Human milk IgA concentrations during the first year of lactation
- aDepartment of Child Health, University of Glasgow, bDepartment of Child Health, University of Newcastle-upon-Tyne, cMRC Dunn Nutrition Unit, Cambridge
- Professor L T Weaver, Department of Child Health, University of Glasgow, Yorkhill Hospitals, Glasgow G3 8SJ.
- Accepted 13 August 1997
AIMS To measure the concentrations of total IgA in the milk secreted by both breasts, throughout the first year of lactation, in a cohort of Gambian mothers of infants at high risk of infection.
SUBJECTS AND METHODS Sixty five women and their infants were studied monthly from the 4th to 52nd postpartum week. Samples of milk were obtained from each breast by manual expression immediately before the infant was suckled. Milk intakes were measured by test weighing the infants before and after feeds over 12 hour periods; IgA concentrations were determined by enzyme linked immunosorbent assay.
RESULTS A total of 1590 milk samples was measured. The median (interquartile range) concentration of IgA for all samples was 0.708 (0.422–1.105) g/l; that in milk obtained from the left breast was 0.785 (0.458–1.247) g/l, and that in milk obtained from the right breast was 0.645 (0.388–1.011) g/l (p < 0.0001). There was no significant change in milk or IgA intakes with advancing infant age, but there was a close concordance of IgA concentrations between the two breasts, with “tracking” of the output of the left and right breasts. There was a significant (p < 0.01) negative correlation between maternal age and parity, and weight of milk ingested by infants. During the dry season (December to May) the median (interquartile range) IgA concentration was significantly higher at 0.853 (0.571–1.254) g/l than during the rainy season (June to November), when it was 0.518 (0.311–0.909) g/l (p < 0.0001).
CONCLUSIONS Sustained IgA secretion is likely to protect suckling infants from microbial infection.
Human milk is rich in protective proteins, including IgA, which plays a part in the prevention of microbial infection in suckling infants
IgA secretion is maintained at around 0.5 g/day by Gambian mothers throughout the first year of lactation
There is a negative correlation between maternal age and parity, and weight of milk ingested by infants
During the dry season, when food is most plentiful, milk IgA concentrations are higher than during the rainy season, when food is scarcer
There is a close concordance of milk IgA concentrations between the two breasts, with “tracking” of output of the left and right breasts, suggesting control of secretion above the level of the mammary gland