Cytotoxic T lymphocyte antigen-4 (CTLA-4) is constitutively expressed on CD25⁺CD4⁺ regulatory T cells (Treg) and is suggested to play a role in Treg-mediated suppression. However, the results of analysis with anti-CTLA-4 have been controversial. We addressed this issue by analyzing mice over-expressing or deficient in CTLA-4. For over-expression, CTLA-4 transgenic mice expressing a full-length (FL) or a truncated (TL) mutant of CTLA-4 were analyzed. FL T cells expressed similar levels of CTLA-4 to Treg, whereas TL T cells expressed much higher levels on the cell surface. The number of Treg in both mice was decreased, although Foxp3 expression was not altered. Treg from both mice exerted suppressive activity, whereas CD25⁻ T cells from FL mice showed no suppression. Furthermore, CD25⁺CD4 thymocytes from young CTLA-4-deficient mice were analyzed and found to exhibit suppressive activity. These results indicate that Treg exert in vitro suppressive activity independent of CTLA-4 expression.

When cells die by necrosis in vivo they stimulate an inflammatory response. It is thought that this response is triggered when the injured cells expose proinflammatory molecules, collectively referred to as damage associated molecular patterns (DAMPs), which are recognized by cells or soluble molecules of the innate or adaptive immune system. Several putative DAMPs and/or their receptors have been identified, but whether and how much they participate in responses in vivo is incompletely understood, and they have not previously been compared side-by-side in the same models. This study focuses on evaluating the contribution of multiple mechanisms that have been proposed to or potentially could participate in cell death-induced inflammation: The third component of complement (C3), ATP (and its receptor P2X7), antibodies, the C-type lectin receptor Mincle (Clec4e), and protease-activated receptor 2 (PAR2). We investigate the role of these factors in cell death-induced inflammation to dead cells in the peritoneum and acetaminophen-induced liver damage. We find that mice deficient in antibody, C3 or PAR2 have impaired inflammatory responses to dying cells. In contrast there was no reduction in inflammation to cell death in the peritoneum or liver of mice that genetically lack Mincle, the P2X7 receptor or that were treated with apyrase to deplete ATP. These results indicate that antibody, complement and PAR2 contribute to cell death-induced inflammation but that Mincle and ATP- P2X7 receptor are not required for this response in at least 2 different in vivo models.

Pulmonary arterial hypertension (PAH) is a life-threatening complication in connective tissue diseases (CTD). It remains controversial whether immunosuppressive therapy is useful for PAH associated with CTD (PAH-CTD). The Dana Point algorithm does not refer such treatments in patients with PAH-CTD due to the lack of evidence. However, some case reports have shown the potential efficacy of immunosuppression for PAH-CTD. Here we report five cases of PAH-CTD treated with corticosteroids and discuss the current management of PAH-CTD with immunosuppressive agents. Our cases consisted of three active systemic lupus erythematosus (SLE), a quiescent SLE and an active polymyositis. WHO functional classes at baseline were class III in three cases and class II in two. Median follow-up period was 44 (28–92) weeks. PAH was diagnosed by right heart catheterization in all cases (median pulmonary arterial pressure was 45 (29–49) mmHg). All patients received 1 mg/kg of prednisolone (PSL) for 2–4 weeks, followed by appropriate dose reduction. Methylprednisolone pulse therapy was performed in patients resistant to the high dosage of PSL. Four patients received vasodilators in combination. The therapy as above improved WHO functional class 4 weeks after the initiation of PSL in all the patients. Two patients required dose increase or additional administration of vasodilators due to the dose reduction of PSL. Corticosteroid therapy may be effective for PAH-CTD at least in the short term, even in low general activity of CTD or moderate PAH. Our experience suggests that corticosteroid therapy, by itself or in conjunction with standard vasodilators, is effective for PAH-CTD patients.

Objectives. To investigate the role of Foxp3⁺ CD25⁺ CD4⁺ regulatory T cells (Treg) and their transcription factor, Runt-related transcription factor 1 (Runx1), in the pathogenesis and development of systemic sclerosis (SSc). Methods. We collected 23 blood samples from patients with SSc including 19 females and 4 males, 11 early-stage cases within 3 years from onset and 12 late-stage cases and 22 samples from age-matched healthy subjects (HS). Total CD4⁺ T cells were assessed for the expression of Treg-related markers, CD25 and CD127, on their surface and intracellular Foxp3 using flow cytometry. Relative expression of Runx1 mRNA in magnetically purified Treg was analyzed using real-time PCR. Results. Proportion of Foxp3⁺ cells in total CD4⁺ T cells was decreased in patients with either early- or late-stage SSc compared with that in HS, and Runx1 mRNA expression in purified Treg was lower in patients with SSc than in HS. Runx1 mRNA expression level was related to the frequency of Treg in SSc. Conclusions. This is the first report on Runx1 expression in Treg of a human autoimmune disease. Low expression of Runx1 along with reduced proportion of Treg in CD4⁺ T cells may be associated with development of SSc even in early disease.