Mast cells have been implicated in the expression of a wide variety of biological responses, including IgE-dependent immediate hypersensitivity reactions, host responses to parasites and neoplasms, and many immunologically non-specific inflammatory processes. While these responses are initiated by distinct stimuli, most of them share common characteristics such as alterations of vascular permeability, recruitment of blood-borne leukocytes, and activation of interstitial fibrin deposition. However, the molecular basis for many of the proposed actions of mast cells in these inflammatory or immunological responses has remained obscure. During the previous funding period of this project, we identified a new mechanism by which mast cells might importantly influence multiple aspects of IgE-dependent or -independent biological responses: the production of a broad panel of multifunctional cytokines, including TNF-alpha, IL-1alpha, IL-3, IL-4, IL-5, IL-6, GM-CSF, MIP-1alpha MIP1-beta, TCA3, JE, IFN-gamma, and TGF-beta. However, virtually all of the published information about mast cell cytokine production, from both our own and other laboratories, has been derived from analyses of mast cells generated in vitro, which express many phenotypic differences from mast cell populations which occur in situ. In fact, the only data available concerning cytokine production by mature, freshly isolated mast cells are derived from our studies of mouse peritoneal mast cells, which constitutively contain significant amounts of TNF-alpha that can be released upon appropriate stimulation. But the ability of these cells to produce other cytokines has not been reported. Moreover, no published studies have evaluated the biological significance of mast cell cytokine production in vivo. We therefore now wish to determine whether mast cell populations in vivo represent a significant source of multifunctional cytokines, and to evaluate the extent to which the production of TNF-alpha and other cytokines can account for specific actions of mast cells in inflammatory or immunological responses in vivo. The patterns of cytokine production induced by various biologically significant stimuli of mast cell activation will be assessed in populations of in vitro-derived and freshly isolated mature mouse mast cells. The same stimuli will then be tested in vivo, and patterns of mast cell cytokine production will be assessed by tissue Northern analysis, in situ hybridization, immunohistochemistry, and assays of tissues for certain cytokine bioactivities. The contributions of mast cell-derived cytokines, as opposed to cytokines derived from other cell types, in specific inflammatory or immunological responses will be assessed by comparing the expression of cytokine-dependent aspects of these responses in genetically mast cell-deficient W/Wv or Sl/Sld mice, the congenic normal (+/+) mice, and W/Wv mice repaired of their mast cell deficiency by adoptive transfer of mast cells of congenic +/+ origin.
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