Natural killer cell cytotoxicity is deficient in newborns with sepsis and recurrent infections

We investigated natural killer (NK) cell cytotoxicity in healthy preterm an d full-term newborns in comparison to adults, to elucidate the possible rol e of delivery mode in influencing the NK activity and to evaluate the NK ac tivity in severe neonatal pathological conditions such as bacterial sepsis and recurrent infections. NK cell cytotoxicity was investigated using a 4 h Cr-51 release assay with K562 cells as targets expressed as percentage kil l in the following study groups: full-term normal spontaneous vaginal deliv ery (n = 55), full-term caesarean section (n = 51), preterm normal spontane ous vaginal delivery (n = 34), preterm caesarean section (n = 28), bacteria l sepsis (n = 15), recurrent neonatal infections (n = 8) and healthy adults aged between 22-42 years (n = 89). NK activity for the normal newborns was determined in paired cord and 2-4 day-old neonate blood. The NK cell cytot oxicity in healthy newborns was significantly lower than in adults (P < 0.0 1). Prematurity was associated with a significant decrease in NK cell activ ity compared to full-term neonates (P < 0.05). The mode of delivery did not influence the NK cytotoxicity. In sepsis and recurrent infections, a drama tic decrease in NK cell cytotoxicity was seen related to healthy newborns ( P < 0.01). Conclusion Natural killer cell cytotoxicity is deficient in both neonatal s epsis and recurrent infections.