OX40 (CD134) engagement drives differentiation of CD4+ T cells to effector cells

Naive, CD4+ T cells proliferate extensively but fail to differentiate when they are transferred into unirradiated recipients that express alloantigen or transgenic antigen on all MHC class II+ cells. Addition of an agonist antibody to OX40 (CD134), a costimulatory TNF receptor family member expressed on activated CD4+ T cells, enables the proliferating T cells to accumulate as differentiated effector cells and kill the host animals. The donor T cells from anti-OX40-treated animals express high levels of IL-2R alpha (CD25) and acquire the ability to secrete IFN-gamma when stimulated with IL-12 and IL-18. OX40 promotes differentiation by 48 h in T cell priming, before changes in Bcl-2 expression or cell recovery become apparent. We found that a Bcl-2 transgene or deficiency in Fas or TNFR1 failed to influence accumulation of differentiated donor cells, and found larger changes in expression of cytokine and cytokine receptor genes than in survival genes. Accumulation of differentiated CD4+ effector T cells is initiated directly through OX40, but some OX40-deficient donor cells can gain effector function as bystanders to OX40+/+ cells. Taken together, these data suggest that CD4+ T cell differentiation to effector function is an important effect of OX40 engagement under conditions of ubiquitous antigen presentation.     

Functional characterization of OX40 expressed on human CD8+ T cells

In the present study, we investigated the expression of OX40 on human CD8(+) T cells with regard to expression induction, costimulatory function and possible involvement in cytotoxicity. Human CD8(+) T cells were purified from peripheral blood mononuclear cell (PBMC) of healthy donors and cocultured with allogeneic monocyte-derived dendritic cells. Flow cytometric analysis showed that expression of OX40 was induced on CD8(+) T cells within 1 day and increased to the maximum levels on day 3. An addition of anti-OX40 ligand (OX40L) mAb suppressed CD25 expression, proliferation and IFN-gamma production of CD8(+) T cells, suggesting that OX40 functions as a costimulatory molecule not only for CD4(+) T cells but also for CD8(+) T cells. In parallel, coculture of pre-activated CD8(+) T cells with OX40L-transfected murine epithelial cells (MMCE-OX40L) resulted in an increase in CD25 expression, proliferation and IFN-gamma producing cells, compared with that with the mock control (MMCE-mock). Finally, non-specific cytotoxic activity of preactivated CD8(+) T cells was examined using OKT3 hybridoma as target cells after coculture with these transfectants. Coculture with MMCE-OX40L induced slightly higher cytotoxicity of CD8(+) T cells than that with MMCE-mock. These results indicate that OX40 is induced transiently on CD8(+) T cells upon activation and its signals contribute to both clonal expansion and functional reinforcement.     

A recombinant vesicular stomatitis virus encoding HIV-1 receptors and human OX40 ligand efficiently eliminates HIV-1-infected CD4-positive T cells expressing OX40

OX40 protein is highly expressed on activated CD4-positive T cells that are susceptible for human immunodeficiency virus type 1 (HIV-1) infection. To target and kill HIV-1-infected OX40(+) T cells, we used a recombinant vesicular stomatitis virus (rVSV) lacking its envelope glycoprotein (ΔG) and instead expressing HIV-1 receptors CD4/CXCR4 and OX40 ligand (OX40L). Expression of OX40L as well as HIV-1 receptors on the VSV particles led to specific infection of OX40(+) T cells, including primary cells, either acutely or chronically infected with X4 HIV-1. Consequently, the rVSV rapidly eliminated these infected cells and caused a marked reduction of HIV-1 viral load in culture. Inclusion of the OX40L gene in the VSV recombinant led to significantly better infection and HIV-1 elimination compared with an rVSVΔG expressing only HIV-1 receptors. A novel rVSVΔG encoding both HIV-1 receptors and OX40L has a potentially greater therapeutic value than an rVSVΔG expressing only HIV-1 receptors.     

