Post-transplant development of C1q-positive HLA antibodies and kidney graft survival.

The development of de novo human leukocyte antigen (HLA) donor specific antibodies (DSA), detected by both cytotoxic or solid phase assays, was considered the major risk factor for allograft failure in kidney transplantation. However, it was shown that not all patients with persistent production of DSA suffered loss of their grafts. Modified Luminex-Single Antigen assays, able to identify C1q-fixing antibodies, represent a new strategy in assessing the clinical relevance of detected DSA. This study demonstrated that C1q-fixing capability of de novo DSA is a clinically relevant marker of worse outcome and inferior graft survival in kidney transplantation. In fact, our findings evidenced a very low graft survival only in the patients who developed DSA able to fix C1q during post-transplant course, while patients producing C1q-negative DSA had good graft survival, which was comparable to that found in our previous study for DSA-negative patients. Moreover, anti-HLA class II antibodies had a higher incidence than anti-HLA class I, and the ability to fix C1q was significantly more frequent among anti-DQ DSA than anti-DR DSA. Monitoring of de novo C1q-DSA production represents a useful, non-invasive tool for risk stratification and prediction of graft outcome in kidney transplantation.