Peripheral blood lymphocytes of patients with common variable immunodeficiency (CVI) produce reduced levels of interleukin-4, interleukin-2 and interferon-gamma, but proliferate normally upon activation by mitogens.

Peripheral blood lymphocytes (PBL) of 11 patients with CVI produced reduced levels of interleukin-4 (IL-4) upon activation by mitogens as compared with those secreted by PBL of healthy donors. The interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production by PBL of a series of 15 patients with CVI was also reduced. Decreased levels of IL-4 or IL-2 and IFN-gamma production were not only observed after activation by phytohaemagglutinin (PHA) at concentrations of 10 and 1 micrograms/ml, but also after activation by concanavalin A (Con A, 10 micrograms/ml). Longitudinal studies indicated that this defective lymphokine production was consistent upon testing periods up to 5 months. No correlation between reduced IL-4, IL-2 or IFN-gamma production was observed. PBL of patients that produced reduced levels of one lymphokine generally secreted normal levels of the other two lymphokines. Despite the reduced synthesis of the T cell growth factors IL-2 and IL-4, the proliferative responses of the PBL of the patients were in the normal range, which is compatible with the finding that IL-2 and IL-4 have synergistic effects on lymphocyte proliferation, particularly when one of these lymphokines is present at suboptimal concentrations. Since IL-2, IL-4 and IFN-gamma can act as B cell growth and differentiation factors, our data suggest that the reduced synthesis of these lymphokines may contribute to the deficient immunoglobulin production in patients with CVI.     

脂氧素对Jurkat T细胞增殖和白细胞介素-2/白细胞介素-2受体表达的影响

目的：研究脂氧素对Jurkat T细胞增殖和白细胞介素-2表达的影响。方法:体外培养Jurkat T细胞，anti-CD3（2 mg/L）和anti-CD28（2 mg/L）单抗刺激Jurkat细胞活化，加入不同浓度脂氧素（0.1 nmol/L-100 nmol/L）共同孵育24h后，加入［3H］-TdR继续孵育6 h，液闪仪测放射性活度；或收集培养上清，ELISA测IL-2水平，收集细胞，流式细胞仪检测细胞表面IL-2受体α亚单位CD25表达，PI染色后经流式细胞仪进行细胞周期分析。结果:脂氧素剂量依赖性抑制anti-CD3和anti-CD28活化的Jurkat T细胞增殖（P<0.05）；细胞周期分析发现脂氧素处理组S期细胞比例减少；脂氧素显著降低培养上清中IL-2 含量（P<0.05）但对CD25表达无明显影响（P>0.05）。结论:脂氧素能抑制活化Jurkat T细胞增殖和白细胞介素-2表达；脂氧素可通过影响T淋巴细胞的活化增殖进而发挥免疫负性调节作用。     

Schistosome-derived inhibitory factor: an immunosuppressive agent preferentially active on T lymphocytes

We have previously shown that schistosome-derived inhibitory factors (SDIF) inhibited lymphocyte proliferation and induced immunosuppression. Crude SDIF was purified by successive gel filtration and reverse-phase high-performance liquid chromatography. Purified SDIF preparations strongly inhibited the proliferation of different T cell line cells, while other cell lines (B cells, macrophages and fibroblasts) were almost not affected by SDIF. The inhibition of T cell proliferation by SDIF was not mediated through an Interleukin-2-dependent mechanism since both Interleukin-2-dependent and -independent T cells were inhibited. SDIF-activity was absorbed by cells in a time- and cell-number-dependent fashion at 4 degrees C, suggesting the existence of a possible receptor for SDIF. However, the difference in sensitivity to SDIF proliferation inhibition could not be attributed to the presence or absence of this receptor since cells from SDIF-sensitive and SDIF-resistant cell lines absorbed SDIF activity in the same way.     

Inhibitory versus stimulatory effects of natural human interferon-alpha on proliferation of lymphocyte subpopulations.

