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Antibodies recognizing infliximab (IFX) may develop in a proportion of treated patients, leading to loss of response or hypersensitivity reactions (HRs). T cell response to IFX has been poorly investigated. This paper was addressed to detect IFX-specific T cells in treated patients with inflammatory diseases developing, or not, anti-drug antibodies (ADA) and to correlate the presence of specific T cells with the clinical outcomes of the treatment. A co-culture system of IFX-loaded dendritic cells and purified autologous CD4+ T cells was used to detect memory T cells in 32 ADA+ and 39 ADA- IFX-treated patients and control groups. The cytokine profile of IFX-specific T cells was also studied in culture supernatants. IFX-specific cell proliferation was detected mainly in cells from ADA+ patients, irrespective of their different diseases. HR patients displayed higher T cell proliferation than non-responder and tolerant patients. A mixed [interferon (IFN)-γ, interleukin (IL)-13, IL-10] cytokine profile was shown in cells from ADA+ patients, while IL-10 was the most frequently detected cytokine in the supernatants of cultures from ADA- patients. Immunoglobulin (Ig)E+ADA+ patients with previous HRs exhibited a more pronounced type 2 profile than IgE-ADA+ patients. This work provides evidence that IFX-specific circulating T cells are detectable mainly in ADA+ patients with HRs, regardless of their disease. The IFX-induced cytokine pattern partially correlates with the ADA isotype. [ABSTRACT FROM AUTHOR]

The mechanisms causing non-responsiveness to hepatitis B surface antigen (HBsAg) vaccines in man remain elusive. The increased incidence of non-responsiveness in subjects with HLA-DR3+ or -DR7+ haplotypes suggests that immune response mechanisms governed by genes of the MHC are involved. Homozygotes for these two haplotypes are found almost exclusively in the non-responder (NR) population. It is conceivable that antigen-presenting cells (APC) of NR are defective in the uptake of HBsAg and that they are unable to present this Ag adequately. Previously, we demonstrated thatDR2+,DR7+ andDP4+ NR were able to present HBsAg. In the present paper we demonstrate that six DR0301+ NR, five of which are homozygous for this marker, were able to take up, process and present HBsAg to HBsAg-specific, DR0301-restricted T cell lines. Non-fractionated peripheral blood mononuclear cells (PBMC) from the DR0301+ NR did not proliferate to HBsAgin vitro, whereas they proliferated vigorously upon stimulation with tetanus toxoid, thus ruling out the presence of a generalized immunodeficiency. We therefore conclude that HLA-DR0301+ NR vaccinees are not deficient in their HBsAg-presentation. Because it was demonstrated that recently activated T cells can apparently bypass the requirement for B7, we may have overlooked the role of the B7-co-stimulation in our set-up that used HBsAg-specific T cell lines. Therefore we examined the expression of B7 co-stimulatory molecules on NR-APC. CD86 was normally present on these cells and was not down-regulated after culturing the PBMC in the presence of HBsAg. We conclude that CD86 expression on CD14+ monocytes of DR0301- and DR07-homozygous poor responders is not deficient and cannot be the mechanism underlying the non-responsiveness of these subjects. [ABSTRACT FROM AUTHOR]

Immunosurveillance requires the migration of lymphocytes and their activation to induce proliferation and effector function. Effective immunity requires an optimal supply of nutrients to lymphocytes. Cells contain nutrient sensing apparatus such as adenosine 5′-monophosphate-activated protein kinase (AMPK) that surveys intracellular ATP levels. Immunity declines during ageing and one possibility is that the energy balance may be altered in old lymphocytes. This paper summarizes recent data identifying a convergence of senescence and nutrient signalling pathways in lymphocytes that inhibit both T cell and natural killer (NK) cell function during ageing. Significantly, these pathways can be inhibited to enhance the activity of these cells. [ABSTRACT FROM AUTHOR]

Objective JIA is a chronic inflammatory disease of unknown origin. The regulation of inflammatory processes involves multiple cellular steps including mRNA transcription and translation. Different miRNAs control these processes tightly. We aimed to determine the roles of specific miRNAs within JIA pathogenesis. Methods We performed a global miRNA expression analysis in parallel in cells from the arthritic joint and peripheral blood of oligoarticular JIA patients and healthy controls. Quantitative RT-PCR analysis was used to verify expression of miRNA in T cells. Ex vivo experiments and flow cytometric analyses were used to analyse proliferation and redox metabolism. Results Global miRNA expression analysis demonstrated a different composition of miRNA expression at the site of inflammation compared with peripheral blood. Bioinformatic analysis of predicted miRNA target genes suggest a huge overrepresentation of genes involved in metabolic and oxidative stress pathways in the inflamed joint. Despite enhanced reactive oxygen species (ROS) levels within the local inflammatory milieu, JIA T cells are hyperproliferative and reveal an overexpression of miR-23a, which is an inhibitor of Peptidyl-prolyl isomerase F (PPIF), the regulator of mitochondrial ROS escape. Mitochondrial ROS escape is diminished in JIA T cells, resulting in their prolonged survival. Conclusion Our data suggest that miRNA-dependent mitochondrial ROS shuttling might be a mechanism that contributes to T cell regulation in JIA at the site of inflammation. [ABSTRACT FROM AUTHOR]

Editor's Highlight: This paper reports an in vitro cell culture system from human donors for the prediction of the allergic potential of drugs. Naive T cells were cultured in the presence of a drug and tested for transformation of the naive phenotype into a memory phenotype. These results demonstrate a system that can predict possible drug allergy resulting in serious adverse effects in a system that does not utilize experimental animals.Adverse drug reactions represent a major stumbling block to drug development and those with an immune etiology are the most difficult to predict. We have developed an in vitro T-cell priming culture method using peripheral blood from healthy volunteers to assess the allergenic potential of drugs. The drug metabolite nitroso sulfamethoxazole (SMX-NO) was used as a model drug allergen to establish optimum assay conditions. Naive T cells were cocultured with monocyte-derived dendritic cells at a ratio of 25:1 in the presence of the drug for a period of 8 days, to expand the number of drug-responsive T cells. The T cells were then incubated with fresh dendritic cells, and drug and their antigen responsiveness analyzed using readouts for proliferation, cytokine secretion, and cell phenotype. All five volunteers showed dose-dependent proliferation as measured by 5-(and 6)-carboxyfluorescein diacetate succinimidyl ester content and by 3H-thymidine uptake. CD4 T cells that had divided in the presence of SMX-NO had changed from a naive phenotype (CD45RA+) to a memory phenotype (CD45RO+). These memory T cells expressed the chemokine receptors CCR2, CCR4, and CXCR3 suggesting a mixture of TH1 and TH2 cells in the responding population, with a propensity for homing to the skin. Drug stimulation was also associated with the secretion of a mixture of TH1 cytokines (interferon γ) and TH2 cytokines (interleukin [IL]-5 and IL-13) as detected by ELISpot. We are currently developing this approach to investigate the allergenic potential of other drugs, including those where an association between specific human leucocyte antigen alleles and susceptibility to an immunological reaction has been established. [ABSTRACT FROM PUBLISHER]

The article presents the findings of a research paper, which analyzed four cases of unilesional mycosis fungoides. The paper was presented at a meeting of the British Society for Dermatopathology. Histological examination of four male patients suffering from unilesional mycosis fungoides revealed that all had solitary erythematous plaques on the trunk or lower limbs. Further diagnosis revealed, in each case, a dense, often band-like, lymphohistiocytic infiltrate in the dermis containing at least 95% T lymphocytes with Pautrier abscess formation in three cases.

