IMMUNE REGULATION AND TOLERANCE II

Y. Tsunetoshi¹, K. Yamashita¹, S. Shibasaki¹, R. Goto¹, K. Wakayama¹, H. Gentaro¹, M. Zaitsu¹, R. Igarashi¹, M. Ozaki¹, K. Umezawa², S. Todo^1
1Department Of General Surgery, Hokkaido University, Sapporo/JAPAN, ²Department Of Applied Chemistry, Keio University, Yokohama/JAPAN

Body: Introduction: The ultimate goal of immunotherapy in organ transplantation is to induce tolerance against transplanted graft. For this purpose, application of donor specific transfusion (DST) has been shown as an attractive approach in both experimental and clinical settings. Recently, we have developed a newly compound, DTCM-glutarimide (DTCM-G), which has been shown to inhibit the activating protein (AP)-1 activity in murine macrophages stimulated with lipopolysaccharide. In this study, we examined the immunomodulatory effects of DST plus DTCM-G on mouse heart allo-transplantation. Methods: Purified T cells in C57BL/6 (H-2^b) mice were used for in vitro studies examining lymphocyte proliferation and apoptosis. A BALB/c (H-2^d) mouse heart was transplanted into a C57BL/6 mouse, and graft survival was assessed. Recipient was given (i.p.) either vehicle or DTCM-G at 20, 40 or 60 mg/kg/day for 14 days (n=4 per group). In some, C57BL/6 mouse was infused BALB/c splenocytes (2x10⁷) as for DST, and transplanted BALB/c heart 7 days later. Either vehicle or DTCM-G at 40 mg/kg/day was administrated intraperitoneally for 14 days after DST (n=6 per group). Results: DTCM-G significantly suppressed aCD3+aCD28 mAbs stimulated T cell proliferation in a dose-dependent manner (Fig. 1A). The number of T cells undergoing apoptosis, as assessed by PI-Annexin-V⁺ staining, following 24 hour-stimulation with aCD3+aCD28 mAbs strikingly increased when treated with DTCM-G at 10 mg/ml, while the drug did not significantly induce apoptosis when T cell were non-stimulated (Fig. 1B). DTCM-G treatment at 20, 40 and 60 mg/kg/day significantly prolonged cardiac allograft survival to a median survival time (MST) of 13, 19 and 18 days, respectively (p<0.05 vs. control), as compared to that of control (MST: 6.5 days) (Fig.2A). DST treatment alone prolonged graft MST to 24 days. In contrast, DST plus DTCM-G treatment markedly prolonged graft MST to 70.5 days. In this treatment group, two of 6 allografts survived for over 100 days (Fig.2B). Conclusion: DTCM-G promotes activation-induced apoptosis on T cells, and suppresses T cell proliferation. Such immunomodulatory property of DTCM-G seems to synergize with DST that permits marked prolongation of cardiac allograft survival in a stringent mouse combination.

Disclosure: All authors have declared no conflicts of interest.