Environmental antigens and atopic disease: underlying mechanisms and prospects for therapy and prophylaxis

Natural exposure to non-pathogenic antigens, the so-called 'environmental antigens', experimentally elicits a characteristic pattern of T-cell immunity, involving selective suppression of the T-cell-dependent IgE responses that trigger allergic reactions. This 'immune deviation' results in the generation of long-lived T-cell memory, which confers active protection against allergic sensitization. Corresponding primary immune responses to environmental antigens in humans occur most frequently during infancy, and the development of allergic sensitization can be viewed as a failure of this natural immune-deviation process. In this article, potential strategies for primary prevention of allergic disease in infants involving, in particular, the exploitation of oral and mucosal tolerance to stimulate protective CD8+ T-cell-mediated immune deviation, are discussed.