T lymphocytes from the normal human peritoneum contain high frequencies of Th2-type CD8+ T cells

The majority of peritoneal T lymphocytes have been shown to be CD8⁺ and to co-express CDw60. Expression of CDw60 characterizes CD8 T cells capable of secreting interleukin (IL)-4 and supporting IgG production by B cells. We analyzed at the clonal level the functional cytokine profile of CD8⁺ T lymphocytes from the normal human peritoneum. While the majority of the clones produced interferon (IFN)-γ and exhibited high alloantigen-specific cytolytic activity, some clones secreted IL-4 and IL-5 but no detectable IFN-γ. These Th2-type CD8⁺ T cell clones provided substantial B cell help for IgG and IgA synthesis and exhibited reduced cytolytic activity. Our results suggest that distinct subsets of CD8⁺ T cell may occur in different immune compartments.     

Signaling via CD28 costimulates lymphokine production,but does not reverse unresponsiveness to interleukin-2 in anti-CD3 triggered Th1 cells

Previously, it has been described that the ability of murine T_h1 cells to proliferate in response to exogenous interleukin (IL)-2 is blocked when these cells are exposed to immobilized anti-CD3 antibodies. In the present study we examined whether simultaneous triggering of the T cell antigen CD28 can prevent the induction of unresponsiveness to IL-2 in T_h1 cells. We report that costimulation of T_h1 cells with anti-CD28 monoclonal antibodies (mAb) did not overcome unresponsiveness to IL-2 induced by various amounts of immobilized anti-CD3 antibodies. However, stimulation with anti-CD28 mAb strongly augmented IL-2 and interferon-γ production in anti-CD3-exposed T_h1 cells. Thus, despite the fact that anti-CD28 mAb is a potent costimulus for lymphokine production, signaling through CD28 does not seem to be sufficient to trigger proliferation in T_h1 cells activated via the T cell receptor. These data suggest the existence of at least three signals to trigger T_h1 cell activation. The first is mediated by ligation of the T cell receptor. One cosignal, delivered by the CD28 molecule, leads to IL-2 production. A third, still undefined, signal is required for proliferation in response to IL-2.     

The interleukin-12 subunit p40 specifically inhibits effects of the interleukin-12 heterodimer

The recently discovered cytokine interleukin (IL)-12 is a heterodimeric protein of two disulfide-bonded subunits of 35 and 40 kDa. IL-12 has multiple effects on T cells and natural killer (NK) cells. In particular it appears to be a major factor for the development of cellular immunity. So far activity of the single subunits alone has not been described, however their expression is regulated independently. In this report we demonstrate for the first time that the mouse IL-12 subunit p40 (IL-12p40) specifically antagonizes the effects of the IL-12 heterodimer in different assay systems. The proliferation of mouse splenocytes activated by phorbol ester and IL-12 was inhibited by IL-12p40, whereas the proliferation induced by phorbol ester and IL-2 was not affected. Furthermore, the synthesis of interferon (IFN)-γ by mouse splenocytes activated with IL-2 and IL-12 was suppressed by IL-12p40. Purified mouse splenic CD4⁺ T cells produced IFN-γ upon activation with plate-bound anti-CD3 monoclonal antibody which was enhanced more than tenfold in the presence of IL-12. In this system IL-12p40 inhibited only the enhancement caused by IL-12 but not IFN-γ synthesis of CD4⁺ T cells stimulated with anti-CD3 alone. Moreover, IL-12p40 inhibited the effects of IL-12 on differentiated T helper type 1 (T_h1) cells. IFN-γ production by T_h1 cells induced in a T cell receptor-independent way by macrophages and IL-2 or macrophages and IL-12 was greatly reduced by IL-12p40 providing evidence for the endogenous synthesis of IL-12 in the Th1 cell, macrophage and IL-2 co-cultures. The specificity of inhibition was clearly demonstrated in the homotypic aggregation assay of Th1 cells. Incubation of Th1 cells with either IL-2 and IL-12 or IL-2 and tumor necrosis factor induces LFA-1/ICAM-1-dependent aggregation. Only IL-2 + IL-12 but not IL-2 + tumor necrosis factor-induced aggregation was inhibited in a dose-dependent manner by IL-12p40. Thus, the IL-12 subunit p40 appears to be a specific inhibitor for the IL-12 heterodimer.     

