The CD28/HLA-DR expressions on CD4+T but not CD8+T cells are significant predictors for progression to AIDS

To investigate the changes of CD28 and HLA-DR molecules on CD4+ and CD8+ T cells during HIV infection, we classified 130 HIV-infected Koreans into four groups by the CD4 level as follows: group I (> or = 500 cells/mm3), group II (201-499 cells/mm3), group III (51-200 cells/mm3), and group IV (< or = 50 cells/mm3). In CD4+ T cells, the proportion of CD28 expression decreased significantly with the CD4 level while the proportion of HLA-DR expression increased gradually. In particular, the changes of HLA-DR expressions on CD4+ T cells were parallel to the loss of CD28 molecules from stage III to IV. However, the CD28 expression on CD8+ T cells decreased dramatically in the early stage of HIV infection, and the sum and pattern of CD28 and HLA-DR expressions on CD8+ T cells was stable after the first stage. Even though CD28 down-regulation on CD8+ T cells was very severe from the early stage of HIV infection, it might not influence the survival time of HIV-infected Koreans. The sum of the CD28+ subsets and HLA-DR subsets in each T cell was stable in all stages of disease progression. The sums of the CD28+ subsets and HLA-DR+ subsets in CD4+ T and CD8+ T cells were constant as approximately 100% and 55-60% of each T cell. These results suggested that the changes of CD28/HLA-DR expressions on CD4+ T cells were more predictable than those on CD8+ T cells in the evaluation of the disease progression during HIV-infected periods. However, we need further studies to understand why the sum of two molecules in each T cell are constant.     

Selective increase of activation antigens HLA-DR and CD38 on CD4+ CD45RO+ T lymphocytes during HIV-1 infection.

Infection with HIV results in a progressive depletion of CD4+ T cells and leads to significant in vivo lymphocyte phenotype changes. In this regard, the expression of HLA-DR and CD38 on CD8+ T cells has been shown to increase dramatically with disease progression. We investigated the expression of both activation markers on CD4+ T cells in HIV-1-infected subjects at different clinical stages of infection and compared the in vivo activation of CD4+ T cells with parameters of viral activity and CD8+ T cell activation. Fresh peripheral venous blood was obtained from 54 HIV-infected subjects and from 28 uninfected healthy controls. Three-colour immunophenotyping of the CD4+ T cell subset showed that the proportion of CD4+ T cells expressing HLA-DR (10% in HIV-negative controls) or CD38 (62% in HIV-negative controls) was higher in asymptomatic (P < 0.05 for CD38) and symptomatic (P < 0.001 for HLA-DR and CD38) HIV-infected subjects than in controls, whereas the proportion of CD4+ T cells expressing CD45RO (54% in controls) remained relatively unchanged. Simultaneous expression of HLA-DR and CD38 on CD4+ T cells increased from 2.3% in controls to 11% (P < 0.001) in asymptomatic and 22% (P < 0.001) in symptomatic HIV-infected subjects. This relative increase of CD38 and HLA-DR expression occurred mainly on CD4+ T cells co-expressing CD45RO. Changes in expression of HLA-DR and CD38 on CD4+ T cells correlated with similar changes on CD8+ T lymphocytes, with the presence of HIV antigen in the circulation, and with the disease stage of HIV infection.     

Increased expression of CD80, CD86 and CD70 on T cells from HIV-infected individuals upon activation in vitro: regulation by CD4+ T cells

T cells express CD28 and CD27 which transduce co-stimulatory signals after interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency virus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8⁺ T cells. On the other hand, T cell stimulation in vitro induced high CD80, CD86 and CD70 expression on T cells from HIV-infected individuals. It appeared that an inverted CD4:CD8 T cell ratio could explain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8⁺ T cells from HIV⁻ individuals cultured in the absence of CD4⁺ T cells. Addition of CD4⁺ T cells prevented this up-regulation. However, in HIV-infected individuals, addition of excess autologous or healthy control CD4⁺ T cells did not completely counteract up-regulation of co-stimulatory ligand expression on CD8⁺ T cells. Thus, to some extent, CD8⁺ T cells in HIV-infected individuals appeared to be refractory to CD4⁺ T cell-mediated regulation of ligand expression in vitro. Activated T cells from HIV-infected individuals and activated CD8⁺ T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell contact. Thus, we showed that T cells from HIV-infected individuals express enhanced levels of co-stimulatory ligands upon activation, which provides them with accessory cell properties. Enhanced stimulatory potential of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progression.     

