LACK OF CORRELATION OF MLC REACTIVITY WITH ACUTE GRAFT-VERSUS-HOST DISEASE AND MORTALITY IN UNRELATED DONOR BONE-MARROW TRANSPLANTATION

Acute graft-versus-host disease (AGvHD) is a significant cause of morb idity and mortality in patients receiving a bone marrow transplant fro m an unrelated donor, and in an effort to reduce this problem, donors are selected for the least possible HLA incompatibility with the recip ient. Selection criteria have included minimal incompatibility for the HLA-A, -B, and -DR loci and low reactivity in mixed lymphocyte cultur e (MLC); however, the value of MLC reactivity for prediction of develo pment of AGvHD has been questioned. We therefore examined the correlat ion of MLC reactivity with AGVHD in recipients of unrelated bone marro w transplants. Reactivity in the GvH direction was assessed as relativ e response (RR) of donor lymphocytes to recipient stimulator lymphocyt es. In 126 transplanted pairs with technically satisfactory MLC tests, the RR was divided into quartiles (0-1, 2-5, 6-16, and 17-117% RR). H LA-DRB1 incompatibilities were more frequent in the highest quartile ( p < 0.001); there were no significant differences among quartiles in d onor or recipient age, diagnosis, or frequency of HLA-A or -B incompat ibility. Incidence of AGVHD during the first 100 days post-transplant was assessed by Kaplan-Meier analysis. There was no significant differ ence in incidence of AGvHD among quartiles for the entire group of 126 pairs, for a subset with hematologic malignancy, for a subset selecte d by a more stringent standard for ''technically satisfactory'' MLC, o r for a subset matched for A, B, and DRB1. The MLC response of donor l ymphocytes to recipient stimulator lymphocytes is thus not predictive of development of AGvHD in our patient population receiving unrelated donor bone marrow. Since there was no difference in mortality related to high and low MLC responses, our data also suggest that MLC results are not predictive of survival in this population.