Role of CD26-adenosine deaminase interaction in the T cell-mediated immunity
ABSTRACT: CD26 is a 110 kDa surface-bound ectopeptidase with intrinsic dipeptidyl peptidase IV (DPP IV) activity, which binds ade- nosine deaminase (ADA) on the surface of T cells. ADA is an enzyme of the purine metabolism that has been the object of consi- derable interest mainly because the congenital defect causes severe combined immunodeficiency (SCID). This review focuses on work demonstrating that CD26-ADA interaction has a key role in T cell mediated immunity. The enzymatic and extra-enzymatic roles of ADA and CD26 in the immune context are discus- sed. Furthermore, the structure of the CD26-ADA complex, the signal transduction pathway triggered by the co-stimulatory ADA- CD26 interaction and the cytokine pattern induced during the immunosynapse are analyzed. In this context, the implications of the impairment of CD26-ADA interaction and its catalytic activities in the pathophysiology of AIDS are discussed.