Defective production of interleukin-6 in very small premature infants in response to bacterial pathogens

In the present study, a whole-blood culture was employed to examine the ability of preterm and term newborn infants to produce interleukin-6 (IL-6) in response to major bacterial pathogens such as group B streptococci, Escherichia coli, Listeria monocytogenes, and Streptococcus pneumoniae. Similarly, in response to stimulation with lipopolysaccharide, a potent stimulant for monocyte cytokine production, appreciable levels of IL-6 activity in the stimulated whole blood from term newborns as well as adults was effectively induced by all of these pathogens. In contrast to that of term infants, the bacteria-induced IL-6 production of preterm infants, especially those born before 30 weeks of gestation, was somewhat decreased (P less than 0.01 for each pathogen). It was also demonstrated that IL-6 responses to lipopolysaccharide stimulation were reduced in preterm newborns (for term versus preterm newborns less than 30 weeks of gestation, P was less than 0.01). These findings imply some inherent abnormality of monocytes in preterm babies. The diminished IL-6 production may be partly responsible for the susceptibility of preterm newborn infants to bacterial infections.