Changes in salivary and fecal secretory IgA in infants under different feeding regimens.

BACKGROUND: One of the causes of food allergy in infancy is assumed to be immunological immaturity of the intestinal tract. The purpose of the present study was to examine changes in salivary and fecal secretory IgA (sIgA) levels in infants under different feeding regimens to evaluate the immunological maturity of the intestinal tract. METHODS: Thirty-four infants were enrolled at the beginning of the study, and 28 of them were followed up to 12 months of age. sIgA was measured on enzyme-linked immunosorbent assay. Changes in the levels of salivary and fecal sIgA during the first 12 months of life were compared among formula-fed infants (F group), breast-formula-fed infants (BF group) and breast-fed infants (B group). RESULTS: Salivary sIgA was detected in almost all neonates on the day of birth. Salivary sIgA was significantly higher in the F group than in the BF group at the age of 2 months (P < 0.05). Fecal sIgA appeared from day 2 and rapidly increased at 1 month of age in all groups. B group infants had significantly higher level of fecal sIgA than F group infants at 1 month of age (P < 0.05). CONCLUSIONS: The level of salivary sIgA hardly changed, whereas fecal sIgA was significantly influenced by intake of breast milk.