthy children demonstrated an association between low levels of milk IgA and a predisposition towards the development of cows' milk allergy.14,15 Milk IgG may also play a protective role in developing allergy in the newborn. Conversely, specific IgE present in milk, as shown for example in OVA-immunized mice, may contribute to the development of allergic predisposition in their offspring,16 possibly by fixing allergens on the surface of dendritic cells. Unfortunately, it is not possible to extrapolate these experimental findings to humans as, at the time of writing, no significant IgE has been observed in human milk. Several cytokines—interleukin-4 (IL-4), IL-6, tumour necrosis factor-α, interferon-γ (IFN-γ), transforming growth factor-β (TGF-β) and IL-10—have been identified in the mother's milk and may skew the development of the newborn's own immunity.17 Some of them, e.g. IFN-γ and IL-4, may bias the immune responses of the newborn in T helper type 1 and type 2 (Th2) directions, respectively. Others, e.g. TGF-β and IL-10, as a result of their immunosuppressive function,18 may provide the tolerogenic background of the mother's milk. In addition, TGF-β in milk may prevent the development of atopic diseases in infants by inducing IgA, and inhibiting IgE, production in infants.19,20 Probiotics up-regulate TGF-β secretion in milk, and are thus thought to protect the newborn against atopic diseases.21 It has been known for over a decade that human milk contains several chemokines22–24 that may play a role in the recruitment of functional leucocyte populations into the milk. Different subsets of milk leucocytes, including T and B cells, endow the newborn with functional active immunity that mirrors the memory immune responses of the mother. There are indications, both experimental and clinical, that milk-born lymphocytes can traverse the gastrointestinal barrier of the newborn, repopulate its lymphoid organs and survive there for prolonged periods of time.25 The downside of such maternal lymphocyte transplantation is that allergic mothers may transfer to their newborns the pathogenic lymphocytes which recognize allergens or produce Th2 cytokines. It is clear that there are many mothers' milk-borne molecular players involved in modulating the immune system of the newborn. Future experimental work will show which of these and other potential mechanisms contribute to the transfer of atopic predisposition from mother to breast-fed newborn, allowing for clear recommendations, preventive interference and therapy. The canine model described by Barrett et al.1 is likely to be a useful tool in achieving these aims. In the long term, to asthmatic parents and children, the dog may truly turn out to be man's best friend.

As a commentary on a recently published paper in Immunology, this article summaries the principle of norovirus P particle as a promising vaccine against noroviruses. It emphasizes the importance of P particle formation in the immune enhancement of the vaccine and methods for production/verification of high quality P particles which may be easily neglected by researchers.

In this issue of Immunology, Liu and colleagues have demonstrated for the first time a crucial role for the physical trauma caused by injection of DNA vaccines, in the enhancement of innate immune responses.1 DNA vaccination delivers a plasmid encoding an antigen, usually administered intradermally. It has the advantages of being relatively cheap, of expressing only the relevant antigen within the host's own cellular machinery, and of lacking any of the potential health risks associated with live vaccines. The antigen is expressed either in resident keratinocytes from where it is taken up by antigen-presenting cells2,3 or in the local dendritic cells themselves.4 DNA vaccination elicits both cellular and humoral immunity5,6 a good memory response, and has been shown to be protective against a number of infections.7–9 However, the precise mechanism by which an antigen delivered in this way can trigger both innate and cognate immunity at the site of vaccination, and the mechanisms determining the type of immunity that results are still unclear. DNA vaccination is often less successful in man than in murine models and therefore understanding the immunology of DNA vaccination, to improve its efficacy, is an important goal. Immunologists have employed a number of strategies to enhance the immunogenicity of DNA vaccines, to deliver the vaccine in such a way that antigen-presenting cells are most effectively targeted and activated. One strategy, for example, has been the use of ‘genetic adjuvants’, the inclusion of genes encoding cytokines, growth factors, or costimulatory molecules that are expressed at the site of injection, to enhance the immune response to the antigen. For example, inclusion of the genes for granulocyte–macrophage colony-stimulating factor,10 interleukin-18 (IL-18),11 IL-2, IL-15, IL-12 and FLt-3 ligand (Flt-3L)12 greatly increases the magnitude of the response to antigens of interest. However, some of the adjuvanticity of DNA vaccines lie in the properties of the plasmid itself, as a result of the presence of CpG motifs.13,14 The deliberate co-administration of CpG-rich plasmids during DNA vaccination can be employed to greatly enhance the immune responses.15 CpG motifs are short sequences of DNA that have been used as strong T helper type 1 (Th1) adjuvants for protein-based vaccines.16 CpG motifs are one of many ‘pathogen-associated molecular patterns’ or