Breast-fed and artifically fed infants are in contact with the O antigen of
Escherichia coli
from the first days after birth. From the mother, the infant obtains antibodies against nonpathogenic
E. coli
strains in low titer, and the infant begins to form its own antibodies during the 2nd month of life. The transition is known to be continuous even though the transferred antibodies could not be differentiated from the infant's own antibodies. Contact with endotoxin caused sensitization which was detected by the skin test at about 2.5 months, and thereafter the skin test data correlated with the presence of serum antibodies against endotoxin. The newborn infant can be colonized with a different
E. coli
serotype; such an antigenic stimulus evokes the formation of antibodies sooner and at a significantly higher titer than (i) the level of maternal antibodies transferred or (ii) the infant's antibodies normally formed later on against other random
E. coli
serotypes.
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.
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