急性冠脉综合征患者循环CD4+CD28nullT细胞增多的意义

目的 研究CD4^＋CD28^nullT淋巴细胞是否参与了急性冠脉综合征（ACS）相关的炎症反应.方法 空腹采肘静脉血,采用流式细胞仪对62例ACS,45例稳定型心绞痛（SAP）患者和60例健康者测定循环CD4^＋CD28^nullT细胞亚群及其表达CD57的情况.结果 ACS患者循环CD^4＋CD28^nullT细胞数量显著高于SAP患者和健康者,并且表达CD57.结论 ACS患者循环CD4^＋CD28^nullT细胞具有细胞毒功能,通过破坏血管内皮细胞参与ACS的发生.     

Th2-like CD8+ T cells showing B cell helper function and reduced cytolytic activity in human immunodeficiency virus type 1 infection

We analyzed at clonal level the functional profile of circulating or skin-infiltrating T lymphocytes from two individuals infected with the human immunodeficiency virus type 1 (HIV-1), suffering from a Job's- like syndrome (eczematous dermatitis, recurrent skin and sinopulmonary infections, and hypergammaglobulinemia E) and showing virtually no circulating CD4+ T cells. Most of the CD3+ T cell clones generated from both patients were CD4- CD8+ TCR alpha beta +. The others were CD4- CD8- TCR alpha beta + which exhibited reduced mRNA expression for the CD8 molecule or no mRNA expression for either CD4 or CD8 molecules. The great majority of both CD4- CD8+ and CD4- CD8- did not produce interferon (IFN) gamma and exhibited reduced cytolytic activity. Rather, most of them produced large amounts of both interleukin (IL) 4 and IL-5 and provided B cell helper function for IgE synthesis. These data suggest that a switch of cytolytic CD8+ T cells showing a Th1-like cytokine secretion profile to cells that make Th2-type cytokines, exhibit reduced cytolytic potential, and provide B cell helper function can occur in the course of HIV-1 infection. These cells may contribute to the reduced defense against viral infections and intracellular parasites and account for the elevated IgE serum levels, eosinophilia, and the allergic-like clinical manifestations seen in a proportion of HIV-1-infected individuals.     

CD8+ cell anti-HIV activity correlates with the clinical state of the infected individual.

The extent of antiviral activity exhibited in vitro by CD8+lymphocytes from individuals infected by HIV-1 correlates significantly with their clinical status. CD8+ lymphocytes from asymptomatic subjects were found to inhibit HIV-1 replication by 90% or greater at effector/target (E/T) ratios ranging from as low as 0.05 to 0.25. CD8+ cells from 17 of 19 (89%) of these subjects suppressed replication at an E/T ratio of 0.10 or less. CD8+ lymphocytes from symptomatic patients (non-AIDS) inhibited HIV-1 replication at E/T ratios ranging from 0.05 to 1.0, and CD8+ cells from 8 of 13 (62%) required ratios greater than 0.10. As a group, patients with AIDS exhibited the lowest degree of anti-HIV activity with their CD8+ lymphocytes. The effective range of E/T ratios from AIDS patients was 0.10-2.0, and 9 of 10 (90%) required E/T ratios greater than 0.25. This anti-HIV activity exhibited by CD8+ cells also correlated significantly with the subject's peripheral blood CD4+ cell count. The relative extent of CD8+ cell anti-HIV-1 activity was not found dependent on variations in the CD4+ target cells and viruses used. These findings suggest that the decreased CD8+ cell antiviral activity is related to progression to disease in HIV-infected individuals.     

Regulatory functions of CD8+CD28- T cells in an autoimmune disease model

CD8+ T cell depletion renders CD28-deficient mice susceptible to experimental autoimmune encephalomyelitis (EAE). In addition, CD8-/-CD28-/- double-knockout mice are susceptible to EAE. These findings suggest a role for CD8+ T cells in the resistance of CD28-deficient mice to disease. Adoptive transfer of CD8+CD28- T cells into CD8-/- mice results in significant suppression of disease, while CD8+CD28+ T cells demonstrate no similar effect on the clinical course of EAE in the same recipients. In vitro, CD8+CD28- but not CD8+CD28+ T cells suppress IFN-gamma production of myelin oligodendrocyte glycoprotein-specific CD4+ T cells. This suppression requires cell-to-cell contact and is dependent on the presence of APCs. APCs cocultured with CD8+CD28- T cells become less efficient in inducing a T cell-dependent immune response. Such interaction prevents upregulation of costimulatory molecules by APCs, hence decreasing the delivery of these signals to CD4+ T cells. These are the first data establishing that regulatory CD8+CD28- T cells occur in normal mice and play a critical role in disease resistance in CD28-/- animals.     

