T-cell Proliferative Responses Research Articles

Lenalidomide enhances anti-myeloma cellular immunity

Lenalidomide is an effective therapeutic agent for multiple myeloma that exhibits immunomodulatory properties including the activation of T and NK cells. The use of lenalidomide to reverse tumor-mediated immune suppression and amplify myeloma-specific immunity is currently being explored. In the present study, we examined the effect of lenalidomide on T-cell activation and its ability to amplify responses to a dendritic cell-based myeloma vaccine. We demonstrate that exposure to lenalidomide in the context of T-cell expansion with direct ligation of CD3/CD28 complex results in polarization toward a Th1 phenotype characterized by increased IFN-γ, but not IL-10 expression. In vitro exposure to lenalidomide resulted in decreased levels of regulatory T cells and a decrease in T-cell expression of the inhibitory marker, PD-1. Lenalidomide also enhanced T-cell proliferative responses to allogeneic DCs. Most significantly, lenalidomide treatment potentiated responses to the dendritic cell/myeloma fusion vaccine, which were characterized by increased production of inflammatory cytokines and increased cytotoxic lymphocyte-mediated lysis of autologous myeloma targets. These findings indicate that lenalidomide enhances the immunologic milieu in patients with myeloma by promoting T-cell proliferation and suppressing inhibitory factors, and thereby augmenting responses to a myeloma-specific tumor vaccine.

Expression of a versatile DC-targeting fusion protein using an Adenovirus expression system

The importance of viral and tumour vaccines in eliciting elicit strong CD8+ T-cell responses has been widely acknowledged. Strategies exploring ways to enhance CD8+ T-cell responses have been developed, including targeting of vaccine antigens to dendritic cell (DC) receptors to access to the cross presentation pathway. Many DC endocytic receptors could potentially lead to augmented CD8+ T-cell responses if antigens were targeted directly to them, however only a few receptors have been explored because current targeting reagents are limited in the number of receptors that they are able to target. Consequently, this study describes the production and purification of a streptavidin-fusion protein that provides a versatile and efficient means to target antigen to more than one DC receptor. A model antigen gene, CMV pp65, and a streptavidin core gene, were spliced together using an overlap-extension PCR technique. The resulting fusion gene was cloned into a vector allowing expression in an Adenovirus-based expression system. Expression was verified and optimised before Ni-NTA affinity chromatography purification. Evaluation of pp65-streptavidin immunogenicity revealed that it elicits similar levels of CD8+ T-cell proliferative responses as pp65 and is able to effectively target specific DC receptors when used in addition to biotinylated receptor-specific antibodies. Additionally, enhancement of CD8+ T-cell responses was shown after directing pp65-strep to selected DC receptors in preliminary in vitro experiments. Collectively, this highlights the ease of production of a streptavidin-fusion protein, and demonstrates its use as a promising strategy to evaluate numerous DC receptors as potential targets in vaccine strategies.

Naturally-Acquired Influenza-Specific CD4+ T-Cell Proliferative Responses Are Impaired in HIV-Infected African Adults

BackgroundSeasonal influenza has been associated with greater morbidity and mortality in AIDS patients. Highly-active antiretroviral therapy (HAART) has led to some reduction in influenza-related complications but the nature of naturally-acquired T-cell immunity to influenza virus in an African setting, and how this changes with immune reconstitution following HAART is unknown. We measured influenza-specific CD4+ T-cell immunity in unimmunized HIV-infected Malawian adults and then investigated immune reconstitution following HAART.MethodsPeripheral blood mononuclear cells were isolated from HIV-infected and HIV-uninfected Malawian adults. CFSE proliferation and CD154 expression flow cytometry-based assays were used to measure influenza-specific CD4+ T-cell immunity.ResultsWe found lower naturally-acquired proliferative influenza-specific CD4+ T-cell responses in AIDS patients that was also present in asymptomatic HIV-infected adults with relatively high CD4 counts (>350 cells/µl). Influenza-specific CD4+ T-cell immune reconstitution in HIV-infected patients on HAART for 12 months was poor despite a marked reduction in viral load and an increase in CD4 count. This poor immune reconstitution was characterised by a low influenza-specific proliferative CD4+ T-cell response and reduced proportions of CD154-expressing influenza-specific CD4+ T-cells in peripheral blood.ConclusionOur data suggest that asymptomatic HIV-infected adults may also be at risk of influenza-related complications and that HAART alone may not circumvent this risk in AIDS patients. This study highlights the need to identify possible interventions early in HIV infection to reduce the risk of influenza and to intensify influenza surveillance in these susceptible African populations.

