The aetiology of bronchial asthma and critical assesment of therapy

S. Romagnanl (Italy) stressed that in the past few years great progress has been made in the knowledge of the cellular and molecular signals responsible for the regulation of human immunoglobulin E (IgE) synthesis. Interleukin-4 (IL-4) and interferon-gamma (IFN-y) are the main regulatory cytokines of lgE production, with opposite effects. T helper (Tii) cells producing IL-4 and IL-5, but no, or limited IFN-y, that resemble murine Tii2 cells, accumulate in the blood and/or target organs of patients with helminthic infections or atopic disorders. These cells account for both lgE antibody formation and eosinophilia. The preferential differentiation of naive Tii cells into the TH2 subset in patients with helminthic infection or atopic disorders seems to depend, at least in part, on the nature of antigens involved. Most T-cell clones specific for allergens or helminthic components have a TH2 profile of cytokine secretion, whereas the majority of T-cell clones specific for bacterial antigens established from the same donors exhibit a THl profile. However, T-cell clones derived from atopic donors show enhanced ability to produce IL-4 and IL-5 in comparison with T-cell clones specific for the same antigens derived from non-atopic donors. These data provide evidence for a deregulation of IL-4 (and IL-5) production in atopic patients.