Expression Of Inducible Costimulator Research Articles

Expression and clinical significance of inducible co-stimulator on peripheral blood T lymphocyte subsets in patients with systemic lupus erythematosus

To investigate the expression of inducible co-stimulator (ICOS) and other immunological molecules on peripheral blood T lymphocyte subsets in patients with systemic lupus erythematosus (SLE) and to find out the relationship with disease-activity, disease-stage and the contents of anti-dsDNA antibody and immunoglobulin in serum so as to pave the way for further studying the possibly immunologically pathological role of ICOS in SLE. Peripheral blood samples were collected from 51 patients with SLE, 3 males and 22 females. Three-color flow cytometry was used to detect the levels of ICOS, CD45RO, CD45RA, and HLA-DR expression on the peripheral blood T lymphocytes subsets. The results were analyzed along with the disease-activity, disease-stage, contents of anti-dsDNA antibody and immunoglobulin in serum. Thirty healthy subjects were used as controls. Compared with the healthy subjects the level of ICOS expression on the peripheral blood CD4+ and CD8+ T cells in the patients with SLE during active- and stable-stages were significantly increased (all P < 0.05), but there was no significant difference between the last two group patients (P > or = 0.05); In the same patients, the level of ICOS expression on the peripheral blood CD4+, CD8+, CD45RO+, CD4+CD45RO+ and CD8+CD45RO+ cells in active-stage were significantly increased compared with those in stable-stage (P <0.05); The level of ICOS expression on the peripheral blood CD45RO+ cells in the untreated primary patients was higher than those with disease-relapse (P <0.05); The levels of ICOS expression on the peripheral blood CD45RO+ and CD4+CD45RO+ cells were significantly increased in the patients with serum anti-dsDNA antibody(+) and the patients with aberrantly high content of immunoglobulin compared with those of the patients with serum anti-dsDNA antibody(-) and the patients with normal content of immunoglobulin, respectively (all P < 0.05). ICOS is aberrantly highly expressed on certain peripheral blood T lymphocyte subsets in patients with SLE, which is related to disease-activity, disease-stage and the contents of serum anti-dsDNA antibody and immunoglobulin, thus ICOS may play a role in SLE pathogenesis.

Human T cell activation by costimulatory signal-deficient allogeneic cells induces inducible costimulator-expressing anergic T cells with regulatory cell activity.

Although immunoregulation by several types of regulatory T cells is now clearly established in mice, the demonstration of such regulatory T cells in humans has been proven more difficult. In this study we demonstrate the induction of anergic regulatory T cells during an MLR performed in the presence of blocking mAb to the costimulatory molecules CD40, CD80, and CD86. Despite this costimulation blockade, which totally blocks T cell proliferation and cytokine production, a nonproliferating T cell subpopulation was activated to express inducible costimulator (ICOS). These ICOS(+) cells were anergic when restimulated with unmanipulated allogeneic stimulator cells at the level of proliferation and Th1 and Th2 cytokine production, but they did produce IL-10. These ICOS-expressing cells also blocked the capacity of reciprocal ICOS-negative cells to proliferate and to produce cytokines. ICOS(+) anergic cells could suppress allogenic responses of either primed or naive T cells through inhibition of IL-2 gene transcription. Suppression was not mediated by IL-10 and did not require ICOS-ICOS ligand interaction, but depended on cell-cell contact. Thus, a subtype of regulatory T cells in human blood can be activated in the absence of costimulatory signals from CD40, CD80, and CD86, and they can be identified by expression of ICOS after activation.

