Differential modulation of IL-12 family cytokines in autoimmune islet graft failure in mice.

Aims/hypothesis: The relative contribution of T helper (Th)1 and Th17 cells in graft rejection is inconclusive, on the basis of evidence provided by different T cell-related cytokine-deficient animal models and graft types.
Methods: We used novel antigen-presenting-cell-specific Il-12p35 (also known as Il12a)-knockout (KO), IL-23p19-knockdown (KD) and IL-27p28-KD strategies to investigate T cell differentiation in islet graft rejection.
Results: In vitro dendritic cell-T cell coculture experiments revealed that dendritic cells from Il-12p35-KO and IL-23p19-KD mice showed reduced ability to stimulate IFN-γ and IL-17 production in T cells, respectively. To further explore the T cell responses in islet graft rejection, we transplanted islets into streptozotocin-induced diabetic NOD/severe combined immunodeficiency (SCID) recipient mice with IL-12-, IL-23-, or IL-27-deficient backgrounds and then challenged them with NOD.BDC2.5 T cells. The survival of islet grafts was significantly prolonged in Il-12p35-KO and IL-23p19-KD recipients compared with the control recipients. T cell infiltrations and Th1 cell populations were also decreased in the grafts, correlating with prolonged graft survival.
Conclusions/interpretation: Our results suggest that IL-12 and IL-23 promote and/or maintain Th1 cell-mediated islet graft rejection. Thus, blockade of IL-12 and IL-23 might act as therapeutic strategies for reducing rejection responses.