Enhanced expression of CTLA-4 (CD152) on CD4+ T cells in HIV infection

CTLA-4 (CD152) is a surface molecule of activated T cells with sequence homology to CD28. Both molecules bind to the same ligands, B7.1 (CD80) and B7.2 (CD86) but have antagonistic functions. While CD28 is an important costimulator, CTLA-4 has an essential inhibitory function in maintaining the homeostasis of the immune system. Down-regulation of CD28 predominantly on CD8+ T cells has been described in HIV infection, but analysis of CTLA-4 is complicated by its low expression levels. Here we have used potent signal enhancement to study CTLA-4 on peripheral blood mononuclear cells (PBMC) during HIV infection. CTLA-4 was expressed only on T cells. Expression levels were significantly increased selectively on CD4+ T cells during all stages of HIV infection, while CTLA-4 expression on CD8+ T cells was always low. In contrast, after stimulation with the mitogen phytohaemagglutinin (PHA), CTLA-4 levels were strongly increased on T cells from controls but in T cells from HIV patients this response was severely impaired. Our data suggest that in HIV infection CD4+ and CD8+ T cells may be less responsive to B7 costimuli due to two different mechanisms: increase in CTLA-4 expression by CD4+ cells and down-regulation of CD28 by CD8+ cells.     

HIV感染后胃黏膜CD4+、CD8+T细胞数量分布及CD38表达的改变

目的 研究不同感染阶段HIV感染者胃黏膜中CD4+和CD8+T细胞数量和分布情况,及免疫细胞激活状态的改变.方法 有胃黏膜组织活检标本的HIV感染者42例,其中有明确临床分期诊断的36例,另选非HIV感染者胃黏膜组织活检标本10例为对照,利用免疫组织化学方法检测研究对象胃黏膜活检组织中CD4、CD8及CD38的表达,以图像分析系统分析其差异.结果 (1)AIDS患者胃黏膜中CD4+T细胞与对照组和无症状者相比,均显著减少(P(0.01),无症状者多数淋巴滤泡中仍有一定量CD4+T细胞,间质中多呈不均匀聚集分布,统计学与正常对照组差异无统计学意义(P>0.05);(2)HIV感染者胃黏膜内CD8+T细胞普遍噬腺体和黏膜上皮,部分病例胃黏膜内CD8+T细胞局部过度增生,与对照组相比,CD8+T细胞在感染者胃黏膜中显著增多(P<0.01),无症状者与AIDS患者CD8+T细胞差异无统计学意义(P>0.05);(3)在HIV感染者胃黏膜内,CD38阳性细胞主要分布于黏膜表层至浅1/3～2/3层,与对照组相比,HIV感染者胃黏膜中CD38表达增强(P<0.01),无症状者与MDS患者CD38表达差异无统计学意义(P>0.05).结论 HIV感染者胃黏膜中CD4+T细胞的数量和分布与疾病进展有密切联系,HIV对CD4+T细胞的感染和破坏导致黏膜免疫系统功能异常,可能是胃黏膜内CD8+T细胞数量增加,CD38表达增强的重要原因之一.     

Comparison of activation marker and TCR V beta gene product expression by CD4+ and CD8+ T cells in peripheral blood and lymph nodes from HIV-infected patients.