Highly purified natural human interferon-alpha (IFN-alpha) inhibited in a dose-dependent manner the proliferation of human peripheral blood lymphocytes (PBL) stimulated with T-cell mitogen concanavalin A (Con A) or with interleukin-2 (IL-2). Contrary to this inhibitory effect, IFN-alpha at the same concentrations significantly increased proliferation of PBL stimulated with B-cell mitogen bacterial lipopolysaccharide (LPS) or with IL-3, and even spontaneous proliferation of PBL was enhanced by IFN-alpha. Proliferation of Con A-stimulated PBL depleted of CD8+ cells was sensitive to the inhibitory action of IFN-alpha, while proliferation of the Con A-stimulated CD4+ cell-depleted PBL was not affected by IFN-alpha. The inhibitory effect of IFN-alpha on PBL proliferation was due to neither inhibition of IL-2 receptor (IL-2R) expression, activation of suppressor cells, nor inhibition of lymphokine production. Rather, IFN-alpha augmented production of IL-1 and IL-2 by PBL. These results show that the suppressive effect of natural IFN-alpha on Con A-induced proliferation of PBL is due to a direct growth-inhibitory effect on CD4+ T cells, and that IFN-alpha simultaneously augments production of lymphokines. This could in turn lead to the increased proliferation of IFN-alpha-resistant cell populations.     

Effects of cyclosporin A on expression of IL-2 and IL-2 receptors in normal and multiple sclerosis patients.

The effects of the immunosuppressant Cyclosporin A (CsA) on T cell activation in vivo and in vitro were examined using the monoclonal antibody, anti-Tac, for interleukin 2 (IL-2) receptors and 3.9C2, for a peptide fragment of human IL-2. Peripheral blood lymphocytes (PBL) were stimulated with PHA in the presence of CsA. The expression of IL-2 receptors and production of IL-2 were reduced. PBL from CsA-treated MS patients had significantly lower proportions of Tac+ cells compared with untreated patients. This inhibition was not reflected in the CSF lymphocyte populations from CsA-treated patients and indicates the urgent need for an immunosuppressant drug which can enter the CNS in sufficient concentrations to inhibit local T cell activation.     

Proliferative response of human CD4+ T lymphocytes stimulated by the lectin jacalin

The Galβ(1–3)GalNAc-binding lectin jacalin is known to specifically induce the proliferation of human CD4⁺ T lymphocytes in the presence of autologous monocytes and to interact with the CD4 molecule and block HIV-1 infection of CD4⁺ cells. We further show that jacalin-induced proliferation is characterized by an unusual pattern of T cell activation and cytokine production by human peripheral blood mononuclear cells (PBMC). A cognate interaction between T cells and monocytes was critical for jacalin-induced proliferation, and human recombinant interleukin (IL)-1 and IL-6 did not replace the co-stimulatory activity of monocytes. Blocking studies using monoclonal antibodies (mAb) point out the possible importance of two molecular pathways of interaction, the CD2/LFA-3 and LFA-1/ICAM-1 pathways. One out of two anti-CD4 mAb abolished jacalin responsiveness. Jacalin induced interferon-γ and high IL-6 secretion, mostly by monocytes, and no detectable IL-2 synthesis or secretion by PBMC. In contrast, jacalin-stimulated Jurkat T cells secreted IL-2. CD3^? Jurkat cell variants failed to secrete IL-2, suggesting the involvement of the T cell receptor/CD3 complex pathway in jacalin signaling. IL-2 secretion by CD4^? Jurkat variant cells was delayed and lowered. In addition to CD4, jacalin interacts with the CD5 molecule. Jacalin-CD4 interaction and the proliferation of PBMC, as well as IL-2 secretion by Jurkat cells were inhibited by specific jacalin-competitive sugars.     

Glycosylation-dependent interaction of Jacalin with CD45 induces T lymphocyte activation and Th1/Th2 cytokine secretion

