Bone marrow transplantation in siblings:correlation of MLC, serological and DNA typing

It is known the relevance of HLA identity in bone marow transplantation. In particular, HLA cla II gene matches are an important factor to avoid fatal graft-Vs-host reaction. In 17 sibling donor-recipient pairs waiting for bone marrow transplantation, showing resological identity, we evaluated the Mixed Lymphocytes Culture (MLC) response before the transplant. MLC was negative in all the pairs. in 16 of them the Stimulation Index (S.I.) was <2. In one pair the S.I. was 2.9. The PCR DNA typing has been used for DPbeta, DQalfa, DRbeta allele evaluation. 9 of this patients were transplanted: the degree of MLC reactivity was compared with the clinical grade of Graft-vs-Host (GVHD). 3, with S.I. ranged from 1 to 2, experienced GVHD grade I; 5, with S.I. ranged from 0 to 1, experienced no GVHD; 1 experienced GVHD grade II. This last patient showed serological identity with the donors sibling (serological tissue typing: A24, 26; B35, w55; Cw4, w3; DR2,7) and S.I.=2.9: using DNA typing method,the siblings resulted DP-disparate, due to genetic recombination between DP and DR loci (DNA typing donor: DPbeta 4,2 ; DQalfa 1,2; DRbeta 2,7 - DNA typing recipient: DPbeta 3,1; DQalfa 1,2; DRbeta 2,7). Our preliminary results suggest that when the S.I. is > 2 it becomes mandatory to employed the PCR typing before the transplant, also between donor-recipient siblings, because of the possibility of genetic recombination.