多发性硬化患者外周血CD8+CD28-调节性T细胞的变化

目的 探讨多发性硬化(MS)患者外周血CD8+CD28-T细胞数量的变化及临床意义.方法 采用前瞻性病例对照研究,收集自2005年10月至2008年8月间在温州医学院附属第一医院神经专科病门诊或病房治疗的处于急性活动期的复发缓解型MS患者51例,均符合2005年修改的Mc-Donald诊断标准[2].所有住院患者均给予甲基强的松龙1.0 g/d,连续使用5 d后改为强的松60mg/d,12 d后减量,总疗程不超过6周,对14例MS患者进行治疗前后的动态观察.以20例健康体检者为对照组(NC组),MS组和NC组在年龄、性别构成上差异无统计学意义.采用流式细胞技术检测外周血CD8+CD28-,CD8+CD28+,CD8+及CD4+CD8-T细胞的百分比.两组间均数比较采用独立样本t检验,治疗前后比较采用配对样本t检验,相关性分析采用Pearson相关检验.结果 急性活动期MS组CD8+CD28-T细胞的百分比为(18.48±9.89)%,低于NC组的(24.48±4.86)%(P<0.01),但CD8+CD28+T细胞百分比为(12.23±4.31)%,高于NC组的(8.55±3.49)%(P<0.01),CD8+T细胞的百分比两组比较差异无统计学意义(P>0.05);MS组CD8+CD28-与CD4+CD8-T细胞的百分比呈负相关性(r=0.488,P<0.01);MS患者激素治疗后CD8+CD28-和CD8+CD28+T细胞卣分比与治疗前相比差异无统计学意义(均P>0.05),且治疗后CD8+CD28-T细胞百分比(16.22±4.25)%低于NC组(P<0.01),CD++CD28+T细胞百分比(13.04±4.23)%高于NC组(P<0.01).结论 CD8+CD28-T细胞数日的减少参与了MS的病理过程,并可能通过调节CD4+T细胞起作用;MS急性期激素治疗并不能恢复CD8+CD28-T细胞的数目,激素可能是通过其他途径发生作用.     

Direct activation of CD8+ cytotoxic T lymphocytes by dendritic cells

Recent experiments (11-13) have shown that antigen-specific, CD8+, CD4- T lymphocytes can be induced to proliferate and become killer cells in the absence of a second population of "helper" CD8-, CD4+ cells. We have studied early events in the activation of CD4+ and CD8+ T cell subsets in the primary mixed leukocyte reaction. Dendritic cells are a major if not essential accessory cell for the activation of both subpopulations. Antigen-bearing macrophages fail to stimulate unprimed CD8+ cells, but act as targets for the sensitized cytolytic lymphocytes that are induced by dendritic cells. The initial proliferative response is comparable for CD4+ and CD8+ lymphocyte subsets. For both subpopulations, dendritic cells efficiently cluster the responding lymphocytes on the first day and induce the release of IL-2. The data indicate that CD4+ and CD8+ lymphocytes can be activated by a similar mechanism, and illustrate the special role of dendritic cells in the sensitization stage of cell-mediated immunity.     

