The role of stem cell factor (c-kit ligand) and inflammatory cytokines in pulmonary mast cell activation

Mast cells play a critical role in allergic airway responses via IgE- specific activation and release of potent inflammatory mediators. In the present study, we have isolated and characterized primary mast cell lines derived from the upper airways of normal mice. The primary mast cell lines were grown and maintained by incubation with interleukin-3 (IL-3) and stem cell factor (SCF) and shown to be c-kit (SCF receptor) positive by flow cytometry. Subsequently, we examined the proliferation of both airway and bone marrow derived mast cell lines in response to inflammatory and hematopoietic cytokines, including SCF, IL-1, IL-3, interferon-gamma, IL-4, and IL-10. The results from the pulmonary mast cell lines were compared with those from bone marrow derived mast cells. Pulmonary mast cell lines were capable of proliferating in response to IL-3, IL-4, IL-10, and SCF, whereas the combination of SCF with the other cytokines did not increase the response over SCF alone. In contrast, the bone marrow-derived mast cells proliferated strongest to SCF or IL-3, but only modestly to IL-4 and IL-10. Furthermore, the combination of SCF with IL-3, but not the other cytokines, exhibited an increase in bone marrow-derived mast cell proliferation. Cytokine- specific stimulation of histamine release in the airway-derived and bone marrow-derived mast cells showed parallel results. SCF was the only cytokine shown to induce substantial histamine release. However, when certain nonhistamine releasing cytokines were combined with SCF, a synergistic increase in histamine release was induced in upper airway, but not bone marrow-derived mast cells. The results of these studies suggest that cytokines differentially modulate induction of proliferation and degranulation of bone marrow and upper airway-derived mast cells and may further indicate a cytokine activational cascade in tissue mast cells.