Since lymphoid organs constitute the site of active and progressive HIV disease, analysis of their lymphocytes may provide more accurate information on T cell abnormalities than that obtained from studying peripheral blood lymphocytes. The objective of this study was to compare the expressions of activation markers and T cell receptor (TCR) V beta gene products by CD4+ and CD8+ T cells in lymph nodes (LN) and peripheral blood (PB) from healthy individuals and asymptomatic HIV-infected patients to determine whether anomalies that could be identified at the HIV replication site could support the hypothesis of T cell activation by HIV-encoded antigens or superantigens. CD4+ and CD8+ T cells in paired LN and PB obtained from six healthy controls and five asymptomatic HIV-infected individuals were analysed by flow cytometry, using anti-CD38, anti-HLA-DR and 13 anti-V beta MoAbs that cover, approximately, 45% of the T cell repertoire. Analysis of T cell activation marker expression indicated that the percentages of CD4+ and CD8+ T cells bearing CD38 or CD38 and HLA-DR molecules were higher in patients than in controls and, in patients, higher in LN than in PB. Comparison between the V beta repertoires of CD4+ and CD8+ T cells in LN and PB showed that, in each healthy individual, a limited number of V beta families expressed by CD4+ or CD8+ T cells had different repartition in LN and PB, whereas in each HIV+ patient, more V beta families exhibited different distributions and these differences recurred among certain V beta segments, such as V beta 5.3 and V beta 21 in the CD4+ T cell population and V beta 5.2/5.3, V beta 12 and V beta 21 in the CD8+ T cell population. Taken together, these data argue for a skewed TCR repertoire in HIV infection and sustained activation of T cells by HIV-encoded antigens at the site of HIV replication, and further demonstrate that a high proportion of CD4+ T cells are in an activation state that may, indirectly, participate in their functional abnormalities.     

CD69, HLA-DR and the IL-2R identify persistently activated T cells in psoriasis vulgaris lesional skin: blood and skin comparisons by flow cytometry

Many lymphocyte-activation-associated molecules are observed by immunohistochemistry in psoriasis vulgaris lesional skin. Non-T cells in lesional skin also express these molecules. We quantitatively measured the number of T cells expressing cell surface activation-associated molecules (CD69, CD25, CD122, HLA-DR) and co-stimulatory molecules (CD28, CTLA-4, CD80, CD86), including a Type 2 T cell marker (CD30) and CD11b, by flow cytometry of skin and peripheral blood. T cells in single cell suspensions of psoriatic lesional-epidermis-expressed HLA-DR (86%), CD69 (59%), CD25 (55%), CD122 (44%), and CD28 (91%). Dermal T cells showed similar percentages except for CD69 (17%). CD69 was found directly in lesional skin biopsies by immunohistochemistry. Both CD4 and CD8 subsets from lesional skin contained large populations of CD25+ cells with a bias towards CD8 activation in the epidermis and towards CD4 activation in the dermis. CD86, CD80, CTLA-4, CD30 and CD11b were expressed by less than 23% of the T cell populations from both the epidermis and dermis. CD30+CD4+ cells were found two-fold over CD8+ T cells. These results show that the majority of lesional lymphocytes are persistently activated. We also found the majority of Type 2 associated markers primarily on the CD4+ epidermal T cell population. Psoriatic blood contained elevated levels of T cells expressing CD25, primarily within the CD8+ subset. Thus the majority of lesional T cells expressed the three primary activation markers, while psoriatic blood T cells were distinguished by an increase in CD25, specifically within the CTL population.     

HIV/AIDS患者CD28在外周血CD4+、CD8+ T细胞上的表达变化

目的　研究国内HIV AIDS患者CD2 8在外周血CD4 + 、CD8+ T淋巴细胞上表达的变化 ,并探讨这些变化的临床意义。方法　用流式细胞仪检测 5 1例正常对照、14例HIV感染者和 36例AIDS患者的外周血CD4 + 、CD8+ T淋巴细胞表面的CD2 8分子的表达 ,用bDNA法检测 11例HIV感染者和 18例AIDS患者的血浆病毒载量。结果　CD4 + CD2 8+ T细胞的绝对计数与百分比、CD8+ CD2 8+T细胞的百分比均显示为正常对照组 >HIV感染组 >AIDS组 ;而CD8+ CD2 8+ T细胞的绝对计数显示HIV感染组和对照组显著大于AIDS组 ,HIV感染组与对照组间差异无显著性。CD4 + 、CD2 8+ CD4 + T淋巴细胞计数与血浆病毒载量显著负相关。结论　HIV AIDS患者外周血CD2 8在CD4 + 、CD8+ T淋巴细胞上表达随着病情进展而降低 ,反映了细胞免疫功能随着疾病进展损害逐渐加重 ,是判断病情进展的指标。     

Increased cytolytic T lymphocyte activity and decreased B7 responsiveness are associated with CD28 down-regulation on CD8+ T cells from HIV-infected subjects.

