Endothelial cells as targets of allograft rejection

Endothelial cells harbor many antigenic determinants that may be targets for antibodies and, as such, induce acute or chronic antibody-mediated rejections. In certain cases of organ transplantation, antibodies reacting with endothelial cells, but not with ABO or human leukocyte antigens, can be observed and these are probably responsible for the rejection of the graft. The antigenic targets, however, are still poorly defined and the mechanisms of action of such antibodies would appear to be diverse, leading to the lack of a relevant in vitro assay for the detection of those antibodies. Increasing data suggest that, apart from direct alloimmune responses, autoimmune mechanisms might be triggered by alloreactivity and also play a significant role in the pathogenesis of the vascular lesions, the so-called chronic rejection, observed in organ allografts.