Temporal and spatial characterization of negative regulatory T cells in HIV‐infected/AIDS patients raises new diagnostic markers and therapeutic strategies

BackgroundNegative regulatory T cells (Tregs) not only deplete effector T cells but also inhibit the clearance of HIV during infection, which may allow Tregs to be used as informative diagnostic markers. To facilitate both diagnosis and treatment, a thorough understanding of these regulators by characterizing them on temporal and spatial scales is strongly required.MethodsHundred HIV‐infected/AIDS patients, including 87 males, with an average age of 35.8 years, as well as 20 healthy controls, were enrolled. Flow cytometry was used to analyze CD3+T cells, CD4+T cells, and CD8+T cells to evaluate the immune status of the participants. Then, a group of representative negative regulatory T cells, including CD4+PD‐1+T cells, CD4+PD‐1^highT cells, CD8+PD‐1+T cells, and CD4+CD25^high Tregs was also analyzed to explore their effects on disease progression and intercorrelation.ResultsThe percentages of CD4⁺PD‐1⁺T cells and CD4⁺CD25^highTregs increased in patients with the same ultrahigh significance. Temporally, the patients with both intermediate‐stage and late‐stage disease had higher percentages of CD4⁺PD‐1⁺T cells; however, the percentage of CD4⁺CD25^highTregs only increased in the patients with late‐stage disease. In addition, CD4⁺PD‐1⁺T cells but not CD4⁺CD25^highTregs were negatively correlated with the absolute CD4⁺T cell count. Spatially, no correlations between CD4⁺PD‐1⁺T cells and CD4⁺CD25^highTregs were observed, which suggests these Tregs function differently during immunosuppression.ConclusionsThis study characterized negative regulatory T cells in HIV‐infected/AIDS patients at both temporal and spatial scales and found that CD4⁺CD25⁺Tregs and CD4⁺PD‐1⁺T cells could be used as potential diagnostic markers for identifying different disease stages and monitoring disease progression.     

CD25+ CD4+ T cells, expanded with dendritic cells presenting a single autoantigenic peptide, suppress autoimmune diabetes

In the nonobese diabetic (NOD) mouse model of type 1 diabetes, the immune system recognizes many autoantigens expressed in pancreatic islet beta cells. To silence autoimmunity, we used dendritic cells (DCs) from NOD mice to expand CD25+ CD4+ suppressor T cells from BDC2.5 mice, which are specific for a single islet autoantigen. The expanded T cells were more suppressive in vitro than their freshly isolated counterparts, indicating that DCs from autoimmune mice can increase the number and function of antigen-specific, CD25+ CD4+ regulatory T cells. Importantly, only 5,000 expanded CD25+ CD4+ BDC2.5 T cells could block autoimmunity caused by diabetogenic T cells in NOD mice, whereas 10(5) polyclonal, CD25+ CD4+ T cells from NOD mice were inactive. When islets were examined in treated mice, insulitis development was blocked at early (3 wk) but not later (11 wk) time points. The expanded CD25+ CD4+ BDC2.5 T cells were effective even if administered 14 d after the diabetogenic T cells. Our data indicate that DCs can generate CD25+ CD4+ T cells that suppress autoimmune disease in vivo. This might be harnessed as a new avenue for immunotherapy, especially because CD25+ CD4+ regulatory cells responsive to a single autoantigen can inhibit diabetes mediated by reactivity to multiple antigens.     

CD4+CD25+ regulatory T cell therapy for the induction of donor-specific clinical transplantation tolerance

Naturally occurring CD4⁺CD25⁺ regulatory T cells (Tregs) have been shown to play a key role in the control of autoimmunity. Interestingly, they are also capable of mediating transplantation tolerance and they can have indirect allospecificity for donor antigens. An increasing body of evidence in experimental studies has indicated that adoptive transfer of in vitro expanded CD4⁺CD25⁺ Tregs with indirect antidonor allospecificity can induce long-term donor-specific transplantation tolerance. Thus, adoptive cell therapy using patient-specific CD4⁺CD25⁺ Tregs as individualised medicine to promote clinical transplantation tolerance is promising.     

