Lymphocyte subsets in patients with aplastic anemia.

Lymphocyte subsets were enumerated in a group of 31 patients with aplastic anemia. Abnormal numbers of immunoregulatory T-cells were found in some patients: 26% of them showed a reversed helper/suppressor ratio. Seven of 18 patients showed significantly decreased proliferation in response to PWM; this hyporesponsiveness was present in 75% of patients with a reversed helper/suppressor ratio and in 10% of those with a normal helper/suppressor ratio (R = 0.66, P = 0.008). Eight of 18 patients showed suppressor activity over PWM-induced allogeneic cell proliferation. This suppressive activity did not correlate with T-cell phenotype. Of the patients with a low number of T-cells, 73% had responded to treatment, whereas of those patients with a normal number of T-cells, 26% had responded (P = 0.016). The results are consistent with abnormal immune response in selected patients with aplastic anemia, and suggest a possible influence of T-cells on disease process.