Background Epidemiological evidence underlines the impact of prenatal environmental factors on the development of postnatal allergies. In this regard an inverse correlation between lipopolysaccharide (LPS) exposure and development of childhood allergy has been found.

Objective To assess the impact of prenatal LPS exposure on the development of postnatal respiratory allergies in a mouse model of experimental asthma.

Methods Female BALB/c mice were exposed to LPS before conception and during pregnancy. Several weeks after birth offspring were sensitized to ovalbumin (OVA) followed by aerosol allergen challenges.

Results Prenatal, maternal LPS‐exposure enhanced neonatal IFN‐γ, but not IL‐4 and IL‐2 production. OVA sensitization of prenatally LPS‐exposed mice was accompanied by a marked suppression in anti‐OVA IgG1 and IgE as well as unchanged IgG2a antibody responses, paralleled by a significant reduction in IL‐5 and IL‐13 levels following mitogenic stimulation of splenic leucocytes. Assessment of bronchoalveolar lavage fluids following allergen challenges revealed a marked reduction in eosinophils and macrophages in these mice. Surprisingly, development of airway hyper‐responsiveness, a hallmark of bronchial asthma, was not affected.

Conclusion This study provides first experimental evidence that LPS may already operate in prenatal life in order to modulate the development of allergies in the offspring.