The CD28 receptor on CD4+ and CD8+ T cells interacts with B7 molecules on antigen-presenting cells (APC) to generate essential costimulatory signals. The cytolytic potential of CD8+ T cells could be linked to CD28 expression. Since HIV induces dysfunction of both CD4+ and CD8+ T cells, we evaluated CD28 expression and function in both subsets during HIV infection. CD28 expression on CD8+ T cells from HIV+ subjects was strongly reduced in a disease stage-related fashion. CD28- CD8+ T cells preferentially expressed CD57 and CD11b, but lacked CD26 and IL-2R alpha. The CD8+ T cells from the patients showed a significantly reduced proliferative response to co-stimulation with cell-bound anti-CD3 and B7. Nevertheless, when stimulated with plate-fixed anti-CD3, CD8+ T cells from HIV-infected subjects proliferated normally, and normal levels of IL-2R alpha and transferrin-receptor could be induced on CD28- CD8+ T cells from the patients. In addition, stimulation with plate-fixed anti-CD3 induced proliferative responses in highly purified CD28- CD8+ T cells from both HIV- and HIV+ persons. Furthermore, the increased cytotoxic activity of peripheral blood mononuclear cells (PBMC) from HIV+ subjects, measured in an anti-CD3 redirected assay, was predominantly exerted by CD28- CD57+ T cells. CD4+ T cells from the patients showed a slight but significant CD28 down-regulation and were slightly hyporesponsive to B7 co-stimulation. Decrease of CD28 on CD8+ T cells from HIV+ subjects is associated with an impaired response to co-stimulation via B7. CD28- CD8+ T cells from seropositives, however, are not completely inert, since they contain in vivo activated CTL and they can be additionally activated through a B7-independent stimulation.     

Expression of CD28 on CD8+ and CD4+ Lymphocytes During HIV Infection

CD28 interaction with B7 molecules, expressed on the membranes of antigen-presenting cells, costimulates cytokine production, T-cell proliferation and generation of cytotoxic lymphocytes. The expression of CD28 markers on CD4⁺ and CD8⁺ lymphocytes was studied in a group of subjects at various stages of HIV infection. A reduction in the percentage of CD28-bearing CD4⁺ and CD8⁺ cell subsets was observed during the asymptomatic stage of the disease. This reduction was more pronounced in AIDS than in non-AIDS patients. At the same time, an increase in the absolute CD8⁺CD28⁻ cell number (greater in stage A than in stage B and C subjects) was observed in HIV-infected patients. The finding of an altered pattern of CD28 expression on T cells might per se explain certain early defects in the cytokine pattern and in the immune response peculiar to HIV-infected patients.     

补肾宁心方对鼠成骨细胞协同刺激分子表达的升调节作用

目的：探讨补肾宁心方药物血清对成骨细胞（OB）及CD4^＋T细胞协同刺激分子表达的调控作用。方法：颅骨酶解法培养OB，体外模拟雌激素撤退；MACS法分离CD4^＋T；将OB或CD4^＋T分别予以20％对照鼠血清、E2及20％中药血清培养并以LPS刺激，流式细胞术分析OB表面CD80、CD86以及CD4^＋T细胞表面CD28、CTLA-4的表达。结果：E2及中药血清组OB表面CD80、CD86的表达显著增加（P〈0．01）；CsA可降低对照鼠血清组及中药血清组OB表面CD80、CD86的表达（P〈0．01）；各组CD4^＋T细胞CD28和CTLA4的表达无显著改变（P〉0．05）。结论：补肾宁心方可上调OB协同刺激分子CD80、CD86表达；该作用可被CsA阻滞；而对T细胞CD28／CTLA-4表达无显著影响，其免疫学意义有待进一步研究：     

Concentrations of Soluble CD95 and CD8 Antigens in the Plasma and Levels of CD8+CD95+, CD8+CD38+, and CD4+CD95+ T Cells Are Markers for HIV-1 Infection and Clinical Status