Jacalin, an alpha-O-glycoside of the disaccharide Thomsen-Friedenreich antigen (galactose beta1-3 N-acetylgalactosamine, T-antigen)-specific lectin from jackfruit seeds, has been shown to induce mitogenic responses and to block infection by HIV-1 in CD4+ T lymphocytes. The molecular mechanism underlying Jacalin-induced T cell activation has not been elucidated completely yet. In the present study, protein tyrosine phosphatase (PTPase) CD45 was isolated from a Jurkat T cell membrane fraction as a major receptor for Jacalin through affinity chromatography and mass spectrometry. CD45, which is highly glycosylated and expressed exclusively on the surface of lymphocytes, is a key regulator of lymphocyte signaling, playing a pivotal role in activation and development. We found that the lectin induced significant IL-2 production by a CD45-positive Jurkat T cell line (JE6.1) and primary T cells. However, this effect did not occur in a CD45-negative Jurkat T cell line (J45.01) and was blocked completely by a specific CD45 PTPase inhibitor in Jurkat T (JE6.1) and primary T cells. Furthermore, we also observed that Jacalin caused a marked increase in IL-2 secretion in response to TCR ligation and CD28 costimulation and contributed to Th1/Th2 cytokine production by activating CD45. Jacalin increased CD45 tyrosine phosphatase activity, which resulted in activation of the ERK1/2 and p38 MAPK cascades. Based on these findings, we propose a new, immunoregulatory model for Jacalin, wherein glycosylation-dependent interactions of Jacalin with CD45 on T cells elevate TCR-mediated signaling, which thereby up-regulate T cell activation thresholds and Th1/Th2 cytokine secretion.     

The role of monocytes in IL-3 enhancement of human T cell proliferation

We have assessed the role of recombinant human interleukin 3 (rIL-3) in the activation and proliferation of peripheral blood lymphocytes (PBL) and their various subsets. rIL-3 significantly enhanced the CD2-responsiveness of unfractionated PBL. Proliferating cells were mainly T lymphocytes and most of them expressed CD4. This effect was absent following adherent cell depletion from PBL. rIL-3 also failed to directly activate purified lymphocytes, nor did it increase T cell responsiveness to mitogens and/or IL-2. By contrast, rIL-3 induced monocyte functions as enhancement of IL-1 production was observed following treatment of these cells by rIL-3. This effect was removed by anti IL-3 mAb addition to these cultures. In addition, anti IL-1 antibody partially inhibits IL-3-derived responses. Together, these data strongly suggest that IL-3 stimulation of T lymphocytes is related mainly to its ability to enhance monocyte functions.     

Immune mechanisms in congenital cytomegalovirus infection: activation of CMV-specific T helper cells (CMV-Th) by exogenous IL-2.

Infants with congenital CMV infection have a specific defect in CMV-induced lymphocyte proliferation, providing a model for investigation of mechanisms of viral immune recognition and immune response. In the present study the possible role of a defect in lymphokine activation of CMV-specific T helper cells (Th) was examined. IL-1 activity was detected in supernatants of patient mononuclear cell (MNC) cultures stimulated with CMV. In contrast, no IL-2 activity could be detected in supernatants of CMV-stimulated MNC cultures, whereas PHA induced normal IL-2 production. Addition of low concentrations of either crude TCGF or recombinant IL-2 (rIL-2) resulted in 2-4 fold augmentation of CMV-specific lymphocyte proliferation; exogenous IL-2 had no effect on MNC responses to HSV. CMV-specific Th lines/clones were established from three congenital CMV patients by initial stimulation of MNCs with CMV antigen and 0.1 U/ml rIL-2, followed by repeated stimulation with CMV, HLA-matched allogeneic feeder cells and 10% TCGF. The resulting CMV Th lines/clones proliferated specifically in response to stimulation with CMV antigen and produced endogenous IL-2. Thus, the immune deficiency associated with congenital CMV may either be due to an intrinsic defect in CMV-Th activation or CMV-specific suppressor cell activity.     

Sheep red blood cells enhance T-lymphocyte proliferation

Small numbers of sheep red blood cells (SRBC) markedly augmented the proliferation of T lymphocytes activated by antigens or mitogens. This effect occurred with as few as one SRBC per T lymphocyte and with intact or osmotically lysed red cells. When increasing numbers of SRBC was added to T lymphocyte cultures stimulated with PHA or autologous cells, T lymphocyte proliferation peaked sharply at 10 to 50 SRBC per T cell. The SRBC did not influence resting T-lymphocytes. Rather, the effect occurred after T lymphocyte activation during cell division. There was a detectable increase in interleukin 2 (IL-2) receptor generation but not in IL-2 production by activated T lymphocytes cultured with SRBC versus medium alone. Finally, anti-T11 antibody could inhibit the SRBC enhancing effect on T-lymphocyte function, suggesting that an empty erythrocyte (E) receptor on the T lymphocyte was necessary for the SRBC action.     