Development in vitro of human CD4+ thymocytes into functionally mature Th2 cells. Exogenous interleukin-12 is required for priming thymocytes to produce both Th1 cytokines and interleukin-10

Fresh postnatal thymocyte cell suspensions were directly cloned under limiting dilution conditions with either phytohemagglutinin or toxic shock syndrome toxin-1 (TSST-1), a bacterial superantigen. Cultures contained allogenic irradiated feeder cells and interleukin (IL)-2, in the absence or presence of exogenous IL-4, interferon (IFN)-γ or IL-12. The resulting CD4⁺ T cell clones generated under these different experimental conditions were then analyzed for their ability to produce IL-2, IL-4, IL-5, IL-10, IFN-γ and tumor necrosis factor (TNF)-β in response to stimulation with phorbol 12-myristate 13-acetate (PMA)+anti-CD3 monoclonal antibody or PMA + ionomycin. Different from T cell clones generated from peripheral blood, virtually all CD4⁺ T cell clones generated from human thymocytes produced high concentrations of IL-2, IL-4 and IL-5, but no IFN-γ, TNF-β or IL-10. Moreover, after activation, these clones expressed on their surface membrane both CD30 and CD40 ligand, but not the product of lymphocyte activation gene (LAG)-3, and provided strong helper activity for IgE synthesis by allogeneic B cells. The Th2 cytokine pattern could not be modified by the addition of IFN-γ. However, upon addition of exogenous IL-12, the resulting CD4⁺ thymocyte clones produced TNF-β, IFN-γ, and IL-10 in addition to IL-4 and IL-5. These results suggest that CD4⁺ human thymocytes have the potential to develop into cells producing the Th2 cytokines IL-4 and IL-5, whereas the ability to produce both Th1 cytokines and IL-10 is acquired only after priming with IL-12.     

T helper type 1 development of naive CD4+ T cells requires the coordinate action of interleukin-12 and interferon-γ and is inhibited by transforming growth factor-β

It was observed in vitro and in vivo that both interferon (IFN)-γ and interleukin (IL)-12 can promote the development of T helper type 1 (T_H1) cells. Since IL-12 was shown to be a costimulator for the production of IFN-γ by T or natural killer (NK) cells, IL-12 might play only an indirect role in T_H1 differentiation by providing IFN-γ which represents the essential differentiation factor. Using anti-CD3 monoclonal antibody (mAb) for activation of naive CD4⁺ T cells in the absence of accessory cells we could demonstrate that costimulation by IFN-γ alone results only in marginal T_H1 development. Similarly, IL-12 in the absence of IFN-γ is only a poor costimulator for inducing differentiation towards the T_H1 phenotype. Our data indicate that both cytokines are required to allow optimal T_H1 development and that IL-12 has a dual role, it promotes differentiation by direct costimulation of the T cells and also enhances the production of IFN-γ which serves as a second costimulator by an autocrine mechanism. Another cytokine that was reported to favor T_H1 differentiation in certain experimental systems is transforming growth factor (TGF)-β. With naive CD4⁺ T cells employed in this study TGF-β strongly inhibited the production of IFN-γ triggered by IL-12 as well as the IL-12-induced T_H1 development. When TGF-β was combined with anti-IFN-γ mAb for neutralization of endogenous IFN-γ the T_H1-inducing capacity of IL-12 was completetly suppressed.     

Cytokine secretion profiles of cloned T cells from human aortic atherosclerotic plaques