CD40-independent pathways of T cell help for priming of CD8(+) cytotoxic T lymphocytes

In many cases, induction of CD8(+) CTL responses requires CD4(+) T cell help. Recently, it has been shown that a dominant pathway of CD4(+) help is via antigen-presenting cell (APC) activation through engagement of CD40 by CD40 ligand on CD4(+) T cells. To further study this three cell interaction, we established an in vitro system using dendritic cells (DCs) as APCs and influenza hemagglutinin (HA) class I and II peptide-specific T cell antigen receptor transgenic T cells as cytotoxic T lymphocyte precursors and CD4(+) T helper cells, respectively. We found that CD4(+) T cells can provide potent help for DCs to activate CD8(+) T cells when antigen is provided in the form of either cell lysate, recombinant protein, or synthetic peptides. Surprisingly, this help is completely independent of CD40. Moreover, CD40-independent CD4(+) help can be documented in vivo. Finally, we show that CD40-independent T cell help is delivered through both sensitization of DCs and direct CD4(+)-CD8(+) T cell communication via lymphokines. Therefore, we conclude that CD4(+) help comprises at least three components: CD40-dependent DC sensitization, CD40-independent DC sensitization, and direct lymphokine-dependent CD4(+)-CD8(+) T cell communication.     

Loss of HIV-1-specific CD8+ T cell proliferation after acute HIV-1 infection and restoration by vaccine-induced HIV-1-specific CD4+ T cells

Virus-specific CD8(+) T cells are associated with declining viremia in acute human immunodeficiency virus (HIV)1 infection, but do not correlate with control of viremia in chronic infection, suggesting a progressive functional defect not measured by interferon gamma assays presently used. Here, we demonstrate that HIV-1-specific CD8(+) T cells proliferate rapidly upon encounter with cognate antigen in acute infection, but lose this capacity with ongoing viral replication. This functional defect can be induced in vitro by depletion of CD4(+) T cells or addition of interleukin 2-neutralizing antibodies, and can be corrected in chronic infection in vitro by addition of autologous CD4(+) T cells isolated during acute infection and in vivo by vaccine-mediated induction of HIV-1-specific CD4(+) T helper cell responses. These data demonstrate a loss of HIV-1-specific CD8(+) T cell function that not only correlates with progressive infection, but also can be restored in chronic infection by augmentation of HIV-1-specific T helper cell function. This identification of a reversible defect in cell-mediated immunity in chronic HIV-1 infection has important implications for immunotherapeutic interventions.     

Essential roles of CD8+CD122+ regulatory T cells in the maintenance of T cell homeostasis

Regulation of immune system is of paramount importance to prevent immune attacks against self-components. Mice deficient in the interleukin (IL)-2/IL-15 receptor beta chain, CD122, are model animals of such immune attacks and characteristically have a high number of abnormally activated T cells. Here, we show that the transfer of CD8+CD122+ cells into CD122-deficient neonates totally prevented the development of abnormal T cells. Furthermore, recombination activating gene-2-/- mice that received wild-type mice-derived CD8+CD122- cells died within 10 wk after cell transfer, indicating that normal CD8+CD122- cells become dangerously activated T cells in the absence of CD8+CD122+ T cells. CD8+CD122+ cells could control activated CD8+ or CD4+ T cells both in vivo and in vitro. Our results indicate that the CD8+CD122+ population includes naturally occurring CD8+ regulatory T cells that control potentially dangerous T cells.     

