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TITLE: ANALYSIS OF HLA–A, B, AND DRB1MISMATCHES USING HIGH RESOLUTION TYPING OF AFRICAN AMERICAN AND NON–AFRICAN AMERICAN RENAL ALLOGRAFT DONOR AND RECIPIENT PAIRS

David N. Feldman,¹ Jane D. Kearns,¹ Regina Zimmerman,¹ Noah Goodman,¹ Marshall M. Joffe,² Kevin C. Mange,² Harold I. Feldman,² Malek Kamoun.<sup>1

1</sup>Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA; ²Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA

African American (AA) renal transplant patients have been observed to have an increased risk of rejection and shorter allograft survival compared to Caucasians. A greater degree of HLA mismatching among AA recipients, detectable with high–resolution (HR) DNA–based techniques, has been hypothesized as a partial explanation. We are conducting a prospective cohort study of cadaveric renal allograft recipients to examine the role of racial differences in HR–mismatching and allograft outcomes. This prospective multicenter study has collected DNA and clinical transplant data from over 940 recipients to date. Low resolution (LR) HLA–A, B, and DR typing were performed by SSOP/SSP methods on all donor–recipient pairs. HR HLA–A, B, and DR typing were performed on all donor–recipient pairs who had HLA antigens that were matched at the serological level. To date, the number of donor–recipient pairs that were typed at the HR–level are as follow: 296 for HLA–DR, 265 for HLA–A and 247 for HLA–B. Based on data from a subset of these patients analyzed, it appears that the use of HR typing for HLA–A, B and DR reveals additional MMs compared to serological–level typing. HR HLA–DR typing detected a significantly greater number of additional MMs in AA subjects than in non–AA subjects. HR HLA–A typing also appeared to detect additional MMs in AA subjects, in comparison to non–AA subjects. This analysis is being updated and the investigation of the effects of HLA MM detected by HR typing in this study on allograft outcomes is in progress.