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The E3 ubiquitin ligase Cbl-b is an established nonredundant negative regulator of T-cell activation. Cbl-b fine-tunes the activation threshold of T cells and uncouples T cells from their vital need of a costimulatory signal to mount a productive immune response. Accordingly, mice deficient in cblb are prone to autoimmunity and reject tumors. The latter has been described to be mediated via CD8+ T cells, which are hyperactive and more abundant in shrinking tumors of cblb-deficient animals. This might at least also in part be mediated by resistance of cblb-deficient T cells to negative cues exerted by tumor-associated immuno-suppressive factors, such as TGF-βand regulatory T cells (Treg). Experiments using cblb-deficient T cells either alone or in combination with vaccines validate the therapeutic concept of enhancing the efficacy of adoptively transferred lymphocytes to treat malignant tumors. This paper summarizes the current knowledge about the negative regulatory role of Cbl-b in T-cell activation and its potential therapeutic implications for cancer immunotherapy. [ABSTRACT FROM AUTHOR]

The Beauchemin model is a simple particle-based description of stochastic lymphocyte migration in tissue, which has been successfully applied to studying immunological questions. In addition to being easy to implement, the model is also to a large extent mathematically tractable. This article provides a comprehensive overview of both existing and new analytical results on the Beauchemin model within a common mathematical framework. Specifically, we derive the motility coefficient, the mean square displacement, and the confinement ratio, and discuss four different methods for simulating biased migration of pre-defined speed. The results provide new insight into published studies and a reference point for future research based on this simple and popular lymphocyte migration model. [ABSTRACT FROM AUTHOR]

Blocking the PD-1/PD-L1 pathway has emerged as a potential therapy to restore impaired immune responses in human immunodeficiency virus (HIV)-infected individuals. Most reports have studied the impact of the PD-L1 blockade on effector cells and neglected possible effects on regulatory T cells (Treg cells), which play an essential role in balancing immunopathology and antiviral effector responses. The aim of this study was to define the consequences of ex vivo PD-L1 blockade on Treg cells from HIV-infected individuals. We observed that HIV infection led to an increase in PD-1+ and PD-L1+ Treg cells. This upregulation correlated with disease progression and decreased under antiretroviral treatment. Treg cells from viremic individuals had a particularly high PD-1 expression and impaired proliferative capacity in comparison with Treg cells from individuals under antiretroviral treatment. PD-L1 blockade restored the proliferative capacity of Treg cells from viremic individuals but had no effect on its suppressive capacity. Moreover, it increased the viral production in cell cultures from viremic individuals. This increase in viral production correlated with an increase in Treg cell percentage and a reduction in the CD4/Treg and CD8/Treg cell ratios. In contrast to the effect of the PD-L1 blockade on Treg cells from viremic individuals, we did not observe a significant effect on the proliferative capacity of Treg cells from individuals in whom viremia was controlled (either spontaneously or by antiretroviral treatment). However, PD-L1 blockade resulted in an increased proliferative capacity of HIV-specific-CD8 T cells in all subjects. Taken together, our findings suggest that manipulating PD-L1 in vivo can be expected to influence the net gain of effector function depending on the subject’s plasma viremia. [ABSTRACT FROM AUTHOR]

Background: Clinical appearance and evolution of Canine Leishmaniosis (CL) are the consequence of complex interactions between the parasite and the genetic and immunological backgrounds. We investigated the effect of an immune-modulating diet in CL. Dogs were treated with anti-Leishmania pharmacological therapy combined with standard diet (SD Group) or with the immune-modulating diet (IMMD Group). CD3+ CD4+ Foxp3+ Regulatory T cells (Treg) and CD3+ CD4+ IFN-γ + T helper 1 (Th1) were analyzed by flow cytometry. Results: All sick dogs showed low platelet number at diagnosis (T0). A platelet increase was observed after six months (T6) SD Group, with still remaining in the normal range at twelve months (T12). IMMD Group showed an increase in platelet number becoming similar to healthy dogs at T6 and T12. An increase of CD4/CD8 ratio was revealed in SD Group after three months (T3), while at T6 and at T12 the values resembled to T0. The increase in CD4/CD8 ratio at T3 was maintained at T6 and T12 in IMMD Group. A reduction in the percentage of Treg of all sick dogs was observed at T0. A recovery of Treg percentage was observed only at T3 in SD Group, while this effect disappeared at T6 and T12. In contrast, Treg percentage became similar to healthy animals in IMDD Group at T3, T6 and T12. Sick dogs showed an increase of Th1 cells at T0 as compared with healthy dogs. We observed the occurrence of a decrease of Th1 cells from T3 to T12 in SD Group, although a trend of increase was observed at T6 and T12. At variance, IMMD Group dogs showed a progressive decrease of Th1 cells, whose levels became similar to healthy controls at T6 and T12. Conclusion: The immune-modulating diet appears to regulate the immune response in CL during the standard pharmacological treatment. The presence of nutraceuticals in the diet correlates with the decrease of Th1 cells and with the increase of Treg in sick dogs. Therefore, the administration of the specific dietary supplement improved the clinical response to the standard treatment in a model of CL. [ABSTRACT FROM AUTHOR]

Antigen-specific CD4+ T cells are implicated in the autoimmune disease systemic lupus erythematosus (SLE), but little is known about the peptide antigens that they recognize and their precise function in disease. We generated a series of MHC class II tetramers of I-Ek-containing peptides from the spliceosomal protein U1-70 that specifically stain distinct CD4+ T-cell populations in MRL/lpr mice. The T-cell populations recognize an epitope differing only by the presence or absence of a single phosphate residue at position serine140. The frequency of CD4+ T cells specific for U1-70(131-150):I-Ek (without phosphorylation) correlates with disease severity and anti-U1-70 autoantibody production. These T cells also express RORγt and produce IL-17A. Furthermore, the U1-70-specific CD4+ T cells that produce IL-17A are detected in a subset of patients with SLE and are significantly increased in patients with mixed connective tissue disease. These studies provide tools for studying antigen-specific CD4+ T cells in lupus, and demonstrate an antigen-specific source of IL-17A in autoimmune disease. [ABSTRACT FROM AUTHOR]

Background Two-dimensional differential gel electrophoresis (2D-DIGE) provides a powerful technique to separate proteins on their isoelectric point and apparent molecular mass and quantify changes in protein expression. Abundantly available proteins in spots can be identified using mass spectrometrybased approaches. However, identification is often not possible for low-abundant proteins. Results We present a novel computational approach to prioritize candidate proteins for unidentified spots. Our approach exploits noisy information on the isoelectric point and apparent molecular mass of a protein spot in combination with functional similarities of candidate proteins to already identified proteins to select and rank candidates. We evaluated our method on a 2D-DIGE dataset comparing protein expression in uninfected and HIV-1 infected T-cells. Using leave-one-out cross-validation, we show that the true-positive rate for the top-5 ranked proteins is 43.8%. Conclusions Our approach shows good performance on a 2D-DIGE dataset comparing protein expression in uninfected and HIV-1 infected T-cells. We expect our method to be highly useful in (re-)mining other 2D-DIGE experiments in which especially the low-abundant protein spots remain to be identified. [ABSTRACT FROM AUTHOR]

