The Fc receptor for IgG (FcγRII; CD32) on human neonatal B lymphocytes

B cells express an Fe receptor fur IgG (Fc gamma RII; CD32) which is involved in feedback inhibition of anti-body production. Engagement of Fc gamma RII during ligation of the antigen receptor provides an inhibitory signal. Fc gamma RII exists as several isoforms, with Fc gamma RIIb (which carries an immunoreceptor tyrosine-based inhibition motif; ITIM) being predominant form on adult B cells. The inhibitory role of Fc gamma RIIb map be unhelpful to the infant, since primary exposure to infectious agents is likely to be in thy presence of maternal IBG. We hypothesized that neonatal D cells would be loss susceptible to feedback inhibition by antibody, either through the expression of activation-competent Fc gamma RII isoforms (Fc gamma RIIa and Fc gamma RIIc) or through reduced expression of the inhibitory Fc gamma RIIb isoforms. Cord and adult B cells were examined for expression of Fc gamma RII isoforms using monoclonal antibodies and RT-PCR. In vitro assays were performed to assess susceptibility of cord and adult cells to Fc gamma RII-mediated suppression. Although there is no phenotypic difference in Fc gamma RII expression (Fc gamma RIIb predominating on both adult and cord B cells), Fc gamma RIIb is expressed at lower levels on cord cells. This quantitative difference in Fc gamma RIIb expression map explain the reduced susceptibility of cord B cells to anti body-mediated inhibition observed in these experiments (C) American Society for Histocompatibility and Immunogenetics, 2001. Published by Elsevier Science Inc.