T cells take part in the chronic inflammatory reaction in atherosclerotic plaques, but their specific role in atherosclerosis has not yet been fully elucidated. Nevertheless, one may anticipate that activated T cells may secrete cytokines capable of modulating the morphology and hence the stability of plaques by regulating cell proliferation, lipid metabolism, and extracellular matrix (ECM) synthesis and/or degradation. This study has been designed to investigate the functional properties of T cells in atherosclerotic lesions. For this purpose, T-cell clones were generated from atherosclerotic plaques isolated from human aortas obtained at autopsy from six subjects. Cloned cells were activated with PMA and OKT-3 to initiate cytokine production and cytokine profiles of CD4-positive clones were measured by ELISA. The majority of the T-cell clones (125/155, 81 per cent) produced both interferon (IFN)-γ and interleukin (IL)-4 (type 0 cytokine profile). Moreover, the production of IFN-γ was dominant in the majority of these clones. A type 1 cytokine profile (high levels of IFN-γ and low levels of IL-4) was found in 17 per cent of the clones (27/155). Only three clones (2 per cent) showed a type 2 cytokine secretion pattern (high levels of IL-4 and low levels of IFN-γ). No cytolytic activity could be established in plaque-derived T cells. Our results show that the T-cell population in atherosclerotic lesions is heterogeneous, but the most dominant T cell by far is the one with a type 0 cytokine profile. The dominant secretion of IFN-γ by T-cell clones suggest an important role for plaque T cells in modulating the growth and differentiation of other cells, such as macrophages and smooth muscle cells in atherosclerotic plaques. Copyright © 1999 John Wiley & Sons, Ltd.     

Diversion of CD4+ T cell development from regulatory T helper to effector T helper cells alters the contact hypersensitivity response

Cutaneous sensitization to reactive haptens and subsequent challenge results in a T cell-mediated response, contact hypersensitivity (CHS). Recent results from this laboratory have indicated that hapten sensitization induces two populations of reactive T cells: CD8⁺ T cells producing interferon (IFN)-γ which mediate the response and CD4⁺ T cells producing interleukin (IL)-4 and IL-10 which negatively regulate the magnitude and duration of the response. Since CD4⁺ T cell development to either IFN-γ- (Th1) or IL-4/IL-10- (Th2)-producing cells is dependent upon the cytokine environment during antigen priming, we hypothesized that CD4⁺ T cell induction in a Th1-promoting environment would not only alter the CD4⁺ T cell cytokine-producing phenotype but also the course of the CHS response. Administration of the Th1-promoting cytokine IL-12 during hapten sensitization resulted in a CHS response of greater magnitude following challenge and extended the duration of the response. In hapten-sensitized mice depleted of CD8⁺ T cells, treatment with IL-12 induced effector CD4⁺ T cells. Histological examination of challenged ear tissue from these mice indicated minimal edema and an acute mononuclear cell infiltration more typical of classical delayed-type hypersensitivity than CHS. Hapten-primed CD4⁺ T cells from IL-12 treated, sensitized mice produced IFN-γ, but not IL-4 in response to T cell receptor-mediated stimulation. Use of neutralizing anti-IFN-γ antibody indicated that IL-12 not only directly promoted Th1 development but also indirectly inhibited Th2 development through stimulation of IFN-γ production at the time of hapten sensitization. Overall, these results demonstrate that diversion of CD4⁺ T cell development to Th1 effector cells rather than to Th2 cells alters the efferent nature of CHS and removes a primary regulatory mechanism of the immune response.     

Selective stimulation of T helper 2 cytokine responses by the anti-psoriasis agent monomethylfumarate

Type 2 cytokines are thought to have a protective role in psoriasis vulgaris by dampening the activity of T helper 1 (Th1) lymphocytes. The aim of the present study was to determine the effect of monomethylfumarate (MMF), the most active metabolite of the new anti-psoriatic drug Fumaderm®, on the production of cytokines and the development of Th subsets. MMF was found to enhance interleukin (IL)-4 and IL-5 production by CD2/CD8 monoclonal antibody-stimulated peripheral blood mononuclear cells (PBMC) in a dose-dependent manner. Maximal effects of MMF were found at a concentration of 200 μM and resulted in tenfold enhanced levels of IL-4 and IL-5 production. MMF did not affect the levels of IL-2 production, interferon (IFN)-γ production or proliferative T cell responses in these cultures. Similar effects of MMF were observed in cultures of purified peripheral blood T cells indicating that this compound can act directly on T cells. MMF did not influence cytokine production by purified CD4⁺CD45RA⁺ (unprimed) T cells, but greatly enhanced IL-4 and IL-5 production without affecting IFN-γ production by purified CD4⁺CD45R0⁺ (primed) T cells. Furthermore, MMF also augmented IL-4 and IL-5 production in established Th1/Th0 clones that were stimulated with CD2/CD28 monoclonal antibody. Finally, when PBMC were challenged with Mycobacterium tuberculosis that typically induces Th1 recall responses with strong IFN-γ secretion, MMF again appeared to induce high levels of IL-4 and IL-5 secretion while IFN-γ production was unaffected. These results may be relevant for the development of therapeutic regimens designed to correct inappropriate Th1 subset development in immunopathologic conditions.     