Apoptosis mediated via the CD95 (FAS/APO-1) receptor is thought to play a role in the depletion of CD4+ T cells in HIV infection. In the present study expression of the CD95 antigen on lymphocyte subsets and the plasma level of soluble CD95 (sCD95) were determined in HIV-1-infected adults. The expression of CD95 was increased on CD8 cells in all groups of HIV+ individuals, while increased expression of CD95+ cells on CD4 cells was limited to individuals with CD4 counts of <200 mm³. The proportion of CD4+ that expressed CD95 was inversely correlated with the percentage of CD4+ PBL. The concentration of sCD95 was significantly higher in the plasma of HIV-infected individuals than in normal controls. The level of sCD95 in HIV-infected subjects showed no correlation with the percentage of PBL expressing CD95, indicating that the increased level of sCD95 did not reflect release from CD95+ PBL. The plasma sCD95 concentration was significantly correlated with the percentage of CD8+ cells and, particularly, with CD8+CD38– cells. A striking inverse correlation was found between the sCD95 plasma concentration and the proportion of CD4+CD95+ cells out of the total CD4+ population. There was no correlation between the serum level of sCD95 and that of soluble CD8 (sCD8), both of which were increased in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals was correlated with the percentage of CD95+ and CD8+CD38+ cells. The present study indicates that plasma sCD95 may be one of the factors that regulate apoptotic death of lymphocytes in HIV infection.     

Importance of CD80/CD86-CD28 interactions in the recognition of target cells by CD8+CD122+ regulatory T cells

CD8+CD122+ regulatory T cells are a newly identified, naturally occurring type of regulatory T cell that produce interleukin-10 (IL-10) and effectively suppress interferon-gamma (IFN-gamma) production from both CD8+ and CD4+ target cells. Molecular mechanisms responsible for the recognition of target cells by CD8+CD122+ regulatory T cells were investigated in this study by using an in vitro culture system that reconstitutes the regulatory action of these cells. CD8+CD122( regulatory T cells did not produce IL-10 and did not suppress the IFN-gamma production of allogeneic target T cells when they were stimulated by immobilized anti-CD3 antibody alone, but they clearly produced IL-10 and suppressed the IFN-gamma production of target cells when stimulated by anti-CD3 plus anti-CD28-coated beads. IFN-gamma production by major histocompatibility complex-class I-deficient T cells was also suppressed by CD8+CD122+ regulatory T cells stimulated with anti-CD3 plus anti-CD28 antibody but was not suppressed by cells stimulated by anti-CD3 alone. Experiments examining the blockade of cell surface molecules expressed on either the regulatory cells or the target cells by adding specific neutralizing antibodies in the culture indicated that CD80, CD86, and CD28 molecules were involved in the regulatory action, but cytotoxic T lymphocyte antigen-4, inducible costimulatory molecule (ICOS) and programmed death-1 (PD-1) molecules were not. Finally, CD8+CD122+ cells isolated from CD28-knockout (CD28-/-) mice showed no regulatory activity. These results indicate that CD8+CD122(+) regulatory T cells recognize target T cells via the interaction of CD80/CD86-CD28 molecules to become active regulatory cells that produce suppressive factors such as IL-10.     

Changes in the number of CD80(+), CD86(+), and CD28(+) peripheral blood lymphocytes have prognostic value in melanoma patients

Our aim was to evaluate whether the number of circulating lymphocytes expressing costimulatory molecules can be associated with melanoma prognosis. We determined the concentration of peripheral blood lymphocytes, which expressed the CD80/CD86 or CD28/CTLA-4 molecules, in 38 patients with cutaneous melanoma and 27 controls. The number of each cell subset was compared between patients and controls, as well as between groups of patients stratified according to Breslow thickness of the primary tumor (< or = 2 mm vs > 2 mm) or to survival after 3 years. The concentration of circulating lymphocytes expressing the CD80/CD86 molecules was not significantly different between patients and controls. There was a lower number of CD3(+)CD8(+)CD28(+) cells, as well as a higher CD3(+)CD8(+)/CD3(+)CD8(+)CD28(+) cell ratio, in melanoma patients than in controls. Melanoma patients with thinner tumors and those surviving revealed an increase of CD19(+)CD80(+) and CD19(+)CD80(+)CD86(+) cells, as well as a higher concentration of CD3(+)CD4(+)CD28(+) cells. CD80(+) B cells and a low CD8 suppressor/cytolytic cell ratio correlate with a good prognosis in melanoma. Our findings support our conclusion that CD80(+) B cells may be important antigen presenting cells that can contribute to an antimelanoma immune response and are candidates to be monitored in melanoma patients.     