急性髓细胞性白血病细胞培养上清对CD4+和CD8+T细胞增殖和凋亡的影响

为了研究不同的急性髓细胞性白血病（AML）细胞株培养上清对CD4^＋和CD8^＋T细胞增殖以及凋亡的影响,探讨AML的免疫抑制的形成机制,将3种AML细胞株（HL-60、NB4和U937）培养上清和普通培养液按不同比例混合,用于培养CFSE染色的淋巴细胞.抗CD3抗体和抗CD28抗体刺激3天后,标记7AAD和相应荧光抗体.利用流式细胞术检测不同T细胞亚群CFSE荧光强度和7AAD表达率的变化,分析其增殖和凋亡变化情况.结果表明：3种AML细胞株中有2种（HL-60和NB4）培养上清可显著抑制CD4^＋T细胞和CD8^＋T细胞的增殖,并随浓度增加而增强.同样,HL-60和NB4细胞株培养上清亦可抑制刺激后的CD4^＋T细胞的凋亡,但对刺激后的CD8^＋T细胞的凋亡并无明显影响.相反,HL-60和NB4细胞株培养上清可显著增加增殖的CD8^＋T细胞的凋亡.结论：AML细胞株培养上清液对CD4^＋T细胞和CD8^＋T细胞增殖的抑制以及对增殖的CD8^＋T细胞凋亡的诱导作用,可能是AML患者免疫功能缺陷的机制之一.     

CD28 costimulation independence of target organ versus circulating memory antigen-specific CD4+ T cells

T cell receptor engagement with CD28 costimulation is generally required for naive T cell activation, whereas reactivation of memory cells is less dependent on CD28 costimulation. We studied this process in chronic beryllium disease, in which the frequency of antigen-specific CD4+ T cells in the lung is large and circulating antigen-specific cells are also detectable. In the lung, a large fraction of CD4+ T cells stopped expressing CD28 mRNA and protein, and this change in phenotype correlated with lung inflammation. In the presence of concentrations of CTLA-4Ig that inhibited the CD28-B7 interaction, beryllium-specific CD4+ T cells in lung were still able to proliferate and secrete IFN-gamma in response to beryllium in culture. This functional independence of CD28 costimulation included lung CD28+ effector cells. Although lung CD4+CD28- cells retained the ability to secrete Th1-type cytokines in response to beryllium, they showed less proliferative capacity and were more susceptible to cell death compared with CD28+ T cells. In contrast to lung cells, inhibition of the CD28-B7 interaction markedly reduced responses of beryllium-specific T cells in blood. Taken together, these findings suggest transition within memory CD4+ T cells from CD28 dependence in central memory cells to functional independence and then loss of CD28 expression in effector cells.     

Restoration of CD28 expression in CD28- CD8+ memory effector T cells reconstitutes antigen-induced IL-2 production

The control of many persistent viral infections by Ag-specific cytolytic CD8+ T cells requires a concurrent virus-specific CD4+ Th cell response. This reflects in part a requirement of activated effector CD8+ T cells for paracrine IL-2 production as a growth and survival factor. In human CMV and HIV infection, the majority of differentiated virus-specific CD8+ T cells notably lose the ability to produce IL-2 but also lose expression of CD28, a costimulatory molecule. Analysis of the fraction of memory CD8+ T cells that continue to express CD28 revealed these cells retain the ability to produce IL-2. Therefore, we examined if IL-2 production by CD28- CD8+ T cells could be restored by introduction of a constitutively expressed CD28 gene. Expression of CD28 in CD28- CD8+ CMV- and HIV-specific CD8+ T cells reconstituted the ability to produce IL-2, which could sustain an autocrine proliferative response after Ag recognition. These results suggest that the loss of CD28 expression during differentiation of memory/effector CD8+ T cells represents a decisive step in establishing regulation of responding CD8+ T cells, increasing the dependence on CD4+ Th for proliferation after target recognition, and has implications for the treatment of viral disease with adoptively transferred CD8+ T cells.     

Quantitative changes in T helper inducer (CD4+ CD45RA-), T suppressor inducer (CD4+ CD45RA+), T suppressor (CD8+ CD11b+), and T cytotoxic (CD8+ CD11b-) subsets in human immunodeficiency virus infection

To determine changes in subsets of CD4 and CD8 in relation to HIV infection and progression to AIDS, we quantitated peripheral blood lymphocytes obtained from 17 heterosexual controls, 22 asymptomatic HIV-seronegative and 18 HIV-seropositive intravenous drug users. 50 patients with AIDS-related complex (ARC), and 9 patients with AIDS using an EPICS "C" flow cytometer by two-color analysis. Both T helper inducer (CD4+ CD45RA-) and suppressor inducer (CD4+ CD45RA+) lymphocytes were decreased significantly in patients with ARC or AIDS. In contrast, T cytotoxic (CD8+ CD11b-) cells were significantly increased and accompanied by a significant decrease in the T suppressor (CD8+ CD11b+) subset in patients with ARC or AIDS. These results suggest that both T helper inducer and T suppressor inducer subsets of the CD4+ population and the T suppressor subset of CD8+ are depleted after HIV infection, while the T cytotoxic subset of CD8+ was increased after HIV infection.     

