257 Low Proportions of Peripheral Blood TCRãä-Cells in Newborn Infants

Abstract

Background: Majority of peripheral blood T-cells express the áâT-cell receptor (TCRáâ), which recognizes specific MHC-bound antigens. In the adult, 5–10% of blood T-cells express the TCRãä-receptor. TCRãä-cells recognize antigens in a non-MHC-restricted manner and are part of innate immunity. They are thought to act in defence against microbial pathogens and may play a role in controlling inflammation and preventing chronic inflammatory reactions. Newborn infants, especially those born very preterm, are susceptible to infections. In preterm infants inflammation may play a role in the development of chronic complications. However, little is known about the T-cell subsets in the perinatal period in newborn infants. The aim of this study was to evaluate the TCR áâ and ãä -subsets in the peripheral blood in newborn preterm and term infants in comparision with adults.Methods: Peripheral blood was drawn on the first day of life from 45 preterm infants [gest. age (GA) 28.3(10.3)wks; birth weight (BW) 1000(1780)g], 12 healthy term infants, and 33 healthy adult volunteers. From the preterm infants, follow-up blood samples were drawn at the age of 1, 2, 4, and 6 weeks. T-cell subpopulations were analyzed by flow-cytometry using fluorescent antibodies.Results: In newborn preterm infants, the proportion of T-cells presenting TCRãä was lower than in term infants [median (range) 1.5(3.8) vs 3.1(3.0) %; p<0.001], and in adult controls [5.9(14.8);p<0.001]. In term newborns the proportion of TCRãä-cells was lower than in adults (p=0.001) (Figure). The blood TCRãä-cell counts were lower in preterm infants than in term infants [0.030(0.11) vs 0.091(0.10) 10E9/L;p<0.001] or adults [0.08(0.25)10E9/L;p<0.001]. The blood TCRãä-cell counts were similar in term infants and adults. The blood TCRãä-cell counts gradually increased during the follow-up in the preterm infants, and at the age of 6 wks they were comparable with the term infants' level at d1 [0.081(0.28) vs 0.091(0.10)].Conclusion: The low proportion of TCRãä-cells in the peripheral blood of newborn infants may contribute to their susceptibility to infections. Furthermore, in preterm infants this may contribute to development of chronic inflammation seen in complications such as bronchopulmonary dysplasia.