High level expression of CD43 inhibits T cell receptor/CD3-mediated apoptosis

In a screen designed to identify genes that regulate T cell receptor (TCR)/CD3-mediated apoptosis, we found that high level expression of CD43 protected T cell hybridomas from activation-induced cell death. The protection appears to result from its capacity to block Fas-mediated death signals rather than from inhibition of the upregulation of Fas and/or Fas ligand after T cell stimulation. We found that peripheral CD4(+) T cells can be divided into two subsets based on the level of CD43 surface expression. The CD4(+)CD43(low) subset exhibits a naive T cell phenotype, being CD62L(high)CD45RB(high)CD44(low), whereas CD4(+)CD43(high) cells exhibit a memory phenotype, being CD62L(low)CD45RB(low)CD44(high). Recent studies have demonstrated that engagement of TCR and Fas induces naive CD4(+) T cells to undergo apoptosis, and the same treatment enhances the proliferation of memory CD4(+) T cells. We confirm here that peripheral CD4(+)CD43(high) T cells are resistant to TCR/CD3-mediated cell death. These results suggest that the expression levels of CD43 on naive and memory CD4(+) T cells determine their susceptibility to Fas-dependent cell death and that high level expression of CD43 may be used as a marker to define CD4(+) memory T cells. Expression of CD43 provides a novel mechanism by which tumor cells expressing abnormally high levels of CD43 may escape Fas-mediated killing.     

Plasmacytoid dendritic cells from mouse tumor-draining lymph nodes directly activate mature Tregs via indoleamine 2,3-dioxygenase

A small population of plasmacytoid DCs (pDCs) in mouse tumor-draining LNs can express the immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO). We show that these IDO+ pDCs directly activate resting CD4+CD25+Foxp3+ Tregs for potent suppressor activity. In vivo, Tregs isolated from tumor-draining LNs were constitutively activated and suppressed antigen-specific T cells immediately ex vivo. In vitro, IDO+ pDCs from tumor-draining LNs rapidly activated resting Tregs from non-tumor-bearing hosts without the need for mitogen or exogenous anti-CD3 crosslinking. Treg activation by IDO+ pDCs was MHC restricted, required an intact amino acid-responsive GCN2 pathway in the Tregs, and was prevented by CTLA4 blockade. Tregs activated by IDO markedly upregulated programmed cell death 1 ligand 1 (PD-L1) and PD-L2 expression on target DCs, and the ability of Tregs to suppress target T cell proliferation was abrogated by antibodies against the programmed cell death 1/PD-L (PD-1/PD-L) pathway. In contrast, Tregs activated by anti-CD3 crosslinking did not cause upregulation of PD-Ls, and suppression by these cells was unaffected by blocking the PD-1/PD-L pathway. Tregs isolated from tumor-draining LNs in vivo showed potent PD-1/PD-L-mediated suppression, which was selectively lost when tumors were grown in IDO-deficient hosts. We hypothesize that IDO+ pDCs create a profoundly suppressive microenvironment within tumor-draining LNs via constitutive activation of Tregs.     

CD137 enhances cytotoxicity of CD3CD56 cells and their capacities to induce CD4 Th1 responses

CD137 (4-1BB) is a TNFR superfamily member that mediates the costimulatory signal resulting in T cells and NK cells proliferation and cytokines production, but the effects of CD137 signaling on CD3⁺CD56⁺ cell subpopulation have not been well-documented. The aim of this study was to investigate the effects of CD137 signaling on regulation of CD3⁺CD56⁺ cell function. Anti-CD137 mAb or mouse IgG1 isotype control was added to CIK cell culture to determine the effects of proliferation and anti-tumor effects on CD3⁺CD56⁺ cells. We observed that anti-CD137 mAb could dramatically promote proliferation of CIK cells. And CD137–CIK cells and CD3⁺CD56⁺ cell subpopulation within them possessed higher ability to kill tumor cell line A549. The SCID mice engrafted with A549 cells and treated with CD137–CIK cells have prolonged survival. Further studies revealed that the percentages of CD3⁺CD56⁺ cells were elevated significantly in CD137–CIK cells. The expression of NKG2D was up-regulated on CD3⁺CD56⁺ cells from CD137–CIK cells. The expression of IFN-γ, IL-2 and TNF-α increased significantly whereas the production of TGF-β₁, IL-4 and IL-10 decreased in CD3⁺CD56⁺ cells from CD137–CIK cells. In addition, anti-CD137 mAb can elevate the capacity of CD3⁺CD56⁺ cells to induce CD4⁺ Th1 responses. We further showed that the anti-CD137 mAb also had the same effects on CD3⁺CD56⁺ cells expanded from the PBMCs of patients with NSCLC. We concluded that CD137 signaling could enhance the abilities of CIK cells to kill tumor cells in vitro and in vivo via increasing the proportion of CD3⁺CD56⁺ cells and their cytotoxicity. Furthermore, CD137 signaling can elevate the capacity of CD3⁺CD56⁺ cells to induce CD4⁺ Th1 responses which may enhance their anti-tumor activity indirectly. Taken together, our studies could be considered as valuable in CIK cells-based cancer immunotherapy.     

