Ontogeny of mRNA expression of pulmonary innate immune factors

Abstract

Prematurely born infants are at an increased risk of developing respiratory infections due in part to decreased function of their innate immune system. It was our goal to examine the ontogeny of innate immune gene expression by respiratory epithelia in our ovine model. Targets of interest are surfactant proteins A and D (SP‐A and SP‐D), sheep beta defensin 1 (SBD‐1), dual oxidases 1 and 2 (Duox1 and Duox2), lactoperoxidase (LPO), SPLUNC1, LPLUNC2, Toll‐like receptors 3, 7, and 8 (TLR 3, 7, and 8). Lung from sheep was collected at 115 and 130 days gestation, full term, 15 days post partum, and adulthood. Levels of mRNA for the target innate immune genes were measured by real‐time RT‐qPCR. LPO, SPLUNC1, LPLUNC2, TLR‐8, SBD‐1, and Duox1 expression increased progressively with age. Surfactant proteins A and D, previously reported to be decreased in preterm lambs, did not follow a steady trend, although SP‐A expression was lower at 130 days gestation than at full term. Duox2 levels were lower in gestational and perinatal lambs than in adults, but did not show a linear increase with age. These results are significant in that they may indicate that reduced expression in fetal lung may underlie susceptibility of the lung to infection with preterm birth. Conversely, upregulation of these genes may have therapeutic potential.