Major Histocompatibility Complex Class 1 Chain-Related Antigen A Antibodies: Sensitizing Events and Impact on Renal Graft Outcomes

Background. Major histocompatibility complex class 1 chain-related antigen A (MICA) antibodies (Abs) have been associated with renal graft loss in one large cohort. The triggering factors for MICA Abs and their autologous or allogeneic specificity have not been well defined. More data on the impact of MICA on renal grafts outcome are needed. Methods. We tested sera from 494 controls and 597 patients with chronic kidney disease (CKD) for MICA using Luminex. Forty CKD MICA+ patients were genotyped for MICA alleles to determine their auto-or allospecificity. We compared MICA+ with MICA- renal transplant recipients with regard to acute rejection episodes and long-term survival. Results. Blood transfusions, previous transplantation, and more than two pregnancies were independent risk factors for the presence of MICA Abs, as were CKD stage V status and male gender. Among the 40 genotyped patients, allo-Abs alone were present in 32 patients, both auto-and allo-Abs in 4 patients, and auto-Abs alone in 4 patients. When we compared MICA+ with MICA- patients, the incidence of acute rejection episodes during the first year (10.2% vs. 12.8%), as well as 1-year creatinine and proteinuria, were similar in both groups. At 10 years, actuarial patient (97.8% vs. 87.6%) and overall graft survival (76% vs. 72%) were similar between MICA+ and MICA- patients. Conclusions. In summary, (1) sensitizing events for MICA Abs are the same as for human leukocyte antigen Abs; (2) MICA Abs did not adversely affect renal graft outcomes in our cohort.