Human Immunodeficiency Virus Type 1 Replication,Immune Activation, and Circulating CytotoxicT Cells Against Uninfected CD4+ T Cells

Cytotoxic T lymphocytes (CTL) that kill uninfected activated CD4⁺ T cells can be induced in vitro by stimulating CD8⁺ T cells with activated autologous CD4⁺ T cells. Similar CTL have been detected in circulating T cells from human immunodeficiency virus type 1 (HIV)-infected individuals. To define the in vivo correlates of this CTL activity, we studied plasma -2 microglobulin and HIV RNA levels, T-lymphocyte subset counts, and expression of CD28 on CD8⁺ T cells concurrently with circulating CTL activity against uninfected CD4⁺ T cells in 75 HIV-infected individuals at different stages of disease progression. Mean values of each parameter were compared in subsets of this group of 75 segregated on the basis of this CTL activity. The group with CTL against uninfected activated CD4⁺ T lymphocytes had more CD8⁺ T cells, a higher percentage of CD28^– CD8⁺ T cells, and higher plasma levels of HIV RNA and -2 microglobulin. CTL against uninfected activated CD4⁺ T cells were predominantly CD28^– and in HIV-infected individuals were associated with immunological or virological evidence of progressive disease. In HIV infection, circulating CTL activity against uninfected activated CD4⁺ T lymphocytes is associated with immune activation, CD8⁺ T cell expansion, accumulation of CD28^– CD8⁺ T cells, and inadequate suppression of HIV replication.     

Effect of CD80 and CD86 on T Cell Cytokine Production

Conjugation of the T cell receptor (TCR) with antigen/MHC proteins must be accompanied by conjugation of T cell counterreceptors (CD28 or CTLA-4) with costimulatory molecules CD80 or CD86 (B7-1 or B7-2) on antigen presenting cells (APC) to avert T cell anergy, and to provide essential signals for T cell activation and cytokine production. However, T cells and APC express changing patterns of counterreceptors and costimulatory molecules during the immune response. To determine the involvement of CD80 and CD86 in costimulation of T cell cytokine production, T cells were incubated with peritoneal exudate macrophages, which express CD80 and CD86, and stimulated in vitro for 48 or 72 hrs with anti-CD3 in the presence or absence of blocking antibody to CD80 or CD86. Alternatively, enriched anti-CD3 stimulated T cells were costimulated with antibody to CD28 and CTLA-4. Production of T cell IL-2, IL-4, and IL-5 was depressed in the presence of anti-CD86 but not anti-CD80. Production of IFN-γ was significantly blocked by either anti-CD80 and anti-CD86. Anti-CD28 was a potent costimulator of IFN-γ and IL-2 production, but a less potent costimulator of IL-4 and IL-5 production. The data suggest that T cell counterreceptors and APC costimulatory molecules act with varying efficacies at stimulating production of T cell cytokines.     

Effect of CD80 and CD86 on T Cell Cytokine Production

Conjugation of the T cell receptor (TCR) with antigen/MHC proteins must be accompanied by conjugation of T cell counterreceptors (CD28 or CTLA-4) with costimulatory molecules CD80 or CD86 (B7-1 or B7-2) on antigen presenting cells (APC) to avert T cell anergy, and to provide essential signals for T cell activation and cytokine production. However, T cells and APC express changing patterns of counterreceptors and costimulatory molecules during the immune response. To determine the involvement of CD80 and CD86 in costimulation of T cell cytokine production, T cells were incubated with peritoneal exudate macrophages, which express CD80 and CD86, and stimulated in vitro for 48 or 72 hrs with anti-CD3 in the presence or absence of blocking antibody to CD80 or CD86. Alternatively, enriched anti-CD3 stimulated T cells were costimulated with antibody to CD28 and CTLA-4. Production of T cell IL-2, IL-4, and IL-5 was depressed in the presence of anti-CD86 but not anti-CD80. Production of IFN-γ was significantly blocked by either anti-CD80 and anti-CD86. Anti-CD28 was a potent costimulator of IFN-γ and IL-2 production, but a less potent costimulator of IL-4 and IL-5 production. The data suggest that T cell counterreceptors and APC costimulatory molecules act with varying efficacies at stimulating production of T cell cytokines.     

