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The article presents a list of forthcoming books about immunology. These include "IL-5 Target Genes Involved in B Cell Terminal Maturation," by Keisuke Horikawa and K. Takatsu, "The Riddle of the Dual Expression of IgM and IgD," by Roland Geisberger, Marinus Lamers and Gernot Achatz, and "Anti-Idiotype Antibody Induced Cellular Immunity in Mice Transgenic for Human Carcinoembryonic Antigen," by Asim Saha, Sunil Chaterjee, Kenneth Foon and Malaya Chatterjee.

Summary: 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. [ABSTRACT FROM AUTHOR]

The ultimate outcome of T cell receptor recognition is determined by the context in which the antigen is encountered. In this fashion both antigen-presenting cells and T cells must integrate multiple environmental cues in the form of pathogen-associated molecular patterns, cytokines and accessory molecule signals. The mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that plays a central role in integrating environmental signals critical to regulating metabolism and cell survival. In this paper we review the data demonstrating that mTOR integrates signals from the immune microenvironment and therefore facilitates the generation of the adaptive immune response. Specifically, we review the role of mTOR in promoting dendritic cell activation and maturation, in regulating full T cell activation versus anergy, and influencing the induction of regulatory T cells. [ABSTRACT FROM AUTHOR]

We demonstrated the efficacy of a long- term cultured cytotoxic T-lymphocyte line, CTLL-D4, on tumour growth inhibition using athymic nude mice as recipients. CTLL-D4, specific for a unique surface determinant on a radiation-induced leukaemia RL♂1 of BALB/c origin, was obtained from the limiting dilution culture of MLTC cells performed between spleen cells of a CS6F1-nu/ + mouse immunized in vivo and RL♂1 stimulator cells, and cultured for several months in the absence of added TCGF as described in our preceding paper (Kuribayashi, 1985). The specific inhibition of tumour growth by CTLL-D4 was demonstrated both in Winn-type neutralization assay and in systemic transfer experiments. A subcutaneous inoculation of the mixture of CTLL-D4 and RL♂1 cells resulted in the complete inhibition of tumour growth, even at the effector to tumour cell ratio of 1 : 1, whereas non-cytolytic D4f, which was self-Ia antigen(s)-reactive, composed entirely of Lyt-l + 23- T cells and derived originally from CTLL-D4 but completely lost its cytotoxic activity during culture with the irradiated syngeneic feeder cells alone, had no inhibitory effect at all. In the adoptive transfer studies, the subcutaneously established tumours were rejected by the single i.v. transfer of 2 × 107 CTLL-D4 cells into CB6F1-nu/nu mice. However, D4f was ineffective again in this systemic transfer system. When the effect of CTLL-D4 cells on tumour rejection in vivo was compared to that of non-cultured spleen cells hyperimmunized with RL♂1 cells, the former exhibited more rapid rejection in nude mice after i.v. transfer than the latter did, suggesting that CTLL-D4 cells also attack the tumour cells much more effectively as effectors in vivo. Thus, it is conceivable that CTLs are mainly involved in tumour rejection in this adoptive transfer system using RL♂ 1 tumour cells and athymic nude mice. [ABSTRACT FROM AUTHOR]

Pretreatment of mice by intravenous injection with killed Listeria provided neither delayed-type hypersensitivity to Listeria protoplasm nor protection against Listeria infection. Assuming that this suppression is due to suppressor cells, we attempted to clarify their induction and characterization. Pretreatment with killed BCG instead of killed Listeria suppressed the induction of DTH and protection in subsequent Listeria-immunized mice. Conversely, pretreatment with killed Listeria suppressed subsequent induction of DTH to PPD or protection from tuberculosis. Thus, these suppressions were. induced antigen non- specifically. Transfer of splenic non-adherent cells from killed Listeria-injected mice which had been treated with anti-BAθ serum plus complement, or had been passed through Sephadex G-10 columns, resulted in both afferent and efferent DTH suppression, suggesting that the DTH suppression is closely associated with suppressor T cells. Moreover, the splenic non-adherent cells from killed Listeria-injected mice showed suppression in vitro of listericidal activity of PEC from Listeria-immune mice in the presence of Listeria protoplasm. [ABSTRACT FROM AUTHOR]

This paper describes the effect of altering liposomal membrane composition on humoral and cellular immunogenicity of haptenated liposomes in mice. Antibody formation was determined by enumeration of direct, plaque-forming cells in the spleen and delayed-type hypersensitivity (DH) was measured with a footpad swelling test. Humoral immunogenicity of haptenated liposomes was strongly influenced by membrane phospholipid, cholesterol and charged amphiphile composition. Haptenated liposomes prepared from phospholipids with a low (diolcoyl- and dilauroyl-phosphatidylcho- line) or high (distearoyl phosphatidylcholine) phase- transition temperature were less immunogenic than those prepared from phospholipids with an intermediate phase-transition temperature (dipalmitoyl phosphatidylcholine and sphingomyelin). In general, increasing the amount of liposomal membrane cholesterol induced a higher humoral response. These results are discussed in relation to liposomal membrane fluidity. Induction of an optimal DH with haptenated liposomes did not occur in the absence of the adjuvant dimethyl dioctadecyl ammonium bromide (DDA). When DDA was used, alterations in membrane composition did not influence cellular immunogenicity. From these results it was concluded that ‘intermediate’ liposomal membrane fluidity is the most important requirement for induction of optimal antibody formation with haptenated liposomes and that a certain physicochemical configuration of the antigen, provided by the adjuvant DDA, is a prerequisite for induction of DH. [ABSTRACT FROM AUTHOR]

This paper describes the induction of delayed-type hypersensitivity (DH) in the mouse and guinea-pig to haptenated liposomes. The tripeptide- enlarged hapten 3-(p-azobenzenearsonate)-N-acetyl- L-tyrosylglycylglycine (A) was coupled to phosphatidylethanolamine (PE) and incorporated into liposomal membranes (A PE-liposomes). In mice DH was measured as footpad swelling and in guinea pigs by skin testing. To induce hapten A-specific DH in mice with A-PE- liposomes the application of the cationic, surface- active lipid, dimethyl dioctadecyl ammonium bromide (DDA) was necessary. The use of Freund's complete adjuvant (FCA) did not result in the induction of DH to hapten A. In guinea-pigs, however, FCA and DDA had equally good adjuvant properties in the induction of DH. The time course of the DH and the optimal time interval between immunization and elicitation were determined for the mouse system. Also, the effect of dose and epitope density was studied in that system. Cyclophosphamide treatment, before immunizing mice with A-PE-liposomes and DDA, resulted in greatly impaired DH, probably caused by the short lifetime of the integrity of liposomes after intracutaneous administration to mice. The results make it very likely that presentation of hapten A in a liposomal or micellar structure is required to induce a cellular immune response to this hapten in mice. [ABSTRACT FROM AUTHOR]