ICOS expression is associated with local immunoglobulin E (IgE) production in lung tissue following allergen airway challenge

Rationale IgE plays a central role in the pathogenesis of allergic asthma. It is detectable in serum as well as in bronchoalveolar lavage and correlates with disease severity. To further define the requirements for induction of local IgE production in lung, we utilized an adoptive transfer model of allergic airway inflammation. Methods and results Purified T cells from DO11.10 mice, carrying a T-cell receptor (TCR) specific for Ovalbumin (OVA), were stimulated in vitro with OVA 323–339-peptide and transferred into naive Balb/c recipients. Repeated intra-nasal challenges of the recipients with OVA provoked the formation of intrapulmonary B-cell clusters preferentially located between bronchi and blood vessels. Immunohistologic characterization of these clusters showed inducible co-stimulator (ICOS) + T cells scattered within the B-cell infiltrates in close proximity to IgG1 and IgE producing plasma cells. To analyze whether the expression of ICOS was required for the induction of pulmonary B-cell infiltration and local IgE production, in vitro stimulated DO11.10 T cells were separated by magnetic cell sorting into ICOS-enriched and ICOS-depleted T-cell fractions, containing equal numbers of activated TCR transgenic T cells. Transfer of ICOS-enriched T-cells provoked markedly pronounced B-cell infiltrates with IgE and IgG1 producing plasma cells, while hardly any infiltrates and no IgE or IgG1 production was observed after transfer of the ICOS-depleted fraction. Conclusion These data suggest that allergen-specific ICOS + T-cells are involved in the development of peripheral T-/B-cell interaction in lung tissue and facilitate local IgE-production following allergen airway challenge.

Acute cellular rejection after human heart transplantation is associated with ICOS+ graft-infiltrating T lymphocytes and increased endothelial expression of inducible costimulator ligand (ICOSL)

The novel costimulatory molecule inducible costimulator (ICOS) mediates effector T cell differentiation and function. Inhibition of the ICOS/ICOS ligand pathway in animal models of heart transplantation led to prolonged engraftment in recent studies. We have recently demonstrated constitutive expression of ICOSL and its upregulation by proinflammatory cytokines on human vascular endothelial cells in vitro. However, no data concerning human heart transplantation are available to date. This pilot study examined the cellular expression pattern of ICOS and ICOS ligand in human cardiac allograft rejection. Immunohistochemical staining was performed on endomyocardial biopsy specimens from individual patients (n = 8 in each group) with histological evidence of moderate (ISHLT 3A) acute cellular rejection comparing it to specimens from patients without signs of rejection (ISHLT 0). ICOS expression was detected on graft-infiltrating T lymphocytes during acute rejection. ICOS ligand (ICOSL) showed a distinct expression restricted to vascular endothelial cells. ICOSL was present on 18 % of vessels (mean) identified by CD31 staining in non-rejecting specimens compared to 55 % of vessels in specimens with evidence of moderate rejection (p = 0.0357). This is the first report implicating the ICOS/ICOSL pathway in human cardiac allograft rejection. Coroborating previous in vitro data, ICOSL is expressed on endothelial cells suggesting a role as antigen-presenting cells, regulated by inflammatory cytokines. Quantitative analysis suggests that ICOSL expression on endothelial cells is correlated with histologically significant acute cellular rejection.

Hyperexpression of inducible costimulator on lamina propria mononuclear cells in rat dextran sulfate sodium colitis

The authors have previously shown that a third member of the CD28 family, inducible costimulator (ICOS), was increased in the inflamed intestinal mucosa of murine experimental colitis, and that the blockade of ICOS ameliorated the development of colitis. However, the role of ICOS in rat intestinal inflammation and its expression profile remains unclear. In the present study, the authors investigated the involvement of ICOS in the development of rat dextran sulfate sodium (DSS)-induced colitis, and the therapeutic potential of anti-ICOS monoclonal antibody (mAb) in colitis. The authors first examined expression of ICOS protein in normal rat by immunohistochemistry and flow cytometry. Sprague-Dawley rats were fed 3.0% DSS. The expression of ICOS on infiltrating lamina propria mononuclear cells and splenocytes were examined. The DSS-fed rats were then administered anti-ICOS mAb to test its effect on the development of colitis. Unlike mice and human, ICOS was expressed on a part of CD4+ T-cells from the thymus, spleen, mesenteric lymph nodes and lamina propria. Levels of ICOS on CD4+ T-cells from the spleen and colonic lamina propria were significantly upregulated after Concanavalin A (Con A) stimulation. In addition, ICOS was also upregulated on CD4+ T-cells from DSS-fed rats compared with those from non DSS-fed rats. However, anti-ICOS mAb did not ameliorate the development of both acute and chronic DSS colitis. These results suggest that the different expression of ICOS in rats plays a distinct role in rat intestinal inflammation.

