Reduction and repopulation of T-lymphocytes after cytoreductive therapy with or without autologous bone marrow rescue.

The reconstitution of peripheral-blood T-lymphocytes following cytoreductive therapy in standard (11 patients) or in high dosages (ten patients) was compared with that after supralethal cytoreductive therapy followed by autologous bone marrow rescue (ABMR, 20 patients). Along with the increasing cytotoxic potential of the three therapy protocols, T-cell counts fell to lower levels. Following all three forms of cytoreductive therapy, T8+ T-cell counts decreased to lower levels than T4+ T-cell counts. The greater relative reduction of T8+ T cells may indicate that T8+ T cells are more sensitive to cytoreductive therapy than T4+ T cells, and/or that T8+ T cells have shorter survival times. The contribution of residual (mainly T4+) T cells to the T-cell repopulation was significant in the patients on standard-dosage chemotherapy, less important in those on high-dosage chemotherapy, and minor in those receiving supralethal cytoreductive therapy and ABMR. The repopulation rates of T8+ T cells following ABMR exceeded those observed after chemotherapy without ABMR. The T3- (T3 negative) T-cell subset, which comprises only 5%-10% of peripheral T cells in normal individuals, decreased rapidly to low levels and remained so for the entire six-week observation period in both chemotherapy groups. Following ABMR, however, those T3- T cells rapidly increased again to normal levels. Since the T cells in bone marrow biopsies have a large T3- fraction, that rapid recovery of T3- T cells may reflect the contribution of marrow precursors in the marrow grafts to the improved T-cell regeneration following ABMR.