Phagocytosis is an important element in host defense, and deficiencies may be reflected in decreased immune competence in neonates. In the present study, we analyzed phagocytosis in monocytes from term and preterm cord blood and adult peripheral blood. Heparinized whole blood was incubated (37C) with formalin-fixed propidium iodide-labeled Staph. aureus (S.a.). Monocytes were identified using the fluorescein-conjugated monoclonal antibody My-4. RBC were then lysed, and papain and DNAse utilized to diminish artifact due to clumping and surface adhesion of bacteria. Internalization of bacteria was confirmed using fluorescent confocal microscopy. Samples were analyzed by flow cytometry. Time course analysis indicated that the initial relative rate of phagocytosis observed in full term cord blood monocytes was 57% lower than adult monocytes. Furthermore, phagocytosis of S.a. by full term cord blood monocytes reached maximal levels within 15 min, while phagocytosis in adult monocytes plateaued at approximately 25 min. The relative quantities of bacteria internalized by monocytes were also determined after 20 min incubation with S.a. Cord blood monocytes from both term and preterm (25-32 wk gestational age) neonates contained 61% less S.a. than adult monocytes. Monocytes from preterm infants did not differ significantly from full term. These data suggest that monocytes from term and preterm neonates exhibit diminished capacity to phagocytize S.a. relative to adult cells. Studies are ongoing to correlate phagocytic activity of monocytes from cord blood samples with diagnoses of perinatal illness and with cord blood IL-6 levels.
|Original language||English (US)|
|Journal||Journal of Investigative Medicine|
|State||Published - Feb 1999|
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)