Abnormal T-lymphocyte colonies (CFU-TL) following bone marrow transplantation

We studied the presence of peripheral- blood- and bone-marrow-derived T-lymphocyte colony formation (CFU-TL) in 28 bone marrow transplant recipients from 1 month to six years after transplantation. Peripheral blood leukocyte and lymphocyte counts were generally normal, and all had morphologic evidence of engraftment without leukemia at the time of study. Both peripheral-blood- and bone-marrow-derived CFU-TL were markedly reduced after transplantation as compared to normal controls, which included bone marrow donors (14.2 ± 5/4 x 10⁴ vs 313 ± 100/4 x 10⁴ [p < 0.001] and 26 ± 4/2 x 10⁵ vs 1004 ± 60/2 x 10⁵ [p < 0.001]. Among the patients, four had no detectable bone-marrow-derived CFU-TL when tested less than six months after transplantation. Peripheral blood CFU-TL, while present in all patients, was markedly decreased for more than 12 months after transplantation. After two years, the number of CFU-TL returned to normal in several patients. The abnormalities in CFU-TL were unrelated to diagnosis, age, sex, graft-versus-host disease (GVHD), pretransplant conditioning, or posttransplant immunosuppressive treatment. Patients receiving autologous bone marrow transplants also had decreased CFU-TL. Cocultures of normal peripheral-blood- or bone-marrow-derived mononuclear cells with recipients' mononuclear cells or sera did not inhibit normal CFU-TL growth. Furthermore, the addition of mononuclear cells or sera from normal individuals, or of exogenous interleukin 1 or interleukin 2, did not correct the deficiency of CFU-TL growth by recipient cells. Depletion of T-lymphocytes from bone marrow or peripheral blood in transplant recipients by physical techniques or with a monoclonal antibody (CT-2) and complement had no effect on CFU-TL recovery. Similarly, addition of recipients' T cells to normal peripheral blood or bone marrow mononuclear cells did not suppress CFU-TL. These data indicate that most transplant recipients have a marked reduction in CFU-TL which persists for up to two years after transplantation. This reduction in the growth of T-cell colonies appears to be due to deficient numbers of these cells or an intrinsic defect in their responsiveness to T-cell lymphokines, rather than a result of growth suppression by inhibitory cells or serum factors. This observed defect in CFU-TL may have implications for therapeutic attempts to facilitate immune reconstitution after bone marrow transplantation.