Summary: Capping protein regulator and myosin 1 linker 2 (CARMIL2) deficiency is characterized by impaired T cell activation, which is attributed to defective CD28‐mediated co‐signaling. Herein, we aimed to analyze the effect of exogenous interleukin (IL)‐2 on in‐vitro T cell activation and proliferation in a family with CARMIL2 deficiency. This study included four children (one male and three females; aged 2·5–10 years at presentation). The patients presented with inflammatory bowel disease and recurrent viral infections. Genetic analysis revealed a novel homozygous 25‐base pairs deletion in CARMIL2. Immunoblotting demonstrated the absence of CARMIL2 protein in all four patients and confirmed the diagnosis of CARMIL2 deficiency. T cells were activated in‐vitro with the addition of IL‐2 in different concentrations. CD25 and interferon (IFN)‐γ levels were measured after 48 h and 5 days of activation. CD25 surface expression on activated CD8+ and CD4+ T cells was significantly diminished in all patients compared to healthy controls. Additionally, CD8+ T cells from all patients demonstrated significantly reduced IFN‐γ production. When cells derived from CARMIL2‐deficient patients were treated with IL‐2, CD25 and IFN‐γ production increased in a dose‐dependent manner. T cell proliferation, as measured by Cell Trace Violet, was impaired in one patient and it was also rescued with IL‐2. In conclusion, we found that IL‐2 rescued T cell activation and proliferation in CARMIL2‐deficient patients. Thus, IL‐2 should be further studied as a potential therapeutic modality for these patients. [ABSTRACT FROM AUTHOR]

T cells play a key role in mounting an adaptive immune response. T cells are activated upon recognition of cognate Ag presented by an APC. Subsequently, T cells adhere to other activated T cells to form activation clusters, which lead to directed secretion of cytokines between communicating cells. T cell activation clusters have been implicated in regulating activation, proliferation, and memory formation in T cells. We previously reported the expression of the protease inhibitor neuroserpin by human T cells and showed that expression and intracellular localization is regulated following T cell activation. To gain a better understanding of neuroserpin in the proteolytic environment postactivation we assessed its role in human T cell clustering and proliferation. Neuroserpin knockdown increased T cell proliferation and cluster formation following T cell activation. This increased cluster formation was dependent on the proteases tissue plasminogen activator (tPA) and plasmin. Furthermore, neuroserpin knockdown or plasmin treatment of T cells increased the cleavage of annexin A2, a known plasmin target that regulates the actin cytoskeleton. Live cell imaging of activated T cells further indicated a role of the actin cytoskeleton in T cell clustering. The inhibition of actin regulators myosin ATPase and Rho‐associated protein kinase signaling completely reversed the neuroserpin knockdown‐induced effects. The results presented in this study reveal a novel role for neuroserpin and the proteolytic environment in the regulation of T cell activation biology. [ABSTRACT FROM AUTHOR]

T cells develop in the thymus and play important roles in protection against infection and tumor development, but the mechanisms by which the thymic microenvironment supports T cell differentiation remain largely unclear. Skint1, a B7-related protein expressed in thymic epithelial cells, was shown to be essential for the development of mouse T cells. The Skint family in mouse consists of 11 members, Skint1-11. Here we generated mutant mice lacking the entire genomic region that contains all of the Skint genes. These mice exhibited a marked reduction of T cells in the thymus and skin, but surprisingly, had normal development of other T cell subsets and leukocytes including αβT, B and myeloid cells. This phenotype is essentially identical to that of Skint1-deficient mice. These results indicate that the Skint family exerts an exclusive function in regulating the development of T cells and is dispensable for development of other leukocytes. [ABSTRACT FROM AUTHOR]

The mechanisms of maintenance of adequate numbers of B lymphocytes and of protective levels of immunoglobulins in the absence of antigenic (re)stimulation remain not fully understood. Meanwhile, our results presented here show that both peripheral blood naive and memory B cells can be activated strongly and non-specifically (in a mitogen-like fashion) in 5-day in vitro cultures of anti-CD3- or concanavalin A (Con A)-stimulated peripheral blood mononuclear cells of healthy people. This polyclonal, bystander activation of the B cells includes multiple divisions of most of them (assessed here by the flow cytometric technique of dividing cell tracking) and significant antibody [immunoglobulin M (IgM) and IgG] secretion. Observed proliferation of the CD19+ B cells depends on contact with stimulated T helper (Th) cells (via CD40-CD40L interaction) and on the response of B cells to secreted interleukins IL-5, IL-10 and IL-4, and is correlated with the levels of these Th-derived molecules, while it does not involve the ligation of the BCR/CD19 complex. We suggest that the effect might reflect the situation occurring in vivo as the homeostatic proliferation of otherwise non-stimulated, peripheral B lymphocytes, providing an always ready pool for efficient antibody production to any new (or cognate) antigen challenge. [ABSTRACT FROM AUTHOR]

Introduction. Though Staphylococcus aureus is a major pathogen, vaccine trials have failed. In contrast, classswitched antibodies specific to S. aureus are common, implying immune memory formation and suggesting a large pool of S. aureus-reactive helper T-cells. Objective. To elucidate the cellular arm of S. aureus-specific immune memory, the T-cell response in humans was characterized. Methods. The proliferative response of human peripheral blood mononuclear cells (PBMCs) to S. aureus antigens and the frequency of S. aureus-specific T-cells were quantified by ³H-thymidine incorporation; cytokine release was measured by flow cytometry. Results. Staphylococcus aureus particles and extracellular proteins elicited pronounced proliferation in PBMCs of healthy adults. This reflected a memory response with high frequencies of T-cells being activated by single S. aureus antigens. The whole S. aureus-specific T-cell pool was estimated to comprise 3.6% of T-cells with 35-fold differences between individuals (range, 0.2%-5.7%). When exposed to S. aureus antigens, the T-cells released predominantly but not solely T helper (Th)1/Th17 cytokines. Conclusions. The large number of S. aureus antigen-reactive memory T-lymphocytes is likely to influence the course of S. aureus infection. To enable rational vaccine design, the naturally acquired human T-cell memory needs to be explored at high priority. [ABSTRACT FROM AUTHOR]

