Cytokine mRNA expression in peripheral blood cells of immunosuppressed human islet transplant recipients

The macrophage derived cytokines interleukin-1 beta (IL-1β), and tumor necrosis factor alpha (TNFα), and the T-cell derived cytokine interferon gamma (IFNγ) have been implicated to play an important role in early attack on islet cells during human islet transplantation (ITx). Therefore, the aim of this study was to investigate the influence of the current immunosuppressive induction therapy in clinical islet transplantation on mRNA expression of these cytokines in blood cells, compared to lipopolysaccharide (LPS) induced cytokine release in vitro and to plasma levels. The cytokine release correlated to lymphocyte counts and significantly decreased after ATG, and partially recovered 2 weeks after ITx. Unexpectedly, there was no correlation between mRNA expression for IL-1β in total blood and the number of lymphocytes and monocytes remaining after anti thymocyte globulin (ATG)- therapy. Even when the blood was nearly totally depleted from mononuclear cells, high amounts of IL-1β mRNA could be detected. However, IL-1β secretion could not be stimulated in vitro. Our results show that application of ATG during ITx might contribute to graft survival during the early posttransplant period by suppression of the synthesis of monocyte derived cytokines IL- 1β and TNFα.