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Allergen immunotherapy and mast cells

After initial enthusiasm for the mast cell as an orchestrator of allergic responses, a lull followed with the observations that mast cell-‘stabilizing’ drugs such as the b-adrenoreceptor agonists and cromones have little impact on the course of many allergic diseases. However, interest in mast cell biology has been rekindled with the observation that mast cells are a source of many pleiotropic cytokines and proteases, with good evidence now that mast cells are involved in many diverse immunopathological events (reviewed in [1]). In fact, a month rarely passes without publication of a novel report on mast cell activity of relevance to human pathophysiology. This issue of Clinical and Experimental Allergy continues this theme, with the observation by Durham and colleagues that administering intradermal allergen immunotherapy to patients with severe hay fever induces a marked reduction in cutaneous mast cell numbers [2]. Interpretation of the mechanism behind this is speculative, so before discussing it further, I will provide a brief outline of the factors which control tissue mast cell numbers in health and disease.