Effect of peripheral blood lymphocytes from patients with aplastic anemia on granulocytic colony growth from HLA-matched and -mismatched marrows: effect of transfusion sensitization

Recent reports that lymphocytes from patients with idiopathic aplastic anemia (AA) could inhibit the growth of CFU-C from normal marrows prompted us to study the effect of transfusions and histocompatibility differences between 16 AA patients and the target marrows. Lymphocytes were obtained from AA patients and their normal HLA-identical family members, separated by Ficoll-Hypaque, and frozen in dimethylsulfoxide. When study marrows were available, the lymphocytes were thawed and incubated with marrow cells for 2 hr at lymphocyte to marrow cell ratios of 1:1 and 2:1. The cells were then plated in 0.8% methylcellulose, 20% fetal calf serum, and alpha medium over a feeder layer of peripheral blood buffy coat cells immobilized in agar. After 14 days of incubation, granulocytic colonies (>50 cells) were counted. Lymphocytes from normal untransfused individuals and 3 untransfused AA patients enhanced significantly CFU-C growth from both HLA-matched and -mismatched mar-rows. However, lymphocytes from 13 transfused patients inhibited CFU-C growth from mismatched marrows to a greater extent than matched marrows (p < 0.01). Lymphocytes from only 2 of 12 transfused patients showed CFU-C growth inhibition with matched marrows;