Jacalin: a lectin mitogenic for human CD4 T lymphocytes.

The major protein component of seeds from jackfruit is the lectin jacalin. Jackfruit crude extracts are known to stimulate human lymphocytes, but the mitogenic properties of purified jacalin have not been studied in detail so far. Study of the proliferative response of cell populations from normal human peripheral blood to purified jacalin showed it to be mitogenic through an interaction with lymphocytes by its lectin-binding site, as shown by inhibition by IgA. Jacalin failed to stimulate B cells to proliferate and to undergo plasma cell maturation. It induced a proliferation of CD4 (and not CD8) lymphocytes, as shown by phenotypic analysis of cells recovered after culture and by studies of the response of isolated T cell subpopulations. The proliferative response to jacalin was autologous monocyte-dependent. The kinetics of jacalin-induced DNA synthesis, expression of CD25 and interleukin-2 secretion was shifted by comparison with that induced by phytohaemagglutinin. The reason for the restricted responsiveness of CD4 T cells is presently unclear; jacalin bound to all blood cells and did not significantly co-cap with CD1, CD2, CD3, CD4, CD8 and CD38, and jacalin response was neither enhanced nor inhibited by antibodies to these surface antigens.     

癌灶CD4~+CD25~+和CD8~+ T细胞亚群与卵巢浆液性癌患者生存期相关

检测卵巢浆液性癌患者癌组织中CD4+CD25+及CD8+T细胞的数目,探讨其两种T细胞介导的免疫功能对疾病发展及预后的影响。免疫组织化学双标及单标的染色方法检测41例卵巢浆液性癌患者手术切除癌组织标本中CD4+CD25+和CD8+T细胞的数目。结果显示,癌灶中CD4+CD25+T淋巴细胞为(19.95±11.50)个/10HPF,CD8+T淋巴细胞为(43.46±16.69)个/10HPF。生存分析发现高CD4+CD25+T细胞组患者总生存期较低CD4+CD25+T细胞组缩短,差异有显著性(P<0.05);而高CD8+T细胞组患者总生存期与低CD8+T细胞组相比延长,且差异有显著性(P<0.05),此外两种T细胞数目与患者年龄、病理分级、临床分期、腹水细胞学及淋巴结转移等临床病理因素均无关(P>0.05)。结果表明,卵巢浆液性癌中高CD4+CD25+T细胞提示患者预后不良,可能与CD4+CD25+T细胞介导的免疫抑制导致肿瘤免疫逃逸有关;癌组织中高CD8+T细胞提示患者预后较好,两种T细胞对卵巢浆液性癌预后的评估有重要的价值,同时可以通过阻断CD4+CD25+T细胞的免疫抑制作用改善卵巢浆液性癌患者的预后,为卵巢癌治疗提供靶目标。     

中国恒河猴(Macaca mulatta)外周血CD4+CD25+T淋巴细胞的研究

目的:研究中国恒河猴外周血中CD4 CD25 T淋巴细胞亚群及其分布频率。方法:利用流式细胞术对50只中国恒河猴外周血CD4 CD25 T淋巴细胞进行了分析。结果:发现所有被检测的恒河猴个体中均存在明显的CD4 CD25 T淋巴细胞亚群;CD4 CD25 T淋巴细胞大约占CD4 T淋巴细胞的9.1%(变化范围为2.6%～18.1%);其中CD4 CD25highT淋巴细胞约占2.5%(0.3%～5.5%)。对不同年龄和性别个体中CD4 CD25 T淋巴细胞频率的初步分析未发现统计学上有年龄或性别差异。结论:中国恒河猴可用于与CD4 CD25 T细胞相关的人类疾病的研究中。     

