IN-VITRO SENSITIVITY OF POST-BONE MARROW TRANSPLANTATION CFU-GM AND BFU-E TO TNF-ALPHA AND IFN-GAMMA

Graft failure remains one of the limitations of successful marrow tran splantation. T cell-depleted (TCD) bone marrow transplantation (BMT) i s reported to have a higher incidence of graft failure than unmodified (UM) BMT. In most cases of secondary graft failure, no cellular immun e mechanism has been identified and etiology remains unclear. In an ef fort to delineate a cytokine-mediated mechanism of secondary graft fai lure, we investigated colony-forming unit-granulocyte/macrophage (CFU- GM) and burst-forming unit-erythroid (BFU-E) growth and pattern of inh ibition by tumor necrosis factor-alpha (TNF-alpha) and gamma-interfero n (IFN-gamma) in the early posttransplant period (day 28). Gradient-se parated bone marrow mononuclear cells (BMMNC) from 38 recipients of TC D BMT, 15 recipients of UM BMT, and 23 normal donors (NLD) were plated in cultures of semisolid, serum-containing medium with the addition o f stem cell factor (SCF), erythropoietin (Epo), and granulocyte colony -stimulating factor (G-CSF) or granulocyte-macropohage colony-stimulat ing factor (GM-CSF). Three to seven times more CFU-GM and BFU-E coloni es were cultured from NLD BM-derived BMMNC than from BMMNC of recipien ts of TCD or UM BMT (p = 0.0001). There was no difference in colony nu mber between recipients of UM and TCD BMT on day 28 posttransplant, ho wever. Under G-CSF culture conditions, CFU-GM colonies from recipients of UM and TCD BMT were more susceptible (p less than or equal to 0.05 ) to suppression by IFN-gamma at concentrations of 1 and 100 U/mL than NLD BMMNC-derived colonies. No other difference in IFN-gamma inhibiti on was detected among the three groups. Under G-CSF and GM-CSF culture conditions, maximal inhibition was obtained at TNF-alpha concentratio ns > 10 ng/mL. Although early posttransplant BMMNC was more sensitive to inhibition than NLD-derived BMMNC, overall, no difference in colony growth or percent of inhibition induced by TNF-alpha or IFN-gamma was observed between recipients of unmodified and T cell-depleted transpl ants. In this series, two recipients of TCD BM and one recipient of UM BMT developed graft failure; no distinct pattern of colony growth or colony inhibition was evident for those patients. The optimized in vit ro conditions and specific cytokines used in this study do not indicat e any quantitative or qualitative differences in the hematopoietic pro genitors present in recipients of unmodified and T cell-depleted bone marrow early posttransplant to explain an increased risk of graft fail ure following a T cell-depleted BMT compared to an unmodified BMT.