Expression of naive and memory T-cells in newborn infants with early-onset sepsis

Abstract

T-cells express two surface antigen isoforms that represent two different maturational stages. Naive T-cells express CD45RA and memory T-cell express CD45RO. Naive T-cells can convert to memory T-cells after antigenic exposure. We hypothesized that naive T-cell expression would be high in healthy newborns compared with adults and that memory T-cell expression would remain low in septic newborns. The expression of naive and memory T-cells was examined using flow cytometry on peripheral blood samples from 15 newborn infants (gestational age 36 ± 1 weeks) with clinical or culture positive sepsis, cord blood samples from 20 healthy newborn infants (gestational age 37 ± 1 weeks) and peripheral blood samples from 24 healthy adults. Both healthy and septic newborns demonstrated a significantly higher percentage of naive T-cells compared with adults (57 ± 2%, 67 ± 4% vs. 40 ± 2%; P < 0.05). Expression of memory T-cells was significantly lower in healthy newborns than adults (8 ± 1 % vs. 46 ± 2%, P < 0.0001). However, septic newborns had a significantly higher percentage expression (14 ± 2% vs. 8 ± 1%, P < 0.01) and absolute number of memory T-cells (812 ± 112/mm³ vs. 600 ± 222/mm³ P < 0.01) than healthy newborns. The percentage expression and absolute number of memory T-cells remained persistently high in septic newborns compared with healthy newborns even after they had completed a full course of antibiotics and recovered from sepsis. The marked predominance of naive T-cells in newborns is consistent with our hypothesis that T-cell immune system is immature at birth. However, newborn infants are capable of increasing expression of memory T-cells in response to sepsis.

Keywords

Memory T-cells - naive T-cells - neonatal sepsis - newborn infants