Effect of LPS addition on murine marrow cultures. Cultures initiated as described in previous figure were treated with LPS (Sigma; catalogue no. L-2143) at the concentrations as indicated. After 24 hours, cultures were washed once with PBS and photographed. E, free erythrocyte; M, erythrocyte-coated mononuclear phagocyte; B, blanket cell or stromal cell with large thin cytoplasm and endothelial-like in morphology.