Foamy Virus Vector-mediated Gene Correction of a Mouse Model of Wiskott–Aldrich Syndrome

The Wiskott-Aldrich syndrome (WAS) is an X-linked disorder characterized by eczema, thrombocytopenia and immunodeficiency. Hematopoietic cell transplantation can cure the disease and gene therapy is being tested as an alternative treatment option. In this study, we assessed the use of foamy virus (FV) vectors as a gene transfer system for WAS, using a Was knockout (KO) mouse model. Preliminary experiments using FV vectors expressing the green fluorescent protein under the transcriptional control of the endogenous WAS promoter or a ubiquitously acting chromatin opening element allowed us to define transduction conditions resulting in high (>40%) and long-term in-vivo marking of blood cells after transplantation. In following experiments, Was KO mice were treated with FV vectors containing the human WAS complementary DNA (cDNA). Transplanted animals expressed the WAS protein (WASp) in T and B lymphocytes, as well as platelets and showed restoration of both T-cell receptor-mediated responses and B-cell migration. We also observed recovery of platelet adhesion and podosome formation in dendritic cells (DCs) of treated mice. These data demonstrate that FV vectors can be effective for hematopoietic stem cell (HSC)-directed gene correction of WAS.

Sexual dimorphisms in the immune system of catechol-O-methyltransferase knockout mice

The enzyme catechol-O-methyltransferase (COMT) is part of the metabolic pathway of 17β-estradiol, converting 2-hydroxyestradiol to 2-methoxyestradiol. We recently showed that administration of the COMT product 2-methoxyestradiol has anti-inflammatory and anti-osteoporotic effects. We have now investigated whether COMT affects the immune system, by immunologically phenotyping COMT deficient (COMT−/−) mice.Immunoglobulin production, T lymphocyte proliferation, NK cell cytotoxicity and oxygen radical production were assessed.In male COMT−/−-mice, the total number of T-, and B-lymphocytes from spleen increased but the T-cell proliferative response decreased. The NK cell population shifted toward less mature cells, leaving cytotoxic capacity unaffected. In COMT−/−-females, a higher frequency of neutrophils was found but the oxygen radical production was unaltered.In conclusion, only minor changes of the immune system were seen in COMT deficient mice, and the changes were usually seen in males. This study provides clues into how COMT activity, and hence gender differences, affects the immune system.

Will There Be a Vaccine to Protect Against the Hepatitis C Virus?