Clinical-grade T cells are genetically modified ex vivo to express chimeric antigen receptors (CARs) to redirect their specificity to target tumor-associated antigens in vivo. We now have developed this molecular strategy to render cytotoxic T cells specific for fungi. We adapted the pattern-recognition receptor Dectin-1 to activate T cells via chimeric CD28 and CD3-ζ (designated "D-CAR") upon binding with carbohydrate in the cell wall of Aspergillus germ-lings. T cells genetically modified with the Sleeping Beauty system to express D-CAR stably were propagated selectively on artificial activating and propagating cells using an approach similar to that approved by the Food and Drug Administration for manufacturing CD19-specific CAR+ T cells for clinical trials. The D-CAR+ T cells exhibited specificity for β-glucan which led to damage and inhibition of hyphal growth of Aspergillus in vitro and in vivo. Treatment of D-CAR+ T cells with steroids did not compromise antifungal activity significantly. These data support the targeting of carbohydrate antigens by CAFT T cells and provide a clinically appealing strategy to enhance immunity for opportunistic fungal infections using T-cell gene therapy. [ABSTRACT FROM AUTHOR]

Skullcap (Scutellaria baicalensis) has been widely used as a dietary ingredient and traditional herbal medicine owing to its anti-inflammatory and anticancer properties. In this study, we investigated the anti-allergic effects of skullcap and its active compounds, focusing on T cell-mediated responses ex vivo and in vivo. Splenocytes from mice sensitized with ovalbumin (OVA) were isolated for analyses of cytokine production and cell viability. Mice sensitized with OVA were orally administered skullcap or wogonin for 16 days, and then immunoglobulin (Ig) and cytokine levels were measured by enzyme-linked immunosorbent assays. Treatment with skullcap significantly inhibited interleukin (IL)-4 production without reduction of cell viability. Moreover, wogonin, but not baicalin and baicalein, suppressed IL-4 and interferon-gamma production. In vivo, skullcap and wogonin downregulated OVA-induced Th2 immune responses, especially IgE and IL-5 prediction. Wogonin as an active component of skullcap may be applied as a therapeutic agent for IgE- and IL-5-mediated allergic disorders. [ABSTRACT FROM AUTHOR]

Toll-like receptor (TLR) mediated recognition of pathogen associated molecular patterns allows the immune system to rapidly respond to a pathogenic insult. The “danger context” elicited by TLR agonists allows an initially non-immunogenic antigen to become immunogenic. This ability to alter environment is highly relevant in tumor immunity, since it is inherently difficult for the immune system to recognize host-derived tumors as immunogenic. However, immune cells may have encountered certain TLR ligands associated with tumor development, yet the endogenous stimulation is typically not sufficient to induce spontaneous tumor rejection. Of special interest are TLR5 agonists, because there are no endogenous ligands that bind TLR5. CBLB502 is a pharmacologically optimized TLR5 agonist derived from Salmonella enterica flagellin. We examined the effect of CBLB502 on tumor immunity using two syngeneic lymphoma models, both of which do not express TLR5, and thus do not directly respond to CBLB502. Upon challenge with the T-cell lymphoma RMAS, CBLB502 treatment after tumor inoculation protects C57BL/6 mice from death caused by tumor growth. This protective effect is both natural killer (NK) cell- and perforin-dependent. In addition, CBLB502 stimulates clearance of the B-cell lymphoma A20 in BALB/c mice in a CD8+ T cell-dependent fashion. Analysis on the cellular level via ImageStream flow cytometry reveals that CD11b+ and CD11c+ cells, but neither NK nor T cells, directly respond to CBLB502 as determined by NFκB nuclear translocation. Our findings demonstrate that CBLB502 stimulates a robust antitumor response by directly activating TLR5-expressing accessory immune cells, which in turn activate cytotoxic lymphocytes. [ABSTRACT FROM AUTHOR]

Reduction in T cell receptor (TCR) diversity in old age is considered as a major cause for immune complications in the elderly population. Here, we explored the consequences of aging on the TCR repertoire in mice using high-throughput sequencing (TCR-seq). We mapped the TCRb repertoire of CD4+ T cells isolated from bone marrow (BM) and spleen of young and old mice. We found that TCRβ diversity is reduced in spleens of aged mice but not in their BM. Splenic CD4+T cells were also skewed toward an effector memory phenotype in old mice, while BM cells preserved their memory phenotype with age. Analysis of Vb and Jb gene usage across samples, as well as comparison of CDR3 length distributions, showed no significant age dependent changes. However, comparison of the frequencies of amino-acid (AA) TCRβ sequences between samples revealed repertoire changes that occurred at a more refined scale. The BM-derivedTCRb repertoire was found to be similar among individual mice regardless of their age. In contrast, the splenic repertoire of old mice was not similar to those of young mice, but showed an increased similarity with the BM repertoire. Each old-mouse had a private set of expanded TCRβ sequences. Interestingly, a fraction of these sequences was found also in the BM of the same individual, sharing the same nucleotide sequence. Together, these findings show that the composition and phenotype of the CD4+ T cell BM repertoire are relatively stable with age, while diversity of the splenic repertoire is severely reduced. This reduction is caused by idiosyncratic expansions of tens to hundreds of T cell clonotypes, which dominate the repertoire of each individual. We suggest that these private and abundant clonotypes are generated by sporadic clonal expansions, some of which correspond to pre-existing BM clonotypes. These organ- and age-specific changes of the TCRβ repertoire have implications for understanding and manipulating age-associated immune decline. [ABSTRACT FROM AUTHOR]

We introduce a series of experimental procedures enabling sensitive calcium monitoring in T cell populations by confocal video-microscopy. Tracking and post-acquisition analysis was performed using Methods for Automated and Accurate Analysis of Cell Signals (MAAACS), a fully customized program that associates a high throughput tracking algorithm, an intuitive reconnection routine and a statistical platform to provide, at a glance, the calcium barcode of a population of individual T-cells. Combined with a sensitive calcium probe, this method allowed us to unravel the heterogeneity in shape and intensity of the calcium response in T cell populations and especially in naive T cells, which display intracellular calcium oscillations upon stimulation by antigen presenting cells. [ABSTRACT FROM AUTHOR]

