[Immunity related to allergic response at the beginning of life]

OBJECTIVE: Given that the most common allergic manifestations (asthma, rhinitis, dermatitis, food allergies) occur during childhood, because the immune system can be induced into sensitization rather than into allergenic tolerance at the beginning of life, we analyzed the main immunological aspects of fetuses and infant in terms of allergic sensitization and response. METHODS: Detailed bibliographic revision concerning nonspecific immune response (physical and chemical barriers, myeloid cells) and specific immune response (T and B lymphocytes, cytokines) of the fetus and infant, with special attention to studies carried out in the last fifteen years. RESULTS: Various compartments of the immune system in fetuses and infants are different from those present in older children and adults. Thus, developmental aspects of nonspecific and specific immunity may contribute to atopic disease. CONCLUSIONS: Atopic predisposition is determined at the beginning of life and seems to originate not only from genetic factors, but also from intrauterine environment and initial stage of childhood, inducing the immune system to increase the synthesis of IgE.