The discovery of the hepatitis C virus (HCV) more than 20 years ago offered the promise of a vaccine to prevent life-long persistent infection and associated progressive liver diseases. To date, only a few candidate vaccines have been tested in human beings for safety and immunogenicity. None have yet been assessed for prevention of HCV infection or persistence. In the event that current vaccine candidates do not advance to efficacy trials, or fail to provide protection against HCV, the pipeline of alternatives appears to be very small. With a sharp reduction in new HCV infections because of effective screening of the blood supply, and the possibility that acute and chronic infections will be curable because of improving therapy, 1 it is reasonable to ask if the considerable effort to develop a preventive HCV vaccine still is needed. The answer is almost certainly affirmative. Vaccines that protect against hepatitis A and B virus infections were first targeted to health care workers. The value of adding a vaccine to prevent accidental HCV infection in the workplace is clear. A preventive HCV vaccine would have a far greater impact on public health. The need is highlighted by a concerning increase in new infections among adolescents and young adults recently observed in Massachusetts. Between 2002 and 2009, confirmed HCV cases shifted from a unimodal to bimodal age distribution because infection rates increased among those aged 15‐24 years, however, they continued to decline among older adults. 2 The increase in new HCV infections in the younger age group is attributable to needle sharing and probably will be confirmed elsewhere in the United States and in other countries. Without a preventive vaccine it will be difficult to contain a smoldering epidemic of unrecognized HCV infections involving those who are least likely to seek or receive antiviral therapy, no matter how effective. A vaccine also would be highly beneficial in regions of the world with high HCV endemicity, for instance, in countries such as Egypt where it has proved difficult to interrupt several decades of HCV transmission by standard public health measures.3 When considering the need for a vaccine, it is important to remember that symptoms of acute hepatitis are often mild or inapparent, therefore years can elapse before infection is recognized and treated. Serious liver disease can develop during that time and the infection remains transmissible to others by high-risk practices. Perhaps as importantly, only a very small percentage of HCV infections were ever treated with pegylated type I interferon and ribavirin. 4 New direct-acting antivirals will improve this situation, but only with a much greater effort to diagnose the large number of unrecognized infections and provide access to costly treatment that must be managed carefully to prevent emergence of resistant viral variants.

HIV Controllers Are Distinguished by Chemokine Expression Profile and HIV-Specific T-Cell Proliferative Potential

HIV controllers demonstrate a natural ability to control HIV replication in the absence of antiretroviral therapy. We performed a comprehensive evaluation of inflammation and T-cell activation in a demographically unique cohort of HIV controllers and noncontrollers. Plasma concentrations of 22 cytokines and chemokines were evaluated using a multiplex bead array approach. Multicolor flow cytometry was used to measure baseline levels of T-cell activation and regulatory T cells (Tregs) and HIV-specific T-cell cytokine (interferon γ, interleukin 2) and proliferation responses. HIV controllers were characterized by elevated macrophage inflammatory protein 1α and low levels of interferon γ-induced protein 10, monocyte chemotactic protein 1, and Transforming growth factor beta. Activated (CD38(+) HLA DR(+)) CD4(+) and CD8(+) T cells were reduced in HIV controllers relative to noncontrollers. HIV controllers and noncontrollers had comparable proportions of Tregs within the CD4(+) T-cell compartment, but absolute Treg counts were depleted in noncontrollers. Absolute Treg counts correlated inversely with T-cell activation. Proliferative CD4(+) and CD8(+) T-cell responses directed against HIV gag epitopes were found most frequently among HIV controllers with the lowest viral loads (elite controllers) and were rarely detected among noncontrollers, supporting a relationship between HIV-specific T-cell proliferation and viral control. Collectively, these data suggest a model in which HIV controllers maintain low levels of viral replication through robust HIV-specific T-cell responses in an environment of low inflammation and reduced availability of activated target cells.

Effects of ultraviolet light on human serum 25-hydroxyvitamin D and systemic immune function

Many immune-mediated diseases are associated with low levels of vitamin D and sunlight. UV light or supplementation with vitamin D can increase regulatory T-cell activity and prevent animal models of autoimmune disease. Increasing population vitamin D levels may therefore alleviate the burden of human immune-mediated disease. To determine the responses of circulating 25-hydroxyvitamin D [25(OH)D] levels, regulatory T-cell numbers, and immune function to UV light exposure in patients being treated for skin disease. Twenty-four subjects with skin disease from the North of Scotland were recruited between December and March. At baseline, and after 2 and 4 weeks of narrowband UV light exposure, we measured peripheral blood 25(OH)D level, numbers of regulatory T cells (CD4(+)CD25(hi)FoxP3(+)), and T-cell proliferative and cytokine responses to anti-CD3/CD28 stimulation. Median (interquartile range) narrowband UV-B received during the study was 39.1 (30.9) as standard erythema dose, comparable to a quarter of the median summer sunlight exposure received locally. This increased the 25(OH)D level from a mean ± SD of 34 ± 17 nmol/L to 58 ± 16 nmol/L after 2 weeks and 78 ± 19 nmol/L after 4 weeks. The mean proportion of circulating regulatory T cells increased from 0.5% to 1.6% CD3(+) cells, which significantly correlated with the increased 25(OH)D level. UV treatment was also followed by reduced proliferative and IL-10 responses to anti-CD3/CD28 independent of the 25(OH)D level. Narrowband UV light reduces systemic immune responsiveness via the induction of regulatory T cells. Light and 25(OH)D levels may affect particular immune functions independently. The levels of serum 25(OH)D over which these effects are apparent should guide future interventions.