Involvement of inducible costimulator-B7 homologous protein costimulatory pathway in murine lupus nephritis.

Inducible costimulator (ICOS)-B7 homologous protein (B7h) is a new member of the CD28-B7 family of costimulatory molecules that regulates T cell-dependent humoral immune responses. In this study, we examined the involvement of this costimulatory pathway in the development and progression of lupus in NZB/W F(1) mice. Expression of ICOS on T cells was enhanced with disease progression, whereas B7h expression on B cells was down-regulated. Administration of anti-B7h mAb before the onset of renal disease significantly delayed the onset of proteinuria and prolonged survival. Blockade of B7h effectively inhibited all subclasses of IgG autoantibody production and accumulation of both Th1 and Th2 cells. Hypercellularity and deposition of IgG and C3 in glomeruli were significantly reduced. B7h blockade after the onset of proteinuria prevented the disease progression and improved the renal pathology. Our results demonstrated the involvement of the ICOS-B7h costimulatory pathway in the pathogenesis of lupus nephritis, and the blockade of this pathway may be beneficial for the treatment of human systemic lupus erythematosus.

Adenovirus-mediated gene transfer of ICOSIg fusion protein ameliorates ongoing experimental autoimmune myocarditis.

Experimental autoimmune myocarditis (EAM) has been used as a model for human myocarditis. We previously demonstrated that blockade of B7/CD28 or CD40/CD40 ligand (CD40L) had a potential preventive effect on EAM, but less therapeutic effect on ongoing EAM. Thus, we searched for the involvement of other costimulatory molecules in EAM. We demonstrated the expression of inducible costimulator (ICOS)/ICOSL molecules in the lymph nodes, spleen, and heart in the EAM rat. We constructed adenovirus vectors containing ICOSIg (Adex1CAICOSIg) to achieve effective inhibition of ICOS/ICOSL interaction, and examined the effects of Adex1CAICOSIg on EAM. Adex1CAICOSIg treatment shortly after the immunization did not inhibit the onset and severity of EAM compared to control rats. On the other hand, delayed treatment with Adex1CAICOSIg significantly inhibited ongoing EAM. The survival rate in rats treated with Adex1CAICOSIg was significantly higher than that of the control group. Furthermore, the affected area ratio of the Adex1CAICOSIg treatment group was significantly lower than that of the control group. This study indicates that ICOS/ICOSL costimulation makes an important contribution to the progression of EAM and that the blockade of this pathway by gene transfer has therapeutic potential for ongoing autoimmune myocarditis.

Expression of ICOS in vivo defines CD4+ effector T cells with high inflammatory potential and a strong bias for secretion of interleukin 10.

The studies performed to date analyzed the overall participation of the inducible costimulator (ICOS) in model diseases, but did not yield information on the nature and function of ICOS-expressing T cells in vivo. We examined ICOS+ T cells in the secondary lymphoid organs of nonmanipulated mice, in the context of an “unbiased” immune system shaped by environmental antigens. Using single cell analysis, ICOSlow cells were found to be loosely associated with the early cytokines interleukin (IL)-2, IL-3, IL-6, and interferon (IFN)-γ. ICOSmedium cells, the large majority of ICOS+ T cells in vivo, were very tightly associated with the synthesis of the T helper type 2 (Th2) cytokines IL-4, IL-5, and IL-13, and these cells exhibited potent inflammatory effects in vivo. In contrast, ICOShigh T cells were highly and selectively linked to the anti-inflammatory cytokine IL-10. Overall, these data seem to indicate that ICOS cell surface density serves as a regulatory mechanism for the release of cytokines with different immunological properties. Further in vivo functional experiments with in vitro–activated T cells strongly suggested that the ICOS+ population, although representing in vivo only around 10% of T cells bearing early or late activation markers, nevertheless encompasses virtually all effector T cells, a finding with major diagnostic and therapeutic implications.

Amelioration of collagen-induced arthritis by blockade of inducible costimulator-B7 homologous protein costimulation.

