A new method to quantify phagocytosis and intracellular degradation using green fluorescent protein-labeled Escherichia coli: comparison of cord blood macrophages and peripheral blood macrophages of healthy adults.

Interactions between innate and adaptive immune functions in neonatal macrophages (MPhi) are still unclear. We therefore established a method to quantify bacterial phagocytosis and intracellular degradation, using green fluorescent protein (GFP)-labeled Escherichia coli in combination with phenotypic analysis. The kinetics of the proportion of phagocyting MPhi, phagocytosed bacteria per MPhi, and bacterial degradation were comparable for cord blood MPhi of term neonates and MPhi of healthy adults. Phenotyping revealed CD14 and CD16 to be down-modulated within minutes. GFP-labeled E. coli may be useful tools to further study MPhi subpopulations and determinants of phagocytosis in cord blood MPhi. (c) 2006 International Society for Analytical Cytology.