RA患者外周血CD4/CD8 T细胞比值及CD4+ CD25+ T细胞的检测及其临床意义

目的 观察活动期类风湿性关节炎（RA）患者外周血T细胞CD4／CD8比值及CD4^＋ CD25^＋T细胞（Tn细胞）的数量,探讨其在RA诊治中的价值。方法 用流式细胞术检测CD4^＋ CD25^＋T细胞及TR细胞的数量。结果 49例急性期RA患者的CD4／CD8比值和TR细胞数量显著高于正常人群组。28例RA患者治疗后的TR细胞数量显著高于治疗前,而CD4／CD8比值的变化无统计学意义。结论 RA治疗后症状改善患者,TR细胞数量明显上升,RA的发病和发展与该细胞数量密切相关。     

Nef protein induces differential effects in CD8+ cells from HIV-1-infected patients

BACKGROUND: The Nef protein of HIV-1 is suspected to play a role in the depletion of uninfected CD4+ lymphocytes that leads to AIDS. By contrast its effect on CD8+ cells, whose functions are also deregulated during HIV-1 infection, is presently unclear. Here we describe a number of derangements induced in vitro by Nef in CD8+ cells from HIV-1-infected patients. DESIGN: Peripheral lymphocytes from 16 HIV-1+ subjects and 9 uninfected individuals were cultivated on a Nef-transfected mouse fibroblast layer exposing the carboxyl-terminal region of the viral protein on cell membrane. The cultures were then measured for both apoptosis and proliferation by subdiploid DNA content and Ki67 expression, respectively, whereas the molecular analysis of purified CD8+ cells investigated the Fas-L mRNA levels in Nef-treated CTLs. In addition, we evaluated the Nef-induced variation in the extent of CD8+/HLA-DR+ subset, which includes non cytotoxic cells secreting T-cell antiviral factor (CAF) and a soluble factor inhibiting the HIV-1 replication. RESULTS: The viral protein induced in peripheral blood lymphocytes (PBL) a moderate tendency to proliferate, as measured by the increment of Ki67 antigen, particularly on the CD8+ subset of HIV-1 infected individuals (P < 0.05). This profile was particularly evident in cultures from patients with severe CD4+ lymphopenia and paralleled an apparent expansion of the CD8+/CD57+ suppressor cell subset. Molecular analysis of purified CD8+ cells revealed a defective expression of Fas-L mRNA in Nef-cultured CTLs, whereas the viral protein exerted a down modulatory effect on the CD8+/HLA-DR+ subset (P < 0.05), thus suggesting a potential inhibition of CAF. CONCLUSIONS: These results support a potential role of Nef in the progression of HIV-1 infection as a number of cellular functions are affected in the CD8+ subset. In particular, the defective functions of CD8+ cells induced by the viral protein could contribute, at least partly, to the escape of HIV-1 from the immune control of these cells.     

CD4+ CD7- CD28- T cells are expanded in rheumatoid arthritis and are characterized by autoreactivity.

Clonal expansion of CD4+ T cells is a characteristic finding in patients with RA and is only infrequently found in patients with psoriatic arthritis and healthy controls. Expanded CD4+ clonotypes are present in the blood, infiltrate into the joint, and persist over years. We have not addressed the question of whether the expanded clonotypes have unique functional and phenotypic properties which may explain the preferential in vivo expansion in RA. In contrast to most CD4+ T cells, expanded clonotypes lacked the expression of the CD28 and CD7 cell surface molecules. Accordingly, the subsets of CD4+ CD28- (9.7 vs 1.7, P = 0.00002) and CD4+ CD7- T cells (21.5 vs 12.26, P = 0.018) were increased in RA patients compared with age-matched normal individuals. Despite the lack of CD28 expression, clonally expanded CD4+ T cells were not anergic but proliferated in response to immobilized anti-CD3 and could be maintained in tissue culture. In vivo expanded CD4+ T cells were autoreactive to ubiquitously distributed autoantigens. They responded in an autologous mixed lymphocyte reaction, and T cell clones isolated from selected patients proliferated to autologous peripheral blood adherent cells. These data suggest that in RA patients selected CD4+ T cells which share the CD7- CD28- phenotype escape from peripheral tolerance.     

