Infiltration of CD8+TCRαβ+ T-effector populations (CD8 effectors) into graft epithelial compartments has long been recognized as a key lesion in progression of clinical renal allograft rejection. While the afferent phase of allograft immunity is increasingly well-defined, the efferent pathways by which donor-reactive CD8-effector populations access and ultimately destroy the graft renal tubules (rejection per se) have received remarkably little attention. This is an important gap in our knowledge of transplantation immunology, because epithelial compartments comprise the functional elements of most commonly transplanted organs including not only kidney, but also liver, lung, pancreas, and intestine. Furthermore, there is increasing evidence that attack of graft epithelial elements by CD8-effector populations not only causes short-term graft dysfunction but is also a major contributor to development of chronic allograft nephropathy and late graft loss, which now represent the salient clinical problems.
Recent studies of the T-cell integrin, αEβ7 (CD103), have provided insight into the mechanisms that promote interaction of CD8 effectors with graft epithelial compartments. The purpose of this communication is to review the known properties of the CD103 molecule and its postulated role in the efferent phase of renal allograft rejection.