738 CHEMILUMINESCENCE RESPONSE OF NEONATAL LEUKOCYTES

Abstract

Neonatal PMN may have abnormal metabolic function leading to defects in intracellular microbicidal activity. We have studied leukocytes from 14 healthy term infants and 5 stressed premature (30-36 weeks gestation) infants in order to determine the presence of functional abnormalities associated with ingestion of opsonized zymosan or group B streptococci. PMN separated by dextran sedimentation with ammonium chloride induced erythrocyte lysis were washed twice and resuspended in PBS. Control cells were obtained from normal adult volunteers. Studies were performed using both a chemiluminescence (CL) and a 3H labeled group B streptococcal uptake technique. Chemiluminescence from term neonatal PMN was comparable to adult controls in all instances when zymosan was used as the ingested particle. Two of the term infants tested, however, showed depressed CL in response to opsonized group B streptococci. In contrast, CL studies of the stressed neonatal PMN were abnormal in 3 of 5 instances using opsonized zymosan and all 5 instances with group B streptococci. No phagocytic defect was evident by radiolabeled group B streptococcal uptake and microscopic examination. Since chemiluminescence is produced when the microbicidal mechanism of the neutrophil is activated, the abnormal results suggest a metabolic abnormality is present in some term and most preterm neonatal PMN. The presence of this defect may contribute to the high mortality observed with infection in stressed, preterm infants.