CD4 T cell traffic control: in vivo evidence that ligation of OX40 on CD4 T cells by OX40-ligand expressed on dendritic cells leads to the accumulation of CD4 T cells in B follicles.

We report here that CD40- but not lipopolysaccharide (LPS)-activated murine dendritic cells (DC) express OX40-ligand (OX40L) as has been reported in humans. To understand how OX40 ligation affects differentiation of CD4 T cells at the time of priming, we constitutively expressed OX40L on DC using the DC-specific promoter of CD11c. Transgenic mice showed greatly increased numbers of CD4 but not CD8 T cells in their B cell areas. This effect was to a great extent immunization dependent, as spleen and lymphoid tissue with no germinal center reactions from mice which had not been deliberately immunized did not show marked CD4 T cell accumulation. The increased numbers of CD4+ CD62low cells in transgenic mice suggest that it is activated CD4 T cells that accumulate within B cell follicles. These data are consistent with the notion that physiological engagement of OX40 (CD134) on activated CD4 T cells either initiates their migration into or causes them to be retained in B follicles. In contrast, LPS-treated CD did not up-regulate OX40L expression. This dichotomy provides a molecular explanation of how DC might integrate environmental and accessory signals to control cytokine differentiation and migration in CD4 effector cells.     

Rapid induction of OX40 ligand on primary T cells activated under DNA-damaging conditions

We have previously demonstrated that normal human T cells either long-term repeatedly stimulated or freshly activated in vitro in the presence of TGF-beta express the cell surface T-cell costimulating molecule OX40 ligand (OX40L). To further elucidate the kinetics of OX40L expression by human T cells, we have examined whether cell proliferation was required for the expression of OX40L. Thus, normal fresh peripheral blood mononuclear cells were stimulated with immobilized anti-CD3 antibody in the presence of the DNA synthesis-blocking agents such as mitomycin C, 5-fluorouracil, or X-ray irradiation. Flow cytometric analyses demonstrated that a significant frequency of these DNA-damaged activated primary CD4(+) and CD8(+) T cells became OX40L(+) as early as 1 hour after treatment. The OX40L induction on the DNA-damaged activated T cells was inhibited by treatment with either RNA or protein synthesis inhibitors, actinomycin D, or cycloheximide, respectively. Induced OX40L on T cells was functional because it bound recombinant OX40. These data indicate that human primary T cells are programmed to rapidly express functional OX40L molecules after stimulation under DNA-damaging conditions, demonstrating that the induction of OX40L by T cells is independent of cell proliferation. The clinical implications of these new findings are discussed.     

Phenotypic characterization of regulatory CD4+CD25+ T cells in rats

CD25 has become widely used as a marker for a subset of regulatory CD4(+) T cells present in the thymus and periphery of mice, rats and humans. However, CD25 is also expressed on conventionally activated T cells that are not regulatory and not all peripheral regulatory T cells express CD25. The identification of a stable and unique marker for regulatory T cells would therefore be valuable. This study provides a detailed account of the phenotype of CD4(+)CD25(+) regulatory T cells in rats. In the thymus, CD4(+)CD8(-)CD25(+) cells were found to have a more mature phenotype than the corresponding CD4(+)CD8(-)CD25(-) cells with respect to expression of Thy1 (CD90), CD53 and CD44, suggesting that CD25 expression, and perhaps commitment to regulatory function, might be a late event in thymocyte development. CD4(+)CD25(+) cells in both the thymus and periphery were found to have enriched and heterogeneous expression of activation markers such as OX40 (CD134) and OX48 (an antibody determined in this study to be specific for CD86). CD4(+)CD25(+) T cells were also found to have enriched expression of CD80, at both the mRNA and protein level. However, functional studies in vitro and in vivo showed that neither OX40 or CD86 were useful markers for the further subdivision of regulatory T cells. Our studies indicate that, at present, CD25 remains the most useful marker to enrich for regulatory CD4(+) T cells in rats and no further subdivision of the regulatory component of CD4(+)CD25(-)CD45RC(low) T cells has yet been achieved.     

