Asthma is an inflammatory disease of the airways. After allergen exposure, IgE bearing cells, such as mast cells and basophils, are first activated. Later, T lymphocytes enter the airways, are activated by allergen and play a key role in regulating this inflammatory response through the elaboration of cytokines such as IL-4, IL-5 and IFN-gamma. This project seeks to examine the cytokine profiles of mast cell, basophil and T cell subpopulations that may be involved in the generation of inflammation in asthmatic airways.To date, we have demonstrated the feasibility of studying basophil cytokine production by flow cytometry, without arduous physical purification. Upon activation with either antigen (Ag) or ionomycin, basophils produced IL-4 and IL-13. After allergen activation, basophils were found to be responsible for 5 times more IL-4 producing cells than were T cells, suggesting that basophils may be a significant source of type 2 cytokines in vivo. Eotaxin is a CC chemokine known to have chemotactic activity, but has not been reported to have an immunoregulatory function. We examined whether eotaxin had any effect on Ag driven basophil IL-4 production. Eotaxin alone had no effect, but further increased allergen stimulated IL-4 expression and release 2 to 5 fold. Addition of eotaxin to cultures resulted in a 40 fold left shift in the dose response to Ag. This effect was obtained with physiologic concentrations of eotaxin (10 ng/ml) and was mediated through the CCR3 receptor. - Asthma, allergy, T cells, basophils, interleukin-4, IgE, Th2, eotaxin, chemokines - Human Subjects