Inhibition of interleukin-2 production by adherent cell factors from lepromatous leprosy patients.

Twenty-four hour supernatants (MoF) were obtained from monocyte rich 2 h adherent cells of 19 leprosy patients and four healthy contacts. MoF from borderline and lepromatous patients produced 52-61% inhibition of human interleukin-2 (IL-2) production by a PHA conditioned T cell line (Jurkat). Non-adherent cell supernatants and MoF from tuberculoid and healthy individuals had little effect on IL-2 production. The suppression effected by MoF was in the first 12 h of initiation of PHA stimulated Jurkat cell cultures. Suppressive MoF did not interfere with (1) IL-2 release, (2) IL-2 utilization by Con A-induced T cell blasts or (3) constitutive proliferation of Jurkat cells. Such MoF were released spontaneously from adherent cells of bacilliferous leprosy patients but required in vitro antigen triggering in long term treated lepromatous patients. It is possible that the unresponsiveness associated with lepromatous leprosy is related to the inhibition of IL-2 production by suppressive factors, thereby, preventing the further expansion of antigen reactive T cells.     

Inhibition of CD28-mediated T cell costimulation by the phosphoinositide 3-kinase inhibitor wortmannin

T lymphocyte activation requires at least two signals, one via the antigen-specific T cell receptor and a second via the surface molecule CD28 which provides signals critical to interleukin-2 (IL-2) production and T cell proliferation. We have previously shown (Ward S. G., Westwick J., Hall N. and Sansom D. M. Eur. J. Immunol. 1993. 23: 2572) that CD28 stimulates phosphoinositide (PI) 3-kinase activity, indicating that D-3 phosphoinositides may act as mediators of CD28-induced T cell costimulation. Here, we report that immunoprecipitation of CD28 molecules from Jurkat cells stimulated with the CD28-ligand B7, results in a ligand-dependent association of CD28 with PI 3-kinase. This association correlates with the appearance of PI 3-kinase enzymatic activity in CD28 immunoprecipitates and the formation of D-3 phosphoinositides. Consistent with the hypothesis that D-3 phosphoinositides are important mediators of CD28 signaling, treatment of T cells with the PI 3-kinase inhibitor wortmannin, inhibited both T cell proliferation and production of IL-2, but not the response of T cells to exogenous IL-2. Hence, abrogation of PI 3-kinase activity by wortmannin, appears sufficient to disrupt the costimulatory pathway utilized by CD28, indicating a central role for this enzyme in the CD28 signaling pathway.     

Interleukin 4 inhibits the interleukin 2-induced production of its functional antagonist, interferon gamma

Interferon gamma (IFN gamma) inhibits many effects of interleukin (IL)-4. Its production largely parallels cell proliferation but is regulated independently. As IL-4 inhibits several IL-2-induced effects including proliferation of human peripheral blood mononuclear cells, we investigated its influence on the IL-2-induced IFN gamma production. We found that both absolute IFN gamma production and IFN gamma production per proliferation unit (1000 cpm) in response to IL-2 were inhibited by IL-4. IL-2-induced interferon production was inhibited by IL-4 in both sheep red blood cell rosetting and non-rosetting cells. In bidirectional mixed lymphocyte culture, IL-4 alone enhanced proliferation but suppressed IFN gamma production. As 48% of IFN gamma-producing cells are known to show T cell phenotype, the nearly total inhibition of IFN gamma production is evidence for suppression of T cell response to IL-2. Additionally, we found that the inhibition of IL-2-induced proliferation by IL-4 was significantly more pronounced at low cell densities. Basal proliferation was only inhibited in serum-containing media. These data stress the importance of other lymphokines or accessory cells in the regulation of early lymphocyte activation.     