An earlier paper showed that 4 days after immunization with the contact sensitizing agent 'uxazolone' there is a peak in the percentage of cells in the draining lymph nodes that move to sites of inflammation. This was assessed by dissociating the lymph nodes, labelling them with 51Cr and injecting them into mice whose ears were painted within an hour with an unrelated contact sensitizing agent or with croton oil. The ears were then removed at about 18 hours and their radioactivity used as a measure of cell arrival. The cells that move to sites of inflammation are not macrophages as they are not removed by filtration through cotton wool. They are θ-positive and control studies show that the activity of the anti-B serum was indeed due to antibody to the θ-antigen. The cells are large and can be labelled both in vivo and in vitro with [125I]-iododeoxyuridine which is incorporated in the DNA of cells during the S phase of the cell mitotic cycle. It was concluded that the cells in immunized lymph nodes that move to sites of inflammation are T blasts. The unitary hypothesis is put forward that following immunization for delayed hypersensitivity a particular class of T cells proliferates and gives rise to large pyroninophilic blast cells; and that these cells or their immediate descendants possess the properties, either at the same time or at closely related times, of' movement to sites of inflammation and non-specific cytotoxicity as well as the capacity to passively transfer cellular immunity. [ABSTRACT FROM AUTHOR]

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-γ (IFN-γ), IL-lβ, 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-γ-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. [ABSTRACT FROM AUTHOR]

The experiments described in this paper extend the observations of previous work in vitro demonstrating a decrease in the frequency of antigenreactive units specific for horse RBC in spleen cells from mice primed with KLH. It was observed that the addition of lymphoid cells having T-cell function reconstituted the anti-HRBC response to normal values. Significant enhancement of the response beyond the normal values could be evoked using two dissimilar methods, (i) addition of allogeneic thymus cells, and (ii) restimulation in vitro with the priming antigen. The latter type enhancement was elicited by the addition of small doses of KLH to cultures of spleen cells from mice recently primed with KLH, including cultures otherwise demonstrating antigen-induced suppression. The stimulus required to enhance the response to HRBC in these cultures was specific for the priming antigen, KLH. These results are discussed in the light of current theories of 'antigenic competition' and specific heterologous enhancement. [ABSTRACT FROM AUTHOR]

Antigen-dependent migration inhibition factor produced in cultures of mouse lymph node lymphocytes was further characterized. It was found to bind to Concanavalin A and could be eluted by the appropriate sugar. The pi of the activity was found to be between 6-4 and 6.5 by isoelectric focusing. [ABSTRACT FROM AUTHOR]

Two methods are described for linking chlorambucil to antibodies. At low pH an association is formed which is not stable under physiological conditions and the cytotoxicity is the result of the independent action of chlorambucil and antibody. At pH 8 a more stable linkage is formed and this complex shows specific toxicity for cells carrying the appropriate antigen. Uncombined chlorambucil and antibody are more cytotoxic than chlorambucil alone, especially if the cells are exposed first to the chlorambucil. [ABSTRACT FROM AUTHOR]

Fowls which tolerate foreign erythrocytes, but which have not received a transplant of variable cells, eventually lose tolerance when the supply of erythrocytes is discontinued. The loss follows, at an interval, after the foreign erythrocytes have been eliminated by the normal mechanism for removal of aged cells; earlier loss can be brought about by eliminating the foreign cells with passive antibody. The interval required for loss varies, for tolerance of homologous erythrocytes, from less than 5 to over 215 days. The age of the tolerance bird, and hence the duration of exposure to antigen, is the main factor influencing the interval required; the preceding level of tolerance exerts comparatively little effect. An attempt to terminate tolerance by adoptive immunization was only partially successful. [ABSTRACT FROM AUTHOR]

Use of an intra-articular route of injection (a single, hind limb knee joint) and a protein antigen (human serum albumin)in water-in-oil emulsion with added mycobacterial peptidoglycolipid (or Wax D) failed to induce an adjuvant effect upon the resulting immunological response observed three weeks later. Serum antibody levels as measured by the Farr Test (ABC30 μg/ml) and cell-mediated immunity as measured by a quantitative corneal test were consistently lower than those which followed use of a footpad route for the same injection mixture. [ABSTRACT FROM AUTHOR]

Summary: At a time when immunology seeks to progress ever more rapidly from characterization of a microbial or tumour antigen to the immune correlates that may define protective T‐cell immunity, there is a need for robust tools to enable accurate predictions of peptide–major histocompatibility complex (pMHC) and peptide–MHC–T‐cell receptor binding. Improvements in the curation of data sets from high throughput pMHC analysis, such as the NIH Immune Epitope Database (IEDB), and the associated developments of predictive tools rooted in machine‐learning approaches, are having significant impact. When such approaches are linked to the powerful empirical immunopeptidome data sets from peptide MHC elution and mass spectrometry, there is considerable potential for rapid translation to T‐cell therapies and vaccines. [ABSTRACT FROM AUTHOR]

The article focuses on the 50th anniversary of the journal "Immunology" in Great Britain. The author traces the beginnings of its existence and its purpose was to become the first committed journal for immunologists. The author mentions the immunological contributions involving immunologists such as the idea of cell-mediated suppression.

