Soluble(s) factor(s) produced by HIV-infected cells have been implicated in bone marrow dysfunction observed in AIDS patients. We have shown previously that infected macrophage but not CBMC-derived conditioned medium inhibited the differentiation of purified CD34+ cells, suggesting that accessory cells play a crucial role in granulopoiesis inhibition induced indirectly by HIV. In order to prevent this inhibition we tested the potential protective effect of Seraspenide, a reversible inhibitor of hematopoietic progenitors. We showed that 20 h pretreatment of mononuclear cells with Seraspenide at 10(-10) mol/l prevents CFU-GM inhibition induced by HIV-infected cell-derived conditioned medium.