Today allergies are a major public health problem. Previous cross-sectional studies have found that children growing up with an anthroposophic lifestyle have a lower prevalence of IgE-mediated allergic diseases. This observation strengthens the hypothesis on importance of interaction between environment and our immune system during early childhood regarding allergy. The focus of this project is to assess if lifestyle and allergy states of the parents can cause differences in the in utero environment, and assess if these in utero differences can influence the risk of allergy development for the child. I will take advantage of a unique prospective multidisciplinary study where 330 families with an anthroposophic or conventional lifestyle will be followed during pregnancy and up to at least five years of age of the child. I will assess the in utero immune states by analysing placenta and blood samples with novel methods for epigenetic studies on immune related genes and microRNA regulation, and with immunohistochemstry, quantitative real-time (Qt-) PCR, flow cytometry, and cytometric bead array, and ELISA for cytokine analyses. The unknown function of the placental IgE will be investigated and its origin and specificity determined. The role of Hofbauer cells, placental macrophages, will be assessed by assays for migration, phagocytosis, radical production, and capacity to activate T cells. Gene expression profiles, indicating polarisation, of the Hofbauer cells will be analysed after differential stimulation by Qt-PCR. The results will be correlated to allergic symptoms and allergen specific serum IgE-levels in parents and child, lifestyle and environmental exposures. Obtained knowledge on the development of our immune system in relation to lifestyle and environment can be further used to develop early diagnostics, primary preventive, and therapeutic measures to decrease allergy in the future, both for the individual at risk as well as for the general population.