The immune system is composed of a variety of cells that act in a coordinated fashion to protect the organism against a multitude of different pathogens. The great variability of existing pathogens corresponds to a similar high heterogeneity of the immune cells. The study of individual immune cells, the fundamental unit of immunity, has recently transformed from a qualitative microscopic imaging to a nearly complete quantitative transcriptomic analysis. This shift has been driven by the rapid development of multiple single-cell technologies. These new advances are expected to boost the detection of less frequent cell types and transient or intermediate cell states. They will highlight the individuality of each single cell and greatly expand the resolution of current available classifications and differentiation trajectories. In this review we discuss the recent advancement and application of single-cell technologies, their limitations and future applications to study the immune system. [ABSTRACT FROM AUTHOR]

CD8 T cells contribute to long-term protection against Listeria monocytogenes infection by differentiating into memory T cells. These rapidly respond to antigen or inflammation upon secondary infection. In this study we used CD8 T cells from OT1 mice and CD4 T cells from OT2 mice expressing a fluorescent chimeric granzyme ( GZMB-Tom) protein to monitor the primary response to infection with ovalbumin-expressing L. monocytogenes ( Lm- OVA). We show that, unlike poorly responding CD4 T cells, CD8 T cells readily proliferated and expressed high levels of GZMB-Tom as early as 2 days after infection. FACS analysis showed GZMB-Tom expression in undivided CD8 T cells, with its level increasing over one to four divisions. OT1 T cells were visualized in the T-cell zone by confocal microscopy. This showed GZMB-Tom-containing granules oriented towards MHCII-positive cells. Twenty hours later, most OT1 T cells had divided but their level of GZMB-Tom expression was reduced. Recently divided OT1 cells failed to express GZMB-Tom. Fourteen hours after secondary infection, GZMB-Tom was re-expressed in memory OT1 T cells responding either to Lm- OVA or L. monocytogenes. Differences in the activation phenotype and in the splenic distribution of OT1 T cells were observed, depending on the challenge. Notably, OTI T cells with polarized granules were only observed after challenge with cognate antigen. This work showed that the GZMB-Tom knock-in mice in which GZMB-Tom faithfully reproduced GZMB expression, provide useful tools to dissect mechanisms leading to the development of anti-bacterial effector and memory CD8 T cells and reactivation of the memory response to cognate antigen or inflammatory signals. [ABSTRACT FROM AUTHOR]

Major histocompatibility complex class I ( MHC-I) molecules play an essential role in the cellular immune response, presenting peptides to cytotoxic T lymphocytes ( CTLs) allowing the immune system to scrutinize ongoing intracellular production of proteins. In the early 1990s, immunogenicity and stability of the peptide- MHC-I (pMHC-I) complex were shown to be correlated. At that time, measuring stability was cumbersome and time consuming and only small data sets were analysed. Here, we investigate this fairly unexplored area on a large scale compared with earlier studies. A recent small-scale study demonstrated that pMHC-I complex stability was a better correlate of CTL immunogenicity than peptide- MHC-I affinity. We here extended this study and analysed a total of 5509 distinct peptide stability measurements covering 10 different HLA class I molecules. Artificial neural networks were used to construct stability predictors capable of predicting the half-life of the p MHC-I complex. These predictors were shown to predict T-cell epitopes and MHC ligands from SYFPEITHI and IEDB to form significantly more stable MHC-I complexes compared with affinity-matched non-epitopes. Combining the stability predictions with a state-of-the-art affinity predictions NetMHCcons significantly improved the performance for identification of T-cell epitopes and ligands. For the HLA alleles included in the study, we could identify distinct sub-motifs that differentiate between stable and unstable peptide binders and demonstrate that anchor positions in the N-terminal of the binding motif (primarily P2 and P3) play a critical role for the formation of stable pMHC-I complexes. A webserver implementing the method is available at www.cbs.dtu.dk/services/NetMHCstab. [ABSTRACT FROM AUTHOR]

While it is known that the anti-inflammatory effects of interleukin (IL)-4 require new protein synthesis, the exact mechanisms by which IL-4 suppresses the production of pro-inflammatory cytokines by human monocytes and macrophages is unclear. IL-4 rapidly induced suppressor of cytokine signalling-1 (SOCS1) mRNA and protein, which peaked at 60 min, much earlier than lipopolysaccharide (LPS)-induced SOCS1 mRNA and protein which were consistently maximal 4 hr post-exposure. SOCS1 is a molecule generally considered to be induced for negative feedback of inflammatory processes. We investigated whether the early induction of SOCS1 by IL-4 was responsible for the suppression of LPS-induced tumour necrosis factor (TNF)-α production by IL-4. IL-4 suppressed LPS-induced TNF-α in freshly isolated monocytes at the level of transcription but acted by a different, possibly translational, mechanism in monocytes cultured overnight in macrophage colony-stimulating factor (M-CSF). Despite different modes of regulation by IL-4, the kinetics and magnitude of induction of SOCS1 mRNA and protein by IL-4 in the two cell types were identical. There was no significant difference in the suppression by IL-4 of LPS-induced TNF-α production by bone-marrow derived macrophages from wild-type mice, Ifnγ−/− mice and mice lacking SOCS1 ( Socs1−/− Ifnγ−/−). These data suggest that SOCS1 is not involved in the suppression of LPS-induced TNF-α production by IL-4. [ABSTRACT FROM AUTHOR]

Hypersensitivity pneumonitis (HP) is a T-cell-driven disease that is histologically characterized by diffuse mononuclear cell infiltrates and loosely formed granulomas in the lungs. We have previously reported that interleukin-17A (IL-17A) contributes to the development of experimental HP, and that the pattern recognition receptor Toll-like receptor 6 (TLR6) might be a factor in the initiation of this response. Using a well-established murine model of Saccharopolyspora rectivirgula-induced HP, we investigated the role of TLR6 in the immunopathogenesis of this disease. In the absence of TLR6 signalling, mice that received multiple challenges with S. rectivirgula-antigen (SR-Ag) had significantly less lung inflammation compared with C57BL/6 mice (wild-type; WT) similarly challenged with SR-Ag. Flow cytometric analysis of whole lung samples from SR-Ag-challenged mice showed that TLR6−/− mice had a decreased CD4+ : CD8+ T-cell ratio compared with WT mice. Cytokine analysis at various days after the final SR-Ag challenge revealed that whole lungs from TLR6−/− mice contained significantly less IL-17A than lungs from WT mice with HP. The IL-17A-driving cytokines IL-21 and IL-23 were also expressed at lower levels in SR-Ag-challenged TLR6−/− mice, when compared with SR-Ag-challenged WT mice. Other pro-inflammatory cytokines, namely interferon-γ and RANTES, were also found to be regulated by TLR6 signalling. Anti-TLR6 neutralizing antibody treatment of dispersed lung cells significantly impaired SR-Ag-induced IL-17A and IL-6 generation. Together, these results indicate that TLR6 plays a pivotal role in the development and severity of HP via its role in IL-17A production. [ABSTRACT FROM AUTHOR]

