An analysis of the effect of HLA-DP in the mixed lymphocyte reaction.

It has recently been reported that HLA-DP antigens may play an important role in the development of graft-versus-host disease (GVHD) following transplantations of haploidentical bone marrow as a treatment for haematological malignancies. Mixed lymphocyte culture (MLC) is routinely performed prior to bone marrow transplantation to assess the suitability of the donor, and we have therefore examined the role of HLA-DP in this test. One-way MLC chequerboard experiments were performed between 17 HLA-Dw3 homozygous typing cells (HTC) with a range of HLA-DP antigens represented, including HLA-DPw1, w2, w3, w4 and CP63. The experiments were performed on multiple occasions and each time a highly significant difference (P = less than 0.001) was observed between the Relative Responses (RR) in the HLA-DP matched responder/stimulator pairs and the HLA-DP mismatched pairs. There was, however, considerable overlap in these results with ranges in the HLA-DP-matched group RRs of 0-17%, and 0-62% in the mismatched group. Only 3.1% of the HLA-DP-matched grou had a RR greater than 5%, while 48% of the HLA-DP mismatched group had a RR greater than 5%. From these results it was calculated that a positive response (greater than 5%) has a 96% chance of being due to an HLA-DP disparity of one or two antigens. Conversely, with a negative MLC the chance of their being no HLA-DP antigen disparity was only 65%.(ABSTRACT TRUNCATED AT 250 WORDS)