PAMPs, molecular signatures found in foreign organisms at a much higher frequency than in host cells, e.g. lipopolysaccharide, double-stranded RNA, flagellin and bacterial lipoproteins. Methylated CpGs seem to have been lost from the genomes of vertebrates (so-called CpG suppression); as a result, sequences of unmethylated DNA are found at a higher frequency in microbial genomes.17 PAMPs are recognized by specific germ-line encoded receptors, which serve as an early warning system, triggering rapid innate immune responses. Toll-like receptors (TLRs) make a family of highly conserved pattern recognition receptors that are able to distinguish a wide array of PAMPs. Among them, TLR9 detects CpG motifs following transport of CpG-DNA into endosomes.18 Following ligand recognition, TLRs can trigger profound changes in antigen-presenting cells and by expressing particular combinations of TLRs different antigen-presenting cells can detect the nature of the invading organism. TLR9 ligation enhances dendritic cell function by up-regulating antigen presentation, increasing co-receptor expression and stimulating production of Th1 polarizing cytokines such as IL-12.19 Consequently, CpG motifs have proved to be an extremely powerful Th1-promoting adjuvant.16 In this issue of Immunology, Liu and colleagues address how DNA vaccination with CpG motifs can cause activation of innate immunity in the skin.1 The ability of the skin to respond to CpG was something of a puzzle, as although both TLR2 and TLR4 are expressed by resident keratinocytes, TLR9 is not constitutively expressed in the skin. The authors injected the ears of BALB/c mice intradermally with plasmid, and detected TLR9 mRNA using a semi-quantitative polymerase chain reaction. Surprisingly, the act of injecting the skin, either with plasmid or with saline alone, caused similar levels of TLR9 up-regulation. As the volume of saline injection was increased from 0 to 5, 10, 15 and 20 μl, the expression of TLR9 mRNA in the skin also increased. TLR9 mRNA expression was transient, appearing after only 6 hr and returning to baseline levels 12 hr later. The authors wished to identify which cells were expressing TLR9 in the skin in response to the physical trauma of injection. Although no clear identification of the cells was made, saline-injected skin did induce a strong inflammatory infiltrate and in situ hybridization revealed clusters of small cells at the inoculation site that appeared to be positive for TLR9 mRNA. The authors suggested that the TLR9 expression was the result of infiltration by blood leucocytes that express TLR9, rather than the de novo synthesis by resident skin cells. The next set of experiments addressed whether the newly up-regulated TLR9 expression could respond to CpG motifs in the plasmid. The increased expression of TLR9 did mediate responses in the skin; induction of the pro-inflammatory cytokines IL-1β, IL-6, tumour necrosis factor-α and IL-12 was significantly higher in mice that had received CpG-containing sequences. This work gives us a number of important insights into DNA vaccination and immunity in the skin. It reveals that vaccine administration into the skin delivers a combination of signals to the innate as well as to the cognate immune system. Among those signals is the physical damage to the skin that occurs following intradermal injection. This is required to make the skin responsive to the PAMP, the CpG motif, which in turn acts to enhance cytokine production at the site of injection. This might explain why gene guns have proved such a good delivery system for DNA vaccines. For gene gun vaccination plasmid is coated onto gold particles that are then propelled into the dermal layer using high-pressure helium. In this technique the dose of plasmid required to generate immunity is far lower than is necessary for intradermal injection. The authors speculate that their observations could thus explain the increased efficacy of gene gun delivery. It would be an obvious next step to examine whether gene gun immunization really does result in a greater increase in TLR9 expression in the skin. This work also sheds some light on the nature of immunity in the skin. It implies that the ability of the skin to respond to various stimuli that trigger the innate immune response can be altered under particular circumstances. The skin is an important first line of defence against infection and this plasticity of response makes sense in terms of function. Following physical damage, the threat of infection from the outside world is increased. By up-regulating the expression of pattern recognition receptors, the skin enters a state of heightened alertness to the threat of foreign invasion. We can speculate upon which mechanisms of tissue damage result in recruitment of TLR9-expressing cells from the blood. Could the TLR9-expressing cells be identified and are these the same cells that present the antigen? What are the chemotactic agents that recruit these cells into the tissues? Are heat-shock proteins released from the damaged tissues as an initial signal that all is not well? As well as a possible role in triggering recruitment of leucocytes, it has been proposed recently that heat-shock protein 90 can act as a ligand transfer molecule which could play a crucial role in the signalling induced by CpG-DNA.20 Identification of the key mediators in the processes described in this paper would offer new candidates for inclusion in future vaccines that exploit the adjuvant effects of tissue damage.