OX40-Mediated cosignal enhances the maturation of naive human CD4+ T cells into high IL-4-producing effectors

Our previous studies have indicated that naive human CD4+ T cells of neonatal or adult origin may be the initial source of IL-4 which is required for their development into Th2 effectors. In addition to minute amounts of IL-4, anti-CD3/B7.1-activated naive cells also release readily detectable levels of IL-13 and IFN-gamma. The production of IL-4 and IL-13 by naive T cells is differentially regulated by TGF-beta and IL-12. Shortly after activation, naive T cells express surface OX40, a TNF-R family member whose ligand (OX40L) is constitutively expressed on a subset of dendritic cells. Engagement of OX40 on activated naive T cells increases their expression of IL-4 and IL-13, suppresses that of IFN-gamma and promotes their development into Th2-like effectors.     

Expression of OX40 (CD134) on CD4+ T-cells from patients with myasthenia gravis

Myasthenia gravis (MG) is commonly regarded as the prototype of an antibody-mediated, organ-specific autoimmune disease. Antibodies against the acetylcholine receptor (AChR) on the muscle endplate trigger its typical clinical manifestations of weakness and fatiguability. T-B cell interactions are thought to play a crucial role in the pathogenesis of MG. OX40 (CD134), a costimulatory molecule that is expressed on activated CD4+ T-cells, might contribute to the development or pathogenesis of immune-mediated diseases such as rheumatoid arthritis and graft-versus-host disease. In the present study, we investigated the expression of OX40 on CD4+ T-cells from patients with MG and healthy individuals. Results from 36 MG patients and 28 healthy controls revealed that more freshly isolated CD4+ T-cells from MG patients expressed OX40 than cells from healthy individuals. High levels of antibodies against the AChR, thymic hyperplasia and onset at an early age were associated with elevated expression of OX40. Upon activation by various concentrations of anti-CD3 antibodies, CD4+ T-cells from MG patients showed a tendency toward higher levels of OX40 expression than cells from healthy individuals. Given the role of OX40 in the immune system, we conclude that OX40 might contribute to the development of MG.     

Expression of chemokine receptors on CD4+ T cells in peripheral blood from HIV-infected individuals in Uganda.

CXCR4, a coreceptor for T cell (T)-tropic HIV-1, is preferentially expressed on naive T cells, whereas CCR5, a coreceptor for macrophage (M)-tropic HIV-1, is preferentially expressed on previously activated memory T cells and the Th1 subset of CD4+ T cells. CCR4 is preferentially expressed on the Th2 subset of CD4+ T cells. A cross-sectional flow cytometry study was conducted to evaluate the expression of CXCR4, CCR5, and CCR4 on the peripheral blood CD4+ T cells from African HIV-1-infected and uninfected Ugandan adults. The plasma viral load in HIV-1-infected individuals was also examined. Upregulation of CCR4 and CCR5 expression but no decrease in CXCR4 expression on CD4+ T cells were obtained in peripheral blood from African adults with progression of the disease. Plasma HIV-1 viremia significantly and inversely correlated with the peripheral CD4+ T cell count but did not correlate with the degree of CCR4 and CCR5 expression on the peripheral CD4+ T cells in HIV-1-infected individuals. Our present data suggest an increase in percentage of activated memory CD4+ T cells in the advanced stage of HIV-1 infection among African adults. There was no evidence of a Th1 to Th2 shift in terms of chemokine receptor expression profile with advancing disease in the peripheral blood of these subjects.     

