Antibody-Dependent Cellular Cytotoxicity to Target Cells Infected With Herpes Simplex Viruses: Functional Adequacy in the Neonate

The functional adequacy of antibody-dependent cellular cytotoxicity (ADCC) in the human neonate was evaluated in a 51Cr release assay which employs tissue culture cells acutely infected with type 1 or type 2 herpes simplex virus (HSV) as targets. Two aspects of ADCC were assessed: cytotoxic effector activity in cord blood mononuclear cells (MC) and the ability of the antibody mediating ADCC to pass the placenta. Although effector cell activity was readily detected in all 13 cord blood specimens tested, cord blood MC showed moderately reduced cytotoxic activity when compared with blood MC from normal adults at the same effector cell:target cell ratio. This finding suggests that effector cells in cord blood make up a reduced proportion of the total circulating MC population and may be of relevance to the newborn's increased susceptibility to HSV infection. On the other hand, the number of MC in cord blood was found to be almost twice that of adult blood, suggesting that the absolute number of ADCC effector cells in cord blood was within the adult range. The antibody mediating ADCC to HSV-infected cells was shown to be transferred quantitatively across the placenta, providing further evidence that it is an IgG immunoglobulin.