Antenatal and perinatal factors responsible for the Th1/Th2 profile?

The immune-allergic reaction is a particular type of inflammatory reaction in which antigen presentation induces T2 differentiation of T lymphocytes, characterized by IL-4 and IL-5 production without IFN-gamma production. Fut ure atopic neonates present a deficient IFN-gamma production capacity and i ncreased total IgE levels. In contrast, although the cord blood contains T lymphocytes specific for the allergens encountered by the mother, this is t rue for both atopic and non-atopic neonates. Cytokine production in respons e to allergen stimulation does not differ between atopic and non-atopic neo nates at birth, but becomes different during the first two years of life, b ecoming type T1 in non-atopics and T2 in atopics. Recent animal studies hav e shown that the neonatal immune system can be modulated and that its capac ity of response to antigenic stimulation is identical to that of adults. Th ese data indicate that potential primary prevention strategies should be di rected more to young children than to the mother. They are primarily based on allergen avoidance in children with a genetic risk, In the future, strat egies of stimulation of the T1 system by microbial antigens or inhibition o f the T2 system by specific immunoprophylaxis could be proposed.