Circulating CD3+ CD4+ CD+ T lymphocytes in multiple sclerosis

Triple-antibody flow cytometry was used to search for distinctive populations of peripheral blood lymphocyte immunophenotypes in multiple sclerosis (MS). Using monoclonal antibodies to the cell surface markers CD3, CD4, and CD8, T cell subsets were quantified on a cohort of 31 MS patients (not treated with corticosteroids for at least 6 months), 30 healthy donors, and 14 patients with other autoimmune diseases (also corticosteroid treatment-free for at least 6 months). Untreated MS patients displayed a significantly greater population of CD3+CD4+CD8+ circulating T cells than healthy donors (P = 0.023). Patients with other autoimmune diseases displayed mean populations of CD3+CD4+CD8+ cells greater than normal donors and less than MS, but not significantly different from either. An additional 45 MS patients who had received corticosteroid therapy within the previous 6 months were phenotyped. Treatment of symptomatic MS with corticosteroids was associated with a smaller population of circulating CD3+CD4+CD8+ cells. Some MS patients have significantly greater numbers of peripheral blood T lymphocytes simultaneously expressing CD3, CD4, and CD8 surface markers than healthy donors and this population of cells may be reduced by corticosteroids treatment. This triple positive phenotype may be a manifestation of a systemic immune abnormality in MS.     

Defective lymphokine production by most CD8+ and CD4+ tumor-specific T cell clones derived from human melanoma-infiltrating lymphocytes in response to autologous tumor cells in vitro

Human melanomas are infiltrated by tumor-reactive T lymphocytes. However, the ability of these cells to elicit a specific anti-tumor response in vivo remains to be established. Because lymphokine production is critical for T cell functions, we have analyzed the capacity of melanoma-specific tumor-infiltrating lymphocyte (TIL) clones to produce major lymphokines: interleukin-2 (IL-2), interferon-γ (IFN-γ) and interleukin-4 (IL-4), as well as tumor necrosis factor (TNF), in response to direct antigen presentation by autologous and allogeneic tumor cells. We report here that, upon stimulation by autologous melanoma cells, all TIL clones secreted TNF but only a few of them produced significant amounts of IL-2, IL-4 or IFN-γ. Nonetheless, all these clones consistently produced two or three of these last lymphokines upon stimulation with phorbol myristate acetate and calcium ionophore, as well as IL-2 upon CD3 stimulation, showing the existence of three lymphokine profiles among them: Th1, Th0 and a profile characterized by IL-2 and IL-4, but not IFN-γ secretion. Stimulation of TIL clones by allogeneic melanoma lines sharing the appropriate HLA-peptide complexes revealed that defective IL-2 production seemed to be a constant feature for some clones, while it was, for other clones, dependent on the antigen-presenting tumor cells. For this last type of clone, we further showed that defective IL-2 induction resulted from an LFA-3 defect of some melanoma cells or from distinct yet undefined defects of other melanoma lines. Our data suggest that defective lymphokine secretion may be an essential component of the in vivo failure of melanoma-reactive TIL to control tumor development. Interestingly both CD4⁺ and CD8⁺ TIL clones from one patient were fully activated by the autologous melanoma cells in vitro, supporting a potential role of such TIL in spontaneous or induced tumor rejection.     

Lysis of CD4+ lymphocytes by non-HLA-restricted cytotoxic T lymphoe from HIV-infected individuals

Individuals infected with HIV have elevated numbers of total and activated CD8⁺ lymphocytes in peripheral blood. CD8⁺ lymphocytes from HIV-infected individuals have been shown to mediate non-human histocompatibility-linked antigen (HLA)-restricted suppression of viral replication, HLA-restricted killing of cells expressing HIV antigens, and killing of uninfected lymphocytes. We studied CD8⁽ T lymphocytes that lysed autologous CD4+ lymphocytes, hetcrologous CD4¹ lymphocytes from HIV-infected individuals and uninfected CD4⁺ lymphocytes. Killing in all cases required T cell receptor (TCR)-mediated recognition or triggering. However, these CD8 cytotoxic T lymphocytes (CTL) killed HLA class I mismatched CD4* lymphocytes and CD4⁴ lymphocytes treated with a MoAb against HLA-A, B and C antigens (PA2.6) which blocks HLA class I-restricted killing. HLA class H-negativc CD4* T lymphoma cells (CEM.NK^R) were also killed by anti-CD3 inhibited CTL. Stimulation of peripheral blood lymphocytes (PBL) from HIV-infected individuals, but not uninfected controls, with concanavalin A (Con A) and IL-2, induced non-HLA-restricted TCR aft¹, CD8^f CTL which lysed CD4⁺ lymphocytes. Activation ofCD4’lymphocytes increased their susceptibility to CD8^f CTL-mediated lysis. In HIV infection, a population of non-HLA-restricted CTL which lyse activated CD4⁺ lymphocytes is expanded. The expansion of CTL with unusual characteristics is interesting, because the stimulus for this expansion is unknown. CTL which recognize activated CD4⁺ cells could play a role in immune regulation and the pathogenesis of A IDS.     

