130  ABSTRACT Background: Evidence supporting deleterious effect of preformed major histocompatibility class I chain-related A (MICA) antibodies in rejection incidence and graft survival is still unclear. Methods: Retrospective analysis of 554 kidney transplanted patients. Comparison between positive or negative for MICA antibodies patients was performed to characterize sensitizing triggers. Further classification according to pre-transplant flow cytometry-recorded anti–MICA and/or anti-human leukocyte antigen (HLA) antibodies was made to determine first year rejection incidence and graft survival. Multivariate analysis was applied to determine predictors for acute rejection. Results: Pre-formed anti-MICA antibod- ies were detected in 41 patients (7.4%). HLA sensitization, blood transfusions and pregnancies were frequently found in anti-MICA+ patients but only pre-formed anti-HLA class I antibodies showed inde- pendent association (OR 2.67, p = 0.02). Comparing to MICA-/HLA–, MICA-/HLA+ group presented sig- nificantly lower first year rejection-free survival (78.6% vs. 89.3%, p < 0.01), mostly occurred in the first six months, while no difference was found in MICA+/HLA– (88.9% vs. 89.3%, p = ns). MICA-/HLA+ showed independent impact in rejection (OR 2.09, p = 0.03), while no evidence was found in MICA+/HLA- (OR 1.08, p = ns). At 4 years, MICA-/HLA+ group presented lower graft survival (85.8% vs. 95.3%, p = 0.03). Again, no difference was found in MICA+/HLA- group (95.1% vs. 95.3%, p = ns). Conclusion: Our results do not support HLA-independent deleterious pathogenic role of pre-formed MICA antibodies on first year rejection incidence and graft survival. Key-Words: HLA; kidney; MICA; rejection; survival; transplant. Impact of pre-transplant anti-MICA sensitization in graft rejection and survival Impacto da sensibilização anti-MICA pré-transplante na rejeição e sobrevida do enxerto Rui Costa 1 , Jorge Malheiro 2 , Sandra Tafulo 3 , Clara Santos 4 , Manuela Almeida 2 , Sofia Pedroso 2 , La Salete Martins 2 , Leonídio Dias 2 , António Castro-Henriques 2 1 Nephrology Department, CHTMAD, Vila Real, Portugal 2 Nephrology and Kidney Trasplant Department, CHP, Oporto, Portugal 3 Centro do Sangue e Transplantação do Porto, Oporto, Portugal 4 Nephrology Department, CHVNG, Vila Nova de Gaia, Portugal Received for publication: 14/10/2014 Accepted in revised form: 10/02/2015 ORIGINAL ARTICLE Port J Nephrol Hypert 2015; 29(2): 130-138 Advance Access publication 20 March 2015