Human adherent cell contact-mediated modulation of normal myeloid colony formation

The effects of coincubation of normal nonadherent bone marrow cells on adherent monolayers created from human peripheral blood mononuclear cells or marrow cells were investigated. Nonadherent marrow cells were coincubated for 4 hours with peripheral blood adherent cells at ratios of adherent cells to marrow cells of 2:1 to 5:1. This coincubation suppressed subsequent neutrophilic agar colony growth but not eosinophilic growth. Further studies suggested that this suppression was a cell-cell-mediated process and not secondary to soluble factors. However, coincubation on marrow adherent cells caused increased neutrophilic colony recovery. The possible in vivo relevance is discussed.