Enhancement of in vitro erythropoiesis by peripheral blood mononuclear cells from allogeneic marrow recipients in the early post-transplant period.

The effect of peripheral blood mononuclear cells (PBMCs) from bone marrow recipients on in vitro growth of erythroid burst-forming units (BFU-E) was studied. PBMCs were obtained from 5 allogeneic, 1 syngeneic and 1 autologous bone marrow recipient(s) at different intervals after transplantation. The number of BFU-E was significantly increased when donor bone marrow cells were co-cultured with PBMCs obtained from allogeneic marrow recipients in the early post-transplant period. No effect was observed using PBMCs obtained in the later post-transplant period, PBMCs from a syngeneic marrow recipient, or PBMCs from an autologous marrow recipient. The BFU-E enhancing activity was present among T cells and was abolished by treating them with OKT3 or OKT4 antibody and complement. These observations suggest that chimeric T lymphocytes, probably of the helper/inducer subset, from allogeneic marrow recipients in the early post-transplant period have a potent enhancing effect on in vitro erythropoiesis.