Monocyte function and lysozyme activity in cord blood.

The role of mononuclear phagocytic system in the expression of immunocompetence in human neonates has not been explored in depth. In the present study, we analysed cord blood monocytes for their ability to a) respond to chemotactic stimuli, b) phagocytize sheep erythrocytes (E) anti-E complexes for detection of Fc receptors, c) phagocytize Zy particles for detection of C3 receptors. Lysozyme activity in newborn sera was also evaluated. Blood donors served as controls. It was found that the response of neonatal cells to chemotactic stimuli as well as phagocytosis via Fc receptors was similar to those of adult monocytes. However, phagocytosis via C3 receptors was significantly lower in neonates compared to adults. Sera from newborns were significantly less potent both in generating chemotactic stimuli after incubation with a bacterial endotoxin (LPS) and in opsonizing Zy particle.s Lysosyme concentrations were significantly higher in neonatal serum samples.