Clinical relevance of preformed anti-mica antibodies for survival of kidney graft from deceased donor

Abstract

Introduction: Anti-HLA preformed or developed antibodies after transplantation are associated to a lower graft survival. It has yet to be further studied if anti-MICA alloantibodies have the same deleterious effect. Purpose: To determine the anti-MICA antibodies prevalence among deceased kidney transplant recipients, and to analyze their effect on graft survival. Patients and Methods: 339 deceased kidney transplants were studied, all of them performed after a negative crossmatch against B and T+AHG lymphocytes. Anti-MICA analysis was performed using Luminex technology, and the sera were classified: negative (Neg , n=251; 74%), weak-positive (WP, n=39; 11.5%), and positive (Pos , n=49; 14.5%). Patient and transplant characteristics were compared, depending on the anti-MICA sera status (Ki-square, Fisher exact, t Student, Mann-Whitney). Graft survival was analyzed based on a Cox-Regression model which included: age, gender, PRA class-I pre-transplant test, induction therapy, initial immunosuppression with MMF, FK and/or rapamicine, and re-transplant (P<0.05 and CI95%). Results: The preformed anti-MICA antibodies prevalence was 26% (n=88). Anti-MICA-positive patients were younger (36.9+12.0 x 44.1+12.8 years old; P=0.00), receiving more frequently a second or third graft (20.4% x 7.6%, P=0.01). The anti-MICA status did not attain a statistical significance to the graft survival (Neg :HR=1; WP:HR=0.7, P=0.25; Pos :HR=0.94, P=0.88). A deleterious effect might not be excluded among the first graft recipients (WP:HR=1.4[0.8-2.7], P=0.28, and Pos :HR=1.6[0.9-3.1], P=0.14), with a Ptrend=0.09 for the antibody levels. Conclusion: The anti-MICA antibodies prevalence upon deceased kidney transplant was 26%, more frequent among young patients receiving a re-graft. A deleterious effect among recipients of first graft might not be excluded. Further studies are needed with a major sampling.