Costimulation Blockade of Both Inducible Costimulator and CD40 Ligand Induces Dominant Tolerance to Islet Allografts and Prevents Spontaneous Autoimmune Diabetes in the NOD Mouse

Costimulation Blockade of Both Inducible Costimulator and CD40 Ligand Induces Dominant Tolerance to Islet Allografts and Prevents Spontaneous Autoimmune Diabetes in the NOD Mouse Sulaiman A. Nanji 1 , Wayne W. Hancock 2 , Bin Luo 1 , Colleen D. Schur 1 , Rena L. Pawlick 1 , Lin Fu Zhu 1 , Colin C. Anderson 1 and A.M. James Shapiro 1 1 Department of Surgery, University of Alberta, Edmonton, Alberta, Canada 2 Department of Pathology and Laboratory Medicine, Children’s Hospital of Philadelphia and the University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Address correspondence and reprint requests to A.M. James Shapiro, MD, PhD, FRCSC, Roberts Centre, University of Alberta, 2000 College Plaza, 8215 112 St., Edmonton, AB, Canada T6G 2C8. E-mail: shapiro{at}islet.ca Abstract Costimulation blockade is a promising strategy for preventing allograft rejection and inducing tolerance. Using a fully allogeneic mouse model, we tested the effectiveness of the combined blockade of the CD40 ligand and the inducible costimulator (ICOS) on islet allograft survival and in the prevention of autoimmune diabetes in the NOD mouse. Recipients treated with blocking monoclonal antibodies (mAbs) to ICOS and the CD40 ligand had significant prolongation of graft survival, with 26 of 28 functioning for >200 days. Long-term engrafted mice maintained antidonor proliferative and cytotoxic responses, but donor-specific immunization did not induce graft rejection, and challenge with second, same donor but not third-party grafts resulted in long-term acceptance. The immunohistology of tolerant grafts demonstrated the presence of CD4 + CD25 + T-cells expressing Foxp3, and islet/kidney composite grafts from tolerant mice, but not from mice lacking lymphocytes, were accepted indefinitely when transplanted into naïve B6 mice, suggesting that recipient T-cells were necessary to generate dominant tolerance. Combined anti-ICOS and anti–CD40 ligand mAb therapy also prevented diabetes in NOD mice, with only 11% of treated recipients developing diabetes compared with 75% of controls. These data demonstrate that the blockade of CD40 ligand and ICOS signaling induces islet allograft tolerance involving a dominant mechanism associated with intragraft regulatory cells and prevents autoimmune diabetes in NOD mice. CTL, cytotoxic lymphocyte ICOS, inducible costimulator mAb, monoclonal antibody STZ, streptozotocin Footnotes Accepted September 23, 2005. Received September 20, 2004. DIABETE