Introductory part of this thesis provides short description of kidney anatomy and pathogenesis of kidney diseases. Unfortunately, kidney pathogenic states often lead to insufficiency, with kidney transplant as the most desirable way of treating the disease. One of the most important factors for successful kidney transplant and graft longevity is the best possible HLA system compatibility between organ donor and recipient. The objective of this research was to test serums of 3 patients and determine presence or absence of HLA antibodies in given samples. Blood samples from patients were provided by Division of Transfusion Medicine (University hospital center Split), while all the tests were performed in Tissue Typing Laboratory. Method used for HLA antibody detection in this research was mikrolimfocitotoxicity (CDC) test. Research results showed that out of three tested patients, one was highly sensitized (against all samples provided for lymphocyte panel), second patient was sensitized specifically to HLA-A2 and HLA-A24(9) antigens, while in the last patient no HLA antibodies were detected. Along with correct and updated data on possible sensitizing events, the results of regular screenings are crucial in defining the recipient's immune status and enable an optimal search for a potential organ donor