Mixed lymphocyte reactions do not predict severity of graft versus host disease (GVHD) in HLA-DR compatible, sibling bone marrow transplants

Mixed lymphocyte reactions (MLRs) were measured in 25 HLA-A, B and DR compatible sibling bone marrow transplants. Only four of 25 MLRs were positive and in these the low reactivity was of doubtful clinical importance. There was no correlation between MLR and the subsequent development or severity of graft versus host disease (GVHD). A survey of bone marrow transplant units in the United Kingdom showed that most centres perform HLA-DR typing as well as an assessment of the MLR. Factors other than histocompatibility are important in the pathogenesis of GVHD and the data from this study suggest that conventional MLRs can be omitted in HLA-A, B and DR compatible sibling bone marrow transplants.