Renal tubular epithelial cells ( TECs) are one of the main targets of alloreactive T cells during acute rejection. We hypothesize that TECs modulate the outcome of alloimmunity by executing immunosuppressive effects in order to dampen the local inflammation. We studied whether TECs possess immunosuppressive capacities and if indoleamine 2,3-dioxygenase ( IDO) might play a role in suppressing T cell alloreactivity. Next, we studied the role of programmed death ligand 1 ( PD- L1) and intercellular adhesion molecule-1 ( ICAM-1 with regard to TEC-related immunomodulatory effects. CD3/ CD28 and alloactivated peripheral blood mononuclear cells were co-cultured with activated TECs. We analysed CD4+ and CD8+ T cell proliferation and apoptosis in the absence or presence of IDO inhibitor 1-methyl- L-tryptophan (1- L- MT), anti- PD- L1 and anti- ICAM-1. Further, we examined whether inhibition of T cell proliferation was cell-cell contact-dependent. We found that TECs dose-dependently inhibited CD4+ and CD8+ T cell proliferation ( P < 0·05). Activated TECs showed significantly increased IDO activity and up-regulated PD- L1 and ICAM-1 expression. Suppressed CD4+ and CD8+ T cell proliferation was only partially restored or failed to restore using 1- L- MT. Activated TECs increased early and late apoptosis of proliferating CD4+ and CD8+ T cells; only CD4+ T cell apoptosis was statistically affected by 1- L- MT. Transwell experiments revealed that TEC-mediated immunosuppression is cell-cell contact-dependent. We found that anti- ICAM-1 affected only CD4+ T cell apoptosis and not T cell proliferation. Our data show that TECs suppress both CD4+ and CD8+ T cell proliferation contact dependently. Interestingly, inhibition of proliferation and enhancement of apoptosis of T cell subsets is differentially regulated by indoleamine 2,3-dioxygenase and ICAM-1, with no evidence for the involvement of PD- L1 in our system. [ABSTRACT FROM AUTHOR]

IDO and p53 interact to modulate the metabolism of T cellsIndoleamine 2,3-dioxygenase (IDO) suppresses adaptive immunity by inhibiting T-cell proliferation and altering glucose metabolism. The tumor suppressor p53 also alters these cellular processes with similar results. The effect of IDO on p53 and on glucose metabolism was evaluated in alloreactive T cells. Mixed-lymphocyte reactions (MLRs) were performed in the presence or not of the IDO inhibitor, 1-dl-methyl-tryptophan (1-MT) and/or the p53 inhibitor, pifithrin-α (PFT). Cell proliferation, glucose consumption and lactate production were assessed. 1-MT increased cell proliferation, glucose influx and lactate production, whereas PFT enhanced cell proliferation and glucose influx, leaving lactate production unaffected. In MLR-derived T cells, protein analysis revealed that IDO activated general control non-derepressible 2 kinase and induced p53, p-p53 (p53 phosphorylated at serine 15) and p21. In addition, both IDO and p53 decreased glucose transporter 1 and TP53-induced glycolysis and apoptosis regulator and increased synthesis of cytochrome c oxidase 2. IDO also reduced lactate dehydrogenase-A and glutaminase 2 levels, whereas p53 left them unaffected. Neither 1-MT nor PFT affected glucose-6-phosphate dehydrogenase. In conclusion, in alloreactive T cells, IDO increases p53 levels, and both IDO and p53 inhibit cell proliferation, glucose consumption and glycolysis. Lactate production and glutaminolysis are also suppressed by IDO, but not by p53. [ABSTRACT FROM AUTHOR]

Activated CD4+ T cells undergo blastogenesis and proliferation and they express several surface receptors, including β2-microglobulin-free human leucocyte antigen ( HLA) heavy chains (open conformers). Intravenous immunoglobulin (IVIg) suppresses activated T cells, but the mechanism is unclear. IVIg reacts with HLA- Ia/ Ib antigens but its reactivity is lost when the anti- HLA- E Ab is adsorbed out. Anti- HLA- E antibodies may bind to the peptides shared by HLA- E and the HLA- I alleles. These shared peptides are cryptic in intact HLA, but exposed in open conformers. The hypothesis that anti- HLA- E monoclonal antibodies ( mAbs) that mimic HLA- I reactivity of IVIg may suppress activated T cells by binding to the shared peptides of the open conformers on the T cell surface was tested by examining the relative binding affinity of those mAbs for open conformers coated on regular beads and for intact HLA coated on iBeads, and by comparing the effects on the suppression of phytohaemagglutinin ( PHA)-activated T cells of three entities: IVIg, anti- HLA- E mAbs that mimic IVIg [Terasaki Foundation Laboratory (TFL)-006 and (TFL)-007]; and anti- HLA- E antibodies that do not mimic IVIg ( TFL-033 and TFL-037). Suppression of blastogenesis and proliferation of those T cells by both IVIg and the anti- HLA- E mAbs was dose-dependent, the dose required with mAbs 50-150-fold lower than with IVIg. TFL-006 and TFL-007 significantly suppressed blastogenesis and proliferation of activated CD4+ T cells, but neither the non- IVIg-mimicking mAbs nor control antibodies did so. The suppression may be mediated by Fab-binding of TFL-006/ TFL-007 to the exposed shared peptides. The mAb binding to the open conformer may signal T cell deactivation because the open conformers have an elongated cytoplasmic tail with phosphorylation sites (tryosine320/serine335). [ABSTRACT FROM AUTHOR]

Systemic sclerosis ( SSc) is a chronic disease, with early activation of the immune system. The aim of our work was to address how SSc-mesenchymal stem cells ( MSCs), although senescent, might preserve specific immunomodulatory abilities during SSc. MSCs were obtained from 10 SSc patients and 10 healthy controls ( HC). Senescence was evaluated by assessing cell cycle, β-galactosidase (β- Gal) activity, p21 and p53 expression; doxorubicin was used as acute senescence stimulus to evaluate their ability to react in stressed conditions. Immunomodulatory abilities were studied co-culturing MSCs with peripheral blood mononuclear cells ( PBMCs) and CD4+ cells, in order to establish both their ability to block proliferation in mixed lymphocyte reaction and in regulatory T cells ( Tregs) induction. SSc- MSC showed an increase of senescence biomarkers. Eighty per cent of MSCs were in G0- G1 phase, without significant differences between SSc and HC. SSc- MSCs showed an increased positive β- Gal staining and higher p21 transcript level compared to HC cells. After doxorubicin, β- Gal staining increased significantly in SSc- MSCs. On the contrary, doxorubicin abolished p21 activation and elicited p53 induction both in SSc- and HC- MSCs. Interleukin ( IL)-6 and transforming growth factor ( TGF)-β-related transcripts and their protein levels were significantly higher in SSc- MSCs. The latter maintained their immunosuppressive effect on lymphocyte proliferation and induced a functionally regulatory phenotype on T cells, increasing surface expression of CD69 and restoring the regulatory function which is impaired in SSc. Increased activation of the IL-6 pathway observed in our cells might represent an adaptive mechanism to senescence, but preserving some specific cellular functions, including immunosuppression. [ABSTRACT FROM AUTHOR]