T cell receptor specificities of Toxoplasma gondii-reactive mouse CD4+ T lymphocytes and Th1 clones

The Toxoplasma gondii-directed CD4⁺ T cell response in chronically infected mice was studied with respect to both T cell receptor diversity and antigen specificities. T cell receptor chains Vβ4, 6, 8, 10, and 14 were predominantly found on toxoplasma-reactive CD4⁺ splenocytes. This repertoire was also detected among T. gondii-specific CD4⁺ T cell clones. Analysis of clonotypic cytokine profiles revealed typical Th1 clones secreting interleukin-2, interferon-γ and tumour necrosis factor activity and Th2 clones producing interleukin-4 and interleukin-10. Five distinct toxoplasma antigens (p26, p40, p55, p58 and p60) were detected in electrophoretically separated toxoplasma lysate by five individual Th1 clones. Parallel testing of CD4⁺ T lymphocytes from infected mice confirmed that these specificities constitute the peak immunogenic fractions of toxoplasma lysate. The expression patterns of two clonotypic, T cell-stimulatory parasite antigens were studied in detail. While p55 was expressed by mouse-virulent and avirulent T. gondii isolates and in both the tachyzoite and bradyzoite stages, p58 was detected only in virulent strains from intraspecies subgroup I. Thus, we describe the heterogeneity of toxoplasmic immunodominant T cell antigens including a 58-kDa group I-restricted molecule which may provide a marker for virulent isolates. Received: 3 February 1997     

Circulating CD4+CD8+ T lymphocytes in patients with Kawasaki disease

We serially monitored cell surface antigen expression on mononuclear cells in peripheral blood isolated from patients with Kawasaki disease (KD), and found, for the first time, that a markedly increased number of CD4⁺CD8⁺ T lymphocytes was present in some of the patients (11 of the 24 cases). The cases of five of these 11 patients were complicated with coronary artery lesion (CAL); the 13 patients with normal numbers of CD4⁺CD8⁺ T lymphocytes did not have CAL. The patients' age, sex and grade of systemic inflammation evaluated by peripheral leucocyte count and serum C-reactive protein levels were not correlated to the number of CD4⁺CD8⁺ T lymphocytes. Other cell surface antigen characteristics of the CD4⁺CD8⁺ T lymphocytes included CD3⁺, CD45RA⁺, CD45RO⁺, CD16^?, and HLA-DR⁺. These results indicate that the surface antigen characteristics of the KD peripheral blood examined were the same as those of Epstein–Barr virus infection without CD45RA⁺. These findings provide useful information for the analysis of the pathogenesis of KD.     

Absence of Epstein-Barr virus-specific, HLA class II-restricted CD4+ cytotoxic T lymphocytes in infectious mononucleosis.

Cytotoxic T lymphocytes (CTL) with the CD4+ phenotype that recognize major histocompatibility complex (MHC) class II antigens are detectable very frequently in cultures of human alloreactive or virus-specific T cells. The significance of these CD4+ CTL for an immune reaction in vivo is not clear. Since Epstein-Barr virus (EBV) transformed B cells express HLA-class I and class II antigens equally well both CD8+ and CD4+ CTL should be stimulated during an acute EBV infection. We analysed the MHC specificity and the phenotype of EBV-specific CTL from patients with infectious mononucleosis (IM). When tested directly without any previous culture, T cells from patients in the acute phase of IM showed specific MHC-restricted cytotoxicity against the autologous B cell line. Addition of a HLA class I specific monoclonal antibody (MoAb) but not of a HLA class II specific MoAb resulted in a complete blocking of the lytic activity. Cell sorting revealed that the entire cytotoxic activity was present in the CD8+ fraction whereas no specific CTL were detectable in the CD4+ fraction. The absence of cytotoxicity in CD4+ cells was not due to a lack of activation of these cells since both CD8+ and CD4+ cells were activated in situ, showing spontaneous growth in interleukin-2 (IL-2) and expressing the activation marker TP103. Frequency estimation revealed that 1/300-1/600 CD8+ but only 1/2000-1/4000 CD4+ T cells gave rise to a specific CTL colony after 10 days. If CD4+ colonies were tested repeatedly for cytotoxicity we found that CD4+ CTL acquired their cytotoxicity during in vitro culture. In addition, we isolated EBV-specific CD4+ T cell clones able to lyse their stimulator cells in the presence but not in the absence of lectin, even after a long period of culture. Taken together our results show that cytotoxicity mediated by CD4+ T cells does not play a role in an anti-viral immune response.     

