In vitro generation of mast cell-like cells from human peripheral mononuclear phagocytes.

An in vitro culture method, previously shown to induce the transformation of rat macrophages to mast cells, has been adapted to humans. Adherent peripheral human blood mononuclear cells were cultured in a medium supplemented with 30% L-cell supernatant and 30% horse serum. During the first week of culture, the cells were phagocytic (80%), lacked histamine, were not metachromatic and stained faintly for naphthol-AS-D-chloroacetate esterase, primarily in a paranuclear location. During the first 2 weeks of culture, the cells grew in size, synthesized DNA, became nonadherent and developed cytoplasmic chloroacetate esterase staining which was strongly positive in 50-60% of the cells during the third week. Intracellular histamine levels increased steadily during culture, and electron-dense metachromatic cytoplasmic granules were present during the third week. Human peripheral blood mononuclear cells contain therefore a subpopulation of cells that can differentiate into mast cells-like cells under specific in vitro culture conditions.