Antibody production by the mammary gland in mothers after artificial oral colonisation of their infants with a non-pathogenic strain E. coli 083.

Twenty five breast-fed and 25 formula-fed infants were colonised by oral administration of a living suspension of E. coli 083. Twenty breast-fed and 13 formula-fed infants were followed as controls. Specific antibody titres in serum, stool filtrates and milk, and secretory IgA levels in stool filtrates and milk were determined in samples taken fortnightly from birth until 20 weeks of age. The haemagglutinating antibody in serum and milk increased in the colonised groups, but in stool filtrates an inhibitory effect of breast-milk was demonstrated. Secretory IgA levels in stool filtrates were significantly higher in colonised infants and breast-fed controls than in bottle-fed infants during the period of breast feeding. Then levels in the colonised groups remained high, but in breast-fed controls they decreased to values found in bottle-fed controls. Artificial colonisation evoked local antibody and secretory IgA responses in the intestine, as well as an antibody response in the mother's mammary gland. The possible protective effect of those responses is discussed.