A novel mitogen released by lipid A-stimulated bone marrow cells.

Lipid A induced bone marrow cells derived from lipopolysaccharide responder strain C3H/HeN to release a component to the extracellular fluid that enhanced DNA synthesis of splenocytes derived from the lipopolysaccharide nonresponder strain C3H/HeJ. The mitogenic component was not selected when C3H/HeN splenocytes were used instead of bone marrow. The target cell in splenocyte populations responding to the mitogenic component released by lipid A-stimulated bone marrow cells is a B cell, as judged by the corresponding of individual cells undergoing DNA synthesis determined by autoradiograph and the presence of surface immunoglobulin detected by immunofluorescence. The mitogenic factor is heat-labile, sensitive to trypsin, and intensive to RNase.