Several tools have proved useful in the study of invariant natural killer T (iNKT) cells, including CD1d-deficient mice, Jα281-deficient mice, synthetic lipid antigens and antigen-loaded CD1d tetramers. However, the generation and examination of long-term primary murine iNKT cell lines in vitro has been challenging. Here, we show the rapid generation of iNKT cell lines from splenic iNKT cells of Vα14 T-cell receptor (TCR) transgenic (Tg) mice. These purified iNKT cells were stimulated by bone marrow-derived dendritic cells (BMDCs) loaded with α-galactosylceramide (αGalCer) and cultured with interleukin (IL)-2 and IL-7. iNKT cells proliferated dramatically, and the cell number exhibited a 100-fold increase within 2 weeks and a 105-fold increase in 8 weeks after repeated stimulation with αGalCer. The iNKT cell lines consisted of iNKT cells expressing Vβ chains including Vβ8.1/8.2, Vβ14, Vβ10, Vβ6 and Vβ7, and responded to stimulation with αGalCer presented both by BMDCs and by plate-bound CD1d. In addition, the iNKT cell lines produced interferon (IFN)-γ when activated by lipopolysaccharide (LPS) or CpG oligodeoxynucleotide (ODN)-stimulated BMDCs. Further, we show that iNKT cell lines produced cytokines in response to microbial antigens. In summary, high-yield iNKT cell lines were generated very rapidly and robustly expanded, and these iNKT cells responded to both TCR and cytokine stimulation in vitro. Given the desire to study primary iNKT cells for many purposes, these iNKT cell lines should provide an important tool for the study of iNKT cell subsets, antigen and TCR specificity, activation, inactivation and effector functions. [ABSTRACT FROM AUTHOR]

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is critical for phagocyte anti-microbial activity and plays a major role in innate immunity. Defects in genes coding for components of the NADPH oxidase enzyme system are responsible for chronic granulomatous disease (CGD), a rare primary neutrophil immunodeficiency associated with recurrent, life-threatening bacterial and fungal infections. Microbial killing and digestion within the neutrophil phagosomal compartment are defective in these patients. NADPH oxidase activity is also crucial for optimal macrophage and dendritic cell function and has recently been implicated in both cross-presentation and T-cell priming. We present evidence of impaired macrophage function in CGD, with attenuated pro-inflammatory cytokine and increased interleukin-10 secretion following bacterial stimulation. These results highlight additional abnormalities in macrophage function associated with CGD and the importance of NADPH oxidase activity in immunity. [ABSTRACT FROM AUTHOR]

Our previous studies demonstrated that lipopolysaccharide (LPS)-stimulated splenocytes, retrovirally transduced with a glutamate decarboxylate 65 (GAD) and immunoglobulin G (IgG) fusion construct, can protect non-obese diabetic (NOD) mice from diabetes by inducing GAD-specific tolerance, and also that there are increased numbers of CD4+ regulatory T cells (Tregs) in GAD-IgG-treated NOD mice. However, little is known about the role of CD8+ Tregs in GAD-IgG gene-transferred tolerance induction in NOD mice. Here, we found that GAD-IgG-transduced splenocytes induced an increase in the number of CD8+ Foxp3+ Tregs in vitro. Using a T-cell depletion assay, we found that, compared with undepleted groups, NOD recipients transfused with CD8– or CD8– CD25– GAD-IgG-transduced splenocytes showed a decrease in the percentage of CD8+ Foxp3+ T cells, a high incidence of diabetes, serious insulitis, GAD-specific hyperresponsiveness at both the cellular and humoral levels, and changes in cytokine expression. These results indicate that CD8+ Tregs, which were induced in vitro by GAD-IgG-transduced splenocytes, were also responsible for GAD-IgG gene-transferred tolerance induction in NOD mice. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) play a central role in activating CD4 T (T helper, Th) cells. As a component of their response to pathogen-associated stimuli, DCs produce cytokines and express surface molecules that provide important cues to modulate the effector functions of responding Th cells. Much is known of how DCs respond to, and influence immune response outcome to, bacterial and viral pathogens. However, relatively little is understood about how DCs respond to helminth parasites. This is an area of considerable interest since it impacts our understanding of the initiation of Th2 responses, which are stereotypically associated with helminth infections, and the regulation of allergic and autoimmune pathologies which evidence suggests are less severe or absent in individuals infected with helminths. This review attempts to summarize our understanding of the effects of helminth products on dendritic cell biology. [ABSTRACT FROM AUTHOR]

Ex-vivo-activated B cells are an alternative source of antigen-presenting cells (APCs) and a potential replacement for dendritic cells (DCs) in immunotherapy. However, the ability of ex-vivo-activated B cells to function as potent APCs has been a concern, especially when compared to DCs. Our study investigated whether modification of activated B cells with immune stimulatory molecules could enhance the ability of activated B cells to stimulate T cells. We show that murine splenic B cells, activated with a combination of Toll-like receptor agonist and agonistic anti-CD40, stimulated antigen-specific CD8+ T cells more efficiently than cells activated with Toll-like receptor agonist or anti-CD40 alone, probably by down-regulation of the immune regulatory cytokine interleukin-10 (IL-10). However, the activated B cells were still poor T-cell stimulators compared to mature DCs. Therefore, we modified the activated B cells by simultaneous electroporation of multiple messenger RNAs encoding costimulatory molecules (OX40L and 4-1BBL), cytokines (IL-12p35 and IL-12p40) and antigen. We found that de novo expression or overexpression of OX40L, 4-1BBL and IL-12p70 on activated B cells synergistically enhanced proliferation as well as IL-2 and interferon-γ production by CD8+ T cells. Furthermore, the RNA-modified activated B cells induced antigen-specific cytotoxic T lymphocyte responses as efficiently as mature DCs in vitro. Unexpectedly, modified activated B cells were inferior to mature DCs at in vivo induction of CD8+ T-cell responses. In summary, activated B cells modified to express immune stimulatory molecules are a potent alternative to DCs in immunotherapy. [ABSTRACT FROM AUTHOR]