Background. Given the high infant measles mortality rate, there is interest in whether a measles immunization regimen beginning at <12 months of age provides lasting immunity.Methods. Measles-specific immune responses were evaluated in 70 children aged 5–10 years after primary measles vaccine administered at 6, 9, or 12 months.Results. At 5–10 years of age, the stimulation index for measles T-cell proliferation was 11.4 (SE, 1.3), 10.9 (SE, 1.5), and 14.4 (SE 2.1) when the first measles dose was given at 6, 9, or 12 months, respectively. Neutralizing antibody concentration (geometric mean titer [GMT]) in those immunized at 6 months of age was 125 mIU/mL (95% confidence interval [CI], 42–377) in the presence of passive antibodies (PAs) and 335 mIU/mL (95% CI, 211–531) in those without PAs; in those immunized at 9 months, GMTs were 186 mIU/mL (95% CI, 103–335) and 1080 mIU/mL (95% CI, 642–1827) in the presence and absence of PAs, respectively. The GMT was 707 mIU/mL (95% CI, 456–1095) when vaccine was administered at 12 months (P ≤ .04).Conclusions. Measles-specific T-cell responses were sustained at 5–10 years of age regardless of age at time of primary measles immunization. Neutralizing antibody concentrations were lower in cohorts given the first vaccine dose at 6 months of age and in the presence of PAs; however, responses could be boosted by subsequent doses. Starting measles vaccination at <12 months of age may be beneficial during measles outbreaks or in endemic areas. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the anti-inflammatory effects of Artemisia princeps extract in T cells and regulatory T cells stimulated by antigen. The study is investigated by enzyme-linked immunosorbent assay, cell proliferation analysis, and gas chromatography-mass spectrometry. Results show that A. princeps can be used in treating autoimmune diseases and the rejection of organ transplant.

Pseudomonas aeruginosa releases a wide array of toxins and tissue-degrading enzymes. Production of these malicious virulence factors is controlled by interbacterial communication in a process known as quorum sensing. An increasing body of evidence reveals that the bacterial signal molecule N-(3-oxododecanoyl)-l-homoserine lactone (OdDHL) exhibits both quorum-sensing signalling and immune-modulating properties. Recently, yet another quorum-sensing signal molecule, the Pseudomonas quinolone signal (PQS), has been shown to affect cytokine release by mitogen-stimulated human T cells. In the present article we demonstrate that both OdDHL and PQS decrease the production of interleukin-12 (IL-12) by Escherichia coli lipopolysaccharide-stimulated bone marrow-derived dendritic cells (BM-DCs) without altering their IL-10 release. Moreover, BM-DCs exposed to PQS and OdDHL during antigen stimulation exhibit a decreased ability to induce T-cell proliferation in vitro. Collectively, this suggests that OdDHL and PQS change the maturation pattern of stimulated DCs away from a proinflammatory T-helper type I directing response, thereby decreasing the antibacterial activity of the adaptive immune defence. OdDHL and PQS thus seem to possess dual activities in the infection process: as inducers of virulence factors as well as immune-modulators facilitating the infective properties of this pathogen. [ABSTRACT FROM AUTHOR]

Background. Human immunodeficiency virus (HIV) infection and disease are accompanied by decreases in the absolute number and function of Vγ2Vδ2 T cells, suggesting that this subset of cells may play an important role in controlling disease. We performed a cross-sectional study involving HIV-infected former blood donors and assessed the association between Vγ2Vδ2 T cells and markers of disease progression. Methods. Changes in Vγ2Vδ2 T cell count and function were compared between HIV-infected individuals and healthy blood donors using the Mann-Whitney U test. The relationships between Vγ2Vδ2 T cell count, plasma viral load, and CD4 T cell count were analyzed using the Spearman correlation. Results. We found significant positive correlations between CD4 T cell count and both total Vγ2Vδ2 T cell count (P< .001 and functional (isopentenyl— pyrophosphate-responsive) Vγ2Vδ2 T cell count (P< .001).We found significant reverse correlations between viral load and both total Vγ2Vδ2 T cell count (P< .05) and functional Vγ2Vδ2 T cell count (P< .05). Conclusions. The association of Vγ2Vδ2 T cells with disease progression in 146 HIV-infected participants supports the view that intact Vγ2Vδ2 T cell populations are important for controlling HIV disease. [ABSTRACT FROM AUTHOR]

Estrogen regulates thymic development and involution and modulates immune function. Despite its critical role in thymus, as well as in autoimmune disorders, the mechanism by which estrogen affects the thymus is not well understood. We previously reported that the estrogenic soy isoflavone genistein, as well as 17β-estradiol (E2), could induce thymic involution, but genistein effects were only partially mediated through estrogen receptors. To provide insights into mechanisms of estrogenic effects in the thymus, we investigated thymic gene expression changes induced by E2 (125 ng/day) and genistein (1500 ppm in feed) in weanling mice using high-density DNA arrays. We identified several E2-responsive genes involved in thymic development and thymocyte signaling during selection and maturation. Functional characterization indicated effects on genes involved in transcription, apoptosis, and the cell cycle. This study also identified changes in several E2-regulated transcripts essential to maintain immune self-tolerance. E2 upregulated more genes than genistein, while genistein downregulated more genes than E2. Though each treatment regulated several genes not altered by the other, there was considerable overlap in the genes regulated by E2 and genistein. Changes in transcription factors and cell cycle factors were consistent with decreases in cell proliferation induced by both genistein and E2. As indicated by the regulation of non-E2-responsive genes, genistein also induced unique effects through non-estrogenic mechanisms. The specific downregulation of the CD4 coreceptor transcript by genistein was consistent with the decline of CD4+ thymocytes in genistein-treated mice in our previous study. This is the first study identifying E2 and genistein target genes in the thymus. These findings provide new mechanistic insights toward explaining estrogen action on thymocyte development, selection, and maturation, as well as the effects of genistein on prenatal and neonatal thymic development and function. [ABSTRACT FROM AUTHOR]

Integral membrane proteins (IMP) represent a serologically distinct class of mycobacterial antigens which are potent stimulators of human T cells (Mehrotra et al., Clin Exp Immunol 1995; 102:626). The range of IMP from Mycobacterium fortuitum was resolved by continuous elution SDS-PAGE to recover 31 discrete fractions covering bands up to &ap; 58 kD. The fractions, after removal of SDS. were subjected to human T cell proliferation assays for the identification of immunodominant molecule(s). A low molecular weight (<20kD) fraction was able to stimulate T cells from 11 out of 12 donors comprising mainly tuberculoid leprosy patients. The described protocol is well suited to situations where large quantities of antigenic protein mixtures must be processed in order to get the purified molecules/fractions in amounts required for immunoepidemiological studies. [ABSTRACT FROM AUTHOR]