Characteristics of inflammatory cells in spontaneous autoimmune thyroiditis of NOD.H-2h4 mice

Thyroid lesions develop in most NOD.H-2h4 mice 6 weeks after they are given 0.05% NaI in drinking water. B cells are required for spontaneous autoimmune thyroiditis (SAT) development, and anti-thyroglobulin autoantibody levels correlate with SAT severity. Immunohistochemical staining of thyroids obtained 2-10 weeks after administration of NaI water suggested that CD4+ T cells initially infiltrated the thryoid, followed by CD8+ T cells and B cells. Intrathyroidal CD4+ T cells are more numerous than CD8+ T cells. CD4+ T cells and B cells form aggregates in the thyroid, while CD8+ T cells are scattered throughout the thyroid. Intrathyroidal germinal centre-like structures could be observed in thyroid lesions with 2-3+ SAT and intrathyroidal B cells co-expressed OX40L. By RT-PCR, intrathyroidal expression of OX40L, OX40, CD40L, IL-2R, CTLA-4 and Igbeta mRNA correlated closely with the SAT severity score. These molecules were not expressed in normal thyroids. In the spleen, OX40L-positive cells were detected at 2 weeks and increased 4-6 weeks after NaI water. OX40, OX40L, CD40L, IL-2R and B7-1 as well as IFN-gamma and IL-4 mRNA were minimally expressed in normal spleens, usually began to be expressed at 2 weeks and increased to maximal level 4-8 weeks after NaI water. These results suggest that in NOD.H-2h4 mice, the OX40L, OX40, CD40L and B7 molecules, which increase in the spleen and thyroid of these mice after receiving NaI water, may play a role in SAT development, implying that one or more of these molecules might be good targets for the prevention or treatment of SAT.     

Anti-OX40 stimulation in vivo enhances CD8+ memory T cell survival and significantly increases recall responses

There is growing evidence that engagement of OX40 (CD134), a member of the TNF receptor superfamily, can directly stimulate antigen-specific CD8+ T cells. It has been shown that CD8+ T cells express OX40 following activation, but the response of antigen-specific CD8+ T cells to OX40 stimulation has not been fully characterized. We utilized an antigen-specific transgenic CD8+ T cell model (OT-I) to determine if OX40 engagement can boost the generation of antigen-specific CD8+ T cell memory. Our results demonstrate that enhanced OX40 costimulation, via an agonist anti-OX40 antibody, increases CD25 and phospho-Akt expression on the antigen-specific CD8+ T cells and significantly increases the generation of long-lived antigen-specific CD8+ memory T cells. The increased numbers of memory CD8+ T cells generated via anti-OX40 treatment still required the presence of CD4+ T cells for their long-term maintenance in vivo. In addition, anti-OX40 costimulation greatly enhanced antigen-specific CD8+ T cell recall responses. These data show that OX40 engagement in vivo increases the number of antigen-specific CD8+ memory T cells surviving after antigen challenge and has implications for the development of more potent vaccines against pathogens and cancer.     

Maturation of dendritic cells for enhanced activation of anti-HIV-1 CD8(+) T cell immunity

Maturation of dendritic cells (DC) to enhance their capacity to activate T cell immunity to HIV-1 is a key step in immunotherapy of HIV-1 infection with DC. We compared maturation of DC derived from HIV-1-uninfected subjects and infected subjects on antiretroviral therapy (ART) or ART na?ve by CD40 ligand (CD40L) and combinations of TLR3 ligand polyinosinic:polycytidylic acid [poly(I:C)] and inflammatory cytokines IFN-gamma, IFN-alpha, IL-1beta, and TNF-alpha. The greatest levels of virus-specific IFN-gamma production by CD8(+) T cells were stimulated by DC treated with CD40L, followed by DC treated with the poly(I:C)-cytokine combination. The highest levels of IL-12p70 were produced by DC treated with CD40L + IFN-gamma, followed by CD40L and the poly(I:C)-cytokine combination. Neutralization of IL-12p70 indicated that it was only partially involved in direct enhancement of antiviral CD8(+) T cell activity. DC stimulation of antiviral CD8(+) T cell reactivity was enhanced by activated CD4(+) T cells at low concentrations but was suppressed at higher CD4(+) T cell concentrations. Maturation of DC with CD40L obviated the need for CD4(+) T cell help and overcame this suppressive activity. Finally, we showed that DC from HIV-1-infected subjects on ART, which were treated with the poly(I:C)-cytokine combination, retained the capacity to produce IL-12p70 and activate anti-HIV-1 CD8(+) T cell responses after restimulation with CD40L, with or without IFN-gamma. Thus, DC from HIV-1-infected subjects can be engineered with CD40L or a poly(I:C)-cytokine combination for enhancing CD8(+) T cell responses to HIV-1, which has potential applications in HIV-1 immunotherapy.     

