Natural killer cell activity and antibody-dependent cellular cytotoxicity in newborn infants.

The ability of lymphocytes from the peripheral blood of preterm and term infants and adult women and men to mediate natural killing (NK) and K cell activity (antibody-dependent cellular cytotoxicity) was analysed in 4 hours 51Cr-release assays. K 562 cells were targets for NK activity. K cell activity was assayed on antibody-coated rat thymocytes. Lymphocytes from adult male donors were significantly more cytotoxic to K 562 cells than were lymphocytes from adult female donors. Lymphocytes from both preterm and term infants had significantly lower NK and K cell activity than lymphocytes from adult donors. During the first month of life no increase in NK activity or K cell activity occurred in 7 infants who were re-examined. It is concluded that neither NK nor K cell activities are fully developed during the first month of life.