Graft-versus-leukemia effects in T lineage and B lineage acute lymphoblastic leukemia.

T and B lineage ALL cells express different levels of HLA-class II antigens, which may serve as targets for graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL). The object of this study was to determine whether GVL effects after HLA-identical sibling bone marrow transplantation differed in T and B lineage ALL. We studied 1132 patients with ALL of T lineage (n = 416) or of B lineage (cALLa+) (n = 716) transplanted in first (n = 605) or second (n = 527) remission with bone marrow from an HLA-identical sibling donor, between 1982 and 1992, and reported to the IBMTR by 165 teams. Cox proportional hazards regression models were used to determine the relative risk (RR) of relapse in patients with acute (grades II-IV) or chronic GVHD vs patients without GVHD. Acute and chronic GVHD were considered as time-dependent covariates. Patients transplanted in first and second remission were analyzed separately. GVHD decreased relapse risks to a similar extent in T and B lineage ALL. For first remission transplants, relative risks of relapse for patients with vs those without GVHD was 0.34 for T lineage ALL and 0.44 for B lineage ALL. Corresponding relative risks in second remission transplants were 0.54 and 0.61. This study confirms earlier findings of an antileukemia effect of GVHD in ALL. This effect was similar in T lineage and B lineage ALL, despite probable differences in HLA-class II antigen expression.