In-vivo immune responses of breast- and bottle-fed infants to tetanus toxoid antigen and to normal gut flora.

The effects of breast- and bottle-feeding on serum immunoglobulin levels and specific antibody responses have been examined in 30 infants on five occasions from 6 days until 9 months of age. No significant differences were found on any sample occasion between the two feeding groups in total immunoglobulin levels of G, M and A classes or in class-specific antibody responses to tetanus toxoid vaccine. This suggests that the capacity of the two groups to make serum antibodies develops similarly. Concentrations of antibodies to commensal Escherichia coli 'O' lipopolysaccharide antigens, however, were significantly greater in the bottle-fed group, and it is suggested that this difference is due to an increase in the exposure of the systemic immune system to these gut antigens in the bottle-fed infants. There are several possible explanations for this increased exposure and the resulting effects on the infants' immune system. These experiments also illustrate a possible role of breast milk in stimulating the immune system.