Fluctuation in the Functional Activity of Human Colostrum Phagocytes to Streptococcus pneumoniae and Enteropathogenic Escherichia coli

Abstract

Colostrum was shown to protect children against gastrointestinal and respiratory infections and to exhibit chronobiological variations in cellular and soluble components. However, circadian variations in the activity of these colostral elements are only partially understood. This study compared colostrum samples collected in the diurnal and nocturnal periods by assessing phagocytic activity against enteropathogenic Escherichia coli (EPEC) and Streptococcus pneumoniae (S. pneumoniae) as well as the role of colostral cells and soluble elements. Colostrum samples were collected from 30 mothers during both day and night. Superoxide anion release, phagocytosis and bactericidal activity by colostral mononuclear (MN) and polymorphonuclear (PMN) phagocytes in the presence of EPEC or S. pneumoniae were determined. Colostrum samples collected in the diurnal period had higher superoxide release in opsonized than in non-opsonized EPEC and S. pneumoniae, whereas in nocturnal samples it was increased in PMN phagocytes incubated with serum-opsonized S. pneumoniae. MN and PMN phagocytes in colostrum collected in both periods exhibited phagocytic activity for the bacteria tested. The highest EPEC killing by MN phagocytes was observed in samples collected in the diurnal period. The bactericidal activity of PMN phagocytes against EPEC was higher when bacteria were opsonized and in samples collected in the diurnal period. For opsonized S. pneumoniae, phagocytes had similar bactericidal activity, irrespective of colostrum collection period. These data support the hypothesis that there is a fluctuation in the functional activity of colostral phagocytes, which is dependent on synchronization among feeding time, pathogen features and infection area.