ANALYSIS OF HLA CLASS I ALLOANTIBODIES IN THE SERA OF SENSITIZED PATIENTS ON HEMODIALYSIS

Background – The specificity of HLA class I (HLA-A and B) alloantibodies was studied in 30 serum samples from antibody-positive, potential kidney transplant recipients who had percent panel reactive antibody values (%PRAs) of more than 5%. Methods . Antibody detection was performed using the microlymphocytotoxicity technique. In this study, the specificity of antibodies was categorized as either private epitopes or crossreactive group (CREG) epitope clusters. A p value of less than 0.05 and χ2 values greater than 3.841 indicated a significant association between a known antigen and an unknown serum sample. Results . No specific antibody was defined in seven (23.33%) serum samples with %PRA values of less than 20%. At 88% to 100% %PRA values (7 patients, 23.33%), most of the serum reactions were positive because the patients had developed multiple antibodies against a large array of HLA antigens. Identifiable antibodies were found in 16 (53.3%) serum samples with %PRA values between 20% and 87%. Anti-CREG antibodies with or without antiprivates were identified in nine of the 16 samples (59.25%), whereas only six (37.5%) of these 16 samples contained an apparent antiprivate antibody without evidence of anti-CREG antibodies and one (6.25%) contained two different private antibodies. Conclusion . Antibody reactivity against CREG clusters was more common among patients with definable antibodies. Knowing the specificity of HLA antibodies in patients’ sera, helps to define a suitable kidney with negative cross-matching for sensitized patients, among previously HLA-typed donor banks. The records of these banks are maintained in computer programs at the IsfahanTransplantation Laboratory.