Delayed recovery of effector memory CD4+ T cells by highly active antiretroviral therapy in a patient with HIV-1 infection

Effector memory T cells, which are potentially important in the protection against various pathogens, have been shown to be CCR7 negative. We report a case with HIV-1 infection in whom the change in the cell numbers of the subsets of CD4+ T cells, including CCR7 negative memory CD4 + T cells, in peripheral blood was monitored for more than one year after the initiation of highly active antiretroviral therapy. Percentage of each subsets in lymphocytes was measured by triple staining on lymphocyte fraction in flow-cytometry. The numbers of total CD4+ T cell, naive T cells, and CCR7 positive memory T cells successfully increased within half a month after the initiation of the therapy. Instead, the recovery of the cell number in CCR7 negative memory T cells delayed, and continued to increase untill 10 months after the initiation of the therapy. It suggests the possibility of delay in recovery of immune systems after the initiation of the therapy in HIV-1-infected patients, despite the prompt recovery of total CD4 + T cells.     

免疫磁珠正负筛选在分离外周血CD8+和 CD4+T细胞亚群中的应用

为了探讨免疫磁珠分离技术及其正、负筛选策略在人外周血T淋巴细胞亚群分离提纯中的应用,应用补 体细胞毒法和正负筛选策略相结合的免疫磁珠法分离健康人外周血中CD4 T细胞、CD8 T细胞;用流式细胞术法 比较两种分离方法分离的靶细胞纯度;台盼蓝染色染色法和细胞培养后平板计数法检测免疫磁珠法分离的CD4 T 细胞、CD8 T细胞的活力和生长情况。结果表明:补体细胞毒法分离后CD4 T细胞纯度、CD8 T细胞纯度分别为 (76.0±2.8)％和(77.0±3.0)％,明显高于分离前的(34.6±3.7)％和(32.0±3.7)％(P<0.05);免疫磁殊法 分离后CD4 T细胞和CD8 T细胞纯度为(94.2±1.4)％和(93.8±3.0)％,显著高于补体细胞毒法(P<0.05)。 磁珠分离法获得的CD4 T细胞、CD8 T细胞细胞活力分别为(96.0±2.4)％和(95.0±3.6)％;细胞计数法表明 磁珠分离法获得的CD4 T细胞、CD8 T细胞对植物血凝素(PHA)的刺激保持了良好的增殖能力。结论:免疫磁珠 法较补体细胞毒法分离效率高,不影响细胞的活力和增殖能力;正负筛选策略相结合的免疫磁珠法在同时获取高 纯度的CD4 T细胞、CD8 T细胞时可获得满意效果,尤其适应于只有较少量血标本的情况,为进一步研究CD4 T 细胞、CD8 T细胞的生物学特性创造了条件。     

CD8+ T cell subsets of cytotoxic T lymphocytes induced by Epstein-Barr virus infection in infectious mononucleosis