Hyaluronic acid viscosupplements from avian and non‐mammalian sources exhibit biocompatibility profiles with unique, source‐specific, antigenic profiles

The objective of this study was to evaluate and compare the biocompatibility profiles of hyaluronic acid (HA) viscosupplements from avian and non-mammalian sources. Inflammatory and immune reactions were assessed in models of both clinically relevant and stringent immunological exposure conditions. Experiments were conducted to evaluate tissue reactions and immunological responses and assess antibody formation with the capacity to bind directly to and cross-react with the different viscosupplements. Mice were exposed to viscosupplements using the air pouch inflammation model and specific immunization using Freund's complete adjuvant (FCA). Murine pouch membrane tissue reactions revealed generally mild to moderate responses, with cellular infiltration and cytokine profiles of pouch tissue characteristic of predominantly fibroblastic responses rather than marked inflammatory reactions. In vitro testing indicated that pouch injections did not elicit detectable T-cell proliferative responses, while antibody assays revealed that mice immunized with viscosupplements in FCA and subsequently boosted were capable of mounting an antibody response with a range of specificities. High reactivity to avian serum albumin was seen in sera from mice injected with HA from an avian source, while low positive reactivity to the bacterial antigen Staphylococcal Lipotechoic Acid was observed in sera from mice injected with HA from bacterial sources. These specificities did not indicate any propensity to cross-react, suggesting that patients with adverse immune responses to HA from an avian source should be unresponsive to subsequent injection with HA from a non-avian source. Overall, the findings demonstrate that viscosupplements exhibit good biocompatibility profiles in the murine air pouch, but when provoked to elicit immunological reactions exhibit unique antigenic spectra. These findings suggest that an immunologically mediated immune reaction directed against avian proteins should not necessarily be a contraindication for the administration of non-avian viscosupplements.

T-cell proliferation and forkhead box P3 expression in human T cells are dependent on T-cell density: physics of a confined space?

T-cell proliferation rates in vitro depend on factors including initial T-cell number, dose of stimulus, culture time, and available physical space. The role of forkhead box P3 (FoxP3) in the identification of T cells with a regulatory phenotype remains controversial in humans. Through 5-carboxyfluorescein diacetate succinimidyl ester labeling of human T cells and subsequent culture of different numbers of T cells and antigen-presenting cells (APC), we studied proliferative T-cell responses and FoxP3 expression in divided T cells. T-cell proliferation rates depended on initial T-cell/APC numbers. Proliferation rates decreased when high initial T-cell numbers were increased. FoxP3 expression was expressed exclusively in virtually all divided T cells cultured at high T-cell densities, irrespective of their CD4 nature or cytokine content, and was coexpressed with T-bet. However, when T cells were cultured on larger surfaces or at lower initial numbers, FoxP3 expression was not induced in divided T cells, even when most of the cells had undergone cell division. FoxP3(+) T cells generated at high cell densities did not elicit a suppressive phenotype and FoxP3 expression was subsequently lost in time when the stimulus was removed. Therefore, caution should be observed in the use of FoxP3 expression to identify regulatory T cells in humans because its expression may be only a consequence of activation status in a restricted environment.

