Adhesion defects of antibody-mediated target cell binding of neonatal natural killer cells

Neonates are unusually susceptible to herpes simplex virus infection, which may be explained in part by defects in killing of herpes simplex virus-inf ected cells by natural killer (NK) cell cytotoxicity and antibody-dependent cellular cytotoxicity. The mechanism for these defects remains poorly defi ned. We have for the first time used immunomagnetically enriched NK cells t o explore neonatal NK cell phenotype and target cell adhesion. CD56-positiv e neonatal NK cells had markedly lower CD57 expression, but adult level exp ression of adhesive glycoproteins (CD18, CD44) and Fe receptor for IgG (CD1 6). Although the cells conjugated normally with target cells in the absence of antibody, antibody-mediated conjugation was significantly lower than th at of NK cells from adults (p < 0.002). These results demonstrate intact ad hesion in neonatal NK cell cytotoxicity. In contrast, defective neonatal an tibody-dependent cellular cytotoxicity is caused, in part, by an adhesion d efect in the presence of antibody.