Receptors for the Fc region of immunoglobulin G (FcγRs) are expressed on a broad range of haematopoietic cell types and are responsible for regulating antibody production and linking the humoral and effector responses. In response to a number of stimuli, such as cytokine signals or inflammation, FcγR expression at the cell surface is dynamically regulated. On B cells, we observed what appeared to be a correlation between CD22 expression and FcγRIIb expression when the latter was varied in a number of models. Further investigation revealed that this was specific to a particular anti-CD22 monoclonal antibody, which appeared to require stabilization by interaction with FcγRIIb for optimal binding to CD22. Since alterations in the regulation of FcγR expression are important in controlling immune responses and have been associated with a number of immune-mediated disease states, we suggest that it might be prudent to confirm the expression of cell surface markers by two independent methods. Furthermore, because the efficacy of therapeutic antibodies may depend upon their interaction with FcγRs, our results are relevant to their design and assessment. [ABSTRACT FROM AUTHOR]

Interleukin (IL)-21 is a novel cytokine that has been shown to enhance proliferation and activation of CD8+ T cells, enhance natural killer (NK) cell activity and costimulate anti-CD40-driven B-cell proliferation in mice. Several studies have furthermore demonstrated antitumour effects of IL-21 administration in mouse models. In this study we have investigated how IL-21 affects the survival and cytotoxicity of human NK cells and modulates their expression of surface receptors and of the effector molecules granzyme B and perforin. In contrast to murine NK cells, where IL-21 alone cannot sustain survival, IL-21 and IL-2 were equally efficient in sustaining survival of human NK cells. In the absence of other cytokines, IL-21 had little effect on expression of a panel of surface receptors on human NK cells. However, IL-21 synergized with IL-2 to up-regulate several surface receptors, including NKG2A, CD25, CD86 and CD69. The CD25+ CD86+ NK cells were CD56bright and were large and granular. Expression of the effector molecules perforin and granzyme A and B was up-regulated by IL-21 at both mRNA and protein levels. Furthermore, IL-21 increased the cytotoxicity of NK cells against K562 target cells. These findings suggest that IL-21 modulates NK cell activity through induction of intracellular effector molecules as well as modulation of surface receptor expression. [ABSTRACT FROM AUTHOR]

The immune evasion mechanisms of pathogenic trypanosomatids involve a multitude of phenomena such as the polyclonal activation of lymphocytes, cytokine modulation and the enhanced detoxification of oxygen reactive species. A trypanothione cascade seems to be involved in the detoxification process. It was recently described and characterized a tryparedoxin ( LiTXN1) involved in Leishmania infantum cytoplasmatic hydroperoxide metabolism. LiTXN1 is a secreted protein that is up-regulated in the infectious form of the parasite, suggesting that it may play an important role during infection. In the present study, we investigated whether recombinant LiTXN1 (r LiTXN1) affects T- and B-cell functions in a murine model. We observed a significant increase in the CD69 surface marker on the B-cell population in total spleen cells and on isolated B cells from BALB/c mice after in vitro rLiTXN1 stimulus. Activated B-cells underwent further proliferation, as indicated by increased [3H]thymidine incorporation. Cytokine quantification showed a dose-dependent up-regulation of interleukin (IL)-10 secretion. B cells were identified as a source of this secretion. Furthermore, intraperitoneal injection of r LiTXN1 into BALB/c mice triggered the production of elevated levels of r LiTXN1-specific antibodies, predominantly of the immunoglobulin M (IgM), IgG1 and IgG3 isotypes, with a minimum reactivity against other heterologous antigens. Taken together, our data suggest that r LiTXN1 may participate in immunopathological processes by targeting B-cell effector functions, leading to IL-10 secretion and production of specific antibodies. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLRs) signal through two main pathways: a myeloid differentiation factor (MyD)88-dependent pathway that acts via nuclear factor κB (NF-κB) to induce proinflammatory cytokines such as tumour necrosis factor-α (TNF-α) and a MyD88-independent pathway that acts via type I interferons to increase the expression of interferon-inducible genes. Repeated signalling through TLR4 and a number of other TLRs has been reported to result in a reduction in the subsequent proinflammatory cytokine response, a phenomenon known as TLR tolerance. In this study we have shown that, whilst NF-κB activation and production of TNF-α and interleukin-12 by murine RAW264.7 and J774.2 cells in response to stimulation by TLR4, -5, -7 or -9, was reduced by prior stimulation with TLR4, -5, -7 or -9 ligands, the primary stimulation of TLR3, which does not use the MyD88 pathway, did not reduce the TNF-α or interleukin-12 responses to subsequent TLR stimulation. The response to TLR3 stimulation was not diminished by prior TLR ligand exposure. Furthermore, the production of interferon-β (IFN-β) following stimulation of TLR3 or -4, which is MyD88-independent, was increased by prior activation of TLR4, -5, -7 or -9. In contrast, TLR9 ligand-induced IFN-β production, which is MyD88-dependent, was tolerized by prior TLR stimulation. These results are consistent with differential regulation of MyD88-dependent and MyD88-independent cytokine production following serial activation of TLRs. [ABSTRACT FROM AUTHOR]

We used various culture conditions to generate type 1 (Tc1) or type 2 (Tc2) cytotoxic T cells in vitro. T-cell receptor (TCR) transgenic T cells were cultured with antigen and spleen cells, or antigen and dendritic cells (DC), or anti-CD3 and anti-CD28. Tc1 cultures contained interleukin (IL)-2 and IL-6, and Tc2 cultures contained IL-2, IL-6 and IL-4. Tc2 cells generated in each culture condition acquired a CD62Llow CD44high phenotype, had high cytotoxic activity, and secreted IL-4, IL-5 and moderate amounts of interferon-γ (IFN-γ). In contrast, the phenotype and function of Tc1 cells varied depending on culture conditions. Tc1 cells from anti-CD3 and anti-CD28 cultures had high cytotoxic activity and were CD62Llow CD44high, while Tc1 cells from antigen and spleen cell cultures had low cytotoxic activity and were CD62Lhigh CD44low. Tc1 cells from antigen and DC cultures had an intermediate phenotype. All Tc1 cells secreted high amounts of IFN-γ, but only Tc1 from anti-CD3 and anti-CD28 cultures had antitumour activity in vivo. Differences were not caused by suboptimal culture conditions, as Tc1 cells divided at a similar rate whether cultured with antigen and spleen cells or with anti-CD3 and anti-CD28. We conclude that IL-4 not only induces‘type 2’ cytokine secretion in CD8+ T cells, but also affects their expression of surface markers and cytotoxic activity. [ABSTRACT FROM AUTHOR]