HIV Tat蛋白增加CD4+ T淋巴细胞bcl-2表达并抑制TRAIL诱导的细胞凋亡

目的探讨HIV Tat蛋白对CD4^＋ T淋巴细胞bcl-2表达的影响，并探讨肿瘤坏死因子相关凋亡诱导配体（TRAIL）与经HIV Tat蛋白刺激后的CD4^＋ T淋巴细胞凋亡的相互关系。方法用Western blot方法测定经HIV Tat蛋白刺激后，CD4＋ T淋巴细胞表达bcl-2的水平，以λ-氨基放线菌素D（7-AAD）和AnnexinV染色方法测定CD4＋ T淋巴细胞的凋亡。结果HIV Tat蛋白能明显增加CD4＋ T淋巴细胞bcl-2的表达，以100ng/ml为最佳浓度；7-AAD染色结果表明100ng/ml重组TRAIL能诱导53．85％±2．63％的CD4^＋ T淋巴细胞发生凋亡，如CD4^＋ T淋巴细胞经HIV Tat蛋白刺激后，则仅有16．04％±5．26％的细胞发生凋亡，此作用能被多克隆抗-Tat蛋白抗体抑制。Annexin V染色取得了同样的结果。结论经HIV Tat蛋白刺激后CD4^＋ T淋巴细胞bcl-2的表达明显增加，并能抑制由重组TRAIL诱导的细胞凋亡，提示HIV Tat蛋白是导致HIV在CD4^＋ T淋巴细胞内持续感染的重要调节蛋白，在HIV感染中起十分重要作用。     

Assessment of alloreactive T cell subpopulations of aged mice in vivo. CD4+ but not CD8+ T cell-mediated rejection response declines with advanced age

The present investigation explored age-related alterations in T cell populations mediating allospecific responses in vivo. Healthy aged and young H-2^b and H-2^bxH-2^k mice were engrafted with major histocompatibility complex (MHC) class II-disparate bm12 skin, rejection of which requires CD4⁺ T cells, and MHC class I-disparate bm1 skin, rejection of which requires CD8⁺ T cells. Aged mice of both genders exhibited prolonged survival of bm12 skin grafts relative to their young counterparts but rejected bm1 skin grafts at a rate equivalent to that of young mice. Consistent with prolonged survival of bm12 skin grafts, markedly diminished levels of Ia^bm12 CTL activity were elicited from T cells of aged mice in vitro. However, no such decline was observed in the level of K^bm1 CTL from T cells of aged mice. The alterations in Ia^bm12 allospecific responses were not attributable to quantitative changes in CD4⁺ T cells of aged mice, and addition of soluble T cell helper factors to response cultures of aged mice did not augment Ia^bm12 cytotoxic T lymphocytes activity. These data demonstrate that aging fundamentally affects CD4⁺ T cell-mediated allospecific responses particularly in vivo, and that deficient generation of soluble T cell helper factors alone cannot explain this deficit.     

