Mammalian mast cell populations exhibit phenotypic and functional heterogeneity, which is a reflection of their stage of development as regulated by the action of cytokines. Immunologic activation of mast cells via their IgE receptors elicits not only the release of mediators of immediate hypersensitivity, but also a wide variety of pro-inflammatory cytokines. Mouse mast cell populations also express three species of receptors for IgG (Fc-gamma-R), and the profile of receptor subtypes changes and their functionality increases substantially with mast cell maturation. Thus, an additional layer of mast cell functional heterogeneity exists, relating to expression of Fc-gamma-R. The overall goals of the proposed research therefore are: 1 ) to continue to characterize the changes in Fc-gamma-R expression during mast cell development; 2) to develop a greater understanding of the molecular mechanisms regulating the differences in the expression of Fc-gamma-R species; and 3) to learn more about the functional consequences of these differences. The overall goals will be achieved by pursuing the following specific aims: 1) to prepare polyclonal anti-mouse Fc-gamma-R peptide antibodies specific for the mast cell Fc-gamma-R species, and to use these reagents to determine if the changes in the cell surface expression of the three Fc-gamma-R that accompany mast cell maturation are due to changes in the rates of receptor protein synthesis and/or degradation; 2) to determine whether the changes in cell surface Fc-gamma-R expression that occur during mast cell maturation are related to differences in the association of the Fc-gamma-R species with other molecules that affect the transport of Fc-gamma-R to the cell surface; 3) to-determine if the changes in steady state mRNA levels for the three species of Fc-gamma-R that accompany mast cell maturation are due to changes in the rates of transcription of the receptor genes and/or mRNA longevity; and 4) to determine the profile of mRNA and bioactivity for a panel of inflammatory cytokines generated by mast cells via Fc-gamma-R perturbation at the stages of maturation studied above, so as to determine if cytokine production is altered by the cell surface presentation of the Fc-gamma-R species.
