Cultures of mast cell-like (MCL) cells from human pleural exudate cells.

Under special culture conditions, rat peritoneal macrophages have previously been shown to transform into mast cells. This method has been adapted here to the human species. Adherent large mononuclear cells from human pleural exudates were cultured in a medium supplemented with horse serum (30%) and fibroblast supernatants (30%). Metachromatic staining (toluidine blue, pH 3.6) of cytoplasmic granules appeared first in a small percentage of cells by days 5-6 of culture and reached a high intensity in 50% of the cells between days 12-22. Histamine levels within the cells increased by a factor of 7 during this same time period and the cell size by a factor of 3. Cultures could be maintained for about three weeks, since viability and total cell number decreased on extended culture. The data suggest that mononuclear cells in inflammatory exudates can transform into mast cell-like cells under the influence of high levels of specific conditioning factors in their microenvironment.