Preferential expression of interleukin‐12 or interleukin‐4 by murine bone marrow mast cells derived in mast cell growth factor or interleukin‐3

In this report we demonstrate that murine bone marrow cells cultured in either interleukin (IL)‐3 or mast cell growth factor (MGF, also known as c‐kit ligand and stem cell factor) differentially express cytokine genes. Bone marrow cells cultured in IL‐3 differentiate and proliferate, taking on a mucosal mast cell‐like phenotype. These cells express the IL‐4 gene. Bone marrow cells cultured in MGF take on a connective tissue mast cell‐like phenotype and possess transcripts for both of the subunits of the IL‐12 cytokine. Bone marrow cells cultured in both IL‐3 and MGF express the IL‐4 gene at lower levels than that seen for the IL‐3 culture alone, but do not possess IL‐12 gene transcripts. The level of IL‐12 subunit transcripts derived from the MGF‐derived bone marrow cells was compared to that found in splenocytes and activated macrophages, the only cells in which IL‐12 production has been previously documented. Both of the IL‐12 subunit transcripts were found, compared to a β‐actin control, to be present within MGF‐derived cells in the same if not higher quantities than the splenocyte or macrophage cultures. Mucosal mast cells have been previously implicated in the development of the T helper type 2 (TH2) T cell phenotype via their expression of IL‐4. The finding that the MGF‐derived connective tissue‐like mast cells possess IL‐12 transcripts suggests that the development of the TH1 T cell pathway may be positively influenced by this type of mast cell.