T-cell autoreactivity to citrullinated autoantigenic peptides in rheumatoid arthritis patients carrying HLA-DRB1 shared epitope alleles

IntroductionAnti-citrullinated peptide antibodies are found in rheumatoid arthritis (RA) patients with HLA-DRβ chains encoding the shared epitope (SE) sequence. Citrullination increases self-antigen immunogenicity, through increased binding affinity to SE-containing HLA-DR molecules. To characterise T-cell autoreactivity towards citrullinated self-epitopes, we profiled responses of SE+ healthy controls and RA patients to citrullinated and unmodified epitopes of four autoantigens.MethodsWe compared T-cell proliferative and cytokine responses to citrullinated and native type II collagen 1,237 to 1,249, vimentin 66 to 78, aggrecan 84 to 103 and fibrinogen 79 to 91 in six SE+ healthy controls and in 21 RA patients with varying disease duration. Cytokine-producing cells were stained after incubation with peptide in the presence of Brefeldin-A.ResultsAlthough proliferative responses were low, IL-6, IL-17 and TNF were secreted by CD4+ T cells of SE+ RA patients and healthy controls, as well as IFNγ and IL-10 secreted by RA patients, in response to citrullinated peptides. Of the epitopes tested, citrullinated aggrecan was most immunogenic. Patients with early RA were more likely to produce IL-6 in response to no epitope or to citrullinated aggrecan, while patients with longstanding RA were more likely to produce IL-6 to more than one epitope. Cytokine-producing CD4+ T cells included the CD45RO+ and CD45RO- and the CD28+ and CD28- subsets in RA patients.ConclusionProinflammatory cytokines were produced by CD4+ T cells in SE+ individuals in response to citrullinated self-epitopes, of which citrullinated aggrecan was most immunogenic. Our data suggest that the T-cell response to citrullinated self-epitopes matures and diversifies with development of RA.

Delayed‐type hypersensitivity responses to HIV Gag p24 relate to clinical outcome after peptide‐based therapeutic immunization for chronic HIV infection

Therapeutic immunization in chronic HIV infection aims to induce durable, HIV-specific immune responses capable of controlling disease progression, but immunological correlates of clinical efficacy are poorly defined. We have previously immunized 38 patients with a mixture of four short Gag p24-like conserved peptides (Vacc-4x) targeting skin dendritic cells. Antiretroviral treatment (ART) was initially stopped after completed immunizations and resumed post-protocol during regular clinical follow-up according to current guidelines. Four years after enrolment, Vacc-4x-specific cellular responses were evaluated in vivo by delayed-type hypersensitivity (DTH) skin test, and in vitro by a T-cell proliferation assay. Kaplan-Meier product-limit estimates were used to analyse time until ART was resumed. Peptide-specific cellular immune responses induced by Vacc-4x had persisted 4 years after the last immunization in terms of unchanged DTH independent of ART and detectable proliferative T-cell responses which correlated to the native peptides (R = 0.73, p = 0.01). Circulating bifunctional (IFN-γ and IL-10) Vacc-4x-specific T-cell clones were detected in 43% of patients. Subjects with the strongest post-immunization DTH responses appeared to start ART later compared with DTH low responders (p = 0.07). These data suggest that DTH responses should be further evaluated as a new and convenient tool for predicting clinical efficacy in trials testing therapeutic immunizations.

