Abstract
Effects of activated lymphocytes were studied in the regulation of in vitro hematopoiesis. Activated lymphocytes were prepared by concanavalin A (Con A) stimulation, alloantigen stimulation in MLC, autologous non-T cell stimulation in autologous mixed lymphocyte reaction (AMLR) and non-HLA antigen stimulation in allogeneic marrow transplant patients. Con A-stimulated lymphocytes produced significant suppression of in vitro growth of myeloid and erythroid progenitor cells (CFU-C, CFU-E and BFU-E). Con A-induced suppressor cells were radiosensitive T cells with an OKT+ Ia- phenotype. Alloantigen stimulated lymphocytes produced significant suppression of in vitro growth of CFU-C. These MLC-induced suppressor cells were radioresistant T cells with an OKT8+ Ia+ phenotype. Responding T cells obtained from an early phase of AMLR caused significant enhancement of both autologous and allogeneic peripheral blood BFU-E growth while those from a late phase of AMLR caused significant suppression of only autologous BFU-E growth. Both of AMLR-induced BFU-E/enhancing and BFU-E/suppressing T cells were radiosensitive and OKT4+ Ia+. Chimera lymphocytes obtained in the early period after transplantation when erythropoiesis was newly developed produced significant enhancement of in vitro growth of BFU-E from the bone marrow donor. This BFU-E/enhancing activity was not detected among peripheral blood lymphocytes from syngeneic or autologous marrow recipients. These observations suggest that hematopoiesis may be regulated by heterogenous subpopulations of activated T lymphocytes.
