Functional evaluation of T helper, T suppressor, and B lymphocytes in lethally irradiated rhesus monkeys injected with autologous bone marrow.

Lethally irradiated rhesus monkeys were treated with autologous bone marrow that had either been (1) nontreated, i.e., normal; (2) depleted of T lymphocytes with a monoclonal antibody directed against rhesus T lymphocytes; (3) fractionated with the soybean agglutinin (SBA- fraction); or (4) fractionated with SBA and further depleted of T cells by E-rosetting. There was no difference in hematologic reconstitution among the animals, but all showed a marked lowering of the T helper/T suppressor ratio during the first 10 months posttransplant and reduced capability of their peripheral blood leukocytes (PBL) to produce Ig upon stimulation with pokeweed mitogen. This subnormal ability of PBL to produce Ig, as measured by plaque-forming cells in a reverse hemolytic plaque assay, was not explained entirely by the altered T-H/T-S ratio but was correlated with the functional status of the T-H, T-S, and B lymphocytes. Isolated populations of the different lymphocyte subsets from PBL of the experimental animals were cocultured with normal cells of the appropriate subset to obtain Ig synthesis when stimulated with PWM. Animals treated with normal bone marrow showed recovery of T-H cell function after 5 months, but their T-S cells showed excessive suppressor activity that persisted for 20 months posttransplant. In contrast, those animals receiving treated marrow (mAb plus complement, or SBA) showed a much-delayed (12 months or more) return to normal T-H cell function and an earlier return of T-S cells expressing a normal level of suppressor activity. Since the SBA- fraction of marrow contains very few or no T-H cells and T cell depletion of marrow with mAb also removes these cells, it is suggested that the kinetics of immune recovery of the different lymphocyte subsets of PBL is influenced by the presence or absence of T-H cells in the marrow inocula.