ANTIGEN-PRESENTING FUNCTION OF HUMAN PERITONEUM MESOTHELIAL CELLS ISOLATED FROM A PANCREATIC-CARCINOMA PATIENT AFTER MUTANT RAS PEPTIDE VACCINATION

Mesothelial cells obtained from ascites fluid of a Ras-peptide vaccina ted pancreatic adenocarcinoma patient were cultured in vitro. Fresh is olated cells expressed HLA class II molecules, which were lost upon cu lture, but could be up-regulated after coculture with human recombinan t interferon-gamma. The antigen-presenting capacity of these me sothel ial cells was tested with allogeneic peripheral blood mononuclear cell s (PBMC) in a mixed lymphocyte mesothelial cell culture and by stimula ting autologous PBMC with purified protein derivative of Mycobacterium tuberculosis. Cloned T cells from the same patient allowed us to test the ability of mesothelial cells to present a mutant Ras-derived pept ide to specific T cells in a DLA-DR-restricted manner. Mesothelial cel ls effectively stimulated allogeneic resting T lymphocytes to prolifer ate and presented soluble protein antigen or a mutant Ras-derived pept ide to specific T cells, indicating that they display processing and p resenting capabilities. Since mesothelial cells are in close anatomica l relationship with intraabdominal malignancies, they may contribute t o stimulation of specific T cells by endocytosing tumour-specific anti gens and presenting them to T lymphocytes. This could be a possible me chanism in which mesothelial cells participate in maintaining local sp ecific immunity in patients already primed.