Several T cell defects have been described in the antibody deficiency disease, CVID, but there have been few data on the generation of responses of specific T cell populations to primary neoantigens. We have now used immunization with the neoantigens, keyhole limpet haemocyanin (KLH) and DNP-Ficoll, to evaluate immune responses in CVID patients and normal donors. B and T cell responses were examined 2 and 4 weeks post-immunization. Sera were examined for IgM and IgG anti-KLH responses by ELISA and for anti-DLP-Ficoll activity by haemagglutination. The frequency of KLH-responsive T cells was measured by DNA synthesis in a limiting dilution culture system. Low density cells enriched for dendritic cells were pulsed with KLH and cultured with different numbers of autologous T cells. T cells from normal donors and from patients showed a low frequency of antigen-specific precursor T cells (≤1:200 000). After KLH immunization the frequency increased in normal donors (1:60 000 and 1:30 000 at 2 and 4 weeks, respectively), while in CVID patients it did not change from the preimmunization level. The defect may extend to a dysfunction of antigen-specific cells, rather than being solely due to the reduced numbers of cells, since mean responses of 'positive' wells were also reduced. The serum-specific antibody response paralleled the T cell data, in that all normal donors but none of the CVID patients generated IgG KLH-specific antibodies. CVID patients did produce IgM antibodies against the T-independent DNP-Ficoll, but at a lower level than normal controls. These data show that both T and B cells from CVID patients have defective responses to specific antigen, implicating both lineages in the antibody deficiency. [ABSTRACT FROM AUTHOR]

Chloroquine (Chl) is an anti-rheumatic drug that is widely used in the treatment of rheumatoid arthritis (RA). It seems that T cells are important in the pathogenesis of RA, but it is not known whether Chl acts via inhibition of T cell function. We here present evidence that Chl, just like cyclosporine A (CsA), inhibits T cell proliferation as induced with immobilized αCD3 MoAb in a concentration-dependent manner, at least partly through interfering with the production of IL-2 protein and the induction of IL-2 mRNA. Furthermore, Chl impedes the responsiveness of T cell clones to IL-2 since (1) the inhibition of αCD3 MoAb-induced proliferation by Chl could not be reversed by rIL-2 and (2) Chl directly blocks IL-2-driven proliferation of cloned T cells. Chl appeared to interfere with the internalization (50% inhibition) and degradation (total blockade) of rIL-2. Finally, the combination of Chl and CsA synergistically inhibited T cell proliferation. We conclude that Chl may inhibit functional properties of human T cells, although the drug is 100- to 1000-fold less potent than CsA in inhibiting T cell proliferation and IL-2 production, respectively. It is speculated that the in vitro effects of Chl might be relevant in explaining the anti-rheumatic effect of this drug in patients with RA. [ABSTRACT FROM AUTHOR]

The IL-2/IL-2 receptor (IL-2R) system has been investigated in 64 patients with multiple myeloma (MM), 31 with monoclonal gammopathies of undetermined significance (MGUS) and 20 normal controls. The MM data were related to clinical status by comparing active disease, i.e. at diagnosis and at relapse, and stable disease, i.e. complete remission and off-treatment plateau phase. Serum and urinary values of the soluble IL-2R (sIL-2R) were significantly increased in MM patients compared with normal controls and this increase was related to activity. MM patients with active disease gave significantly higher values than those with stable disease. Compared with normal controls, enriched B cell (but not T cell) preparations from peripheral blood mononuclear cells (PBMC) showed significantly increased proportions of IL-2R+ cells in MM and MGUS. However, the highest proportions were detected in active MM compared with stable MM and MGUS, Also, 16% of all MM patients, as opposed to 9%, of MGUS, had well-defined bone marrow IL-2R+ plasma cell populations. The lowest serum IL-2 values were found in active MM. Serial follow up of serum sIL-2R suggested that this peptide can be used as an additional marker of active malignancy. The data indicate that a disturbance of IL-2/IL-2R system is most pronounced in active MM. These findings may provide clues as to the T cell abnormalities in MM. [ABSTRACT FROM AUTHOR]

T cell reactivity to the 70 and 65 kD (p70 and p65) protein antigens derived from Mycobacterium bovis BCG strain was studied by measuring the proliferative responses of peripheral blood mononuclear cells from members of an isolated Aboriginal community resident in the Torres Straits islands. In the nine index leprosy cases the pattern of responsiveness to the purified antigens paralleled that to whole sonicates from M. leprae and BCG. In the 40 contacts of the index cases, a high correlation was observed between the responses to p70 and p65 as well as to the crude sonicates. Significant T cell responses to the purified antigens. as well as the crude sonicates, were obtained with cells from the majority of contacts. Limiting dilution analysis of precursor frequencies in the contacts confirmed the immunogenicity of the purified antigens and excluded both a mitogenic component and the presence of suppressor cells in those moderate or low responders whose blood contained sufficient precursors to be tested. p70 appeared to be more potent in stimulating a proliferative response than p65 at equivalent protein concentrations. No correlation between responder status to either antigen and disease type was detected in families. These findings provide confirmation of the importance of p70 and p65 as major T cell immunogens in man and indicate that they are both potential candidates for inclusion in a bivalent vaccine for leprosy and tuberculosis. [ABSTRACT FROM AUTHOR]

T cell-derived helper factors can cause activated B cells to proliferate and differentiate into immunoglobulin (Ig)-secreting cells. In the pokeweed mitogen (PWM)-driven Ig production system, the cell-cell interaction necessary for the production of the helper factors was analysed. T cells were pulsed with PWM with or without autologous monocytes. The T cells were then isolated, and incubated for 48 h. Supernatants were tested for their ability to promote differentiation of activated B cells. We found that cell-cell contact between T cells and monocytes for the first 3 h of culture is required to produce the T cell-derived helper factors upon stimulation with PWM. We next examined which T cell subsets are involved in the production of helper factors and which surface molecules either on T cells or on monocytes are responsible for the cell-cell interaction to produce helper factors. A series of monoclonal antibodies were added to T cell subsets with monocytes during the PWM-pulsed period. Although T4+ and T8+ cells could produce almost equal amounts of helper factor activity upon PWM-stimulation, the interactions between T3 and T4 antigens on T4+ cells and Ia-like antigens on monocytes and those between T3 and T8 antigens on T8+ cells and HLA class I antigens on monocytes are respectively essential for the production of T4+ cell-derived and T8+ cell derived helper factors. [ABSTRACT FROM AUTHOR]

A commercially available polyspecific, monomeric IgG preparation suitable for intravenous administration (IgSRK; Sandoglobulin) can inhibit pokeweed mitogen (PWM)-induced proliferation of peripheral blood mononuclear cells (PBMC) by a small, but statistically significant, amount compared to control cultures. Such inhibition could not be demonstrated when PBMC were stimulated with the T cell mitogen phytohaemagglutinin. Surface phenotype analysis of the PWM-stimulated cells indicated that in IgSRK-containing cultures, the proportion of B cells was decreased and the proportion of T cells was increased compared to control cultures. This alteration in T:B ratio was not due to antigenic modulation of B or T cell markers from their surfaces. In addition, IgSRK inhibited the proliferation of T cell-depleted PBMC cultures stimulated by B cell proliferation factors (BCPF) but not by fixed protein A-bearing Staphyococcus aureus strain Cowan I. The capacity to inhibit B cell proliferation was independent of and distinct from its capacity to inhibit B cell differentiation, since IgSRK inhibited the differentiation of a B cell differentiation factor (BCDF)-sensitive line by BCDF (which contains no BCPF activity). IgSRK inhibited PWM-induced generation of cytoplasmic Ig+cells but had no effect on Ig secretion from mature Ig-secreting cells. Taken together, these findings suggest that IgSRK (which contains the IgG fraction from pooled plasma from 2,000 healthy donors) can inhibit T cell-dependent or T cell factor-dependent B cell proliferation and B cell differentiation. [ABSTRACT FROM AUTHOR]

