Mast cell growth on fibroblast monolayers: two-cell entities.

Clonal mast cell differentiation occurs when mesenteric lymph node cells from mice immunized with an antigen are grown in its presence on fibroblast monolayers prepared from mouse embryonic skin. Two types of mast cell clones are identified: the first, originates from a precursor present in the lymphoid cell suspension and the second, from a precursor in the fibroblast monolayer. Clones of the first type fail to appear when T cells are eliminated from the suspension; but they grow luxuriantly in the presence of fluid, harvested from cultures containing the antigen-sensitive T cells exposed to the antigen. The two mast cells differ in the clonal size and rate of growth, life span, cell size, shape and size of the granules and numbers of IgE receptors. It is concluded that the rapidly multiplying lymphoid mast cells associate with the mucosae of the respiratory and gastrointestinal tracts and appear in large number in response to immunological stimuli; the long lived mast cells derived from the embryonic skin monolayer are found in the general connective tissue.