In vitro studies on immunotoxic potential of Orange II in splenocytes

Orange II, an azo dye, is not permitted in food preparations, but high levels of the dye have been detected in different food commodities. Though there are reports on the toxicity of Orange II but knowledge based on the immunomodulatory properties of Orange II is scanty. The present investigation was undertaken to study the in vitro immunotoxic potential of Orange II in splenocytes. Splenocytes were isolated, cultured and subjected to immunophenotypic analysis, mixed lymphocyte reaction (MLR) assay or stimulated with lipopolysaccharide (LPS) or concanavalin A (Con A) for 72 h. The supernatant was collected for cytokine assays. Orange II showed cytotoxic effects at 100–1000 μg/ml concentrations and 50 μg/ml was determined as the highest non-cytotoxic dose. Orange II at the non-cytotoxic dose (50 μg/ml) significantly altered the relative distribution of T and B-cells, MLR response and the mitogen induced proliferative response of T-cells and B-cells. Consistent with the hypo-responsiveness of the T and B-lymphocytes, Orange II induced a concomitant decline in the secretion of cytokines IL-2, IL-4, IL-6, IFN-γ, TNF-α and IL-17. On the contrary, there was an increase in the production of IL-10, an anti-inflammatory regulatory cytokine, which may be one of the causative factor for immunosuppressive property of Orange II. These results suggest that non-cytotoxic dose of Orange II may have immunomodulatory effects.

Early treatment of NOD mice with B7-H4 reduces the incidence of autoimmune diabetes.

OBJECTIVEAutoimmune diabetes is a T cell–mediated disease in which insulin-producing β-cells are destroyed. Autoreactive T cells play a central role in mediating β-cell destruction. B7-H4 is a negative cosignaling molecule that downregulates T-cell responses. In this study, we aim to determine the role of B7-H4 on regulation of β-cell–specific autoimmune responses.RESEARCH DESIGN AND METHODSPrediabetic (aged 3 weeks) female NOD mice (group 1, n = 21) were treated with intraperitoneal injections of B7-H4.Ig at 7.5 mg/kg, with the same amount of mouse IgG (group 2, n = 24), or with no protein injections (group 3, n = 24), every 3 days for 12 weeks.RESULTSB7-H4.Ig reduced the incidence of autoimmune diabetes, compared with the control groups (diabetic mice 28.6% of group 1, 66.7% of group 2 [P = 0.0081], and 70.8% of group 3 [group 1 vs. 3, P = 0.0035]). Histological analysis revealed that B7-H4 treatment did not block islet infiltration but rather suppressed further infiltrates after 9 weeks of treatment (group 1 vs. 2, P = 0.0003). B7-H4 treatment also reduced T-cell proliferation in response to GAD65 stimulation ex vivo. The reduction of diabetes is not due to inhibition of activated T cells in the periphery but rather to a transient increase of Foxp3+ CD4+ T-cell population at one week posttreatment (12.88 ± 1.29 vs. 11.58 ± 1.46%; n = 8; P = 0.03).CONCLUSIONSOur data demonstrate the protective role of B7-H4 in the development of autoimmune diabetes, suggesting a potential means of preventing type 1 diabetes by targeting the B7-H4 pathway.

Epigallocatechin-3-Gallate Ameliorates Experimental Autoimmune Encephalomyelitis by Altering Balance among CD4 + T-Cell Subsets

The green tea component epigallocatechin-3-gallate (EGCG) may be beneficial in autoimmune diseases; however, the underlying mechanisms are not well understood. In this study, we determined the effect of EGCG on the development of experimental autoimmune encephalomyelitis, an animal model for human multiple sclerosis, and the underlying mechanisms. Female C57BL/6 mice were fed EGCG (0%, 0.15%, 0.3%, and 0.6% in diet) for 30 days and then immunized with specific antigen myelin oligodendrocyte glycoprotein 35-55. EGCG dose dependently attenuated clinical symptoms and pathological features (leukocyte infiltration and demyelination) in the central nervous system and inhibited antigen-specific T-cell proliferation and delayed-type hypersensitivity skin response. We further showed that EGCG reduced production of interferon-γ, IL-17, IL-6, IL-1β, and tumor necrosis factor-α; decreased types 1 and 17 helper T cells (Th1 and Th17, respectively); and increased regulatory T-cell populations in lymph nodes, the spleen, and the central nervous system. Moreover, EGCG inhibited expression of transcription factors T-box expressed in T cells and retinoid-related orphan receptor-γt, the specific transcription factor for Th1 and Th17 differentiation, respectively; the plasma levels of intercellular adhesion molecule 1; and CCR6 expression in CD4(+) T cells. These results indicate that EGCG may attenuate experimental autoimmune encephalomyelitis autoimmune response by inhibiting immune cell infiltration and modulating the balance among pro- and anti-autoimmune CD4(+) T-cell subsets. Thus, we identified a novel mechanism that underlies EGCG's beneficial effect in autoimmune disease.

