Affiliations: Department of Pediatrics and Human Development,
College of Human Medicine, Michigan State University, East Lansing, Michigan,
USA | Division of Neonatology, Sparrow Regional Children's
Center, Sparrow Health System, Lansing, Michigan, USA | Immunology Laboratory, Sparrow Health System, Lansing,
Michigan, USA | Department of Pediatrics, College of Physicians and
Surgeons, Columbia University, New York, NY, USA
Note: [] Correspondence: Said A. Omar, MD, Division of Neonatology
Sparrow Hospital, 1215 E. Michigan Avenue, Lansing, MI 48912, USA. Tel.: +1 517
364 2670; Fax: +1 517 364 3994; E-mail: [email protected]
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/mm^{3} vs. 600 ± 222/mm^{3}; 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.
