Aplastic anemia: failure of patient leukocytes to stimulate allogeneic cells in mixed leukocyte culture.

One-way mixed leukocyte cultures were used to study the ability of cells from 53 patients with aplastic anemia and 65 of their HLA-identical siblings to stimulate and to respond to cells from unrelated individuals. The capacity of leukocytes from 28 of 53 patients to stimulate was diminished or absent, wheras their ability to respond remained comparable to that of cells from their HLA-identical siblings. Leukocytes from the group of patients with the lowest peripheral lymphocyte count were least stimulatory. The results indicate that in acquired aplastic anemia there exists a dissociation between stimulation and response in mixed culture.