Cytokines in allergic inflammation.

One of the features,ns, particularly asthma, is tissue inflammation charact erized by accumulation of activated leukocytes, especially eosinophils and type Th2 T lymphocytes. Bronchial accumulation of eosinophils and their act ivation, the correlation between these parameters and the severity of asthm a, and the capacity of these cells to synthesize mediators potentially invo lved in the development of tissue lesions (cationic proteins, lipids, cytok ines), are all arguments in favour of their harmful role in this disease. B lood and tissue eosinophilia can be due to increased eosinopoiesis, but als o increased adhesion, recruitment and survival of mature eosinophils. These phenomena are largely regulated by cytokines, especially IL-5. Consequentl y, treatments designed to effectively and selectively inhibit the synthesis and/or effects of this cytokine could present useful prospects in the trea tment of asthma and atopic reactions in general. Various strategies are cur rently being investigated, including antibodies specifically directed again st IL-5 and the use of certain cytokines able to block the Th2 response, es pecially IL-10 and interferons, particularly IFN-alpha and -gamma Several s tudies conducted in animal models and in man have demonstrated the capacity of these cytokines to inhibit accumulation of eosinophils in the blood and tissue during allergic reactions, as well as some of the functions of thes e cells in vitro. Although these findings suggest a possible therapeutic ap plication of these compounds, in the context of atopic diseases, especially asthma, more detailed clinical studies must be conducted in order to evalu ate their real efficacy and to define their potential adverse effects.