Accessory signaling by CD40 for T cell activation: induction of Th1 and Th2 cytokines and synergy with interleukin-12 for interferon-γ production

The interaction of CD40 ligand (CD40L) on activated T cells with CD40 on B cells, monocytes and dendritic cells is essential for humoral immunity and for up-regulation of antigen-presenting cell (APC) functions, as a result of signaling through CD40. There are also some indications that after interaction with CD40, CD40L can directly signal T cells. In this study we demonstrate that upon stimulation of human peripheral blood T cells through the T cell receptor (TCR)/CD3 complex, CD40/CD40L interaction strongly enhances the production of Th1 cytokines such as interleukin (IL)-2 and interferon (IFN)-γ and Th2 cytokines such as IL-4, IL-5 and IL-10 by a direct effect on T cells. Furthermore, CD40/CD40L interaction synergizes with IL-12 in selectively enhancing IFN-γ production by purified anti-CD3-stimulated T cells. These effects were observed at both the protein and the mRNA level. Both CD4⁺ and CD8⁺ T cells were able to produce IFN-γ in the presence of helper signals from IL-12 and CD40, although CD8⁺ T cells were less active. Since CD40/CD40L interaction also up-regulates IL-12 production and B7 expression by APC, our results suggest that CD40/CD40L interaction is bidirectional, and promotes activation of both APC and T cells.     

Human Th1 cells preferentially induce interleukin (IL)-1β while Th2 cells induce IL-1 receptor antagonist production upon cell/cell contact with monocytes

The role of human T cells in the induction and regulation, upon cell/cell contact, of inflammatory responses by monocytic cells was investigated. The production of interleukin (IL)-1β and IL-1 receptor antagonist (IL-1Ra) by the monocytic THP-1 cell line was measured upon contact with either Th1 or Th2 cell clones. CD4⁺ T cell clones specific for purified protein derivative of Mycobacterium tuberculosis, predominantly Th1 [high interferon (IFN)-γ and low IL-4 producers], or tetanus toxoid, predominantly Th2 (low IFN-γ and high IL-4 producers), were generated. Cell membranes from antigen-stimulated, but not from resting T cell clones induced dose-dependent cytokine production by THP-1 cells. Th1 clones induced higher levels of IL-1β production (484–806 pg/ml) than did Th2 clones (21–114 pg/ml). In contrast, Th1 clones induced lower levels of IL-1Ra (0.9–7.8 ng/ml) than did Th2 clones (7.0–49.6 ng/ml). Similar results were obtained when T cell clones were activated by cross-linked CD3 and CD28. IL-1β production by THP-1 cells correlated with IFN-γ production by T cell clones but was unaffected by IFN-γ neutralization. IL-1Ra production by THP-1 cells correlated with IL-4 production by T cells and was partially inhibited by IL-4 neutralization. These data indicate that activated Th1 and Th2 cells express different molecules on the cell surface able to induce distinct pro-inflammatory (IL-1β) or anti-inflammatory (IL-1Ra) responses in monocytes. This differential induction of molecules with opposite effects on inflammation stresses the functional heterogeneity in CD4⁺ T cells.     

