Daily ingestion of immunologic components in human milk during the first four months of life.

The amounts of lactoferrin, lysozyme, SIgA and SIgA antibodies to E. coli somatic antigens in human milk ingested per day and per kg per day by breast-fed infants were determined during the first four months of life. A gradual decline in the amounts of lactoferrin, SIgA, and SIgA antibodies ingested per day or per kg per day was found, whereas the quantities of lysozyme ingested by the infants rose during that period. These data suggest that the production and secretion of these immunologic factors by the mammary gland may be linked to the ontogeny of the production or catabolism of those components at mucosal tissues of the recipient infant.