Vitamin D deficiency in pregnancy is common, and is linked to increased risk of adverse outcomes including preterm birth, preeclampsia, infection, gestational diabetes and asthma. Vitamin D possesses well-recognized immunomodulatory functions, and programming of the immune system during foetal development can influence asthma-related risk factors and health outcomes in later life. We hypothesized that influencing vitamin D status during pregnancy would impact the immune profile of the baby at birth. The effect of maternal supplementation with 4400 IU/d vitamin D3 from the end of the first trimester of pregnancy through to term on neonatal immunity was investigated using a subset of cord blood samples from a randomized, double-blind, placebo-controlled clinical trial (the Vitamin D Antenatal Asthma Reduction Trial). Cord blood samples from neonates born to mothers supplemented with 4400 IU/d (n=26) or 400 IU/d (n=25) of vitamin D3 were analysed for immune cell composition and function by flow cytometry quantitative PCR, and cytokine secretion by cytometric bead array. Higher maternal supplementation of 4400 IU/d resulted in an enhanced broad-spectrum pro-inflammatory cytokine response to TLR-ligation and mitogen stimulation, that corresponded with higher gene expression for select TLR, a trend for increased frequency of myeloid dendritic cells and a four-fold increase in IL-17A secretion following T cell receptor stimulation. Parallel in vitro studies increasingly implicate immunoregulatory pathways in the neonate that are distinct from those in adults, and emerging data on a potential role for neutrophils will be discussed. We conclude that increasing vitamin D status in the mother during pregnancy influences the immune profile of her baby. This is predicted to have a beneficial impact and reduce asthma-related risk factors, such as infection, in early life.
Disclosure: The authors declared no competing interests.