Common lymphoid progenitors (CLPs) are thought to represent major intermediates in the transition of hematopoietic stem cells (HSCs) to B lineage lymphocytes. However, it has been obvious for some time that CLPs are heterogeneous, and there has been controversy concerning their differentiation potential. We have now resolved four Flt3+ CLP subsets that are relatively homogenous and capable of forming B cells. Differentiation potential and gene expression patterns suggest Flt3+ CLPs lacking both Ly6D and RAG-1 are the least differentiated. In addition to B cells, they generate natural killer (NK) and dendritic cells (DCs). At the other extreme is a subset of the recently described Flt3+ Ly6D+ CLPs that have a history of RAG-1 expression and are B lineage restricted. These relatively abundant and potent CLPs were depleted within 48 hours of acute in vivo estrogen elevation, suggesting they descend from hormone regulated progenitors. This contrasts with the hormone insensitivity of other CLP subsets that include NK lineage progenitors. This progenitor heterogeneity and differentiation complexity may add flexibility in response to environmental changes. Expression of RAG-1 and display of Ly6D are both milestone events, but they are neither synchronized nor dependent on each other. [ABSTRACT FROM AUTHOR]

The role of Gai proteins coupled to chemokine receptors in directed migration of immune cells is well understood. In this study we show that the separate class of Gαq/11 proteins is required for the underlying ability of T cells to migrate both randomly and in a directed chemokine-dependent manner. Interfering with Gaq or Ga11 using dominant negative cDNA constructs or siRNA for Gaq causes accumulation of LFA-1 adhesions and stalled migration. Gαq/11 has an impact on LFA-1 expression at plasma membrane level and also on its internalization. Additionally Gαq co-localizes with LFA-1- and EEA1- expressing intracellular vesicles and partially with Rap1- but not Rab11-expressing vesicles. However the influence of Gαq is not confined to the vesicles that express it, as its reduction alters intracellular trafficking of other vesicles involved in recycling. In summary vesicle-associated Gαq/11 is required for the turnover of LFA-1 adhesion that is necessary for migration. These G proteins participate directly in the initial phase of recycling and this has an impact on later stages of the endo-exocytic pathway. [ABSTRACT FROM AUTHOR]

The article discusses a study which examines the use of a WAVE bioreactor to generate high cell numbers of lymphocytes in adoptive cell transfer therapy. It details the methodology using an optimized rapid expansion protocol in investigating the clinical relevance of the bioreactor. The findings reveal that WAVE bioreactor can simplify the process of rapidly expanding tumor reactive lymphocytes and provides an alternate approach to cell generation.

IgE antibodies, administered to mice together with their specific antigen, enhance antibody and CD4+ T cell responses to this antigen. The effect is dependent on the low affinity receptor for IgE, CD23, and the receptor must be expressed on B cells. In vitro, IgE-antigen complexes are endocytosed via CD23 on B cells, which subsequently present the antigen to CD4+ T cells. This mechanism has been suggested to explain also IgE-mediated enhancement of immune responses in vivo. We recently found that CD23+ B cells capture IgE-antigen complexes in peripheral blood and rapidly transport them to B cell follicles in the spleen. This provides an alternative explanation for the requirement for CD23+ B cells. The aim of the present study was to determine whether B-cell mediated antigen presentation of IgE-antigen complexes explains the enhancing effect of IgE on immune responses in vivo. The ability of spleen cells, taken from mice 1-4 h after immunization with IgEantigen, to present antigen to specific CD4+ T cells was analyzed. Antigen presentation was intact when spleens were depleted of CD19+ cells (i.e., primarily B cells) but was severely impaired after depletion of CD11c+ cells (i.e., primarily dendritic cells). In agreement with this, the ability of IgE to enhance proliferation of CD4+ T cells was abolished in CD11c- DTR mice conditionally depleted of CD11c+ cells. Finally, the lack of IgE-mediated enhancemen of CD4+ T cell responses in CD23-/- mice could be rescued by transfer of MHC-II-compatible as well as by MHC-II-incompatible CD23+ B cells. These findings argue against the idea that IgE-mediated enhancement of specific CD4+ T cell responses in vivo is caused by increased antigen presentation by B cells. A model where CD23+ B cells act as antigen transporting cells, delivering antigen to CD11c+ cells for presentation to T cells is consistent with available experimental data. [ABSTRACT FROM AUTHOR]

CD4+CD25+ regulatory T cells (Treg) play a crucial role in the regulation of immune responses. Although many mechanisms of Treg suppression in vitro have been described, the mechanisms by which Treg modulate CD8+ T cell differentiation and effector function in vivo are more poorly defined. It has been proposed, in many instances, that modulation of cytokine homeostasis could be an important mechanism by which Treg regulate adaptive immunity; however, direct experimental evidence is sparse. Here we demonstrate that CD4+CD25+ Treg, by critically regulating IL-2 homeostasis, modulate CD8+ T-cell effector differentiation. Expansion and effector differentiation of CD8+ T cells is promoted by autocrine IL-2 but, by competing for IL-2, Treg limit CD8+ effector differentiation. Furthermore, a regulatory loop exists between Treg and CD8+ effector T cells, where IL-2 produced during CD8+ T-cell effector differentiation promotes Treg expansion. [ABSTRACT FROM AUTHOR]

Vasectomy is a well accepted global contraceptive approach frequently associated with epididymal granuloma and sperm autoantibody formation. To understand the long-term sequelae of vasectomy, we investigated the early immune response in vasectomized mice. Vasectomy leads to rapid epithelial cell apoptosis and necrosis, persistent inflammation, and sperm granuloma formation in the epididymis. Vasectomized B6AF1 mice did not mount autoimmune response but instead developed sperm antigen-specific tolerance, documented as resistance to immunization-induced experimental autoimmune orchitis (EAO) but not experimental autoimmune encephalomyelitis. Strikingly, tolerance switches over to pathologic autoimmune state following concomitant CD4+CD25+Foxp3+ regulatory T cell (Treg) depletion: unilaterally vasectomized mice produce dominant autoantibodies to an orchitogenic antigen (zonadhesin), and develop CD4 T-cell- and antibody-dependent bilateral autoimmune orchitis. Therefore, (i) Treg normally prevents spontaneous organ-specific autoimmunity induction by persistent endogenous danger signal, and (ii) autoantigenic stimulation with sterile autoinflammation can lead to tolerance. Finally, postvasectomy tolerance occurs in B6AF1, C57BL/6, and A/J strains. However, C57BL/6 mice resisted EAO after 60% Treg depletion, but developed EAO after 97% Treg reduction. Therefore, variance in intrinsic Treg function—a possible genetic trait—can influence the divergent tolerogenic versus autoimmune response to vasectomy. [ABSTRACT FROM AUTHOR]

A hallmark of cells comprising the mammalian adaptive immune system is the requirement for these rare naïve T (and B) lymphocytes directed to a specific microorganism to undergo proliferative expansion upon first encounter with this antigen. In the case of naïve CD8+ T cells the ability of these rare quiescent lymphocytes to rapidly activate and expand into effector T cells in numbers sufficient to control viral and certain bacterial infections can be essential for survival. In this report we examined the activation, cell cycle time and initial proliferative response of naïve murine CD8+ T cells responding in vivo to Influenza and Vaccinia virus infection or vaccination with viral antigens. Remarkably, we observed that CD8+ T cells could divide and proliferate with an initial cell division time of as short as 2 hours. The initial cell cycle time of responding CD8+ T cells is not fixed but is controlled by the antigenic stimulus provided by the APC in vivo. Initial cell cycle time influences the rate of T cell expansion and the numbers of effector T cells subsequently accumulating at the site of infection. The T cell cycle time varies with duration of the G1 phase of the cell cycle. The duration of G1 is inversely correlated with the phosphorylation state of the retinoblastoma (Rb) protein in the responding T cells. The implication of these findings for the development of adaptive immune responses and the regulation of cell cycle in higher eukaryotic cells is discussed. [ABSTRACT FROM AUTHOR]

