ABSTRACT
The secretory immunoglobulin A (sIgA) antibodies function mainly by binding microbes, preventing their contact with mucosal membranes primarily in the respiratory and gastrointestinal tracts. Human milk is very rich in antibodies. Several years ago, it was demonstrated that these antibodies were primarily composed of sIgA antibodies and especially adapted for the defense of mucosal membranes. Milk, as the first nutrient source in postnatal life, provides key elements for the developing infant and supplies essential immune protection through antibodies and receptor analogs. An earlier study suggested that infants on a low-protein formula responded less well than breast-fed infants or infants on a high-protein formula to tetanus and diphtheria toxoid as well as to poliovirus vaccination. Vaccination can be used to increase the specific sIgA antibodies in the mother’s milk. Such antibody responses may include anti-idiotypic antibodies which may prime the breast-fed infant to active immunity.
