T lymphocytes and their products in atopic allergy and asthma.

Various cells are associated with inflammatory events characteristic of atopic allergy and asthma. As well as T cells and eosinophils, mast cells, basophils, mononuclear phagocytes and platelets have all to be considered particularly as their mediators have potential for contributing directly to the features of bronchial asthma. Nevertheless, mast cell/T lymphocyte/eosinophil interactions may be of particular significance. For instance, the acute symptoms of allergy and asthma such as sneezing, bronchospasm and hives are believed to be largely the result of mediator release from mast cells whereas chronic symptoms (the result of allergic inflammation) can be explained on the basis of eosinophil-mediated tissue damage. Allergen is recognized directly by T cells. Specialized T cell subsets, possibly the Th2 equivalent, predominate in allergy and elaborate IL-4 (an essential co-factor for IgE production) and IL-5 which brings about terminal differentiation and activation of the eosinophil. Basic proteins derived from the crystalloid granule together with PAF and leukotrienes produce chronic wheeze, bronchial irritability, and might also be involved in permanent nasal blockage in chronic rhinitis. This general hypothesis is continually being tested. It is clearly important to identify precise molecular targets in allergy and asthma in order to construct therapeutic strategies.