EBV-specific immune responses in patients with multiple sclerosis responding to IFNβ therapy

Background: Symptomatic primary infection with the human γ-herpesvirus Epstein–Barr virus (EBV) and elevated immune responses to EBV are associated with the development and progression of multiple sclerosis (MS). Interferon-beta (IFNβ), first-line treatment for relapse-onset MS, exhibits complex immunoregulatory and antiviral activities. Objective: To determine EBV-specific immune responses in patients with MS during IFNβ therapy. Methods: We evaluated cellular and humoral immune responses to EBV- and human cytomegalovirus (HCMV)-encoded antigens in patients with MS before and 1 year after IFNβ treatment by ELISA and flow cytometry. Twenty-eight patients with MS who showed a clinical response to IFNβ as defined by the absence of relapses and lack of progression on the Expanded Disability Status Scale score during the first 2 years of treatment were included. Results: Clinically effective IFNβ-therapy was associated with a downregulation of proliferative T cell responses to the latent EBV nuclear antigen-1 (EBNA1). EBNA1-specific IgG responses as well as cellular and humoral immune responses to MHC class I restricted EBV antigens expressed during lytic replication and viral B cell transformation were similar before and after IFNβ therapy. Although HCMV-specific IgG levels slightly decreased, proliferative T-cell responses towards HCMV antigens remained unchanged during IFNβ therapy. Conclusion: Clinically effective IFNβ therapy is associated with a reduction of proliferative T-cell responses to EBNA1.

T-cell recognition of acetylcholine receptor provides a reliable means for monitoring autoimmunity to acetylcholine receptor in antibody-negative myasthenia gravis patients

Myasthenia gravis (MG) is an autoimmune disease usually associated with autoantibodies (auto-Abs) against nicotinic acetylcholine receptor (AChR). Some MG patients appear negative for anti-AChR Abs (seronegative), and a fraction of these have auto-Abs against muscle-specific kinase. The remaining patients, although displaying MG symptoms, show no detectable auto-Abs. We describe here a possible association of a rare human leukocyte antigen (HLA)-DQ type and AChR Ab-negative MG. We also found that the majority of seronegative patients exhibit an anti-AChR autoimmune T lymphocyte response. We investigated the existence of AChR-reactive T cells in peripheral blood lymphocytes from seronegative patients by their proliferative responses against a mixture of 18 overlapping synthetic peptides encompassing the extracellular part of human AChR α-chain. Of the 10 samples, eight exhibited positive T-cell proliferative responses against the peptide mixtures. The proliferative assay was equally efficient using a mixture of eight peptides frequently recognized by MG T cells. This T-cell proliferative assay should provide a reliable method for monitoring seronegative MG patients.

Delayed type hypersensitivity‐induced myeloid‐derived suppressor cells regulate autoreactive T cells