Background: With an estimated 38 million people worldwide currently infected with human immunodeficiency virus (HIV), and an additional 4.1 million people becoming infected each year, it is important to understand how this virus mutates and develops resistance in order to design successful therapies. Methodology/Principal Findings: We report a novel experimental method for amplifying full-length HIV genomes without the use of sequence-specific primers for high throughput DNA sequencing, followed by assembly of full length viral genome sequences from the resulting large dataset. Illumina was chosen for sequencing due to its ability to provide greater coverage of the HIV genome compared to prior methods, allowing for more comprehensive characterization of the heterogeneity present in the HIV samples analyzed. Our novel amplification method in combination with Illumina sequencing was used to analyze two HIV populations: a homogenous HIV population based on the canonical NL4-3 strain and a heterogeneous viral population obtained from a HIV patient's infected T cells. In addition, the resulting sequence was analyzed using a new computational approach to obtain a consensus sequence and several metrics of diversity. Significance: This study demonstrates how a lower bias amplification method in combination with next generation DNA sequencing provides in-depth, complete coverage of the HIV genome, enabling a stronger characterization of the quasispecies present in a clinically relevant HIV population as well as future study of how HIV mutates in response to a selective pressure. [ABSTRACT FROM AUTHOR]

Background: Despite high potential for HIV-1 genetic variation, the emergence of some mutations is constrained by fitness costs, and may be associated with compensatory amino acid (AA) co-variation. To characterize the interplay between Cytotoxic T Lymphocyte (CTL)-mediated pressure and HIV-1 evolutionary pathways, we investigated AA co-variation in Gag sequences obtained from 449 South African individuals chronically infected with HIV-1 subtype C. Methodology/Principal Findings: Individuals with CTL responses biased toward Gag presented lower viral loads than individuals with under-represented Gag-specific CTL responses. Using methods that account for founder effects and HLA linkage disequilibrium, we identified 35 AA sites under Human Leukocyte Antigen (HLA)-restricted CTL selection pressure and 534 AA-to-AA interactions. Analysis of two-dimensional distances between co-varying residues revealed local stabilization mechanisms since 40% of associations involved neighboring residues. Key features of our co-variation analysis included sites with a high number of co-varying partners, such as HLA-associated sites, which had on average 55% more connections than other co-varying sites. Conclusions/Significance: Clusters of co-varying AA around HLA-associated sites (especially at typically conserved sites) suggested that cooperative interactions act to preserve the local structural stability and protein function when CTL escape mutations occur. These results expose HLA-imprinted HIV-1 polymorphisms and their interlinked mutational paths in Gag that are likely due to opposite selective pressures from host CTL-mediated responses and viral fitness constraints. [ABSTRACT FROM AUTHOR]

This article describes the preparation and characterization of anticancer drug-loaded poly(lactide-coglycolide) (PLGA) microparticles. PLGA microparticles loaded with doxorubicin HCl (DOX) were prepared via o/w emulsion solvent evaporation. The release characteristics, encapsulation efficiency, size, and morphology of the PLGA microparticles were also determined. A cytotoxicity test was performed by using Glioma RG2 cancer cells to investigate the cytotoxicity of DOX-loaded PLGA microparticles. The DOXloaded PLGA microparticles had an average diameter of 500 ± 9 nm. The DOX encapsulation efficiency and drug loading were 22.75% and 0.78%, respectively. DOX-loaded PLGA microparticles displayed a significant cytotoxicity toward the RG2 cells as compared to the unloaded PLGA microparticles. [ABSTRACT FROM AUTHOR]

CD4+ T helper cells are well known for their role in providing critical signals during priming of cytotoxic CD8+ T lymphocyte (CTL) responses in vivo. T-cell help is required for the generation of primary CTL responses as well as in promoting protective CD8+ memory T-cell development. However, the role of CD4 help in the control of CTL responses at the effector stage is unknown. Here we show that fully helped effector CTLs are themselves not self-sufficient for entry into the infected tissue, but rely on the CD4+ T cells to provide the necessary cue. CD4+ T helper cells control the migration of CTL indirectly through the secretion of IFN-γ and induction of local chemokine secretion in the infected tissue. Our results reveal a previously unappreciated role of CD4 help in mobilizing effector CTL to the peripheral sites of infection where they help to eliminate infected cells. [ABSTRACT FROM AUTHOR]

The article presents information on a study conducted in Kombewa District, western Kenya to determine the molecular impact of RTS,S/AS02A and RTS,S/AS01B on the multiplicity of infection (MOI) and the circumsporozoite protein (CSP) allelic characteristics of subsequent parasitemias. It was found that parasite isolates used for determining MOI and divergence of csp T cell-epitopes were 191 at baseline and was 87 from break-through infections. It has been concluded that both RTS,S/AS vaccines reduce multiplicity of infection.

Whether and how cold causes changes in cell-membrane or lipid rafts remain poorly characterized. Using the NSOM/QD and confocal imaging systems, we found that cold caused microscale redistribution of lipid raft markers, GM1 for lipid and CD59 for protein, from the peripheral part of microdomains to the central part on Jurkat T cells, and that cold also induced the nanoscale size-enlargement (1/3- to 2/3-fold) of the nanoclusters of lipid raft markers and even the colocalization of GM1 and CD59 nanoclusters. These findings indicate cold-induced lateral rearrangement/coalescence of raft-related membrane heterogeneity. The cold-induced re-distribution of lipid raft markers under a nearly-natural condition provide clues for their alternations, and help to propose a model in which raft lipids associate themselves or interact with protein components to generate functional membrane heterogeneity in response to stimulus. The data also underscore the possible cold-induced artifacts in early-described cold-related experiments and the detergent-resistance-based analyses of lipid rafts at 4°C, and provide a biophysical explanation for recently-reported cold-induced activation of signaling pathways in T cells. Importantly, our fluorescence-topographic NSOM imaging demonstrated that GM1/CD59 raft markers distributed and re-distributed at mounds but not depressions of T-cell membrane fluctuations. Such mound-top distribution of lipid raft markers or lipid rafts provides spatial advantage for lipid rafts or contact molecules interacting readily with neighboring cells or free molecules. [ABSTRACT FROM AUTHOR]

