Effect of gamma interferon on expression of Fc gamma receptors in monocytes of newborn infants and adults

Fc gamma receptors provide an essential link between cellular and humoral immunity, and little is known about their expression in monocytes of newborn infants. We compared baseline and gamma interferon (IFN-gamma)-induced expression of Fc gamma RI and Fc gamma RII protein and Fc gamma RI mRNA in monocytes from healthy, term infants and adults. Fluorescence-activated cell sorter analysis demonstrated that baseline expression of monocyte Fc gamma RI in newborn infants was not significantly different from that in adults, while Fc gamma RII protein expression in monocytes derived from newborns was significantly higher than that for adults (mean channel fluorescence [MCF] for newborns and adults, 5.53 and 4.50, respectively [P = 0.039]). In vitro treatment with recombinant IFN-gamma increased the expression of Fc gamma RI in monocytes of newborns and adults to the same extent (2.4- and 2.2-fold increase in MCF in newborns and adults, respectively, at 42 h). We developed a semiquantitative fluorescence reverse transcriptase PCR which demonstrated a significant increase in mRNA for Fc gamma RI in monocytes of newborns and adults with in vitro IFN-gamma exposure, indicating that IFN-gamma acts by increasing the transcription or transcript stability of Fc gamma RI mRNA. While there was no significant effect of IFN-gamma treatment on Fc gamma RII expression in monocytes from adults, there was a 20% increase in Fc gamma RII in monocytes from newborns (P = 0.009). Monocytes from healthy, term newborns and adults exhibit comparable baseline and IFN-gamma-induced levels of expression of Fc gamma RI and higher baseline and IFN-gamma-induced levels of expression of Fc gamma RII.