Association of CD40 ligand expression on HTLV-I-infected T cells and maturation of dendritic cells

Human T lymphotropic virus type I (HTLV-I) induces HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia (ATL). The development of HAM/TSP is associated with rapid maturation of dendritic cells (DCs), while ATL is accomplished with their maturation defect. The DC maturation is induced by cell-to-cell contact with CD4+ T cells expressing CD40 ligand (L). We determined the influence of CD40L expressed on various HTLV-I-infected T cells on the DC maturation. Around 60% of CD4+ T cells infected with HTLV-I for 1 week, expressed CD40L molecules involved in DC maturation. DCs matured by the CD40L+ T cells activated autologous CD4+ and CD8+ T cells. HTLV-I-immortalized T-cell lines established from healthy donors consistently expressed CD40L molecules for 3 months, however, some lines lost the expression soon thereafter. Interleukin (IL)-2-independent and transformed lines lacked that expression. Furthermore, T cells obtained from HAM/TSP patients expressed CD40L molecules for at least 3 weeks, whereas T cells from ATL patients did not express that. The CD40L T cells did not induce DC maturation, and required exogenous CD40L molecules for maturation. The CD40L+ T-cell-induced maturation was blocked by anti-CD40L antibody. Therefore, the lack of CD40L expression on HTLV-I-infected T cells may be associated with the development of ATL.     

Dysregulation of CD30+ T cells by leukemia impairs isotype switching in normal B cells

Chronic lymphocytic leukemia (CLL) is associated with impaired immunoglobulin (Ig) class-switching from IgM to IgG and IgA, a defect that leads to recurrent infections. When activated in the presence of leukemic CLL B cells, T cells rapidly up-regulate CD30 through an OX40 ligand and interleukin 4 (IL-4)-dependent mechanism. These leukemia-induced CD30+ T cells inhibit CD40 ligand (CD40L)-mediated S mu-->S gamma and S mu-->S alpha class-switch DNA recombination (CSR) by engaging CD30 ligand (CD30L), a molecule that interferes with the assembly of the CD40-tumor necrosis factor receptor-associated factor (TRAF) complex in nonmalignant IgD+ B cells. In addition, engagement of T cell CD30 by CD30L on neoplastic CLL B cells down-regulates the CD3-induced expression of CD40L. These findings indicate that, in CLL, abnormal CD30-CD30L interaction impairs IgG and IgA production by interfering with the CD40-mediated differentiation of nonmalignant B cells.     

OX40: targeted immunotherapy--implications for tempering autoimmunity and enhancing vaccines

OX40 (CD134), a membrane-bound member of the tumor-necrosis-factor-receptor superfamily, is expressed primarily on activated CD4+ T cells. Recently, several groups have reduced clinical signs of autoimmunity in animal models by blocking the OX40-OX40-ligand interaction or depleting OX40+ T cells. By contrast, engagement of OX40 in the setting of active immunization has potent adjuvant properties, leading to enhanced cytokine production and increased numbers of antigen-specific memory T cells. These potent adjuvant effects lead to an enhancement of anti-tumor responses. OX40 has several unique features that make it a clinically relevant target. They include: (1) T cells isolated from a site of inflammation that express OX40 are T cells that have been stimulated recentlythrough the T-cell receptor in vivo; (2) OX40 is only expressed on T cells found at the site of inflammation, therefore, targeting this receptor does not interfere with the peripheral T-cell repertoire; and (3) the biological function of OX40 is limited primarily to effector CD4+ T cells, which are a major source of cytokines to induce and maintain ongoing immune responses.     

