Fluctuation of specific IgA antibodies in human milk.

The concentration of secretory IgA and the levels of IgA specific antibodies against Escherichia coli labile-toxin, Shigella flexneri 6, and rotaviruses were determined in milk samples obtained serially from women during the first 16 weeks postpartum. The mean concentration of secretory IgA followed the expected pattern; the levels of specific antibodies fluctuated in an unpredictable manner and independently of milk secretory IgA content, becoming undetectable in many instances. Under some circumstances, continued breast-feeding may not guarantee continued intake of antibodies against intestinal pathogens by the breast-fed infant.