Neonatal T-cell maturation and homing receptor responses to Toll-like receptor ligands differ from those of adult naive T cells: relationship to prematurity

Introduction: Inflammation and infection are associated with premature birth and with activation of the fetal immune system. We hypothesized that exposure to microbial Toll-like receptor (TLR) ligands plays an important role in neonatal T-cell maturation and that early exposure to microbial products may result in early T-cell maturation and a tendency for these matured effector cells to change their homing receptor patterns. Results: Expression of the CD45RO marker was induced in term neonatal T cells after in vitro exposure to TLR ligands for 7 days. Interestingly, naive T cells from adult blood were unaffected by TLR ligand exposure. In addition, neonatal T cells had more cells with decreased expression of the α4β7 integrins and increased expression of CCR4 after in vitro exposure of TLR ligands—similar to the expression of these molecules in adult naive T cells. Discussion: These findings are relevant for the understanding of neonatal T-cell maturation and may contribute to our understanding of multiorgan inflammatory complications of prematurity. Methods: Cord blood was obtained from term and preterm infants. Using flow cytometry, we identified a mature (CD45RO + ) phenotype in preterm infant cord blood (CB) T cells that had decreased expression of the α4β7 integrins and increased expression of the C-C chemokine receptor 4 (CCR4) as compared with term infant CB.