Essential role of the adaptor protein Nck1 in Jurkat T cell activation and function

The non-catalytic region of tyrosine kinase (Nck) is proposed to play an essential role in T cell activation. However, evidence based on functional and biochemical studies has brought into question the critical function of Nck. Therefore, the aim of the present work was to investigate the role of Nck in T cell activation. To study this, the human Jurkat T cell line was used as a model for human T lymphocytes. The short interfering (si) RNA targeting Nck1 gene was used with electroporation to knock-down Nck1 protein expression in Jurkat T cells. Primary human CD4 T cells were also transfected with the siRNA of Nck1. The results showed that decreased Nck1 protein expression did not affect the apoptosis of the transfected Jurkat T cells compared with control siRNA-transfected cells and non-transfected cells. Upon CD3ε/CD28 stimulation, knock-down of Nck1 in Jurkat T cells caused a decrease in CD69 expression and in interleukin (IL)-2 secretion. Similarly, knock-down of Nck1 in primary CD4 T cells also caused decreased CD69 expression. However, no significant alterations of CD69 and IL-2 expression were found upon phytohaemagglutinin (PHA)/phorbol myristate acetate (PMA) stimulation. Knock-down of Nck1 had no effect on the proliferation of Jurkat T cells stimulated with either PHA or anti-T cell receptor (TCR) monoclonal antibody (C305). The reduced Nck1 expression in Jurkat cells was also associated with a reduced phosphorylation of extracellular regulated kinase (Erk)1 and Erk2 proteins upon CD3ε/CD28 stimulation. In conclusion, the decreased Nck1 protein in Jurkat T cells resulted in an impairment of TCR-CD3-mediated activation involving a defective Erk phosphorylation pathway.     

Glutamine protects activated human T cells from apoptosis by up-regulating glutathione and Bcl-2 levels

Glutamine is the most abundant amino acid in the body. A decrease of plasma glutamine concentrations is found in catabolic stress and is related to susceptibility to infections. Glutamine is known to modulate lymphocyte activation; however, little is known about glutamine modulation of cell death of activated human T cells. Using Jurkat T cells, we investigated glutamine modulation of T-cell apoptosis activated by PMA plus ionomycin. We found that glutamine at various concentrations significantly enhanced IL-2 production, cell proliferation, and cell viability of Jurkat T cells. Glutamine also decreased the number of apoptotic cells stimulated with PMA plus ionomycin as demonstrated by flow cytometry. Meanwhile, glutamine down-regulated CD95 and CD95L expression, but up-regulated CD45RO and Bcl-2 expression in activated T cells. Further investigation of CD95-mediated caspase activities revealed that supplementation of glutamine significantly decreased caspase-3 and caspase-8 activities in activated T cells. Since oxidative stress is closely associated with induction of lymphocyte apoptosis, we found that glutamine significantly increased glutathione (GSH), but decreased reactive oxygen species levels in activated T cells. Blockade of intracellular GSH formation enhanced, but exogenous GSH supplementation decreased, activated T-cell apoptosis. Studying normal peripheral lymphoproliferation, we also found that the presence of glutamine increased lymphoproliferation as well as Bcl-2 and CD95 expression; but decreased CD95L and activation-induced T-cell death. Taken together, glutamine appeared to augment lymphoproliferation but suppressed activation-induced T-cell death in both Jurkat T cells and human peripheral T lymphocytes.     

In vivo effect of isoprinosine on interleukin-2 production, lymphocyte mitogenesis and NK activity in normal and cyclophosphamide immunosuppressed mice

The in vivo effect of isoprinosine on IL-2 production, mitogen-induced proliferation and NK activity of lymphocytes from normal as well as cyclophosphamide (CY) treated mice has been investigated. Isoprinosine was given in a single dose (50 mg/kg or 5 mg/kg) to normal or CY treated mice (250 mg/kg i.p. simultaneously to isoprinosine). An enhancement of T lymphocyte proliferation and IL-2 production was observed in both cases. There was no correlation between the small effect observed in T lymphocyte proliferation and the enhancement of IL-2 levels found in the supernatants of Con A activated spleen cells, specially in normal mice. Administration of isoprinosine every day (50 mg/kg) augmented Con A induced mitogenesis, IL-2 production and NK activity in animals treated with cyclophosphamide, but not in normal mice. Isoprinosine could be of interest in a combined treatment with immunosuppressants for the restoration of certain immune functions. The effect of isoprinosine on immune responses may be mediated in part by changes in IL-2 activity.     

Hereditary deficiency of OKT4-positive cells: studies for mode of inheritance and lymphocyte functions.