In this study, we sought to elucidate the sequence or events by which mitogenic monoclonal anti-CD3 antibodies (anti-CD3-MoAb) initiate T cell activation. In cultures of monocyte-depleted resting T cells, two anti-CD3-MoAb, OKT3 and anti-Leu 4, induced a state of interleukin 2 (IL-2) receptiveness which culminated in T lymphocyte proliferation when recombinant IL-2 was provided. Evidence that Fc-receptor mediation by monocytes did not contribute to this mitogenesis was supported by studies showing that polyclonal F(ab')2anti-mouse IgG Fc antibody did not alter the magnitude of the IL- 2 driven T cell proliferaitve response, and by the use of T cells from donors whose monocytes were unable to assist in the induction of anti-Leu 4 (IgGl subclass) initiated proliferation. Anti-CD3-MoAb, in the absence of IL-2, induced IL-2 receptor expression on purified T cells, and anti-IL 2 receptor antibodies inhibited T cell proliferation in the presence of this growth factor. Furthermore, following modulation of the CD3 molecular complex in the presence of monocytes, depletion of accessory cells rendered the modulated T cells mitogenically dependent on exogenous IL-2, IL-2 itself did not suffice to promote T cell proliferation in the absence of anti-CD3-MoAb. These results indicate that the binding of monoclonal antibody to CD3 is capable of initiating, in an accessory cell independent manner, premitotic alterations in T cells which can culminate in proliferation when exogenous IL-2 is provided. [ABSTRACT FROM AUTHOR]

During autologous mixed lymphocyte reaction (AMLR) both helper and suppressor T cells capable of regulating B cell responses are generated. The proliferative response of T cells as well as the generation of T suppressor cells in the AMLR of patients with active systemic lupus erythematosus (SLE) is diminished. In contrast, the T helper cells generated in the AMLR show a hyperactivity. The diminished HLA-class II antigen expression observed on non-T cells of SLE origin was restored by treatment of the cells with gamma-interferon (γ-IFN). When tested by immunoglobulin secretion, γ-IFN enhanced T helper cell activity but failed to affect T cell proliferation and T suppressor cell generation in the AMLR derived from patients with SLE. Human recombinant interleukin 2 restores both the proliferative response of T cells and the induction of T suppressor cells in AMLR. [ABSTRACT FROM AUTHOR]

In this study we have examined the interactions between accessory cells (AC) and T cells in response to Con A. Highly purified peripheral blood T cells and AC exposed to a variety of treatments were used. We found that untreated AC provided optima! help for T cell proliferation and this was not mediated by soluble factors since whole cells could not be replaced with supernatants from activated AC. Furthermore, cycloheximide-treated AC were able to supply the accessory signal although unable to elaborate soluble activation factors. To find out more about the accesory signal, we examined the ability of monocytes mildly fixed with glutaraldehyde to supply help. These cells were completely unable to perform as AC, although they were viable and had unaltered surface antigen expression. They could not secrete activation factors, but this alone could not explain their inability to supply help because this function was not restored with the addition of soluble activation factors. This indicated that AC-T cell contact was of prime importance to accessory function. To investigate the possibility that AC work by cross-linking structures on the lymphocyte surface, we attempted to substitute for the soluble Con A plus AC with Con A bound to the surface of erythrocytes. Comparable stimulation was observed, suggesting that the cross-linking of Con A-bound structures on the lymphocyte surface generates the accessory signal. [ABSTRACT FROM AUTHOR]

In the burn patient, the mechanisms leading to impaired T lymphocyte activity are unclear. The capacity for T cell proliferation and the expression of Tac antigen (IL-2 receptor) was assessed during the post-burn period in patients with injuries ranging from 5-68%, total body surface area. T cell-dependent (polyclonal) immunoglobulin synthesis, mixed lymphocyte reaction and Interleukin-2 production were also determined in these patients and correlated with survival. Surviving patients demonstrated a transient reduction while terminal patients exhibited a permanent reduction in the number of Tac lymphocytes, unrelated to the absolute number of T cells, during the post-burn period. The reduced percentage of lL-2 receptor-expressing T cells coincided with the suppressed antibody response and reduced alloreactivity. Although the concentration of IL -2 was decreased in all patients throughout the hospitalization period, surviving patients showed a gradual increase in its production while terminal patients gradually decreased to undetectable levels. Exogenous recombinant IL-2 induced a significant enhancement of in-vitro polyclonal immunoglobulin production and blastogenesis in the mixed lymphocyte reaction in immunosuppressed patients who demonstrated up to 50%, reduction in the percentage of IL-2 receptor positive cells. Thus, the reduced capacity for production of and response to lL-2 alter thermal injury may lead to the immunosuppression due to a lack of T lymphocyte clonal expansion. The permanent nature of this detect in patients who died from fatal sepsis may suggest a causative relationship. [ABSTRACT FROM AUTHOR]

The phenotypic and functional characteristics of the leukaemic cells from one patient with T suppressor ALL were studied at the time of diagnosis and in relapse. At the time of diagnosis, the phenotype corresponded to the intermediate stage between the cortical and medullary phases of normal thymocyte differentiation with a high proportion of T8+ cells (E-R+, TdT+, C3Br-, T3-, T4-, T6+, T8+ +, T10+). Functionally, the cells did not respond to mitogens but mediated strong suppressor activity to allogeneic B-cells, as measured in a reverse haemolytic plaque test. Clinically, the patient exhibited the uncommon feature of hypogammaglobulinaemia. Induction therapy led to complete remission, which continued for 12 months. In the relapse, the phenotype remained essentially stable except for a dramatic decrease of the T8+ cell fraction and an increase of the T10+ cell fraction. Functionally, the suppressor activity was completely lost, indicating a close correlation between phenotype and functional activity in this leukaemic cell population. [ABSTRACT FROM AUTHOR]

Human T lymphocytes cultured in vitro for 5 days with Candida albicans purified polysaccharide (MPPS) produce and antigen non-specific inhibitor (nsINH) which blocks ceil proliferation when added at the beginning of the culture. The antigen presenting function of antigen pulsed adherent cells (macrophages) is significantly impaired by incubation in nsINH. Further analysis shows that nsINH blocks the production of interleukin-1 both from human mononuclear cells stimulated with lipopolysaccharide. Furthermore, the production of interleukin-2 (IL-2) is also suppressed when MPPS stimulated cells are cultured in presence of nsINH. However nsINH does not affect the appearance of lL-2 responsive cells as the addition of gibbon IL-2 to the culture fully reverses the suppressive effect of nsINH on blast transformation. [ABSTRACT FROM AUTHOR]