Differential regulation of IL-13 and IL-4 production by human CD8+ and CD4+ Th0, Th1 and Th2 T cell clones and EBV-transformed B cells

In the present study, the requirements and characteristics forthe production of IL-13 by human T cells, T cell clones andB cells were determined and compared with those of IL-4. IL-13was produced by human CD4⁺ and CD8⁺ T lymphocyte subsets isolatedfrom peripheral blood mononuclear cells and by CD4⁺ and CD8⁺T cell clones. CD4⁺ T cell clones belonging to T_h0, T_h1-likeand T_h2-like subsets produced IL-13 following antigen-specificor polyclonal activation. In addition, EBV-transformed B celllines expressed IL-13 mRNA and produced small amounts of IL-13protein. Expression of IL-13 mRNA and production of IL-13 proteinby peripheral blood T cells and T cell clones was induced rapidlyand was relatively long lasting, whereas IL-4 production bythese cells was transient In addition, IL-13 mRNA expressionwas induced by modes of activation that failed to induce IL-4mRNA expression. IL-13 shares many biological activities withIL-4 which Is compatible with the notion that the IL-13 andIL-4 receptors share a common component required for signaltransduction. However, IL-13 lacks the T cell-activating propertiesof IL-4. Here we have shown that this is related to the factthat T cells fall to bind radiolabeled IL-13 and do not expressthe IL-13-speclflc receptor component Taken together, theseresults indicate that the differences In expression and biologicalactivities of IL-4 and IL-13 on T cells may have consequencesfor the relative roles of these cytokines In the immune response.     

慢性乙肝患者树突状细胞对Th1/Th2分化的影响

探讨慢性乙肝患者树突状细胞(dendritic cells,DC)对CD4+Th细胞亚群分化的影响。分离慢性乙肝患者外周血单个核细胞(PBMC),以rhIL-4(50 ng/ml)、rhGM-CSF(10 ng/ml)和rhTNF-α(100 u/ml)诱导培养DC。以流式细胞仪检测DC表面CD1a、CD83、CD80、CD86、HLA-DR分子表达情况。MTT法检测DC刺激同种异体淋巴细胞增殖能力。免疫磁珠分离外周血CD4+T细胞亚群,PMA+Ionomycin刺激后胞内荧光染色,流式细胞仪检测辅助性T细胞(helper T cell,Th)内特征性细胞因子IFN-γ/IL-4以判断Th1/Th2分化。ELISA法检测DC或Th细胞培养上清中IL-6、IL-12、IFN-γ和IL-4的含量。结果:慢性乙肝患者的DC表达CD1a、CD83、CD80、CD86、HLA-DR分子水平明显低于正常人(P<0.01);培养至第7天,慢性乙肝患者DC分泌的IL-12水平低于正常人(P<0.01),而分泌的IL-6水平增高(P<0.05)。与正常人相比,慢性乙肝患者外周血中Th1细胞占CD4+T细胞的百分比较低(P<0.01),其Th细胞培养上清中IFN-γ的量也较低(P<0.01)。患者DC与同种异体的健康人Th细胞共培养,刺激Th1型细胞因子IFN-γ产生的能力低于正常人(P<0.01)。慢性乙肝患者体内DC功能的异常可能导致了外周血Th1细胞分化不足。     

Th1 cells induce and Th2 inhibit antigen-dependent IL-12 secretion by dendritic cells

Dendritic cells are the most relevant antigen-presenting cells (APC) for presentation of antigens administered in adjuvant to CD4⁺ T cells. Upon interaction with antigen-specific T cells, dendritic cells (DC) expressing appropriate peptide-MHC class II complexes secrete IL-12, a cytokine that drives Th1 cell development. To analyze the T cell-mediated regulation of IL-12 secretion by DC, we have examined their capacity to secrete IL-12 in response to stimulation by antigen-specific Th1 and Th2 DO11.10 TCR-transgenic cells. These cells do not differ either in TCR clonotype or CD40 ligand (CD40L) expression. Interaction with antigen-specific Th1, but not Th2 cells, induces IL-12 p40 and p75 secretion by DC. The induction of IL-12 production by Th1 cells does not depend on their IFN-γ secretion, but requires direct cell-cell contact mediated by peptide/MHC class II-TCR and CD40-CD40L interactions. Th2 cells not only fail to induce IL-12 secretion, but they inhibit its induction by Th1 cells. Unlike stimulation by Th1, inhibition of IL-12 production by Th2 cells is mediated by soluble molecules, as demonstrated by transwell cultures. Among Th2-derived cytokines, IL-10, but not IL-4 inhibit Th1-driven IL-12 secretion. IL-10 produced by Th2 cells appears to be solely responsible for the inhibition of Th1-induced IL-12 secretion, but it does not account for the failure of Th2 cells to induce IL-12 production by DC. Collectively, these results demonstrate that Th1 cells up-regulate IL-12 production by DC via IFN-γ-independent cognate interaction, whereas this is inhibited by Th2-derived IL-10. The inhibition of Th1-induced IL-12 production by Th2 cells with the same antigen specificity represents a novel mechanism driving the polarization of CD4⁺ T cell responses.     

