New sources of human and mouse mast cells, which were isolated from individual organs (i.e., lung, colon, synovium, skin, uterus, heart), developed from progenitors in vitro in the presence of
stem cell factor and/or
interleukin (IL)-3, or enriched from fetal or adult blood, spleen or bone marrow by cell sorting, have made possible new studies of the cell biology of mast cells. Advances resulting from these new mast cell sources as well as from new methods for labeling specific products in subcellular sites and structures in resting and functional mast cells are the subject of this review. Specific advances discussed are as follows: identification of an Fc epsilonRI+ c-kit- mouse basophil population from bone marrow and spleen that is associated with
IL-4 production and an Fc epsilonRI- c-kit- granulated mouse mast cell progenitor in fetal blood; identification of
hyperplasia and functional activation of human skin mast cells in vivo when exposed to recombinant
stem cell factor and spontaneous degranulation in X-linked immunodeficient mouse mast cells; use of an
enzyme-affinity-
gold method to detect
histamine in mature and immature human mast cell granules, in secretion and recovery of
histamine during anaphylactic degranulation of human lung mast cells ex vivo, and in secretion of
histamine in vivo by piecemeal degranulation of
IL-4 transgenic mouse mast cells in inflammatory
eye disease and of human gut mast cells in
inflammatory bowel disease; use of immunogold methods to localize
cyclooxygenase and
tumor necrosis factor-alpha to subcellular structures in human and rat mast cells and to localize the
Charcot-Leyden crystal protein in human basophils to aid in the identification of mast cells arising in mixed cellular populations; use of a
low-density lipoprotein (
LDL)-
gold affinity method to demonstrate a rat mast cell granule-mediated uptake of
LDL by macrophages in peritoneal fluid.