The bone marrow peptide (myelopeptide-2) abolishes induced by human leukemia HL-60 cell suppression of T lymphocytes

Myelopeptide-2 (MP-2) Leu-Val-Val-Tyr-Pro-Trp originally isolated from the supernatant of porcine bone marrow cell culture was examined for its capacity to restore the mitogen responsiveness of human T lymphocytes inhibited by conditioned media from HL-60 leukemia cells (HL-60 CM). MP-2 added to phytohemagglutinin (PHA)-stimulated T lymphocytes together with HL-60 CM abolished the suppression of T-lymphocyte proliferative response in a dose-dependent manner. Another bone marrow hexapeptide Phe-Leu-Gly-Phe-Pro-Thr, MP-1, did not display this action in that experimental system. MP-2 was also effective being added after T-lymphocyte exposure to HL-60 CM which suggests its recovery but not protective effect on T-lymphocytes treated with tumor cell products. Flow cytometry analysis revealed HL-60 CM influence on the expression of CD3 and CD4 T-cell surface antigens. It decreased the content of CD3- and CD4-positive cells and induced the appearance of T lymphocytes with reduced density of CD3 and CD4 antigens. MP-2 was able to restore the T-cell phenotype altered by HL-60 CM. MP-2 seems to be promising in anti-tumor therapy.     

Evidence for a CD4-associated calcium influx independent of the phosphoinositide transduction pathway in human T cells

We recently showed, using human Jurkat T cell variants lacking the T cell receptor (TCR)/CD3 complex, that the lectin jacalin is able to trigger intracellular calcium increase provided that CD4 is expressed on the cell surface. Involvement of the CD4 molecule in jacalin-induced biological effects was furthermore demonstrated in differentiated U937 myelomonocytic cells expressing or not expressing CD4, and is confirmed here in human CD4-transfected mouse thymoma cells. In the present paper, we analyze the CD4-associated calcium response triggered by jacalin independently of the TCR/CD3 complex. We show that the observed calcium rise results from a direct long-lasting calcium influx from the outside without release of calcium from intracellular stores. We demonstrate that it is independent of the phosphoinositide phospholipase C transduction pathway. Moreover, we show that this peculiar calcium response can be blocked by protein tyrosine kinase inhibitors (herbimycin and genistein) giving evidence of the involvement of a protein tyrosine kinase, the best candidate of which is the CD4-associated p56^lck. Altogether, our results suggest that, independently of the TCR/CD3 complex, CD4 may be involved in the triggering of a calcium signal dependent on a protein tyrosine kinase and independent of the phosphoinositide transduction pathway.     

CD4-mediated functional activation of human CD4+CD25+ regulatory T cells

Naturally occurring CD4(+)CD25(+)FoxP3(+) regulatory T cells (CD25(+) Tregs) constitute a specialized population of T cells that is essential for the maintenance of peripheral self-tolerance. The immune regulatory function of CD25(+) Tregs depends upon their activation. We found that anti-CD4 antibodies activate the suppressive function of human CD25(+) Tregs in a dose-dependent manner. We demonstrate that CD4-activated CD25(+) Tregs suppress the proliferation of CD4(+) and CD8(+) T cells, their IL-2 and IFN-gamma production as well as the capacity of CD8(+) T cells to re-express CD25. By contrast, anti-CD4 stimulation did not induce suppressive activity in conventional CD4(+) T cells. These results identify CD4 as a trigger for the suppressive function of CD25(+) Tregs and suggest a possible CD4-mediated exploitation of these cells.     

RA患者外周血CD8＋CD28-和CD4＋CD25＋调节性T细胞的表达及疾病活动性指标相关性分析

目的：检测类风湿性关节炎（RA）患者外周血CD8＋CD28-、CD4＋CD25＋调节性T细胞亚群,探讨其与临床活动性指标的关系。方法：采用流式细胞术检测台州医院RA患者外周血CD8＋CD28-、CD4＋CD25＋ T细胞亚群比例,探讨调节性T细胞与RA活动性、类风湿因子（RF）、免疫球蛋白（Ig）、C反应蛋白（CRP）、补体C3、抗CCP抗体、抗核抗体（ANA）、血小板（PLT）及血沉（ESR）的关系。结果：活动期RA患者外周血CD4＋CD25＋调节性T细胞亚群比例显著低于正常对照组（P〈0.01）,但稳定期RA患者与正常对照组结果差异无统计学意义（P〉0.05）。活动期和稳定期RA患者CD8＋CD28-与正常对照组相比较,结果无统计学意义（P〉0.05）;CD4＋CD25＋与CRP密切相关（r=-0.593,P〈0.05）,CD8＋CD28-与ESR相关系数呈弱相关。CD4＋CD25＋和CD8＋CD28-细胞与RF、IGG、C3、ANA、anti-CCP和PLT未见明显相关性。结论：活动期RA患者外周血CD4＋CD25＋ T细胞亚群比例减少,CD4＋CD25＋ T细胞可能与类风湿性关节炎疾病进展有关。     

