A Study of Receptor Expression in Leukocytes by Quantitative Fluorescence Measurement

ABSTRACT

PURPOSE: It is well known that the receptors for Fcgamma moiety of IgG(FcgammaR) are instrumental in antibody-mediated clearance of microorganisms by granulocytes and monocytes, and immune regulation in lymphocytes. Furthermore, complement receptor-3(CR3) is also important in neutrophilic adhesion, diapedesis, and phagocytic functions. In an attempt to examine their roles in neonates, we compared the expressions of FcgammaRs and CR3 in cord blood leukocytes with those expressed in leukocytes in samples of blood obtained from adult subjects. METHODS: Cord blood was obtained from 30 full-term newborn and peripheral blood from 30 adult volunteers. In both groups, we measured three Fcgamma receptors and one adhesion molecule, CR3 on granulocytes, monocytes and lymphocytes using a whole blood method with flow cytometry and quantitative bead standards to enumerate the cell surface receptors. RESULTS:Compared to those observed in adult blood, the proportions of FcgammaRI+ granulocytes were significantly higher in cord blood. By contrast, the proportions of FcgammaRII+ or FcgammaRIII+ granulocytes and the number of FcgammaRIII were significantly lower in cord blood. The proportions of FcgammaRI+, FcgammaRII+, and CD18+ bearing monocytes and the number of FcgammaRII in lymphocytes were also significantly lower in cord blood as compared to adult blood. CONCLUSION: There were differences in the proportions of cells expressing FcgammaRs and CR3 and in the number of FcgammaRs and CR3 in granulocytes, monocytes, and lymphocytes between cord blood and peripheral blood from adult subjects. These may contribute to the difference in immune capability that is known to exist between neonates and adult subjects.