Umbilical cord plasma 25-hydroxyvitamin D concentration and immune function at birth: the Urban Environment and Childhood Asthma study

P>Background Recent studies have reported conflicting data on the association between maternal intake of vitamin D during pregnancy and asthma. Objective To assess the influence of prenatal vitamin D status on immune function at birth. Methods In an inner-city birth cohort of 568 newborns, 520 of whom had at least one atopic parent, we measured the umbilical cord (UC) plasma concentration of 25-hydroxyvitamin D (25(OH)D) and the cytokine responses of UC blood mononuclear cells (UCMCs) to stimuli including phytohaemagglutinin (PHA), lipopolysaccharide (LPS), and peptidoglycan. In a subset, the UCMC expression of regulatory T cell markers and the suppressive activity of CD4+CD25+UCMCs were measured. Results The 25th, 50th, and 75th percentiles of UC plasma 25(OH)D level were 15.0, 20.2, and 25.6 ng/mL, respectively. Most cytokine responses of UCMC were not correlated with UC 25(OH)D concentration; however, IFN-gamma release after LPS stimulation was weakly positively correlated with UC 25(OH)D concentration (r=0.11, P=0.01). PHA responses were not significantly correlated with 25(OH)D concentration. The UC plasma 25(OH)D concentration was inversely related to the number of CD25+ (r=-0.20, P=0.06), CD25Bright (r=-0.21, P=0.05), and CD25+FoxP3 (r=-0.29, P=0.06) cells as a proportion of CD4+ T cells in UC blood (r=-0.26, P=0.04) but not to the suppressive activity of CD4+CD25+cells (r=0.17, P=0.22). Conclusion and Clinical Relevance UC 25(OH)D concentration was not correlated with most UCMC cytokine responses to multiple stimuli. There was a suggestion of a weakly positive correlation with IFN-gamma release after LPS stimulation. The proportions of CD25+, CD25Bright, and CD25+FoxP3 cells to total CD4+ T cells were inversely correlated with UC 25(OH)D concentration. Our findings suggest that higher vitamin D levels at birth may be associated with a lower number of T-regulatory cells. Vitamin D status in utero may influence immune regulation in early life.