Mild but efficient treatments of autoimmune diseases are urgently required. One such therapy, long-term maintenance of chronic delayed type hypersensitivity, has been described for alopecia areata (AA), a hair follicle-affecting autoimmune disease. The molecular mechanisms underlying the therapeutic efficacy are unknown, but may involve myeloid-derived suppressor cells (MDSCs). AA-affected mice were treated with squaric acid dibutyl ester (SADBE). The immunoreactivity of SADBE-treated AA lymphocytes and of AA lymphocytes co-cultured with SADBE-induced MDSCs was analyzed. The curative effect of SADBE was abolished by all-transretinoic acid, which drives MDSCs into differentiation, confirming a central role for MDSCs in therapeutic SADBE treatment. SADBE and SADBE-induced MDSCs strongly interfered with sustained autoreactive T-cell proliferation in response to AA skin lysate (autoantigen), which was accompanied by weak ζ-chain down-regulation and strongly impaired Lck activation. In contrast, activation of the mitochondrial apoptosis pathway and blockade of the anti-apoptotic PI3K/Akt pathway by SADBE-induced MDSCs did not require T-cell receptor engagement. Apoptosis induction correlated with high TNF-α expression in SADBE-induced MDSCs and elevated TNFRI levels in AA lymphocytes. SADBE-induced MDSCs interfere with persisting autoreactive T-cell proliferation and promote apoptosis of these T cells, which qualifies MDSCs induced and maintained by chronic delayed type hypersensitivity reactions as promising therapeutics in organ-related autoimmune diseases.

Identification of prostatic acid phosphatase (PAP) specific HLA‐DR1‐restricted t‐cell epitopes

Prostatic acid phosphatase (PAP) is a prostate cancer tumor antigen and is an immunological target in several active immunotherapy clinical trials for the treatment of prostate cancer. We and others have demonstrated that PAP-specific T-cell responses can be elicited and augmented following antigen-specific immunization in both humans and animal models. We have previously reported that prostate cancer patients immunized with a DNA vaccine encoding PAP (pTVG-HP) developed both CD4+ and CD8+ T-cell responses. PAP-specific, CD4+ T-cell proliferative responses were generated in three out of four HLA-DRB1*0101 patients suggesting the possibility that DR1-restricted epitopes exist. To identify PAP-specific HLA-DRB1*0101 restricted epitopes, we immunized HLA-A2.01/HLA-DRB1*0101 (A2/DR1) transgenic mice with the pTVG-HP DNA vaccine. To map DRB1*0101-restricted epitopes, splenocytes from immunized mice were screened against a library of overlapping 15-residue, PAP-derived peptides using an IFNγ ELISPOT assay. We identified four HLA-DRB1*0101 epitopes for PAP in A2/DR1 mice (PAP(161-175) , PAP(181-195) , PAP(191-205) , and PAP (351-365) ). T cells specific for one epitope (PAP(181-195) ) were found to be augmented after immunization in a HLA-DRB1*0101+ prostate cancer patient. The identification of MHC class II epitopes may provide tools to directly monitor immune responses after vaccination and may be important for the design of future prostate cancer vaccines.

Double‐ and monofunctional CD4+ and CD8+ T‐cell responses to Mycobacterium tuberculosis DosR antigens and peptides in long‐term latently infected individuals

More than 2 billion individuals are latently infected with Mycobacterium tuberculosis (Mtb). Knowledge of the key Mtb antigens and responding T-cell subsets mediating protection against Mtb is critical for developing improved tuberculosis (TB) vaccines. We previously reported that Mtb DosR-regulon-encoded antigens are recognized well by human T cells in association with control of Mtb infection. The characteristics of the responding T-cell subsets, however, remained unidentified. We have therefore studied the cytokine production and memory phenotypes of Mtb DosR-regulon-encoded antigen-specific T cells from individuals who had been infected with Mtb decades ago, yet never developed TB (long-term latent Mtb-infected individuals). Using multi-parameter flow cytometry and intracellular cytokine staining for IFN-γ, TNF-α and IL-2, we found double and single cytokine-producing CD4(+) as well as CD8(+) T cells to be the most prominent subsets, particularly IFN-γ(+) TNF-α(+) CD8(+) T cells. The majority of these T cells comprised effector memory and effector T cells. Furthermore, CFSE labeling revealed strong CD4(+) and CD8(+) T-cell proliferative responses induced by several "immunodominant" Mtb DosR antigens and their specific peptide epitopes. These findings demonstrate the prominent presence of double- and monofunctional CD4(+) and CD8(+) T-cell responses in naturally protected individuals and support the possibility of designing Mtb DosR antigen-based TB vaccines.