Expression of X chromosome-linked TLR4 signalling molecules in female versus male neonatal cord blood

Neonates display a marked gender disparity in morbidity and mortality. A higher percentage of premature male than female infants require invasive respiratory support and preterm males have a higher incidence of lung disease e.g. bronchopulmonary dysplasia (BPD).The TLR4 pathway is an essential component of innate immunity and results in NFκB activation. Many TLR4 signalling genes are encoded on the X chromosome, including IKBKG/NEMO, IRAK-1, and BTK. Genes which escape X chromosome inactivation (XCI) may contribute to the immune advantage observed in female neonates. The aim of this study was to quantify expression of X-linked TLR4 signalling intermediates in umbilical cord blood from term female versus male neonates. Cord blood samples were collected from neonates (≥37w+0) delivered by elective Caesarean section (M:F, 10:10, n=20). RNA was isolated from the buffy coat, cDNA was synthesised and used in qRT-PCR reactions with IKBKG/NEMO (Xq28), IRAK-1 (Xq28), and BTK (Xq21) gene-specific primers. IRAK-1 protein expression was quantifed by Western blot and subcellular localisation was characterised in PBMCs by confocal microscopy. At the mRNA level, there was no significant difference in relative expression of IKBKG/NEMO or BTK. IRAK-1 gene and protein expression was significantly higher in females versus males (p