Background: In recent years, the impact of antituberculous treatment on interferon (IFN)-c response to Mycobacterium tuberculosis antigens has been widely investigated, but the results have been controversial. The objective of the present study was: i) to evaluate longitudinal changes of IFN-c response to M. tuberculosis-specific antigens in TB patients during antituberculous treatment by using the QuantiFERON-TB Gold (QFT-G) assay; ii) to compare the differences in T-cell response after a short or prolonged period of stimulation with mycobacterial antigens; iii) to assess the CD4+ and CD8+ T cells with effector/memory and central/memory phenotype; iv) to investigate the direct in vitro effects of antituberculous drugs on the secretion of IFN-γ. Principal Findings: 38 TB patients was evaluated at baseline and at month 2 and 4 of treatment and at month 6 (treatment completion). 27 (71%) patients had a QFT-G reversion (positive to negative) at the end of therapy, while 11 (29%) TB patients remained QFT-G positive at the end of therapy. Among the 11 patients with persistent positive QFT-G results, six had a complete response to the treatment, while the remaining 5 patients did not have a resolution of the disease. All 27 patients who became QFT-G negative had a complete clinical and microbiological recovery of the TB disease. In these patients the release of IFN-γ is absent even after a prolonged 6-day incubation with both ESAT-6 and CFP-10 antigens and the percentage of effector/memory T-cells phenotype was markedly lower than subjects with persistent positive QFT-G results. The in vitro study showed that antituberculous drugs did not exert any inhibitory effect on IFN-α production within the range of therapeutically achievable concentrations. Conclusions: The present study suggests that the decrease in the M. tuberculosis-specific T cells responses following successful anti-TB therapy may have a clinical value as a supplemental tool for the monitoring of the efficacy of pharmacologic intervention for active TB. In addition, the antituberculous drugs do not have any direct down-regulatory effect on the specific IFN-γ response. [ABSTRACT FROM AUTHOR]

CD8 T cells play an important role in controlling viral infections. We investigated the in situ localization of simian immunodeficiency virus (SIV)-specific T cells in lymph and genital tissues from SIV-infected macaques using MHC-class I tetramers. The majority of tetramer-binding cells localized in T cell zones and were CD8+. Curiously, small subpopulations of tetramer-binding cells that had little to no surface CD8 were detected in situ both early and late post-infection, and in both vaginally and rectally inoculated macaques. These tetramer+CD8low/- cells were more often localized in apparent B cell follicles relative to T cell zones and more often found near or within the genital epithelium than the submucosa. Cells analyzed by flow cytometry showed similar populations of cells. Further immunohistological characterization revealed small populations of tetramer+CD20- cells inside B cell follicles and that tetramer+ cells did not stain with γδ-TCR nor CD4 antibodies. Negative control tetramer staining indicated that tetramer+CD8low/2 cells were not likely NK cells nonspecifically binding to MHC tetramers. These findings have important implications for SIV-specific and other antigen-specific T cell function in these specific tissue locations, and suggest a model in which antigen-specific CD8+ T cells down modulate CD8 upon entering B cell follicles or the epithelial layer of tissues, or alternatively a model in which only antigen-specific CD8 T cells that down-modulate CD8 can enter B cell follicles or the epithelium. [ABSTRACT FROM AUTHOR]

It is generally thought that during the contraction phase of an acute anti-viral T cell reponse, the effector T cells that escape activation-induced cell death eventually differentiate into central memory T cells over the next several weeks. Here we report that antigen-specific CD8T cells with the phenotype and function of central memory cells develop concomitantly with effector T cells during vaccinia virus (vv) infection. As soon as 5 days after an intraperitoneal infection with vv, we could identify a subset of CD44hi and CD62L+ vv-specific CD8 T cells in the peritoneal exudate lymphocytes. This population constituted approximately 10% of all antigen-specific T cells and like central memory T cells, they also expressed high levels of CCR7 and IL-7R but expressed little granzyme B. Importantly, upon adoptive transfer into naïve congenic hosts, CD62L+, but not CD62L- CD8 T cells were able to expand and mediate a rapid recall response to a new vv challenge initiated 6 weeks after transfer, confirming that the CD62L+ vv-specific CD8 T cells are bonafide memory cells. Our results are thus consistent with the branched differentiation model, where effector and memory cells develop simultaneously. These results are likely to have implications in the context of vaccine design, particularly those based on vaccinia virus recombinants. [ABSTRACT FROM AUTHOR]

T helper cells that produce IL-17 (TH17 cells) promote autoimmunity in mice and have been implicated in the pathogenesis of human inflammatory diseases. At mucosal surfaces, TH17 cells are thought to protect the host from infection, whereas regulatory T (Treg) cells control immune responses and inflammation triggered by the resident microflora. Differentiation of both cell types requires transforming growth factor-β (TGF-β), but depends on distinct transcription factors: RORγt (encoded by Rorc(γt)) for TH17 cells and Foxp3 for Treg cells. How TGF-β regulates the differentiation of T cells with opposing activities has been perplexing. Here we demonstrate that, together with pro-inflammatory cytokines, TGF-β orchestrates TH17 cell differentiation in a concentration-dependent manner. At low concentrations, TGF-β synergizes with interleukin (IL)-6 and IL-21 (refs 9–11) to promote IL-23 receptor (Il23r) expression, favouring TH17 cell differentiation. High concentrations of TGF-β repress IL23r expression and favour Foxp3+ Treg cells. RORγt and Foxp3 are co-expressed in naive CD4+ T cells exposed to TGF-β and in a subset of T cells in the small intestinal lamina propria of the mouse. In vitro, TGF-β-induced Foxp3 inhibits RORγt function, at least in part through their interaction. Accordingly, lamina propria T cells that co-express both transcription factors produce less IL-17 (also known as IL-17a) than those that express RORγt alone. IL-6, IL-21 and IL-23 relieve Foxp3-mediated inhibition of RORγt, thereby promoting TH17 cell differentiation. Therefore, the decision of antigen-stimulated cells to differentiate into either TH17 or Treg cells depends on the cytokine-regulated balance of RORγt and Foxp3. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor best known for mediating the toxicity of dioxin. Environmental factors are believed to contribute to the increased prevalence of autoimmune diseases, many of which are due to the activity of TH17 T cells, a new helper T-cell subset characterized by the production of the cytokine IL-17. Here we show that in the CD4+ T-cell lineage of mice AHR expression is restricted to the TH17 cell subset and its ligation results in the production of the TH17 cytokine interleukin (IL)-22. AHR is also expressed in human TH17 cells. Activation of AHR by a high-affinity ligand during TH17 cell development markedly increases the proportion of TH17 T cells and their production of cytokines. CD4+ T cells from AHR-deficient mice can develop TH17 cell responses, but when confronted with AHR ligand fail to produce IL-22 and do not show enhanced TH17 cell development. AHR activation during induction of experimental autoimmune encephalomyelitis causes accelerated onset and increased pathology in wild-type mice, but not AHR-deficient mice. AHR ligands may therefore represent co-factors in the development of autoimmune diseases. [ABSTRACT FROM AUTHOR]

