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 humo ral immunity, and little is known about their expression in monocytes of newborn infants. We compared baseline and gamma interferon (IFN-gam ma)-induced expression of Fc gamma RI and Fc gamma RII protein and Fc gamma RI mRNA in monocytes from healthy, term infants and adults. Fluo rescence-activated cell sorter analysis demonstrated that baseline exp ression of monocyte Fc gamma RI in newborn infants was not significant ly different from that in adults, while Fc gamma RII protein expressio n in monocytes derived from newborns was significantly higher than tha t for adults (mean channel fluorescence [MCF] for newborns and adults, 5.53 and 4.50, respectively [P = 0.039]). In vitro treatment with rec ombinant IFN-gamma increased the expression of Fc gamma RI in monocyte s of newborns and adults to the same extent (2.4- and 2.2-fold increas e in MCF in newborns and adults, respectively, at 42 h). We developed a semiquantitative fluorescence reverse transcriptase PCR which demons trated 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-gam ma treatment on Fc gamma RII expression in monocytes from adults, ther e was a 20% increase in Fc gamma RII in monocytes from newborns (P = 0 .009). Monocytes from healthy, term newborns and adults exhibit compar able baseline and IFN-gamma-induced levels of expression of Fc gamma R I and higher baseline and IFN-gamma-induced levels of expression of Fc gamma RII.