Neutrophils from term and preterm newborn infants express the high affinity Fc gamma-receptor I (CD64) during bacterial infections

The high affinity Fc gamma-receptor I(Fc gamma RI, CD64) is normally expres sed only to a very low extent by neutrophils. During bacterial infections, however, neutrophils from adult patients significantly increase their expre ssion of Fc gamma RI. Stimulation through Fc gamma RI is a highly effective way to improve various aspects of neutrophil function, including phagocyto sis. In our study the expression of Fc gamma RI on neutrophils from preterm (n = 9) and term (n = 3) newborn infants, children (n = 14), and adults (n = 6) during the early phase of an acute bacterial infection was investigat ed. Our results showed that neutrophils from newborn infants with bacterial infection expressed Fc gamma RI to a significantly higher extent than both noninfected preterm (p < 0.001) and term (p < 0.001) newborn infants and t hat neutrophils from preterm neonates expressed Fc gamma RI to the same ext ent as neutrophils from term neonates and older infants, children, and adul ts. No difference in the neutrophil cell surface expression of Fc gamma RI during bacterial infections was found among newborn infants, children, and adults. Expression of Fc gamma RI probably represents an important mechanis m to improve neutrophil phagocytosis as well as other aspects of neutrophil function during bacterial infections, especially in preterm infants. Our s tudy indicates that measurement of cell surface expression of Fc gamma RI o n neutrophils could be a useful indicator of severe bacterial infections in preterm and term neonates, as well as in older children and adults.