Different cytokine production profiles of γδ T cell clones: Relation to inflammatory arthritis

This study was performed to investigate whether γδ T cells could also be divided into subsets, identified by a cytokine profile, as described for αβ T helper (Th) cell subsets. Cytokine production was studied in 22 γδ T cell clones obtained from the synovial fluid and peripheral blood of one patient with inflammatory arthritis and compared to that of 26 αβ T cell clones of the same and different patients. Interferon-γ (IFN-γ) was produced by 18 (82%) and interleukin-4 (IL-4) by 17 (77%) out of 22 γδ T cell clones, respectively. In contrast, IL-10 was not produced, except at very low level in one case. The mean levels of IL-4 were lower for clones derived from synovial fluid. When considering the production of IFN-γ as an indicator of Th1 and that of IL-4 as an indicator of Th2, respectively, the most common pattern was a γδTh1-like pattern, with the combination of high levels of IFN-γ and low levels of IL-4. This pattern was found in Vδ1⁺ clones, all from synovial fluid. Additional patterns were also observed: a mixed, probably γδ Th0-like pattern with a more balanced production of both IFN-γ and IL-4; a γδTh1 pattern with the production of IFN-γ alone; a γδTh2 pattern with the production of IL-4 alone. These three patterns were also seen in blood γδ T cells which were all Vδ2, indicating that these patterns were independent of the γδ phenotype. γδ T cell clones produced lower levels of IFN-γ (p = 0.001) and higher levels of IL-4 than αβ clones (p < 0.02). These differences in cytokine production between αβ and γδ subsets and within these subsets may contribute to their respective role in chronic inflammation.     

Differential effects of interleukin-12 on the development of naive mouse CD4+ T cells

The influence of interleukin (IL)-12 and IL-4 on the differentiation of naive CD4⁺ T cells was studied in an accessory cell-free in vitro system. Dense CD4⁺ T cells were purified from unimmunized mice and activated using immobilized anti-CD3 monoclonal antibodies (mAb) in the presence of IL-4, IL-12, or a combination of both cytokines, and restimulated after 6 days by re-exposure to anti-CD3-coated culture wells. T cells initially activated in the presence of IL-4 produced substantial amounts of IL-4 and trace amounts of interferon (IFN)-γ after restimulation at day 6 with plate-bound anti-CD3 mAb. By contrast, T cells primed in the presence of IL-12 produced high levels of IFN-γ and only minimal amounts of IL-4, thus indicating that IL-12 and IL-4 by acting directly on stimulated naive CD4⁺ T cells support the development of T_H1 and T_H2 cells, respectively. When naive CD4⁺ T cells were stimulated in the presence of IL-12 together with IL-4 in comparable concentrations, the effect of IL-12 on T_H1 differentiation was largely inhibited by IL-4. On the other hand, IL-12 exerted no inhibitory effect on IL-4-induced T_H2 differentiation but rather enhanced the production of IL-4 after restimulation of the respective T cells. Decreasing amounts of IL-4 in combination with a high level of IL-12 led to an increasing production of IFN-γ by the emerging T cells and, simultaneously, to a relatively high production of IL-4. These data were confirmed by time-course experiments which revealed that the delayed addition of IL-4 to IL-12-primed T cell cultures resulted in a gradual restoration of IFN-γ production whereas in parallel the secretion of IL-4 was not reduced over a wide period of delay (6–72 h). These results, therefore, demonstrate that (a) IL-4 dominates the effect of IL-12, (b) IL-12 promotes the development of T_H1 cells; however, in the presence of IL-12 and relatively high levels of IL-4 also the development of T_H2-like cells is slightly but significantly enhanced by IL-12, and (c) high amounts of IL-12 in combination with relatively low levels of IL-4 give rise to a T cell population that upon rechallenge exhibited a cytokine profile resembling that of T_H0 cells.     