Two Graves' patients were found to have no OKT4+ cells in their peripheral blood lymphocytes (PBL). However, the reactivity of their lymphocytes with T4(T4A) and anti Leu-3a was normal and no autoantibodies to the OKT4 determinant were found in their sera. Cytofluorographic analysis of PBL from their family members showed three types of immunofluorescence profiles with OKT4. The first type was the complete OKT4+ cell deficiency, the second was the normal percentage of OKT4+ cells with half immunofluorescence intensity and the third was the normal staining pattern with OKT4. Phytohaemagglutinin (PHA) and pokeweed mitogen (PWM) induced blastogenesis; PWM induced IgG synthesis, autologous and allogeneic mixed lymphocyte reaction, and Interleukin-2 (IL-2) production of their PBL were also normal. These results suggest that (i) the expression of determinant to OKT4 is transmitted as autosomal incomplete dominant trait and (ii) OKT4+ cell deficiency is not accompanied by a lack of the inducer/helper subset of T cells.     

Suppressor activity of anergic T cells induced by IL-10-treated human dendritic cells: association with IL-2- and CTLA-4-dependent G1 arrest of the cell cycle regulated by p27Kip1

We have previously shown that human IL-10-treated dendritic cells (DC) induce an antigen-specific anergy in CD4+ T lymphocytes. These anergic T cells are characterized by an inhibited proliferation, a reduced production of IL-2, and additionally display antigen-specific suppressor activity. In this study we investigated the mechanisms underlying the anergic state and regulatory function of these T cells. We did not observe enhanced rates of programmed cell death of anergic CD4+ suppressor T cells compared to T cells stimulated with mature DC. Cell cycle analysis by DNA staining and Western blot experiments revealed an arrest of anergic CD4+ T suppressor cells in the G1 phase. High levels of the IL-2-dependent cyclin-dependent kinase (cdk) inhibitor p27Kip1 were found in anergic CD4+ suppressor T cells resulting in an inhibited activation of retinoblastoma protein and an arrest of cell cycle progression in the G1 phase. Addition of IL-2, but not blocking of the CTLA-4 pathway restored the proliferation of the suppressor T cells. In contrast, both treatments induced a down-regulation of p27Kip1 and acomplete inhibition of the antigen-specific regulatory function as demonstrated by high proliferation and enhanced IFN-gamma production of co-cultured T cells. Further experiments demonstrated that p27Kip-expressing regulatory CD4+CD25+ T cells did not contribute to induction of T cell anergy in this model. Our data show that regulatory function of anergic CD4+ suppressor T cells is associated with an arrest in the G1 phase of the cell cycle mediated by increased levels of the IL-2- and CTLA-4-dependent cdk inhibitor p27Kip1.     

Trypanosoma cruzi trans-sialidase potentiates T cell activation through antigen-presenting cells: role of IL-6 and Bruton's tyrosine kinase

Polyclonal lymphocyte activation and hypergammaglobulinemia characterize the acute phase of Chagas' disease, a debilitating condition caused by Trypanosoma cruzi. Such pathogenic hyper-reactivities not only compromise specific host defense against the pathogen, but may also contribute to infection-induced chronic autoimmune responses. Recent studies showed that T. cruzi trans-sialidase (TS) directly stimulates the polyclonal proliferation and Ig secretion of normal murine B cells in a T-independent, Bruton's tyrosine kinase (Btk)-dependent manner. Related to this observation, we now show that parasite-derived and recombinant TS potentiate the proliferation and cytokine secretion of normal T cells triggered by antigen-specific and non-specific stimuli. TS potentiates T cell activation through stimulating B cells and macrophages, independent of CD40/CD40L and CD43 pathways. In contrast, optimal TS potentiation requires interleukin-6 (IL-6) and Btk, as it is significantly reduced in splenocytes from IL-6-/- and Btk-defective Xid mice. The results suggest that TS, directly and indirectly, activates both antigen-presenting cell and T cell compartments, and that TS-induced IL-6 may further amplify such activation. These observations open up the possibility that TS drives the polyclonal lymphocyte activation in acute T. cruzi infection, a phenomenon contributing to the pathogenesis of Chagas' disease.