Clinical value of non-HLA antibodies in kidney transplantation: Still an enigma?

HLA antibodies play a major role in the recipient's immune response against the renal allograft and are an established risk factor for antibody-mediated rejection and subsequent impaired graft survival. Evidence originating from HLA-identical donor-recipient pairs indicates that non-HLA antibodies may play a role as well. Numerous non-HLA antibodies have been identified in renal organ transplantation, directed against a heterogeneous subset of both allo- and autoantigens including MHC Class-I-related chain A (MICA) and Angiotensin II type 1 receptor (AT1R). In this review, we will discuss the mechanisms predisposing to non-HLA antibody formation, the possible synergy with HLA-antibodies in their pathologic potential and the mechanisms involved in allograft damage. Furthermore, an overview of the identified non-HLA antibodies and antigens and their relation with rejection and graft survival will be provided.