CD4~+效应T细胞在自身免疫性溶血性贫血患者外周血的变化研究

目的研究自身免疫性溶血性贫血(AIHA)患者外周血中效应T细胞亚群Th1和Th17数量和比例的变化,探讨其在AIHA发病中的作用。方法选择30例AIHA患者,分离外周血单核细胞(PBMC),采用流式细胞术检测Th1和Th17细胞频率,用ELISA测定培养上清中IFN-γ和IL-17水平,并与健康对照组比较。结果 AIHA患者PBMC中IFN-γ+Th1和IL-17+Th17细胞频率均显著高于健康对照组(P<0.01);而且,AIHA患者外周血IL-17水平明显高于健康对照组(P<0.05),但IFN-γ水平在患者和正常人之间差异不显著。结论Th17与Th1细胞亚群可能参与AIHA患者的免疫学发病机制。     

Interleukin-12 increases interleukin-4 production by established human ThO and Th2-like T cell clones

Interleukin (IL)-12 is a potent inducer of cell-mediated immunity: it favors the generation of interferon (IFN)-γ-producing T cells, increases IFN-γ production by T cells and natural killer cells and prevents the generation of a Th2 response in murine in vivo models. Nevertheless, the effects of IL-12 on an established Th2 response remain poorly documented. In the present paper, we analyzed the effect of IL-12 on the profile of lymphokines produced by established IL-4-producing Th0 and Th2-like human T cell clones (TCC) and by polyclonal T cells. We found that IL-12 (i) enhances, as previously reported, IFN-γ production by Th0 TCC and, to a smaller extent, by Th2-like TCC, (ii) increases the proliferation of Th0 and Th2-like TCC and (iii) unexpectedly, synergizes with T cell receptor-associated or nonspecific stimuli in increasing IL-4 production by these TCC. Thus, IL-12 potentiates the production of IFN-γ and also of IL-4 by established IL-4-producing TCC. Although IL-12 has been widely reported to induce a Th1 response and to prevent the development of a Th2 response in vivo, IL-12 may on the contrary potentiate an established Th2 response in humans.     

Interleukin-12 is produced by dendritic cells and mediates T helper 1 development as well as interferon-γ production by T helper 1 cells

Interleukin-12 (IL-12), a 70-kDa heterodimeric cytokine composed of covalently linked p35 and p40 chains, is to date the most critical factor for skewing the immune response towards a T helper 1 (Th1) of cytokine profile [high interferon-γ (IFN-γ), low IL-4]. Established sources of IL-12 are stimulated macrophages, neutrophils and B cells. As dendritic cells (DC) process antigen in the periphery and then migrate to lymphoid organs to sensitize T cells and induce cell-mediated immunity, we reasoned that DC should constitute a critical source of IL-12. The criteria used to detect IL-12 in DC were the demonstration of p40 and p35 mRNA (semiquantitative polymerase chain reaction, Northern blotting, and in situ hybridization) as well as IL-12 protein (p70 enzyme-linked immunosorbent assay, p70 antigen capture followed by IFN-γ bioassay, free p40 chain radioimmunoassay or immunoprecipitation). We found that conventional stimuli such as Staphylococcus aureus induced production of IL-12 bymurine as well as human DC in amounts comparable to spleen cells, peritoneal macrophages or peripheral blood mononuclear cells. DC exhibited, however, features that had not been seen with other antigen-presenting cells: they produced bioactive IL-12 upon antigen-specific interaction with T cells without any other stimuli; in an allogeneic mixed leukocyte reaction model, neutralizing anti-IL-12 antibodies showed that DC-derived IL-12 was critical for optimal proliferation and IFN-γ production by activated Th1 blasts; and finally, the priming of resting, naive allogeneic T cells by DC, followed by restimulation of primed T blasts by DC, skewed the response to Th1 without the need for any exogenous cytokines or stimuli such as microorganisms. This skewing to Th1 cytokine production, which depended on DC-derived IL-12, but did not require anti-IL-4, exogenous IL-12, or microbes, might be a major function of DC.