B7 homologous protein (B7h)/B7-related protein 1 (B7RP-1) is a new member of the B7 family of costimulatory molecules that specifically interacts with inducible costimulator (ICOS) expressed on activated T cells. Collagen type II (CII)-induced arthritis (CIA) is an experimental model of arthritis that has been used to dissect the pathogenesis of human rheumatoid arthritis. In this study, we have investigated the effect of neutralizing anti-B7h mAb on the development and disease progression of CIA. Administration of anti-B7h mAb significantly ameliorated the disease as assessed by clinical arthritis score and histology in the joints, and a beneficial effect was also obtained by a delayed treatment after the onset of disease. Expression of ICOS and B7h was observed in the inflamed synovial tissue as well as in the draining lymph nodes (LNs) and expansion of ICOS(+) T cells in the LN was reduced by the anti-B7h mAb treatment. Expression of mRNA for proinflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6 in the joints was inhibited by the treatment. Proliferative responses and production of IFN-gamma and IL-10 upon restimulation with CII in vitro were significantly inhibited in LN cells from the anti-B7h mAb-treated mice. Serum anti-CII IgG1, IgG2a, and IgG2b levels were also reduced. Our present results showed a beneficial effect of the B7h blockade on CIA through anti-inflammatory actions and inhibition of both Th1- and Th2-mediated immune responses, suggesting that the ICOS-B7h interaction plays an important role in the pathogenesis of CIA and thus the blockade of this pathway may be beneficial for the treatment of human rheumatoid arthritis.

Inducible Costimulator Costimulates Cytotoxic Activity and IFN-γ Production in Activated Murine NK Cells

The functions of NK cells are regulated by the balance of activating and inhibitory signals. The inhibitory NK cell receptors are well understood; however, less is known about the activating signaling pathways. To explore whether a costimulatory receptor, inducible costimulator (ICOS), is involved in NK cell function, we assessed the role of ICOS in NK cell-mediated cytotoxicity and cytokine production. In addition, to determine whether ICOS contributes to the elimination of tumors in vivo, we examined the tumor growth survival of mice injected with a tumor expressing the ICOS ligand, B7RP-1. We found that ICOS was up-regulated by cytokine stimulation in murine NK cells. Consistent with ICOS expression on activated NK cells, ICOS-dependent cytotoxicity and IFN-gamma production were observed, and appeared to require signaling through the phosphoinositide 3-kinase pathway. Interestingly, ICOS-mediated stimulation allowed activated NK cells to kill more efficiently tumor cells expressing MHC class I. Furthermore, fewer metastases appeared in the liver and spleen of mice injected with the ICOS ligand-expressing tumor compared with mice bearing the parental tumor. These results indicate that NK cell functions are regulated by ICOS.

Prolonged survival in rat liver transplantation with mouse monoclonal antibody against an inducible costimulator (ICOS).

An inducible costimulator (ICOS), a recently identified costimulatory receptor with a close structural homology to CD28 and CTLA4, is expressed on activated T cells. Interaction with its ligand on antigen-presenting cells stimulates T-cell proliferation to produce a different spectrum of cytokine. The inhibition of ICOS-mediated signal transduction by an anti-ICOS antibody is considered to be capable of protecting against graft rejection in organ transplantation. An anti-rat ICOS antibody was intravenously administered into recipients of dark Agouti-to-Lewis liver transplantations. The recipient lymphocytes from mesenteric lymph nodes were harvested on day 7 after transplantation for fluorescence-activated cell sorting analysis, and tissue specimens from the grafts were removed for histologic evaluation. Antigen-specific T-cell proliferation responses were assessed in vitro with anti-ICOS antibody. Monotherapy with the antibody significantly prolonged the graft survival time by inhibiting T-cell activation and its proliferation response. The graft-infiltrating cells, both CD4 and CD8 T cells, were not completely reduced even when rats were administered the antibody, whereas the expression of ICOS almost completely disappeared in these cells. T-cell activation through the ICOS costimulatory pathway plays an important role in graft rejection, and manipulating its pathway is an effective method for modulating transplantation immunity.