Schistosoma egg-induced liver granuloma is a dynamic inflammatory reaction that results from complex immune responses to the infection. However, the role of B cells in inflammatory granuloma development is not yet fully understood. We report here that B cell function is required for S. japonicum egg-induced granuloma pathology in early infection. Both OBF-1 knockout mice and μMT mice develop severely reduced hepatic granulomas at five weeks post-infection compared to their wild-type counterparts. In contrast, they display no significant difference in granuloma pathology at eight weeks post-infection. Moreover, we find that B cells and antibodies accumulate in the granulomas of wild-type mice early in the infection, indicating a contribution of the B cell response to the granulomatous inflammation. Furthermore, defects in B cell function markedly reduce liver egg burden. These results suggest an important role for B cells in early granuloma pathology. Surprisingly, we found that the S. japonicum infection destroys the structure of the lymphoid follicles. This disruptive effect is correlated with a severely impaired T cell-dependent antibody response upon challenge with ovalbumin. Thus, these findings reveal a novel aspect of the interaction between Schistosoma and the host immune system. [ABSTRACT FROM AUTHOR]

The interaction of T cells and antigen-presenting cells is central to adaptive immunity and involves the formation of immunological synapses in many cases. The surface molecules of the cells form a characteristic spatial pattern whose formation mechanisms and function are largely unknown. We perform computer simulations of recent experiments on geometrically repatterned immunological synapses and explain the emerging structure as well as the formation dynamics. Only the combination of in vitro experiments and computer simulations has the potential to pinpoint the kind of interactions involved. The presented simulations make clear predictions for the structure of the immunological synapse and elucidate the role of a self-organizing attraction between complexes of T cell receptor and peptide-MHC molecule, versus a centrally directed motion of these complexes. [ABSTRACT FROM AUTHOR]

On activation, T cells undergo distinct developmental pathways, attaining specialized properties and effector functions. T-helper (TH) cells are traditionally thought to differentiate into TH1 and TH2 cell subsets. TH1 cells are necessary to clear intracellular pathogens and TH2 cells are important for clearing extracellular organisms. Recently, a subset of interleukin (IL)-17-producing T (TH17) cells distinct from TH1 or TH2 cells has been described and shown to have a crucial role in the induction of autoimmune tissue injury. In contrast, CD4+CD25+Foxp3+ regulatory T (Treg) cells inhibit autoimmunity and protect against tissue injury. Transforming growth factor-β (TGF-β) is a critical differentiation factor for the generation of Treg cells. Here we show, using mice with a reporter introduced into the endogenous Foxp3 locus, that IL-6, an acute phase protein induced during inflammation, completely inhibits the generation of Foxp3+ Treg cells induced by TGF-β. We also demonstrate that IL-23 is not the differentiation factor for the generation of TH17 cells. Instead, IL-6 and TGF-β together induce the differentiation of pathogenic TH17 cells from naive T cells. Our data demonstrate a dichotomy in the generation of pathogenic (TH17) T cells that induce autoimmunity and regulatory (Foxp3+) T cells that inhibit autoimmune tissue injury. [ABSTRACT FROM AUTHOR]

Helicobacter pylori induces infiltration of the gastric mucosa by polymorphonuclear cells and macrophages, as well as T and B lymphocytes. Paradoxically, this robust immune/inflammatory response cannot clear the infection, and thus leaves the host prone to complications resulting from chronic inflammation. One adverse consequence of this inflammatory response may be gastric cancer, as inflammation has been implicated in the development of intestinal metaplasia and mutations in oncogenes that precede the development of gastric adenocarcinoma. The gastric inflammatory response is affected somewhat, by the strain of H. pylori that infects the host. Thus, the more severe clinical manifestation associated with some strains may be attributed to the higher grade of inflammation that they induce. Both H. pylori and cytokines induced during infection can stimulate the recruitment and activation of inflammatory cells including neutrophils and macrophages. When activated, these cells produce inflammatory mediators that include reactive oxygen species (ROS). These mediators impart an oxidative stress on the cells in the immediate vicinity, in this case, the gastric epithelium. Normally, oxidative stress is neutralized by natural antioxidants such as vitamin C, however, levels of this antioxidant in the gastric juice are decreased during infection. The increased levels of oxidants and decreased antioxidants create a stress that can change many processes in the gastric epithelium. For example, an accumulation of intracellular ROS regulates the expression of many genes and can induce DNA damage. Point mutations in the DNA that disrupt the expression and function of genes that inhibit cell growth (i.e. p53) are believed to contribute to the pathogenesis of gastric cancer. Several studies suggest that epithelial cell turnover is affected by the inflammatory response to H. pylori. This notion is supported by studies describing an increase in both epithelial cell proliferation, as well as cell death by apoptosis, in response to infection. Apoptosis is a regulated process of cell death that is triggered by H. pylori as well as various inflammatory mediators, including tumour necrosis factor and interferon-),. Activated T-cells also kill gastric epithelial cells directly. Moreover, the host response increases the expression of receptors for H. pylori and thus increases bacterial binding and the induction of apoptosis by the bacteria. There are several other immune/inflammatory responses that contribute to epithelial cell damage mucosa and the pathogenesis of gastric cancer. For example, gastric B cells produce autoreactive antibodies that bind to gastric epithelial cells. As a consequence of this antigen-antibody complex formation, complement becomes activated suggesting that some of the inflammation and epithelial cell damage is attributable to immune-complex formation. Epithelial cell death can then stimulate the proliferative response of epithelial cell precursors. In summary, the proposed model may explain how the gastric inflammatory response contributes to the pathogenesis of cancer. This model raises the possibility that it could be preferable to identify the patients at highest risk of developing gastric cancer and then apply an intervention that eliminates the infection and inflammatory response. Alternatively, clinical interventions should at least attenuate the oxidative stress that is directly attributed to inflammation. These mechanisms have to be examined in the paediatric population. [ABSTRACT FROM AUTHOR]

The relationship between antibody (Ab) and lymphoproliferative responses to herpes simplex virus (HSV) and recrudescent orofacial HSV lesions were investigated in 65 patients. All had HSV-specific Ab and cell mediated immune responses (CMIR) demonstrated by ELISA and in vitro lymphoproliferation respectively. Thirteen control subjects were negative in both tests. Thirty-three patients were repeatedly investigated for 6-38 months during which time they suffered 1-8 recrudescences. HSV-induced lymphoproliferation was depressed during recrudescences, rose to a peak several weeks later, and declined slowly to a background level. However, ELISA titres and lymphoproliferative responses to Concanavalin A (Con A) were high throughout and circulating peripheral blood mononuclear cell (PBMC) subsets did not change. Depressed lymphoproliferative responses to HSV antigen (Ag) during recrudescences were enhanced by removal of CD8+ cells from PBMC using either a panning technique or cell sorting; reconstitution of CD8+ cells suppressed the HSVspecific lymphoproliferative response. CD8+ cell depletion affected neither HSV-induced lymphoproliferation recrudescence, nor lymphoproliferative responses to another Ag (PPD) during recrudescence. Depressed HSV-induced lymphoproliferation during recrudescences might thus be due to CD8+ suppressor T cell (Ts) function rather than low numbers of circulating lymphocytes. Suppression or delay of normal CMIR to asymptomatic recurrent epidermal HSV infection by Ts might allow development of recrudescent HSV lesions. [ABSTRACT FROM AUTHOR]

The article examines the significance of 5'-nucleotidase in lymphocyte purine metabolism. Studies conducted suggest that lymphocyte 5'-nucleotidase plays little part in providing purine nucleosides from extracellular sources of mononucleotides. It is also unlikely that mononucleotides exist in significant concentrations in the extracellular environment. Brief discussion about the present knowledge on purine metabolism in lymphocytes is presented.