Mononuclear peripheral blood lymphocytes (PBL) from patient with infectious mononucleosis (IM) were tested in a 51Cr-release assay for cytotoxicity against autologous and allogeneic lymphoblastoid cell line (LCL), or Epstein-Barr virus (EBV)-genome positive and negative cell line. In acute phase, PBL lyse an autologous LCL as well as allogeneic LCL (Wa cells). High levels of cytotoxicity were observed in the combinations between effector and target cells sharing HLA-Class 1 product. EBV-genome positive Daudi and Raji cells which lack HLA-Class 1 antigen and have mismactched HLA-Class 1 antigen, respectively showed resistance to killing. EBV-genome negative tumor cells except NK sensitive K562 cells were not killed by IM lymphocytes. However, the IM lymphocytes without atypical form in convalescent phase failed to show killing activity against autologous and allogeneic LCL. These findings suggest that cell surface membrane antigen structure on EBV-infected LCL may be able to explain the recognition and triggering of lysis of target cells by HLA-Class 1 restricted cytotoxic T cells (CTL) from acute IM. Phenotypic analysis of PBL with atypical form from IM was made by two-color flow cytometry. The data demonstrate that CD8+ T cells quantitatively represent the major population of lymphocytes expanded during acute IM. Furthermore, approximately 70% of these CD8+ T cells express HLA-DR on these surface, suggesting that they have undergone activation. However, IL 2R (CD25 antigen) expression was not significantly elevated on activated T cells. The salient profile on cytofluorographs of an acute IM was the increased number of CD3+CD19-, CD8+CD11b-, CD8+CD28+ and CD8+S6F1+ cells. However, CD3-CD19+, CD8+CD11b+, CD8+S6F1-, CD4+Leu8- and CD25+HLA-DR+ antigens were little expressed. Increased number of CD8+CD11b-, CD8+CD28+ and CD8+S6F1+ cells, which are regarded as CTL were reduced according to the improvement of the clinical symptoms and laboratory findings. These results together with HLA typing analysis suggested a possibility HLA-Class 1 restriction of the CTL with surface phenotype of CD8+CD11b-, CD8+CD28+, and CD8+S6F1+.     

CDw60: a marker for human CD8+ T helper cells

The existence of helper cells among the CD8+ T cell subset has been recognized for a long time. However, the phenotype of these cells has remained elusive. In this study, we provide evidence that the expression of the CDw60 antigen on human CD8+ T cell allows one to distinguish between CD8+ T helper cells and CD8+ T cells with cytotoxic and suppressor capacity. CDw60 monoclonal antibodies (mAb) recognize the 9-O-acetylated disialosyl group on ganglioside GD3 expressed on 20- 40% of CD8+ cells. By use of the direct and indirect mAb-rosetting technique, we were able to isolate the CDw60+CD8+ and CDw60-CD8+ cells at high purity. The alloantigen-specific cytotoxic activity of CD8+ cells resided entirely in the CDw60- population. Helper and suppressor capacity of both CD8 subsets was assayed by the pokeweed mitogen- induced differentiation of B cells into immunoglobulin-secreting cells. These studies clearly indicate that the CDw60+CD8+ subset provided substantial help to B lymphocytes, whereas the CD8+ cells with the CDw60- phenotype were suppressing B cell differentiation. Both subsets produced similar amounts of interleukin 2 (IL-2) after stimulation with phytohemagglutinin. Activation with phorbol myristate acetate in combination with Ca-ionophore induced IL-4 secretion in both populations, but preferentially in the CDw60+ subset, whereas the vast majority of interferon gamma was produced by the CDw60-CD8+ cells. When used in combination with other markers, CDw60 may prove to be useful in defining CD8+ subsets with reciprocal functional activities.     

Comparative clonal analysis of human immunodeficiency virus type 1 (HIV- 1)-specific CD4+ and CD8+ cytolytic T lymphocytes isolated from seronegative humans immunized with candidate HIV-1 vaccines

The lysis of infected host cells by virus-specific cytolytic T lymphocytes (CTL) is an important factor in host resistance to viral infection. An optimal vaccine against human immunodeficiency virus type 1 (HIV-1) would elicit virus-specific CTL as well as neutralizing antibodies. The induction by a vaccine of HIV-1-specific CD8+ CTL in humans has not been previously reported. In this study, CTL responses were evaluated in HIV-1-seronegative human volunteers participating in a phase I acquired immune deficiency syndrome (AIDS) vaccine trial involving a novel vaccine regimen. Volunteers received an initial immunization with a live recombinant vaccinia virus vector carrying the HIV-1 env gene and a subsequent boost with purified env protein. An exceptionally strong env-specific CTL response was detected in one of two vaccine recipients, while modest but significant env-specific CTL activity was present in the second vaccinee. Cloning of the responding CTL gave both CD4+ and CD8+ env-specific CTL clones, permitting a detailed comparison of critical functional properties of these two types of CTL. In particular, the potential antiviral effects of these CTL were evaluated in an in vitro system involving HIV-1 infection of cultures of normal autologous CD4+ lymphoblasts. At extremely low effector-to-target ratios, vaccine-induced CD8+ CTL clones lysed productively infected cells present within these cultures. When tested for lytic activity against target cells expressing the HIV-1 env gene, CD8+ CTL were 3-10-fold more active on a per cell basis than CD4+ CTL. However, when tested against autologous CD4+ lymphoblasts acutely infected with HIV-1, CD4+ clones lysed a much higher fraction of the target cell population than did CD8+ CTL. CD4+ CTL were shown to recognize not only the infected cells within these acutely infected cultures but also noninfected CD4+ T cells that had passively taken up gp120 shed from infected cells and/or free virions. These results were confirmed in studies in which CD4+ lymphoblasts were exposed to recombinant gp120 and used as targets for gp120-specific CD4+ and CD8+ CTL clones. gp120-pulsed, noninfected targets were lysed in an antigen-specific fashion by CD4+ but not CD8+ CTL clones. Taken together, these observations demonstrate that in an in vitro HIV-1 infection, sufficient amounts of gp120 antigen are produced and shed by infected cells to enable uptake by cells that are not yet infected, resulting in the lysis of these noninfected cells by gp120-specific, CD4+ CTL.(ABSTRACT TRUNCATED AT 400 WORDS)     

