In vitro suppression of erythropoiesis by bone marrow adherent cells from some patients with fungal infection

We present evidence that alterations in marrow adherent cell (Mø) function may play a role in the suppression of erythropoiesis in some patients with fungal infection. Bone marrow (BM) cells from 12 normals and 10 patients with histoplasmosis were cultured in plasma clots before and after removal of Mø. BM from five patients (Group A) produced normal numbers of erythroid colonies (EC). In the remaining patients (Group B), smaller numbers of EC were detected (P<0.01). Removal of Mø from BM of normals and Group A patients resulted in decreased growth of EC. In contrast, Mø depletion of BM from patients in Group B resulted in greater EC formation (P< 0.01). When normal Mø were admixed with normal or patients’BM‐Mø, enhanced EC formation resulted. Whereas, at similar concentrations, Mø from group B patients caused inhibition of EC formation (P< 0.005). The erythro‐regulatory function of Mø, including the inhibitory action of patients’Mø, was mediated via a soluble agent(s) since media conditioned by Mø mimicked the action of these cells. Three patients in Group B were restudied 14 months after treatment with amphotericin B, when blood parameters had returned to normal. At this time, normal patterns of EC formation and Mø activity were observed.