Naturally susceptible mice (C57BL/6) infected with M. avium (strain Weybridge) developed a population of splenic T cells which, on transfer to syngeneic recipient mice, conferred significant protection against a subsequent challenge inoculum of M. avium. Similar T cells from naturally resistant mice (A/J) did not protect syngeneic recipient mice. Growth of M. avium in donor mice only occurred in the C57BL/6 strain. Replication of M. avium in donor mice was necessary for the development of protective T cells. High numbers of killed mycobacterium did not induce immune T cells. In addition. A/J mice inoculated with increasing numbers of viable M. avium (which still did not replicate) failed lo develop protective T lymphocytes. Further studies indicated that no protective T cells were present in the M. avium-infected A/J mouse, although evidence for non-specific immunity in these mice was obtained. In addition, BCG (which grows progressively in A/J mice) stimulated a population of splenic T cells which protected recipient mice from subsequent infection with M. tuberculosis. [ABSTRACT FROM AUTHOR]

The effect of interleukin 2 (IL-2) on cord blood mononuclear cells (CBMC) was studied, with special reference to B cell function. The study shows that CBMCs proliferate in response to recombinant interleukin 2 (rIL-2) without in-vitro preactivation. The response was also detected when whole blood cultures were used. CBMCs not preactivated in vitro proliferated in response to rIL-2 even after T cell and monocyte depletion. Thus, rIL-2 affects both non-T cells and T cells of newborns without preactivation in vitro. IL-2 receptors on unstimulated CBMCs appear to be distinct from Tac antigen, as the mean number of Tac antigen-positive cells among CBMCs was only 0.8%. Furthermore, rIL-2 inhibited PWM-induced proliferation and the response was more prominent in newborns than in adults. Thus, rIL-2 seems to cause a higher increase of suppressor cell function in CBMCs than in adult peripheral blood mononuclear cells. Neither rIL-2 nor Staphylococcus aureus Cowan 1 (SAC) stimulated any IgM synthesis, but a dose-dependent IgM synthesis was obtained by combining SAC and rIL-2. Alone, however, rIL-2 appears to be an insufficient factor to induce differentiation of SAC-activated cord blood B cells, as no IgM production in response to rIL-2 occurred in T cell and monocyte-depleted cell populations. The results of this study suggest both increased suppressor cell function and intrinsic B cell deficiency as causes of a weak humoral immune response in newborns. [ABSTRACT FROM AUTHOR]

The possibility that shared idiotypes may be present on antibodies of different specificities was explored using sera from 13 patients with systemic lupus erythematosus. Eleven sera had anti-DNA and seven carried the 16/6 idiotype (ID). Two of the sera with 16/6 ID also had lymphocytotoxic antibodies, the activity of which was blocked by antibody to the 16/6 ID. Our studies reveal that 16/6 ID is present on two antibodies with different binding specificities. [ABSTRACT FROM AUTHOR]

Patients with acquired hypogammaglobulinaemia usually have near normal numbers of B cells and normal T cell function. When hypogammaglobulinaemia occurs in association with thymoma, then B cell numbers have been reported as low, and distinctive T cells are present which inhibit immunoglobulin production by normal cells. It has been suggested that these T cells are responsible for the observed hypogammaglobulinaemia. We report a patient with thymoma and hypogammaglobulinaemia who lacks these distinctive suppressor cells and has normal B cell numbers. It is therefore incorrect to propose a single pathogenic mechanism for hypogammaglobulinaemia in association with thymoma. [ABSTRACT FROM AUTHOR]

Peripheral blood lymphocytes (PBL) from rheumatoid arthritis (RA) patients and healthy controls (NC) were assayed for Fc receptors by four methods. Three of the four assays showed RA PBL to contain a greater proportion and number of Fc receptor-bearing cells than PBL from healthy controls. This confirmed our earlier report and indicated that the proportion of Fc receptor-bearing cells detected can be influenced by the test system. Neither the proportion of B, nor of non-B, non-T lymphocytes was consistently increased in RA PBL, suggesting that the increase found results from an increase in Fcγ receptor-positive T cells. [ABSTRACT FROM AUTHOR]

The human cytotoxic T lymphocyte (CTL) response to challenge with influenza A vaccine was studied. Six of eight volunteers given killed whole influenza virus A/USSR (HlNl) vaccine showed substantial increases on the level of CTL memory 1 month after immunization. The CTL measured at this time showed complete cross-reactivity in their specificity for influenza A/USSR (HINI) and A/X31 (H3N2) infected cells and also showed HLA restriction. The level of CTL memory increased in only three out of nine donors given subunit vaccine and showed no change in those not given vaccine. If cytotoxic T cells are important in influenza prophylaxis, killed whole virus vaccine should offer better protection than subunit vaccine. [ABSTRACT FROM AUTHOR]

A simultaneous analysis was made of numbers and proportions of T cell subsets (Tμ and Tγ cells), lymphocyte responsiveness to non-specific mitogens in vitro and `short-lived suppressor cell activity' in peripheral blood mononuclear cells (PBMC) of normal individuals. No correlation was found between either Tγ or Tμ cells and the `short-lived suppressor cell activity', suggesting that suppression in this system is not a reflection of quantitative alteration in these subsets. However, a highly significant positive correlation was found between numbers of Tμ cells and PBMC responses to the mitogens phytohaemagglutinin. concanavalin A and pokeweed mitogen. This may reflect either a helper effect of Tμ cells on lymphocyte proliferation in response to mitogens or the presence of the majority of mitogen-responsive cells within this subpopulation. As in normal individuals lymphocyte responsiveness correlates with the number of circulating Tμ cells, it is possible that a reduction in these cells in disease states may contribute to defects in cell-mediated immunity. [ABSTRACT FROM AUTHOR]

Subpopulations of human peripheral blood T lymphocytes were examined in twenty-three myasthenic patients. T lymphocytes bearing receptors for the Fc portion of IgG (Ty) were significantly increased in a third of the patients examined. T lymphocytes bearing receptors for the Fc portion of IgM (Tγ) were within normal values in all but two patients. Possible implications of these cells in the pathogenesis of myasthenia gravis are discussed. [ABSTRACT FROM AUTHOR]