血必净注射液对脂多糖刺激大鼠调节性T细胞凋亡及其介导效应T细胞免疫功能的影响

目的 探讨中药血必净注射液对体外脂多糖(LPS)刺激CD4+CD25+调节性T细胞(Treg)凋亡及其介导效应T细胞(Teff)增殖反应、分泌白细胞介素-2(IL-2)功能的影响.方法 40只雄性清洁级Wistar大鼠,实验前禁食12 h.免疫磁珠法分选大鼠脾脏CD4+CD25+Treg,分为对照组(n=8)、抗CD3/CD28组(n=8)、抗CXB/CD28+LPS组(/1,=8)、抗CD3/CD28+血必净组(n=8)和抗CD3/CD28+LPS+血必净组(n=8).培养3 d后流式细胞术检测CD4+CD25+Treg凋亡率、叉头翼状螺旋转录因子(Foxp3)和T淋巴细胞毒性相关抗原4(CTLA-4)表达,酶联免疫吸附试验检测IL-10分泌.同时,CD4+CD25+Treg与CD4+CD25-T细胞1:1培养,刀豆素A刺激68 h后分析Treg对Teff增殖的抑制效应,并检测上清中IL-2/可溶性IL-2受体水平.结果 抗CD3/CD28诱导Treg凋亡率为(33.70±3.06%),显著高于对照组(12.84±0.84)%;抗CD3/CD28+LPS+血必净组(45.13±2.70)%凋亡率明显高于抗CD3/CD28+LPS组[(29.41±1.63)%,P＜0.01].同时,CD4+CLY25+Treg roxp3和CTLA-4表达及IL-10分泌随凋亡增加而降低.抗CD3/CD28+血必净组(31.26%)Teff增殖反应平均抑制率显著低于对照组(54.48%,P＜0.05),抗CD3/CD28+LPS+血必净组抑制率与抗CD3/CD28+LPS组比较亦明显下降(P＜0.01).此外,抗CD3/CD28+血必净组和抗CD3/CD28+LPS+血必净组IL-2分泌水平均显著高于抗CD3/CD28+LPS组(P＜0.01).结论 LPS刺激可明显上调大鼠Treg对Teff的抑制功能,血必净注射液能通过促进Treg凋亡而有效改善其对Teff的抑制效应.     

Low dose Leishmania major promotes a transient T helper cell type 2 response that is down-regulated by interferon gamma-producing CD8+ T cells

An unresolved issue in the field of T helper (Th) cell development relates to the findings that low doses of antigen promote Th2 cell development in vitro, whereas several classic in vivo studies suggest the opposite. Here we resolve this paradox by studying the early immune response in mice after infection with different doses of Leishmania major. We found that low parasite doses induced a Th2 response in C57BL/6 (B6) mice, whereas high doses induced a Th1 response. However, the Th2 response in low dose-infected mice was transient and the animals healed. The appearance of a Th1 response after low dose infection was dependent upon the concomitant activation of interferon gamma-producing CD8+ T cells. In the absence of CD8+ T cells, the Th2 response was maintained. However, either neutralization of interleukin (IL)-4 or administration of IL-12 promoted a Th1 response after low dose infection of CD8-deficient mice, indicating that the required role for CD8+ T cells was limited to modulation of CD4+ T cell responses. Thus, the discrepant results seen between in vivo and in vitro studies on the effects of antigen dose on Th cell differentiation may depend upon whether CD8+ T cells participate in the immune response.     