Mice homozygous for an inactivation of the interleukin-2 (IL-2) gene develop a T-cell dependent colitis. Heterozygous (IL-2+/–) mice are clinically healthy but have been shown to express reduced levels of IL-2 in the colon. Splenocytes from the IL-2+/– mice had a poorer proliferative response to polyclonal T-cell activation and these mice have reduced numbers of intestinal regulatory T cells (CD4+ CD25+ cells) when compared to wild type mice. When exposed to dextran sulphate sodium (DSS) IL-2+/– mice showed a markedly reduced susceptibility to DSS-induced colitis. While DSS treatment caused a marked increase in both CD4+ and CD8+ colonic T cells expressing increased levels of IL-2, IL-4, and IL-10 in wild type mice none of these changes were seen in IL-2+/– mice. On the contrary, cytokine expression in intestinal T cells of IL-2+/– mice was actually reduced after DSS treatment. These results suggest that reduced levels of IL-2 leads to attenuated activation and function of intestinal T cells in IL-2+/– mice and a failure to react adequately to DSS exposure. [ABSTRACT FROM AUTHOR]

Discusses the abstract of the paper 'Cell mediated immunity in subroups of patients with common variable immune deficiency (CVID) correlation to clinical phenotype,' by P. Antrobus et al, presented during the annual congress of the British Society for Immunology held in Great Britain on December 5-8, 2000.

Efforts to identify the signal transduction pathways used by interleukin-10 (IL-10) have resulted in limited success. The anti-inflammatory effects elicited by IL-10, and the mechanisms by which these are mediated, are still relatively unknown. Understanding the signalling mechanisms behind the suppression of cytokine expression by IL-10 could be of potential therapeutic interest. Although the consensus is that the Janus kinase, Jak1, as well as the signal transducer and activator of transcription STAT3 are central, much controversy exists about the participation and roles of many other signalling pathways targeted by IL-10. The mechanisms of cytokine suppression proposed by various groups have included transcriptional, post-transcriptional and post-translational regulation of IL-10 target genes; nevertheless no unifying model has emerged thus far. Here we would like to highlight novel findings and discuss their implications in the context of current understanding of IL-10 signalling. [ABSTRACT FROM AUTHOR]

SummaryWhether CD5 on B cells marks a subset functionally distinct from the conventional CD5 negative (CD5neg) adult population or is more an indicator of activation, remains contentious. Here we have investigated whether CD5 positive (CD5pos) and CD5neg B cells can be distinguished in terms of their response to surrogate signals aimed to model, in vitro, T-cell dependent (TD) and T-independent (TI) encounters with antigen in vivo: the predominantly CD5pos B-cell population found in cord blood, CD5 B cells positively selected from tonsils and their CD5neg counterparts, were compared. Neonatal B cells displayed a near-identical phenotype to that of adult CD5pos B cells, being characterized by uniform immunoglobulin M (IgM), immunoglobulin D (IgD), CD23 and CD44 coexpression. When cultured with anti-IgM maintained at high density on CD32-tranfected mouse L cells to model TI responses or on CD40 ligand (CD40L)-bearing L cells (with or without captured anti-IgM) to model TD encounters, DNA synthesis was stimulated to a similar extent in all three populations. Focusing on CD5 and CD23, we found that – although the signals delivered promoted distinct profiles of expression – under each condition of activation, the phenotypes that emerged for adult CD5pos and CD5neg B cells were remarkably similar. Neonatal B cells displayed a greater diminution in CD5 expression than adult CD5pos B cells following CD40 signals but otherwise the two populations again behaved similarly. The inclusion of interleukin-4 (IL-4) to cultures where cells were costimulated via surface (s)IgM and CD40 resulted in a complete loss of CD5 expression and a corresponding hyperexpression of CD23, irrespective of the population studied. The near-identical response of CD5pos and CD5neg B cells to surrogate TD or TI signals in vitro and their convergence to... [ABSTRACT FROM AUTHOR]

The human high affinity receptor for immunoglobulin G, FcγRI, in dibutyryl cyclic AMP (dbcAMP)-differentiated U937 cells, is coupled to the activation of phospholipase C (PLC) and the conventional protein kinase C (PKC) isoforms, α, β, and γ. Here we demonstrate that aggregation of FcγRI activates the tyrosine-kinase regulated form of phosphatidylinositol-3-kinase (PI-3-kinase) and that an increase of phosphatidylinositol trisphosphate (PIP3) is essential for the activation and translocation of PLCγ1 in these cells. In addition, activation of the PKC isoforms was ablated by specific inhibitors of PI3-kinase or by overexpression of a dominant negative p85 subunit of PI3-kinase. The findings reported here demonstrate that PLCγ1 and PKC activation by FcγRI are downstream of PI3-kinase, and that in contrast to cytokine primed cells, only the tyrosine-kinase activated isoform of PI3-kinase is coupled to FcγRI in dbcAMP-differentiated cells. [ABSTRACT FROM AUTHOR]

The ability of T cells from rheumatoid factor (RF)-positive patients with rheumatoid arthritis (RA) to respond to immunoglobulin G (IgG) was assessed. Peripheral blood mononuclear cells (PBMC) from RA patients and normal individuals were cultured with and without human IgG or Mycobacterium tuberculosis-purified protein derivative (PPD) for 7 days and their proliferative response measured at intervals by their ability to take up tritiated thymidine. PBMC from 14/26 RA patients proliferated in response to IgG (taking a stimulation index of 3 or above as positive). The peak response varied between individuals but usually occurred on day 5, the same day, or 1 day later than the peak response to PPD. By contrast, PBMC from a significantly lower proportion (1/9) of normal individuals and patients with other arthritides (0/6) responded to IgG, although all responded to PPD. PBMC from 9/14 RA patients responded to Fab fragments of IgG but only 3/9 to the Fc fragment. Higher proliferative responses from RA PBMC were elicited by IgG aggregates than the original IgG preparation, but PMBC from 5/5 normal individuals and 5/6 patients with other arthritides failed to respond to the aggregates. The response to IgG was human leucocyte antigen (HLA)-DR restricted and mediated by CD4+ T cells. It is considered that these results advance the hypothesis that IgG-reactive T cells contribute to the initiation or perpetuation of RA. [ABSTRACT FROM AUTHOR]

