| Abstract: | Long-term in vitro growth of murine mast cells was dependent on the presence of a mast cell growth factor (MCGF) present in media conditioned by mitogen-activated splenic leukocytes or by various murine leukemic cell lines. MCGF shared a number of properties with granulocyte colony-stimulating factor (G-CSF). Both factors were present in media conditioned by the myelomonocytic leukemic WEHI-3 and the T cell lymphoma, LBRM-33 cell lines. They were relatively sensitive to trypsin treatment, and were resistant to boiling temperature. NZB mice that failed to respond to WEHI-3-derived G-CSF also failed to respond to MCGF. MCGF differed from G-CSF, however, in sensitivity to neuraminidase and lactoferrin, an inhibitor of macrophage CSF production, suppressed G-CSF production by WEHI-3 cells without affecting MCGF production. Furthermore, peritoneal cells produced G-CSF but not MCGF when stimulated with lipopolysaccharide. In vitro production of MCGF by normal spleen cells required the presence of T lymphocytes and is relatively macrophage-independent. The role of T cells in the maturation and growth of mast cells and the physiologic function of MCGF are discussed. |