Inhibition of human immunodeficiency virus infection by the lectin jacalin and by a derived peptide showing a sequence similarity with gp120

Jacalin is a plant lectin known to specifically induce the proliferation of CD4⁺ T lymphocytes in human. We demonstrate here that jacalin completely blocks human immunodeficiency virus type 1 (HIV-1) in vitro infection of lymphoid cells. Jacalin does not bind the viral envelope glycoprotein gp120. Besides other T cell surface molecules, it interacts with CD4, the high-affinity receptor to HIV. Binding of jacalin to CD4 does not prevent gp120-CD4 interaction and does not inhibit virus binding and syncytia formation. The anti-HIV effect of the native lectin can be reproduced by its separated a-subunits. More importantly, we have defined in the a-chain of jacalin a 14-amino acid sequence which shows high similarities with a peptide of the second conserved domain of gpl20. A synthetic peptide corresponding to this similar stretch also exerts a potent anti-HIV effect. This peptide is not mitogenic for peripheral blood mononuclear cells and does not inhibit anti-CD3-induced lymphocyte proliferation. These results make jacalin a chain-derived peptide a potentially valuable therapeutic agent for acquired immunodeficiency syndrome.     

Communication between human mast cells and CD4+ T cells through antigen‐dependent interactions

Mast cells (MCs) are immune cells residing in tissues where pathogens are first encountered. It has been indicated that MCs might also be involved in setting the outcome of T‐cell responses. However, little is known about the capacity of human MCs to express MHC class II and/or to capture and present antigens to CD4⁺ T cells. To study the T‐cell stimulatory potential of human MCs, CD34⁺ stem cell derived MCs were generated. These cells expressed HLA‐DR when stimulated with IFN‐γ, and, importantly, presented peptide and protein for activation of antigen‐specific CD4⁺ T cells. The interplay between MC and T cell led to increased HLA‐DR expression on MCs. MCs were present in close proximity to T cells in tonsil and expressed HLA‐DR and CD80, indicating their ability to present antigens to CD4⁺ T cells in T‐cell areas of human LNs. Our data show that MCs can present native antigens to human CD4⁺ T cells and that HLA‐DR expressing MCs are present in tonsil tissue, indicating that human MCs can directly activate T cells and provide a rationale to study the potential of MCs to prime and/or skew human T‐cell responses.     

Non-antigen specific CD8+ T suppressor lymphocytes

Abstract. The homeostasis of peripheral immune system function is maintained by the activity of regulatory lymphocytes. Among these cells, a subset of CD8+CD28- T suppressor lymphocytes has recently been characterized for the capacity to mediate their effects without antigen restriction. These non-antigen-specific CD8+ T suppressor lymphocytes originate from circulating CD8+CD28- T lymphocytes after stimulation with interleukin-2 and interleukin- 10. CD8+ suppressor cells inhibit both antigen-specific CD4+ T cell proliferation and cellular cytoxicity through secretion of cytokines such as interferon-, interleukin-6, and interleukin-10. The function of CD8+ suppressor cells is impaired in patients with systemic lupus erythematosus in relapse as well as in patients with systemic sclerosis with disease progression, suggesting the involvement of CD8+ suppressor cells in the pathogenesis of autoimmune diseases. Interestingly, CD8+ suppressor cells have been found among tumor-infiltrating lymphocytes, which could be related to tumor-induced-immunosuppression. Failure to generate CD8+ suppressor cells from the peripheral blood is frequently observed in HIV-infected patients. It remains to be clarified whether this phenomenon is due to depletion and/or functional impairment of this cell subset or to their compartmentalization in peripheral tissues and immunocompetent organs where they could contribute to the induction of immunodeficiency.