Insufficient production and tissue delivery of CD4+ memory T cells in rapidly progressive simian immunodeficiency virus infection

The mechanisms linking human immunodeficiency virus replication to the progressive immunodeficiency of acquired immune deficiency syndrome are controversial, particularly the relative contribution of CD4+ T cell destruction. Here, we used the simian immunodeficiency virus (SIV) model to investigate the relationship between systemic CD4+ T cell dynamics and rapid disease progression. Of 18 rhesus macaques (RMs) infected with CCR5-tropic SIVmac239 (n=14) or CXCR4-tropic SIVmac155T3 (n=4), 4 of the former group manifested end-stage SIV disease by 200 d after infection. In SIVmac155T3 infections, naive CD4+ T cells were dramatically depleted, but this population was spared by SIVmac239, even in rapid progressors. In contrast, all SIVmac239-infected RMs demonstrated substantial systemic depletion of CD4+ memory T cells by day 28 after infection. Surprisingly, the extent of CD4+ memory T cell depletion was not, by itself, a strong predictor of rapid progression. However, in all RMs destined for stable infection, this depletion was countered by a striking increase in production of short-lived CD4+ memory T cells, many of which rapidly migrated to tissue. In all rapid progressors (P <0.0001), production of these cells initiated but failed by day 42 of infection, and tissue delivery of new CD4+ memory T cells ceased. Thus, although profound depletion of tissue CD4+ memory T cells appeared to be a prerequisite for early pathogenesis, it was the inability to respond to this depletion with sustained production of tissue-homing CD4+ memory T cells that best distinguished rapid progressors, suggesting that mechanisms of the CD4+ memory T cell generation play a crucial role in maintaining immune homeostasis in stable SIV infection.     

抗CD3单克隆抗体对人CD4^＋CD25^＋T淋巴细胞凋亡和自噬的影响

目的观察抗CD3单克隆抗体对分离培养的人外周血CD4^＋CD25^＋T淋巴细胞自噬、凋亡及其分泌的代表性因子转化生长因子β（TGF-β）的影响。方法采用密度梯度离心法及尼龙棉柱法分离32例健康者外周血T淋巴细胞,磁性细胞分离器（MACS）分离得到CD4^＋CD25^＋T淋巴细胞,分别利用电镜及流式细胞仪观察、检测各组（抗CD3单克隆抗体1mg/L组、IgG1同型抗体对照组）干预72h后细胞的凋亡率、自噬率,用ELISA法检测细胞培养上清液中细胞因子TGF-β的水平。结果抗CD3单克隆抗体组CD4^＋CD25^＋T淋巴细胞自噬率、凋亡率及TGF-β水平均增加（均P〈0.01）,凋亡率和自噬率之间无相关性（P〉0.05）。结论抗CD3单克隆抗体可促进CD4^＋CD25^＋T淋巴细胞凋亡和自噬及TGF-β分泌,且自噬与凋亡间相互独立。     

Defective regulatory and effector T cell functions in patients with FOXP3 mutations

