COMBINATION THERAPY WITH CYCLOSPORINE AND INTERLEUKIN-4 OR INTERLEUKIN-10 PROLONGS SURVIVAL OF SYNGENEIC PANCREATIC-ISLET GRAFTS IN NONOBESE DIABETIC MICE - ISLET GRAFT-SURVIVAL DOES NOT CORRELATE WITH MESSENGER-RNA LEVELS OF TYPE-1 OR TYPE-2 CYTOKINES, OR TRANSFORMING-GROWTH-FACTOR-BETA IN THE ISLET GRAFTS

Background. The recurrent autoimmune response to syngeneic pancreatic islet grafts transplanted into nonobese diabetic (NOD) mice is cell-me diated and relatively resistant to cyclosporine (CsA) therapy, Therefo re, we asked whether interleukin (IL)-4 and IL-10, cytokines that inhi bit cell-mediated immunity, might improve the therapeutic effect of Cs A Methods, We compared the survival of syngeneic islet grafts transpla nted into diabetic NOD mice treated with IL-4, IL-10, and CsA, adminis tered as single agents and in combinations, Additionally, we measured mRNA levels of type 1 cytokines (interferon-gamma [IFN-gamma 3, IL-2, and IL-12), type 2 cytokines (IL-4 and IL-IO), and transforming growth factor-beta (TGF-beta) to determine whether graft rejection or surviv al might correlate with expression of these cytokines in the grafts, R esults, CsA (20 mg/kg/day) significantly prolonged islet graft surviva l (median: 20 days vs, 10 days for vehicle-treated mice), Neither IL-4 (2.5 mu g, twice dally), nor IL-10 (10 mu g, twice daily) significant ly prolonged islet graft survival, By contrast, combination therapy wi th CsA and IL-10 significantly prolonged islet graft survival (median: 34 days) compared with vehicle-treated mice (median: 10 days), and co mbination therapy with CsA and IL-4 significantly prolonged islet graf t survival (median: 59 days) compared with both vehicle-treated mice ( median: 10 days) and mice treated with CsA alone (median: 20 days), Is let grafts from normoglycemic mice treated with CsA plus IL-IO, and wi th CsA plus IL-4, were surrounded but not infiltrated by mononuclear l eukocytes and beta cells were intact, whereas islet grafts from mice t reated with vehicle, IL-4, IL-10, and CsA (as single agents) were infi ltrated by mononuclear leukocytes and fewer beta cells were detected. Polymerase chain reaction analysis of cytokine mRNA expression in isle t grafts at 8-12 days after transplantation revealed that CsA decrease d mRNA levels of type 1 cytokines (IFN-gamma and IL-12p40), whereas Cs A plus IL-10 did not, and CsA plus IL-4 increased mRNA levels of IFN-g amma, IL-12p40, and TGF-beta, Conclusions. These results demonstrate t hat IL-4, and to a lesser extent IL-10, improves the ability of CsA to prevent autoimmune destruction of beta cells in syngeneic islets tran splanted into diabetic NOD mice; however, there is no simple correlati on between the protective effects of the different treatment regimens (CsA, CsA plus IL-4, and CsA plus IL-10) and mRNA levels of type 1 cyt okines (IFN-gamma, IL-2, and IL-12), type 2 cytokines (IL-4 and IL-10) , or TGF-beta in the islet grafts.