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 vaccinated pancreatic adenocarcinoma patient were cultured in vitro. Fresh isolated cells expressed HLA class II molecules, which were lost upon culture, but could be up-regulated after coculture with human recombinant interferon-gamma. The antigen-presenting capacity of these mesothelial cells was tested with allogeneic peripheral blood mononuclear cells (PBMC) in a mixed lymphocyte mesothelial cell culture and by stimulating 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 peptide to specific T cells in a DLA-DR-restricted manner. Mesothelial cells effectively stimulated allogeneic resting T lymphocytes to proliferate and presented soluble protein antigen or a mutant Ras-derived peptide to specific T cells, indicating that they display processing and presenting capabilities. Since mesothelial cells are in close anatomical relationship with intraabdominal malignancies, they may contribute to stimulation of specific T cells by endocytosing tumour-specific antigens and presenting them to T lymphocytes. This could be a possible mechanism in which mesothelial cells participate in maintaining local specific immunity in patients already primed.