The type of leprosy which develops after infection with Mycobacterium leprae is influenced by the presence or absence of HLA-DR3, as has been demonstrated in an ethnic group originating from Surinum. In the present study we investigated in this same ethnic group the role of HLA-DR. and of HLA-DR3 in particular, in monocyte-T cell interactions during leprosy specific proliferative responses in vitro. HLA-DR3 heterozygous T cells from tuberculoid leprosy patients were cultured with antigen and either HLA-DR3 positive or HLA-DR3 negative homozygous H LA-DR compatible allogeneic monocytes as antigen presenting cells (APCs), T cell proliferative responses with DR3 homozygous monocytes as APCs. were observed to be decreased as compared to T cell proliferative responses with DR3 negative homozygous monocytes as APCs. Furthermore, although the leprosy specific monocyte-T cell interactions were shown to be restricted for HLA-DR, in the anti-MLW-1 response HLA-DR3 appeared to function as a restricting element poorly or not at all. These observations may imply, that an in vitro correlate has been found for an (HLA associated) genetic control of leprosy in vivo. [ABSTRACT FROM AUTHOR]

Interleukin-1 (IL-1) is a monocyte product with diverse amplifying effects on immune cell reactions. We have studied 16 untreated SLE patients to determine the production of IL-1 by their monocytes under the stimulus of E. Coli lipopolysaccharide (LPS) or phorbol myristate acetate (PMA) and measured by the capacity of their supernatants to augment normal autologous mixed lymphocyte cultures (AMLR) or to replace accessory cells in Con A-induced proliferation of T lymphocytes. Concurrently, we studied the response of T lymphocytes from these same patients to IL-1 by its capacity to increase the percentage of stable E rosette forming cells and by the enhancement of T cell proliferation in AMLR. Monocytes from SLE patients produced significantly less IL-l activity than those of age matched controls, regardless of the stimulus (LPS or PMA), as well as of the indicator system. All patients with active disease and seven of the 10 patients with inactive disease had decreased production of IL-1 activity as determined by at least one method. Response of T lymphocytes from SLE patients to IL-1 produced by normal monocytes was also found decreased as compared to normals. This defect was more marked in the T cells from patients with active than in those of patients with inactive disease. These findings indicate that the immunoregulatory disturbance that SLE patients have encompasses monocytes as well as T and B lymphocytes and suggest that the defect is either multicentric or originates in the stem cell. [ABSTRACT FROM AUTHOR]

Among 12 cases of chronic T lymphoproliferative disorders we observed, six patients showed an expansion of mononuclear cells with azurophilic granules usually referred to as large granular lymphocytes or LGL. Cells obtained from five patients with these abnormal LGL proliferations were studied with several surface markers including their reactivity with the HNK-1 monoclonal antibody reported to be specific for LGL. Ceils in four out of five cases were HNK-t positive. Whereas normal LGL have been reported to be unreactive with several T cell markers, three cases showed the co-existence of HNK-1 and surface markers expressed by T cells. Two cases were characterized by the proliferation of OKT8 cells. Cells from one patient were HNK-l positive but did not express T or monocytic antigens. These cells were apparently not completely mature since 2-naphthyl acetate acid esterase activity was negative. Cells from the remaining case were HNK-1 negative and positive for T and monocytic antigens. An increase of OKT-10 cells was observed in only one patient. Our data indicate that proliferations of LGL represent a remarkable proportion of the rare cases of sheep erythrocyte rosetting chronic lymphocytic leukaemias or lymphomas. Besides the morphology of LGL, the rosetting ability and the negativity for peroxidase, cells from these cases showed a vast heterogeneity of other structural and functional markers, possibly reflecting different stages in the maturation of these cells. The HNK-1 monoclonal antibody proved to bean important marker in the identification of these cases. [ABSTRACT FROM AUTHOR]

Peripheral blood mononuclear cells (PBMC), obtained from BCG vaccinated healthy donors, were induced to proliferation by BCG for five days in vitro. When re-exposed to BCG, they failed to proliferate. However, they partially retained the ability to respond to Con A and allogeneic cells. The addition of graded numbers of such cultured cells to fresh autologous PBMC suppressed their proliferative response to BCG. These suppressor cells could also inhibit the proliferation of fresh cells to other mycobacterial antigens, both in particulate form, i.e. Mycobacterium leprae, or in soluble form, i.e. PPD and SPA30. However, these pre-cultured cells did not inhibit the response of fresh cells to non-specific mitogens, i.e. Con A and alloantigens. The inhibition of the response to non-mycobacterial soluble antigens, i.e. tetanus toxoid (TT) and diphtheria toxoid (DT) varied with little suppression in some individuals and stronger suppression in others. The suppression to BCG was found to be mediated by T cells. Subfractionation of T cells by monoclonal antibodies OKT4 and 0KT8 allocated the suppressor cells to the 0KT4+ class of T cells. The suppression in the autologous system was quite strong, whereas it was much weaker in allogeneic systems. [ABSTRACT FROM AUTHOR]

A therapeutic trial of a pan-T monoclonal antibody is described in a patient with a low grade mature T cell proliferation and haemopoietic suppression. The study shows that non-complement fixing IgGl antibodies can be highly effective opsonins, and the dose required can be estimated from in vitro studies. It is demonstrated that therapeutic failure occurred due to the appearance of anti-mouse antibodies and not to anligenic modulation or reticuloendothelial blockade. The literature is reviewed and the potential role of serotherapy in malignant disorders is discussed. [ABSTRACT FROM AUTHOR]

Previously, we described a system allowing the study of murine T cell-dependent proliferative responses to Trypanosoma brucei antigens. It was observed that T. brucei-specific T cells could be demonstrated in the regional lymph nodes of primed mice for only 2 to 3 weeks following priming. The results of the present study indicate that this inability to demonstrate a long-lived memory response is due to an immunosuppressive effect of the resulting T. brucei infection. The exact mechanism of the suppression is not known, and appears to function in the absence of demonstrable suppressor cells. Since the T cell responses are strictly dependent on the presence of macrophages, we have investigated whether the loss in responsiveness is due to a defect in the T cell population, or to a loss of macrophage function. Our results show that T cells taken from mice 3 weeks after priming with T. brucei are unable to mount a proliferative response in the presence of a normal macrophage population, and conversely that macrophages taken 3 weeks after infection with T. brucei are unable to elicit a normal proliferative response using a competent primed T cell population. Thus these results indicate that both populations are affected by the parasite infection. [ABSTRACT FROM AUTHOR]

A new case of hairy-cell leukaemia (HCL) in which the hairy cells (HCs) formed spontaneous sheep erythrocyte (E) rosettes is described, and this E-rosette formation is shown to be an active process independent of surface immunoglobulin (SIg). Sequential studies with a panel of markers of this and of a case of HCL with T-cell features previously described from this laboratory show that both these cases, at certain times of study, possessed combined T- and B-cell features. Extensive follow-up study revealed wide fluctuations in the surface phenotype of peripheral blood (PB) mononuclear cells, while the total leucocyte count remained stable. At various times, the PB mononuclear cells showed the following phenotypes: E+SIg+yFc+C3-E-SIgyFcC3-, E-SIg-yFC+yFc+C3-, E+SIg-yFc+/-C3- and the significance of these phenotypic changes is discussed. The importance of sequential studies with a panel of markers in the characterization of lymphoproliferative disorders is emphasized. [ABSTRACT FROM AUTHOR]

The article reports that the use of lymphocyte markers in the assessment of HIV infection has largely centered on the well documented progressive loss of the CD4+ T cell population throughout the course of HIV infection [1,2]. One of the great strengths of the CD4 count is its biological plausibility as a reflection of HIV pathogenesis. The CD4+ T cell is the main target for HIV infection and the accumulating deficiency can be largely accounted for by the progressive and selective deletion of this key population of lymphocytes [3].