Early reduction of the over-expression of CD40L, OX40 and Fas on T cells in HIV-1 infection during triple anti-retroviral therapy: possible implications for lymphocyte traffic and functional recovery.

Fas, CD40L and OX40 are members of the tumour necrosis factor (TNF) receptor superfamily with critical roles in T cell activation and death, B cell function, dendritic cell maturation and leucocyte traffic regulation. The aim of this study was to evaluate the effects of anti-retroviral therapy (HAART) on CD40L, OX40 and Fas expression on freshly isolated peripheral blood T cells by three-colour flow cytometry and compare them with lymphoproliferative responses, peripheral blood cell counts and viral load. Fourteen asymptomatic HIV-1+ patients treated with Lamivudine, Stavudine and Nelfinavir were prospectively investigated sequentially for 48 weeks. At baseline, patients exhibited significantly enhanced proportions and counts of CD40L+ and OX40+ cells within the CD4 subset which were corrected by weeks 8-16 of HAART. Interestingly, in the five patients showing viral load rebound during therapy in spite of increasing CD4 counts, the reduction of the levels of these costimulatory molecules was similarly maintained. Therapy induced a decrease in the over-expression of Fas, particularly in the CD4 subset where normal levels were reached at week 8. This reduction occurred in parallel with the major recovery of lymphoproliferative responses. Higher basal levels and lower reduction of Fas were associated with suboptimal suppression of viraemia. In conclusion, this previously undescribed increased expression of CD40L and OX40 may play a role in the HIV-associated pan-immune activation and represent a possible target for immunointervention, as suggested for several immunologically mediated diseases. Moreover, HAART induced an early correction of the over-expression of Fas, CD40L and OX40 in CD4 T cells which could be involved in the recovery of the cell traffic disturbances and in the T cell renewal capacity.     

4-1BB and OX40 stimulation enhance CD8 and CD4 T-cell responses to a DNA prime, poxvirus boost vaccine

4-1BB (CD137) is a tumour necrosis factor receptor (TNFR) family member, expressed primarily on CD8 T cells after activation. Signalling through 4-1BB has been reported to enhance CD8 T-cell expansion and to protect activated CD8 T cells from death, resulting in an enlarged memory population. Although stimulating 4-1BB has been shown to significantly improve the immune response to weak immunogens such as tumours, little is known about its effect on the CD8 T-cell response to a powerful viral vector such as vaccinia. To test 4-1BB's ability to improve the murine CD8 T cell response to a DNA prime, poxvirus boost vaccine, similar to those used for human immunodeficiency virus and simian immunodeficiency virus vaccines, we administered 4-1BB agonist antibody at the time of the poxvirus boost. 4-1BB stimulation increased the number of functional memory CD8 T cells by two- to fourfold. However, we saw a similar enhancement at the peak of the response and in the memory phase, thus we found no evidence in the context of virus infection that 4-1BB stimulation could increase the percentage of CD8 T cells that survive the acute activation phase to become memory cells. OX40 (CD134) is an analogous TNFR family member expressed primarily on activated CD4 T cells. OX40 stimulation increased the number of antigen-specific CD4 T cells approximately threefold. Stimulating both 4-1BB and OX40 enhanced the CD8 T-cell response more than 4-1BB alone. Thus stimulating these receptors can improve the response to a powerful virus vector, and may be useful in vaccine development.     

