Fecal secretory immunoglobulin A in breast milk versus formula feeding in early infancy.

We studied the effects of breast milk feeding versus formula feeding during the first 8 weeks of life on the development of local gastrointestinal humoral immune response by measuring fecal secretory immunoglobulin A (SIgA). Forty-four infants were studied and classified into two groups: breast milk (n = 21) and standard Enfamil without iron (n = 23). The fecal specimens were analyzed at birth and 2, 4, and 8 weeks of age. Radial immune diffusion (RID) technique was used to assay the fecal SIgA during these four ages. Marked SIgA changes were detected in the breast milk-fed group. At birth, no fecal SIgA was detected in either group. At 2, 4, and 8 weeks, significant differences were found between the two groups (p4 less than or equal to 0.001 and p8 less than or equal to 0.001). This phenomenon of enhanced fecal SIgA in breast-fed infants versus standard formula-fed infants is not caused solely by the presence of IgA in breast milk; it represents a stimulatory effect of breast milk on the gastrointestinal humoral immunologic development. The possible active stimulatory role of breast milk on the development of immunologic competence and host defense is discussed. These data suggest an additional advantage of breast milk feeding during early life by the protective role of the earlier and enhanced production of SIgA in the gastrointestinal tract.