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 and mediator profiles of mast cell, basophil and T cell subpopulations that may be involved in the generation of inflammation in asthmatic airways. We have developed sensitive intracellular cytokine assays to measure allergen specific T cell cytokine responses almost directly ex vivo. Using these methods, we have shown that allergen specific T cells are predominantly of the classic Th2 phenotype and that on the single cell level IL-4, IL-5 and IL-13 are highly co-expressed. Interestingly, IL-2, which is often considered a Th1 cytokine was also highly coexpressed. Allergen specific T cell expressed high levels of the CCR4 and CRTH2 chemoattractant receptors. These results provide a detailed view of the T cell response to allergens with a fidelity heretofore not possible.