The contribution of B7 molecules to the induction and maintenance of the T-cell response to the human pathogenic fungus Cryptococcus neoformans was investigated. T-cell activation by C. neoformans was regulated by B7 molecules. This costimulatory signal was necessary for initiation and maintenance of the T-cell response, through early and late requirements for B7–CD28 interaction. Blocking B7-2 inhibited the normal T-cell proliferative response. This inhibition was due, in part, to a reduced capability of T cells to produce interleukin-2 (IL-2). In contrast, the same T-cell population produced more interferon-γ. Suppression of the normal lymphoproliferation and IL-2 secretion responses to encapsulated C. neoformans by antibodies to B7 was largely reversed by addition of the monoclonal antibody 2H1, that is reactive with the major capsular polysaccharide, glucuronoxylomannan. Overall, our data indicate that B7 molecules play a critical role in T-cell activation by C. neoformans and suggest that appropriate manipulation could drive T helper type 1 cell development. [ABSTRACT FROM AUTHOR]

Presents a correction to the article "HIV-1-Specific Cell-Mediated Immunity is Enhanced by Co-Inoculation of TCA3 Expression Plasmid With DNA Vaccine," by T. Tsuji, J. Fukushima, K. Hamajima, N. Ishii, I. Aoki, H. Bukawa, Y. Ishigatsubo, K. Tani, T. Okubo, M. E. Dorf and K. Okuba published in the Volume 90 issue of the journal "Immunology."

We studied IL-6 gene expression in human monocytes stimulated by muramyl dipeptide (MDP), a synthetic immunomodulator derived from mycobacterial cell walls. In control monocytes, two IL-6 transcripts of 3-4 kb and U6 kb were easily detected at 2-5 hr of culture and remained stable until 18 hr. In MDP-treated monocytes, three IL-6 RNA species displayed different kinetics of accumulation: a 3.4 kb RNA whose expression already reached its maximum after 2.5 hr exposure to MDP; a 1.6 kb RNA whose expression peaked at 5 hr; and a new RNA species of 1.4 kb which was transiently induced in early time of cell stimulation. TNF-α co-operated with MDP to increase IL-6 gene expression and secretion of biological active protein (measured by the hybridoma plasmacytoma growth factor assay). MDP exhibits a broad spectrum of immunomodulation properties such as adjuvant activity, enhancement of macrophage cytotoxicity against tumour and induction of non- specific resistance to intracellular agents. The results reported here suggest that these properties might be linked to the stimulation by M DP of genes coding for key cytokines such as IL-6, TNF and IL- I. [ABSTRACT FROM AUTHOR]

Agglutinating activity of the major serum lectin of Periplaneta americana against mammalian erythrocytes has been found previously to be inhibited most effectively by galactose and glycoproteins rich in non-reducing terminal galactose, such as porcine stomach mucin (PSM) and desialylated fetuin and bovine submaxillary mucin. Antibody raised against the purified lectin was found, by immunofluorescence, to bind to the surface of washed fixed haemocytes (the cells responsible for cellular immunity in insects). The experiments described here were carried out in order to investigate whether or not the lectin plays any role in mediating the haemocytic response, by measuring the in vivo cellular response to galactose- or sialic add-rich glycoproteins, either in solution or conjugated to Sepharose beads. Comparison of the ability of injected solutions to stimulate haemocytic aggregates (nodules) showed that PSM, whether native, desialylated or pronase-digested to produce small galactose-containing fragments, stimulated large numbers of nodules, in contrast to either sialic acid-rich glycoproteins such as bovine submaxillary mucin (BSM) and fetuin, or the protein bovine serum albumen (BSA). Multicellular capsules formed around Sepharose conjugated to galactose-rich molecules such as PSM, asialo-PSM, asialo-fetuin or asialo-BSM were highly significantly thicker than those formed around control untreated beads, whereas capsules around BSA, fetuin or BSM conjugates were significantly thinner. It is unlikely that the different results for sialylated and desialylated molecules are due merely to a non-specific charge effect, since the response due to charge alone is directly opposite to that found when specific carbohydrate groups are considered. The results tentatively support the idea that soluble and/or cell-associated lectins may be involved in immuno-recognition in insects. [ABSTRACT FROM AUTHOR]

We have identified a neutrophil chemotactic factor (NCF) in supernatants from human blood mononuclear cells (MNC) cultured in the presence of phytohaemogglutinin (PHA). Maximal activity was observed 48 hr after culture. Following gel filtration, NCF eluted as a single major peak, together with proteins, having a molecular size of approximately 10,000 MW. The material gave a single band on SDS-PAGE but was heterogeneous following chromatofocusing (pls approximately 6.8-7.0, 5.5-6.0 and 5.0). The biological activity of the partially purified material was abolished by trypsin and chymotrypsin treatment. NCF was heat stable (70°, 60 min) and promoted both directional migration (chemotaxis) of neutrophils and, to a lesser extent, stimulated random locomotion (chemokinesis). The factor was not associated with detectable amounts of IL-1, IL-2 or interferon- gamma (IFN-γ). MNC-derived NCF had a molecular size lower than recombinant granulocyte- monocyte colony-stimulating factor (rGM-CSF) and recombinant tumour necrosis factor (rTNF), and was considerably more active in chemotaxis. Optimal chemotactic concentrations of partially purified MNC-derived NCF were of comparable potency to FMLP and LTS4 and had about 60% of the activity of optimal concentrations of C5a, C5a-des-Arg and platelet-activating factor (PAF). These experiments indicate that human MNC-derived NCF is a potent chemoattractant distinct from other cytokines previously reported to promote neutrophil locomotion. [ABSTRACT FROM AUTHOR]

We have investigated the characteristics of antigen-specific reductions in routine immune responses to rat collagen type I (R-CI), chick collagen type II (C-CII) or bovine collagen type II (B-CII). Intravenous pretreatment with the appropriate soluble collagen or collagen-coupled spleen cells led to the development of antigen-specific reduced immune responses, the former treatment being more effective than the latter. In the case of CII, pretreatment with R-CI or non-related antigens was ineffective. However, pretreatment with denatured bovine-CII, native bovine-CII or chick-CII led to immune hyporesponsiveness for either the homologous or heterologous CII molecule. A delayed development of the diminished immune responses was observed for the cell-mediated immune response (CMI), as measured by in vivo delayed-type hypersensitivity (DTH), in that no reduction was evident at Day 7 but a significantly decreased response was observed at Day 14. Collagen-specific IgG and IgM antibody responses were consistently reduced by the pretreatment and remained reduced daring the study period. The antigen-specific hyporesponsive state was not sensitive to cyclophosphamide treatment and was not transferable with hyporesponsive spleen cells. Additionally, we have induced unresponsiveness to CII by treating mice with an antibody directed to T helper cells (GK1.5). This treatment led to profound reductions in CII CMI responses as well as CII antibody levels. However, this unresponsive state is not permanent and not transferable with spleen cells from treated mice. Them two types of procedures, soluble B-CII i.v. or GK1.5 treatment, not only resulted in CII hyporesponsive states, but also produced delayed onset and decrease incidence of arthritis in the appropriate strains. [ABSTRACT FROM AUTHOR]