Phenotypic analysis of complement receptor 2+ T lymphocytes: reduced expression on CD4+ cells in HIV-infected persons.

While expression of complement receptor 2 (CR2) (CD21) on some CD4+ cell lines renders them more susceptible to infection by complement-treated human immunodeficiency virus (HIV), coexpression of CR2 and CD4 on peripheral blood lymphocytes has not, until recently, been observed. Several recent studies, however, have found that human T lymphocytes express low levels of CR2. Additionally, complement treatment of HIV before addition to these cells has been reported to increase virus expression in peripheral blood lymphocyte cultures. These findings suggest that complement-mediated enhancement of infection of human T cells could occur in vivo and have prompted us to examine both the phenotypic properties of CD4+CR2+ T cells in healthy persons and the expression of CR2 on CD4+ lymphocytes during HIV infection. As was previously reported, we observed CR2 on a proportion (10-50%) of both CD8+ and CD4+ T cells. Approximately half of CD4+CR2+ cells expressed the memory cell markers CD45RO and CD29, 80% expressed the naive marker CD45RA, while 22% expressed CD25. These values were not substantially different from total CD4+ cells. Stimulation of lymphocytes with phytohaemagglutinin (PHA), OKT3 or calcium ionophore but not with phorbol myristate acetate (PMA) or interleukin-2 (IL-2) decreased expression of CR2 on CD4 cells by half over a 3-day culture period. The per cent of CD4+ cells expressing CR2 was significantly decreased in patients with asymptomatic and symptomatic HIV infection compared to uninfected control donors (P = 0.0001). In contrast, the decrease in CR2 expression was not observed with CD8+ lymphocytes from HIV-infected persons. These results confirm that CR2 is expressed on human T lymphocytes and suggest that a subset of CD4+ lymphocytes is selectively affected in HIV-infected individuals.     

Decreased CD40 ligand induction in CD4 T cells and dysregulated IL-12 production during HIV infection.

During HIV infection various cytokines are overproduced in early stages, whereas in advanced disease cytokines of the T helper 1 type (e.g. interferon-gamma (IFN-gamma)) are selectively deficient. During antigenic stimulation, the production of type-1 cytokines is enhanced by IL-12, secreted by antigen-presenting cells (APC) after their interaction with activated CD4 T cells. Two factors are essential in this process: priming APC with IFN-gamma and triggering the CD40 receptor on APC by CD40 ligand (CD40L). In view of the importance of this pathway, we compared its regulation in HIV-infected and control subjects. After cross-linking of the T cell receptor (TCR)/CD3 complex, the proportional expression of CD40L was similar on CD4+ T cells from controls and from patients with high circulating CD4 T counts (> 500/microl), but CD40L up-regulation was significantly reduced in patients with more advanced disease. Simultaneous triggering of the costimulatory receptor CD28 on T cells through its natural ligand CD80 partly corrected the CD40L defect in patients with intermediate CD4 T counts (200-500), but not in AIDS patients. Early production of IFN-gamma was preserved in lymphocytes from HIV+ patients. The expression of CD40 on peripheral monocytes from HIV+ subjects was increased in a disease stage-related fashion. Stimulation of mononuclear cells through cell-bound CD40L and soluble IFN-gamma induced significantly higher IL-12 in cultures from patients with > 200 circulating CD4 T cells, whereas IL-12 production was marginally decreased in cultures from patients with < 200 CD4 T cells, compared with healthy control cultures. In conclusion, our data suggest that impaired CD40L induction on CD4 T cells contributes to deficient type-1 responses through decreased IL-12 production in AIDS infection, whereas enhanced CD40-mediated IL-12 production in less advanced stages might contribute to increased levels of various cytokines in early disease