The autoimmune disease immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) is caused by mutations in the forkhead box protein P3 (FOXP3) gene. In the mouse model of FOXP3 deficiency, the lack of CD4+ CD25+ Tregs is responsible for lethal autoimmunity, indicating that FOXP3 is required for the differentiation of this Treg subset. We show that the number and phenotype of CD4+ CD25+ T cells from IPEX patients are comparable to those of normal donors. CD4+ CD25high T cells from IPEX patients who express FOXP3 protein suppressed the in vitro proliferation of effector T cells from normal donors, when activated by "weak" TCR stimuli. In contrast, the suppressive function of CD4+ CD25high T cells from IPEX patients who do not express FOXP3 protein was profoundly impaired. Importantly, CD4+ CD25high T cells from either FOXP3+ or FOXP3- IPEX patients showed altered suppression toward autologous effector T cells. Interestingly, IL-2 and IFN-gamma production by PBMCs from IPEX patients was significantly decreased. These findings indicate that FOXP3 mutations in IPEX patients result in heterogeneous biological abnormalities, leading not necessarily to a lack of differentiation of CD4+ CD25high Tregs but rather to a dysfunction in these cells and in effector T cells.     

Targeting T lymphocytes for immune monitoring and intervention in autoimmune diabetes

Recognition of a peptide-MHC complex by the T cell receptor (TCR) is a key interaction that initiates T lymphocyte activation or silencing during an immune response. Fluorochrome-labeled recombinant MHC class II-peptide reagents function as soluble mimetics of this interaction, bind to their specific TCR, and allow for detection of antigen-specific CD4+ T cells. These reagents are now under scrutiny for "immune staging" of patients at risk of type 1 diabetes, in an effort to diagnose islet autoimmunity early enough to block immune-mediated beta cell destruction. Several issues are currently being addressed to improve the performance of these T cell assays: enrichment steps for better sensitivity, multiplexing of several islet epitopes, simultaneous monitoring of CD4+ and CD8+ responses, detection of low avidity T cells, combination of quantitative (number of positive cells) and qualitative (cytokine secretion, naive/memory phenotype) readouts. CD4+ T cells are key effectors of autoimmunity, and these MHC class II peptide reagents, through their signaling properties, might also provide therapeutics to block the autoimmune process at its onset, analogous to the use of OKT3gammao1(AlaAla) anti-CD3 antibody but in an antigen-specific fashion. The aim of such therapeutics is to potentiate different physiological control mechanisms to restore immune tolerance. Mechanisms initiated by this pathway may be capable of triggering elimination of pathogenic T cells through antigen-specific apoptosis and anergy, combined with the induction of regulatory T cells with broad suppressive function.     

CD4+CD25+ regulatory T cell therapy for the induction of donor-specific clinical transplantation tolerance

Naturally occurring CD4+CD25+ regulatory T cells (Tregs) have been shown to play a key role in the control of autoimmunity. Interestingly, they are also capable of mediating transplantation tolerance and they can have indirect allospecificity for donor antigens. An increasing body of evidence in experimental studies has indicated that adoptive transfer of in vitro expanded CD4+CD25+ Tregs with indirect antidonor allospecificity can induce long-term donor-specific transplantation tolerance. Thus, adoptive cell therapy using patient-specific CD4+CD25+ Tregs as individualised medicine to promote clinical transplantation tolerance is promising.     

Both CD8+ and CD16+ human T cell clones can provide B cell help for immunoglobulin production

Summary The functional properties of two CD4⁺CD8⁻CD16⁻, five CD4⁻CD8⁺CD16⁻ and three CD4⁻CD8⁻CD16⁺ human T cell clones were compared. All CD4⁻ T cell clones displayed strong cytolytic activity in the lectin-dependent lytic assay against the P815 murine mastocytoma cell line, but only the CD4⁻CD8⁻CD16⁺ T cell clones exhibited lytic activity against the natural killer-sensitive K562 cell line. Upon activation with anti-CD3 monoclonal antibody, all T cell clones were able to support IgM and IgA synthesis in autologous B cells. Both CD4⁺ and CD4⁻ T cell clones required cell-to-cell interaction with the B cells in order to exert their helper activity for immunoglobulin production. However, unlike CD4⁺, CD4⁻CD8⁺CD16⁻ and CD4⁻CD8⁻CD16⁺ T cell clones provided helper function for immunoglobulin synthesis only when low T/B cell ratios were used in culture. At higher T/B cell ratios, there was a decline in the B cell helper activity of CD4⁻ T cell clones that was probably related to the expression of cytolytic capacity against the antigen-presenting B cell. These data support the notion that under certain experimental conditions even cytotoxic T lymphocytes and natural killer cells may provide B cell helper function.     