Previous studies of cellular immunity in asymptomatic HBV carriers have been limited to evaluation of responses to plasma-derived HBsAg preparations. We have explored the specificity of cellular immune responses to HBV antigens in these subjects using an indirect T-lymphocyte migration inhibitory factor assay and three antigen preparations (recombinant nucleocapsid antigen (HBcAg), plasma-derived HBsAg with or without pre-S2, and Saccharomyces cerevisiae-synthesized HEsAg without pre-S2 region). T cells from 10 asymptomatic chronic HBV carriers with normal liver function tests were responsive to nucleocapside determinants (mean migration index = 0.55 ± SD 0.07) and to pre-S2-positive plasma-derived HBsAg (MI = 0.62 ± 0.05). However, none responded to HBsAg devoid of pre-S2 sequences (M1=0.98±0.04). In further experiments, T cells from three HBV carriers, cultured with six different HBsAg preparations, exhibited responsiveness only to those preparations containing significant pre-S2 activities. Our results show that T-cell immunity to nucleocapsid determinants of the virus and HBsAg in present in asymptomatic HBV carriers; the latter is restricted to antigenic preparations containing significant pre-S2 activities. Hence, T-cell immunity to pre-S determinants may not always be associated with HBV clearance. [ABSTRACT FROM AUTHOR]

Delayed-type hypersensitivity (DTH) reactions to allogeneic histocompatibility antigens in mice could be systemically suppressed by a single exposure to UV-B irradiation. The extent of suppression reached its maximum 4 days after irradiation, gradually waned thereafter, and disappeared at Day 21. Re-exposure of these mice to UV-B after waning reinduced the state of suppression. The suppression could be transferred to naive mice by means of splenic T lymphocytes. The suppressor T (Ts) cells suppressed the proliferative activity in the lymph nodes draining the site of immunization, but not the activity of already activated DTH-reactive T cells. Phenotypical analysis of these Ts cells revealed that two subpopulations of T cells are involved: one with the Lyt-1+, 2- phenotype, the other with the Lyt-1-, 2+ phenotype. [ABSTRACT FROM AUTHOR]

Using cloned human T lymphocytes reactive with a 24 amino acid peptide (p20) of the carboxyl terminus of the HA-1 molecule of influenza haemagglutinin (HA), we have investigated the ability of solid-phase antigen to induce antigen-specific T-cell proliferation. The activation by nitrocellulose- bound virus and p20 was accessory-cell dependent and was not caused by immobilized antigen directly cross-linking the specific receptors. Furthermore, we report that separation of complex antigen mixtures such as influenza virus and HA by polyacrylamide gel electrophoresis under denaturing conditions (SDS-PAGE) followed by transfer to a nitrocellulose membrane can be used to allow direct screening of individual polypeptides in T-cell proliferation assays. With this immunoblotting procedure the antigenic site recognized by HA-reactive T cells was confirmed to reside in the HA-i molecule of influenza virus of only the appropriate subtype. The general application of this approach is discussed in the case of infections and autoimmune diseases in which the immune response is predominantly T-cell mediated and where antibody studies may fail to identify key antigenic determinants involved in the activation of T cells. [ABSTRACT FROM AUTHOR]

Monoclonal antibodies were raised against a human natural killing system and screened against targets lysed either by human lymphocytes in anti- body-dependent cellular cytotoxicity (A DCC), or by human complement. Two monoclonals were identified which bound specifically to both types of killed targets. More detailed studies with one antibody showed that it inhibited ADCC, both as intact anti- body and as the F(ab')2 fragment. Intact antibody enhanced natural (NK) killing, although the F(ab')2 fragment inhibited NK killing. The data support the hypothesis that lymphocyte-mediated killing involves a complex analogous in nature to the complement membrane attack complex. In addition, the antibodies provide evidence to suggest that this complex has antigenic determinants in common with the complement membrane attack complex, and indicate the possibility that the two systems are derived from a common ancestor. [ABSTRACT FROM AUTHOR]

High dietary intakes (4000-650,000 IU/kg diet) of vitamin A (retinyl palmitate, RP) modified the functions of peritoneal macrophages (PM). The number of peritoneal exudated cells (PEC) obtained from CD- 1 mice increased significantly at both 7 and 10 weeks after initiation of the RP diets. The percentage of PM in PEC showed no significant difference between dietary groups and was at levels of 55-60%. PM from mice fed high RP diets showed higher tumoricidal activities than PM from controls without any preincubation with macrophage activators. Enhancement of in vitro tumoricidal activity of PM increased with increasing contents of RP in the diets, reaching 30% lysis by PM isolated from mice fed the highest RP (650,000 IU/kg diet) diet. However, the in vitro activation of tumoricidal ability of PM by macrophage-activating factor (MAF) was inversely correlated with the dietary RP content. The tumoricidal activities of PM from mice fed the highest RP diet were not enhanced by MAF. However, these PM showed an increased ability to phagocytose SRBC and opsonized SRI3C compared to controls. Splenocytes and thymocytes were incubated with [³H]thymidine immediately after isolation and their mitogenic activities were measured. Splenocytes, but not thymocytes, isolated from mice fed the highest RP diet had increased mitogenesis. On the other hand, NK activity was dot affected by dietary RP intake. There was a similar lysis of target cells by both splenocytes and thymocytes from mice fed diets with various RP levels. IL-I was produced from PM by incubation with LPS, and its production was assessed using the proliferation of normal mice thymocytes. Production of IL-i in vitro showed about a two-fold increase using cells from mice fed the highest RP diet compared to controls. High RP diets induced increased phagocytic ability and tumoricidal activity of PM but did not enhance NK activity. These findings suggest that high RP diet may cause activation of PM. [ABSTRACT FROM AUTHOR]