IL-15 promotes activation and expansion of CD8+ T cells in HIV-1 infection

In HIV-1–infected patients, increased numbers of circulating CD8⁺ T cells are linked to increased risk of morbidity and mortality. Here, we identified a bystander mechanism that promotes CD8 T cell activation and expansion in untreated HIV-1–infected patients. Compared with healthy controls, untreated HIV-1–infected patients have an increased population of proliferating, granzyme B⁺, CD8⁺ T cells in circulation. Vβ expression and deep sequencing of CDR3 revealed that in untreated HIV-1 infection, cycling memory CD8 T cells possess a broad T cell repertoire that reflects the repertoire of the resting population. This suggests that cycling is driven by bystander activation, rather than specific antigen exposure. Treatment of peripheral blood mononuclear cells with IL-15 induced a cycling, granzyme B⁺ phenotype in CD8⁺ T cells. Moreover, elevated IL-15 expression in the lymph nodes of untreated HIV-1–infected patients correlated with circulating CD8⁺ T cell counts and was normalized in these patients following antiretroviral therapy. Together, these results suggest that IL-15 drives bystander activation of CD8⁺ T cells, which predicts disease progression in untreated HIV-1–infected patients and suggests that elevated IL-15 may also drive CD8⁺ T cell expansion that is linked to increased morbidity and mortality in treated patients.     

Coexpression and functional cooperation of CTLA-4 and CD28 on activated T lymphocytes

T cell costimulation by molecules on the antigen presenting cell (APC) is required for optimal T cell proliferation. The B7 molecule on APC binds the T lymphocyte receptor CD28, triggering increased interleukin 2 (IL-2) production and subsequent T cell proliferation. CTLA-4 is a predicted T cell membrane receptor homologous to CD28, which also binds the B7 counter receptor, but whose distribution and function are unknown. Here we have developed monoclonal antibodies (mAbs) specific for CTLA-4 and have investigated these questions. mAbs were produced that bound CTLA-4 but not CD28, and that blocked binding of CTLA-4 to B7. CTLA-4 expression as measured by these mAbs was virtually undetectable on resting T cells, but was increased several hundred-fold during T cell activation. On activated lymphocytes, CTLA-4 was expressed equally on CD4+ and CD8+ T cell subsets and was coexpressed with CD25, CD28, and CD45RO. CTLA-4 expression was lower than that of CD28, reaching a maximum of approximately 1/30-50 the level of CD28. Despite its lower expression, CTLA-4 was responsible for much of the B7 binding by large activated T cells. Anti-CTLA-4 mAb 11D4 and anti-CD28 mAb 9.3 acted cooperatively to inhibit T cell adhesion to B7, and to block T cell proliferation in primary mixed lymphocyte culture. When coimmobilized with anti T cell receptor (TCR) mAb, anti-CTLA-4 mAbs were less effective than anti-CD28 mAb 9.3 at costimulating proliferation of resting or activated T cells. However, coimmobilized combinations of anti-CD28 and anti-CTLA-4 were synergistic in their ability to augment anti-TCR-induced proliferation of preactivated CD4+ T cells. These results indicate that CTLA-4 is coexpressed with CD28 on activated T lymphocytes and cooperatively regulates T cell adhesion and activation by B7.