Heat shock protein 60 enhances CD4+ CD25+ regulatory T cell function via innate TLR2 signaling

CD4+CD25+ Tregs regulate immunity, but little is known about their own regulation. We now report that the human 60-kDa heat shock protein (HSP60) acts as a costimulator of human Tregs, both CD4+CD25int and CD4+CD25hi. Treatment of Tregs with HSP60, or its peptide p277, before anti-CD3 activation significantly enhanced the ability of relatively low concentrations of the Tregs to downregulate CD4+CD25- or CD8+ target T cells, detected as inhibition of target T cell proliferation and IFN-gamma and TNF-alpha secretion. The enhancing effects of HSP60 costimulation on Tregs involved innate signaling via TLR2, led to activation of PKC, PI3K, and p38, and were further enhanced by inhibition of ERK. HSP60-treated Tregs suppressed target T cells both by cell-to-cell contact and by secretion of TGF-beta and IL-10. In addition, the expression of ERK, NF-kappaB, and T-bet by downregulated target T cells was inhibited. Thus, HSP60, a self-molecule, can downregulate adaptive immune responses by upregulating Tregs innately through TLR2 signaling.     

Compromised function of regulatory T cells in rheumatoid arthritis and reversal by anti-TNFalpha therapy

Regulatory T cells have been clearly implicated in the control of disease in murine models of autoimmunity. The paucity of data regarding the role of these lymphocytes in human autoimmune disease has prompted us to examine their function in patients with rheumatoid arthritis (RA). Regulatory (CD4(+)CD25(+)) T cells isolated from patients with active RA displayed an anergic phenotype upon stimulation with anti-CD3 and anti-CD28 antibodies, and suppressed the proliferation of effector T cells in vitro. However, they were unable to suppress proinflammatory cytokine secretion from activated T cells and monocytes, or to convey a suppressive phenotype to effector CD4(+)CD25(-) T cells. Treatment with antitumor necrosis factor alpha (TNFalpha; Infliximab) restored the capacity of regulatory T cells to inhibit cytokine production and to convey a suppressive phenotype to "conventional" T cells. Furthermore, anti-TNFalpha treatment led to a significant rise in the number of peripheral blood regulatory T cells in RA patients responding to this treatment, which correlated with a reduction in C reactive protein. These data are the first to demonstrate that regulatory T cells are functionally compromised in RA, and indicate that modulation of regulatory T cells by anti-TNFalpha therapy may be a further mechanism by which this disease is ameliorated.     

In vivo cytotoxic T lymphocyte elicitation by mycobacterial heat shock protein 70 fusion proteins maps to a discrete domain and is CD4(+) T cell independent

To gain insights into the mechanisms by which soluble heat shock protein (hsp) fusions can elicit CD8(+) cytotoxic T lymphocytes (CTLs) against the fusion partner, mycobacterial (Mycobacterium tuberculosis) hsp70 was dissected to ascertain whether a particular hsp domain is necessary, and knockout mice were used to determine whether the fusion protein's immunogenicity is dependent on CD4(+) T lymphocytes. We found that the ability to elicit CD8(+) CTLs depends on a discrete 200-amino acid protein domain, indicating that the fusion protein's immunogenicity for CD8(+) T cells does not require coupled chaperone function or peptide binding. Further, we found that ovalbumin (OVA).hsp70 fusion protein elicited anti-OVA CD8(+) CTLs about equally well in CD4 knockout and wild-type C57BL/6 mice, and also when the hsp70 was of murine (self) origin. The ability of hsp70 fusion proteins to elicit CD4-independent CTL responses suggests that hsp70 fusion proteins may be useful for immunological prophylaxis and therapy against disease in CD4(+) T cell-deficient individuals.