Scrum from eleven of fifty-four patients with Hodgkin's disease inhibited phytohaemagglutinin (PHA) stimulation of both autologous and homologous lymphocytes. The inhibitory effect resided in the macromolecular fraction of these sera. PHA was shown to bind to serum substances in inhibitory sera and the degree of PHA binding in the macromolecular fraction correlated directly with the extent of inhibition. [ABSTRACT FROM AUTHOR]

A herpes simplex virus (HSV)-specific long-term T-cell clone has been established from the draining lymph node cells of BALB/c mice; the cells required repeated in vitro restimulation with UV-irradiated virus. The established T-cell clone expresses the Thy-1 and Lyt-1+2,3- surface antigens. For optimal proliferation of the cloned cells, both the presence of specific antigen and an exogenous source of T-cell growth factor are required. The proliferative response of the cloned T cells was found to be virus-specific but it did not distinguish between HSV-1 and HSV-2. Adoptive cell transfer of the cloned T cells helped primed B cells to produce anti-herpes antibodies: the response was antigen-specific and cell dose-dependent. The clone failed to produce a significant DTH reaction in vivo, but did produce high levels of macrophage-activating factor. Furthermore, the T-cell clone could protect from HSV infection, as measured by a reduction in local virus growth, and by enhanced survival following the challenge of mice with a lethal dose of virus. The mechanism(s) whereby this clone protects in vivo is discussed. [ABSTRACT FROM AUTHOR]

Two PPD-reactive T-cell lines and two clones derived from them have been characterized. The lines were maintained for a period of 10–12 weeks in 11–2 containing medium. The clones were derived from the uncloned lines by the limiting dilution method and maintained in culture for 12 weeks. The cloning efficiency was 1%, Both the cloned and the uncloned lines were highly reactive to tuberculin in a proliferation assay and produced migration inhibition factors following antigenic stimulation. Both these functions were dependent on the addition of antigen-presenting cells and genetically regulated by Class II molecules of the MHC. Each uncloned line and the clones derived from them were restricted by just one of he DR alleles of the autologous host. An analysis of ell types involved in antigen presentation showed that macrophages and Epstein-Barr virus-transformed B-cell lines induced both proliferation and MIF secretion in the T-cell lines and clones cultured with PPD. Phenotypic studies indicate that the cells are Sheep E+, OKT4+, OKT8- and HLA-DR+. [ABSTRACT FROM AUTHOR]

Effector T cells (Td) which mediate delayed-type hypersensitivity reactions to influenza A virus can be generated in tissue culture using normal mouse spleen cells as the responder population. Addition of helper T cells enhances but is not essential for the production of Td cells. Both Ly 1 positive, I region restricted and Ly 2,3 positive, K,D region restricted effector cells are generated. Treating the responder cell population with anti-Ly I or anti-Ly 2,3 antibodies and complement prevented the generation of both classes of effector T cell, suggesting that the precursor Td cells are Ly 1,2,3 positive. Effector cells which are specific for the homologous virus or cross-reactive within the A strains of influenza virus are produced, as has been found previously in in vivo experiments. Depleting the cell population of phagocytic and plastic adherent cells resulted in a failure to produce Td cells, which showed a requirement for macrophage-like cells as accessory cells in the primary in vitro generation of Td cells. A variety of cells, such as peritoneal exudate cells, mitogen stimulated blasts or L929 fibroblast cells could serve as stimulator cells. Only Ly 2,3 positive, K,D region-restricted Td cells were produced when L929 cells were used as they lack I region-coded surface antigens. The 1 region-restricted DTH response was mapped to the IA sub-region of the H-2 gene complex. [ABSTRACT FROM AUTHOR]

Immune responses against bovine serum albumin by chickens were dependent upon thymusderived cells. Thirty-five of seventy chickens that had been neonatally thymectomized and subsequently immunized with bovine serum albumin produced lgM antibodies, but not IgG antibodies, against the antigen. T cells (IgM-T cells) of such chickens were able to help B cells to produce IgM antibody responses but were not able to help them to switch IgM- to IgG-antibody responses. Helper activity of the IgM-T cells was much less susceptible to the cytotoxic effect of anti-thymus cell serum and complement than was that of normal T cells. The introduction of the IgM-T cells into normal chickens at the same time as the initiation of immunization of the chickens did not affect immune responses by them at all, indicating the absence of suppressor T cells in the IgM-T cell preparations. Injection of chicken thymus factor into immunodeficient chickens transplanted with normal B cells and IgM-T cells developed the capability to help B cells to switch IgM- to IgG-antibody responses. On the basis of these findings the authors propose the existence of helper T cells which are characterized by peripheralization in early periods of ontogeny, the possession of helper activity for only IgM-antibody responses, the lack of helper activity for the switch from IgM- to IgG-antibody responses and relative insusceptibility to the cytotoxic effect of anti-thymus cell serum and complement. [ABSTRACT FROM AUTHOR]

Haemopoietic cells from several murine organs were examined for the presence of peanut agglutinin (PNA) receptors. Foetal liver and adult bone marrow contained a number of cells, which were PNA+ but did not stain with conventional T and B markers. Some of the PNA+ cells, however, were pre-B cells, as shown by the presence of cytoplasmic IgM in the absence of cell surface Ig. Cells in the T lineage retained their PNA receptors during maturation, although these became masked by sialic acid on mature peripheral blood T cells. Cells of the B lineage, in contrast, gradually lost their PNA receptors as they matured from pre-B to mature surface immunoglobulin positive B lymphocytes. [ABSTRACT FROM AUTHOR]

Relationships among T-cell mediated cytotoxicity, tuberculin type hypersensitivity, Jones-Mote type hypersensitivity and activation of helper T cells were studied in AKR mice by means of target cell destruction (51Cr-release), footpad reaction, migration inhibition test and antibody production against the trinitrophenyl group. (1) Immunization with chicken red blood cells (CRBC) in saline, Freund's incomplete (FIA) or complete adjuvant (FCA) and fixed-CRBC (FRBC) in FIA or FCA induced delayed hypersensitivity as demonstrated by footpad swelling. (2) Migration inhibition was positive in the group immunized with CRBC in saline or FCA, or FRBC in FCA, but negative in those immunized with CRBC or FRBC in FIA. This may suggest that the former has to be assigned to tuberculin type and the latter to Jones-Mote type. (3) T-cell mediated cytotoxicity by immune spleen cells was detected only in mice immunized with CRBC in saline, (4) Pre-treatment with cyclophosphamide augmented delayed footpad reaction in mice immunized with CRBC in saline, but suppressed cytotoxic activity. (5) FRBC in saline scarcely induced delayed footpad reaction and cytotoxic activity, whereas they activated helper function efficiently. Thus, four types of immunological phenomena, attributable to the functions of T cells, may depend upon distinct subpopulations of differentiated T cells which are raised by different methods of immunization. [ABSTRACT FROM AUTHOR]