Characterization of a T-cell-derived mast cell costimulatory activity (MCA) that acts synergistically with interleukin 3 and interleukin 4 on the growth of murine mast cells

The proliferation of mucosal mast cells (MMC) depends on the presence of interleukin 3 (IL 3) and can be further enhanced by interleukin 4 (IL 4). The supernatant of a TH2 cell clone (ST2/K.9) stimulated by concanavalin A was found to contain a factor, provisionally termed mast cell costimulatory activity (MCA), that substantially enhances the proliferation of MMC promoted by a combination of IL 3 and IL 4. In comparison to other lymphokines MCA is rather resistant to tryptic digestion but is very sensitive to pH values lower than 6.0 and to organic solvents. Chromatographic fractionation of MCA revealed that activity is associated with protein(s) or glycoprotein(s) of 35 to 40 kDa. Partially purified MCA that was functionally free of other T-cell-derived lymphokines did not stimulate mast cell proliferation in the absence of a combination of IL 3 and IL 4. In addition, MCA did not affect the proliferation of mast cells when employed together with either IL 3 or IL 4 alone. Control experiments demonstrated that MCA is identical to neither the T-cell-derived lymphokines IL 2 to IL 6, IL 9, interferon gamma, tumor necrosis factor alpha or beta, or granulocyte-macrophage colony-stimulating factor (CSF), nor to IL 7, granulocyte CSF, macrophage CSF, erythropoietin, leukemia inhibitory factor, or epidermal growth factor (EGF). Finally, experiments using a panel of PPD-reactive TH1- and TH2-like cell lines revealed that MCA is preferentially produced by TH2 cells. These data, especially the relative resistance of MCA to trypsin and the high sensitivity to low pH values and organic solvents, indicate that MCA is distinct from known T-cell-derived lymphokines.(ABSTRACT TRUNCATED AT 250 WORDS)