[Studying the mast cell. Recent data].

In the light of recently published data, the mast cell can now be viewed as a key cell, not only in allergic reactions such as immediate hypersensitivity responses, but also in a broad spectrum of other biologic responses including host-parasite interactions, nonspecific inflammatory reactions, fibrosis, angiogenesis, tissue reconstruction, and wound healing. Nevertheless the molecular basis for the intervention of mast cells in many of these biologic responses is still unclear. Very recent studies have demonstrated that mast cells are capable of producing a wide range of cytokines, a property which may influence various physiologic, immunologic and disease processes. Furthermore, although substantial differences have been reported between mast cells located in different tissues, the reasons and mechanisms underlying this heterogeneity long remained obscure. The recent development of two original experimental approaches, i.e., in vitro culture of mast cells, mainly derived from mouse bone marrow precursors, and replenishment of mast cell-deficient mice, has provided new insight into the mechanisms by which tissue microenvironment influence of regulation mast cell phenotype. Extrapolation to humans of data obtained in rodents is, however, hazardous. In the review presented here, the most recent data from the literature provide the basis for outlining avenues of research which can be expected, in the near or remote future, to solve what mast cell experts term "the riddle of the mast cells".