THE RELEVANCE OF HLA-DP ANTIBODIES IN KINDEY ALLOGRAFT OUTCOME.

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THE RELEVANCE OF HLA-DP ANTIBODIES IN KINDEY ALLOGRAFT OUTCOME.
M. Buckingham , L. McDonald , Y. Barabanove , R. Diaz , N. Polyakov , D. Trathen and A.R. Tambur . ¹ Surgery, Northwestern University, Chicago, IL, USA .

HLA-DP antigens can function as classical restriction elements for antigen presentation. Yet, neither HLA-DP typing, nor DP antibody analysis, are included in routine compatibility testing.
A 35 yo, non-sensitized, Caucasian male received a deceased donor - 6 antigen matched kidney. Four months post transplant immunosuppression (IS) was withdrawn due to BK virus infection. No HLA-directed antibodies were identified at that time, however, antibodies against class II molecules were evident one month post IS secession, and the kidney was nephrectomized 2 months later.
Recently, 4 potential donors underwent flow cytometry crossmatch (FCXM) analysis, resulting in T cell negative (neg) and strong B cell positive (pos) reactions. The presence of HLA-class I, as well as DR or DQ directed antibodies was excluded using solid phase assays. High definition bead analysis revealed HLA-DP*0101, 0301, 0501, 1101, 1301, and *1701 directed antibodies. The recipient was typed as HLA-DP* 0401, 0402.
Additional FCXM were performed using cells from HLA-DR, DQ identical volunteers. Interestingly, one FCXM [1] was T neg B pos while the other [2] was T and B neg. In concordance with the FCXM results, volunteer [2] was typed as homozygous HLA-DP*04 whereas volunteer [1] carried HLA-DP*03, and *04. The deceased donor was retrospectively typed as HLA-DP*0201, 0301, thus suggesting the generation of donor-specific DP antibodies in association with the BK viral infection.
Conclusion: T cell neg B cell pos FCXM, in the absence of HLA-DR, DQ antibodies should not be dismissed as due to non-HLA antibodies / irrelevant to transplant outcome. Analysis of recipient DP-directed antibodies and potentially of donor HLA-DP typing should be pursued.