Plasma vitamin D levels at birth and immune status of preterm infants

Vitamin D has an important immunomodulatory role. We investigated whether vitamin D levels at birth may associate with immune status in preterm infants.

Cord blood samples were collected from 28 preterm infants born ≤30 weeks of gestation. Infants were divided into groups below and above median vitamin D level. We measured plasma cortisol and cytokine levels and also assessed the peripheral prevalence of distinct immune cell subsets using flow cytometry. The mixed effect model was used to analyse the effects of vitamin D, plasma cortisol levels and gestational age on cytokine levels and immune phenotype.

Vitamin D level in our cohort was 23.3 [9.9-45.4]ng/ml (median [range]). In infants with vitamin D level below the median the prevalence of CD4+ CXCR3+ (Th1) and CD8+ CXCR3+ cell subsets was higher, while the prevalence of CD4+ CCR4+ (Th2), CD8+ CCR4+ and plasmacytoid dendritic cell (pDC) subsets was lower than in those with vitamin D level above median. pDCs and Th2 lymphocytes were the only cell subsets which were only influenced by vitamin D levels, but not by plasma cortisol and gestational age. No association between vitamin D level and any of the tested plasma cytokine levels was detected.

Vitamin D levels may together with cortisol levels and gestational age have an effect on Th1/Th2 balance and the prevalence of plasmocytoid dendritic cells in the preterm newborn.