ANTIGEN-DEPENDENT STIMULATION BY BONE-MARROW-DERIVED MAST-CELLS OF MHC CLASS-II-RESTRICTED T-CELL HYBRIDOMA

This paper describes a new role for mast cells as being able to presen t Ag to immune T cells. A mouse bone marrow-derived mast cell populati on obtained after 3 wk of culture in a conditioned medium has been sho wn to express a variety of membrane-associated Ag, including MHC class II and class I Ag, CD23, CD32, high affinity receptor for IgE, and CD 4. Expression of MHC class II molecules was up-regulated upon stimulat ion with LPS but not with IFN-gamma and was down-regulated after expos ure of mast cells to IL-3 treatment. We have demonstrated that mast ce lls were able to present native Ag as well as immunogenic peptides to MHC class II-restricted T cell hybridoma. The inhibition of Ag present ation after mast cells have been treated with ammonia suggests that Ag catabolism in intracytoplasmic compartment as a key step in Ag handli ng takes place in these cells. The MHC class II molecule is the restri cting element for the presentation of OVA and the lambda repressor fro m bacteriophage lambda to a panel of specific T cell hybridomas, as de monstrated by the blocking effect of anti-MHC class II mAb on the Ag-p resenting function. A characteristic feature of mast cells is the gene ration of a narrower immunogenic peptide repertoire as compared with A 20 and LBB 3.4.16, a B lymphoma cell line, and a B cell hybridoma, res pectively. This novel function of mast cells brings to a much closer c onnection inflammatory and immunologic processes and sheds new light o n the biology of mast cells and particularly on the specific allergic responses. Immunology, 1993, 151: 6318.