Tolerogenic microenvironment in neonatal period induced by maternal immunization with ovalbumin

Maternal immunization with allergens, such as ovalbumin (OVA), can inhibit the development of an allergic response in offspring. The regulatory mechanisms seem to be mediated by maternal antibodies (MatAbs) and factors generated by the maternal–fetal interface. The aim of this study was to verify the pathways of inhibitory Ab transference after maternal immunization with OVA and the effect of the offspring's dendritic cells (DCs) on the generation of regulatory T (Treg) cells. We verified that preconceptional OVA immunization induces high levels of proinflammatory and regulatory cytokines in the amniotic fluid, allowing the transference of high levels of anti-OVA IgG1 Abs to the offspring. Using an adoptive nursing protocol, we verified that maternal immunization leads to MatAb transference by the placental route and by breastfeeding contribute to the inhibition of anaphylactic IgE and IgG1 Ab responses in immunized offspring. We observed that maternal immunization decreased eosinophil numbers in recovered bronchoalveolar lavage fluid and in the lung tissue, whereas with a lack of control of airway responsiveness to methacholine. Maternal immunization induced in young offspring a decreased percentage of CD11c+ DCs expressing MHC class II and CD40 molecules. Moreover, DCs from both groups of offspring when pulsed with OVA, were able to induce Treg cells in vitro. Similarly, OVA immunization at the neonatal stage increased the frequency of Treg cells, regardless of the mother's immunization status. These findings emphasize that maternal immunization leads to a complex interaction of regulatory factors, with MatAbs, DCs and Treg cells affecting the tolerance of offspring during an allergic response.