Role of increased CD8/CD28(null) T cells and alternative co-stimulatory molecules in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory lung disease; it is a leading cause of death and existing treatments have no proven disease-modifying effect. The mechanisms underlying this resistance are largely unknown, but suggest the presence of some self-maintaining pathogenic process, possibly initiated by cigarette smoking, that prevents the normal resolution of inflammation. We have previously reported increased production of proinflammatory cytokines and granzyme b by CD8(+) T cells in COPD; costimulatory receptor/ligand interactions required include CD80:86/CD28, B7-1/CTLA4, 4-1BB/1BBL and OX40/OX40L. We hypothesized that a dysregulated expression/function of these molecules may play a role in inflammatory/autoimmune components of COPD. We analysed T cell co-stimulatory molecules in blood from 34 controls, 15 smokers and 48 COPD subjects. We assessed the potential functional relevance of CD8/CD28(null) cells in COPD by measuring their production of proinflammatory cytokines, co-stimulatory molecules, granzyme and perforin. A smoke-exposed murine model was applied to investigate the relative expression of CD8/CD28(null) T cells in blood, lung tissue and airway. CD8/CD28(null) cells were increased in both current- and ex-smoker COPD groups; these cells expressed significantly more interferon (IFN)-γ, OX40, 4-1BB, CTLA4, granzyme and perforin when stimulated than CD8/CD28(+) T cells. There were no changes in CD4/CD28(null) T cells. In mice exposed to cigarette smoke for 12 weeks, CD8/CD28(null) T cells were significantly increased in the airway with a trend for an increase in lung tissue and blood. Increased production of proinflammatory cytokines and expression of alternative co-stimulatory molecules by CD8/CD28(null) T cells may play a role in inflammatory or autoimmune responses in COPD and identify therapeutic targets.     

Graves病患者外周血OX40和OX40L分子表达的研究

探讨OX40和OX40L分子在Graves病患者外周血T淋巴细胞和单核细胞上的表达及其在Graves病发病机制中的可能作用。采用流式细胞仪检测技术对50例初发Graves病患者和30例健康志愿者外周血T细胞上OX40和单核细胞上OX40L的表达水平进行分析,并对28例治疗前后病人淋巴细胞上OX40/OX40L的表达进行了比较。结果:与正常对照组比,初发Graves病患者外周血CD4+T细胞上OX40表达水平明显升高,而CD8+T细胞上OX40表达水平无显著变化;同时,还检测到单核细胞上OX40L表达水平也明显增加。治疗后,FT3(游离三碘甲腺原氨酸)值恢复至健康对照组表达范围的Graves病患者其CD4+T细胞上OX40和单核细胞上OX40L的表达均显著降低至正常水平;而FT3值仍偏高的患者单核细胞上OX40L的表达降低,但未降至健康对照组表达范围,CD4+T细胞上OX40的表达则无显著变化。Graves病患者外周血T细胞和单核细胞上分别存在OX40和OX40L的异常表达,且与治疗效果密切相关,提示OX40/OX40L信号在T细胞与单核细胞相互作用过程中可能有助于自身反应性T细胞的持续活化,从而参与Graves病的免疫发生发展。     

CD28 co-stimulation stabilizes the expression of the CD40 ligand on T cells

The ligand for CD40 (CD40L) is a protein which is expressed on CD4 T cells following their activation: CD40-CD40L interactions are absolutely required for the induction of T cell-dependent antibody responses, yet little is known about the mechanisms whereby CD40L+ primary T cells activate naive B cells, since the protein is only transiently expressed and is rapidly down-regulated following T cell-B cell contact. We show here, using a variety of assays, that co- stimulation of primary murine T cells via CD3 and CD28 stabilizes the expression of the CD40L protein. Firstly, T cells stimulated in this manner express higher levels of CD40L when activated in the presence of B cells, compared to CD3-activated T cells. Secondly, the CD40L expressed on CD28-co-stimulated T cells is more resistant to B cell- induced down-regulation. Finally, CD3/CD28-preactivated, rested T cells re-express higher levels of CD40L more rapidly following re-stimulation via CD3 than T cells preactivated via CD3 alone. CD3/CD28-preactivated T cells, but not CD3-activated cells, are competent to induce DNA synthesis in naive B cells, and this requires re-stimulation via CD3 and prolonged ligation of CD40. These data therefore reinforce the concept that naive T cells need to be activated initially by cognate interaction with B7-bearing antigen-presenting cells (such as dendritic cells), before becoming competent helper effector cells capable of driving B cells into proliferation via a CD40-dependent pathway.