Immunological adjuvants, such as bacterial LPS, increase the mRNA levels of the IkB-related NF-κB transcriptional transactivator, Bcl-3, in activated T cells. Adjuvants also increase the life expectancy of activated T cells, as does over-expression of Bcl-3, suggesting that Bcl-3 is part of the pathway whereby adjuvants affect T cell lifespans. However, previous reports, confirmed here, show that adjuvants also increase the life expectancies of Bcl-3-deficient T cells, making Bcl-3’s role and effects in adjuvant-induced survival uncertain. To investigate the functions of Bcl-3 further, here we confirm the adjuvant-induced expression of Bcl-3 mRNA and show Bcl-3 induction at the protein level. Bcl-3 was expressed in mice via a transgene driven by the human CD2 promoter. Like other protective events, over-expression of Bcl-3 slows T cell activation very early in T cell responses to antigen, both in vitro and in vivo. This property was intrinsic to the T cells over-expressing the Bcl-3 and did not require Bcl-3 expression by other cells such as antigen-presenting cells. [ABSTRACT FROM AUTHOR]

IL-7 signaling is essential for optimal CD8 T cell function, homeostasis and establishment of memory. We have previously shown decreased expression of the IL-7 receptor α-chain (CD127) on CD8 T cells from HIV-infected patients with active viral replication. We have also shown that soluble HIV Tat protein specifically down-regulates CD127 on the surface of CD8 T cells and impairs cell proliferation and cytolytic potential following stimulation with IL-7 in vitro. We now show that soluble HIV Tat protein and IL-7 at near physiologic concentrations act synergistically to suppress CD127 expression. While soluble HIV Tat protein and IL-7 both independently reduce CD127 expression on the surface of CD8 T cells, Tat concentrations of 10 μg ml−1 and IL-7 concentrations of 500 pg ml−1 are required in vitro to have an appreciable effect. However, where 0.5 μg ml−1 of Tat has no effect on CD127 expression and 200 pg ml−1 of IL-7 decreases CD127 by only 14%, these two together at these same concentrations induce a 35% reduction in CD127 expression after 24 h. Inhibition of Janus kinase (JAK) completely blocks IL-7s ability to down-regulate CD127 on the surface of CD8 T cells and also abolishes synergy with Tat. Interestingly, while Tat acts synergistically with IL-7 to reduce CD127 expression, it antagonizes IL-7-induced cell proliferation and Ki-67 expression and has no effect on IL-7-mediated signal transducer and activator of transcription 5 (STAT5) phosphorylation or expression of the anti-apoptotic gene Bcl-2. Thus, by affecting different IL-7 signal transduction pathways, HIV Tat protein is able to impair both CD8 T cell activation and proliferation without inducing apoptosis. [ABSTRACT FROM AUTHOR]

Monomorphic MHC class II determinants are attractive targets for immunomodulation. HLA-DR ligation on antigen-presenting cells (APCs) can dramatically alter their function or induce cell death. In monocytes, HLA-DR triggering diminishes their capacity to stimulate T cell proliferation. To further investigate this monocyte-dependent T cell inhibition, we activated human T cells ± HLA-DR triggering on APCs and tested whether this can induce T cell anergy. Only anti-HLA-DR, but not anti-proliferative control agent anti-CD45, could modulate monocytes in primary cultures with stimulated T cells, so that T cells were hyporesponsive during re-stimulation. Cell separation studies demonstrated that HLA-DR ligation on monocytes is sufficient for mediating T cell anergy. Secretion of monokines was severely reduced after primary culture. Monocytes anergized independently of soluble factors. Extracellular signal-regulated kinase (ERK) phosphorylation occurred early with anti-HLA-DR, but late with anti-CD45 antibody. However, ERK inhibition did not reverse the T cell-anergizing potential of HLA-DR-ligated monocytes implicating other signaling pathways involved in tolerance induction. When analyzing the anergized T cells, they were refractory to exogenous IL-2 and characterized by defective secretion of various cytokines. Expression of CD25, CD28, intracellular CD3ζ and CTLA-4 was reduced. The hyporesponsive T cells up-regulated cell-cycle inhibitors p27kip1 and p21cip1 in correlation with human T cell anergy. In contrast, caspase-3 and -8, known to contribute to T cell proliferation, were equally decreased in anti-HLA-DR- and anti-CD45-inhibited cultures. In summary, anti-HLA-DR treatment can generate tolerogenic monocytes transmitting T cell anergy that may be exploited for future immunomodulatory strategies to treat immune-mediated disease states. [ABSTRACT FROM AUTHOR]

Summary Diets enriched in n-3 polyunsaturated fatty acids (PUFA) suppress several functions of murine splenic T cells by acting directly on the T cells and/or indirectly on accessory cells. In this study, the relative contribution of highly purified populations of the two cell types to the dietary suppression of T cell function was examined. Mice were fed diets containing different levels of n-3 PUFA; safflower oil (SAF; control containing no n-3 PUFA), fish oil (FO) at 2% and 4%, or 1% purified docosahexaenoic acid (DHA) for 2 weeks. Purified (>90%) T cells were obtained from the spleen, and accessory cells (>95% adherent, esterase-positive) were obtained by peritoneal lavage. Purified T cells or accessory cells from each diet group were co-cultured with the alternative cell type from every other diet group, yielding a total of 16 different co-culture combinations. The T cells were stimulated with either concanavalin A (ConA) or antibodies to the T cell receptor (TcR)/CD3 complex and the costimulatory molecule CD28 (α CD3/α CD28), and proliferation was measured after four days. Suppression of T cell proliferation in the co-cultures was dependent upon the dose of dietary n-3 PUFA fed to mice from which the T cells were derived, irrespective of the dietary treatment of accessory cell donors. The greatest dietary effect was seen in mice consuming the DHA diet (P = 0·034 in the anova; P =0·0053 in the Trend Test), and was observed with direct stimulation of the T cell receptor and CD28 costimulatory ligand, but not with ConA. A significant dietary effect was also contributed accessory cells (P = 0·033 in the Trend Test). We conclude that dietary n-3 PUFA affect TcR-mediated by T cell activation by both direct and indirect (accessory cell) mechanisms. [ABSTRACT FROM AUTHOR]