The human maternal antibody that is present in colostrum and milk is a special kind—"secretory immunoglobulin A." This special antibody is produced in, or passes through, the slippery surfaces that line hollow internal organs, like the nose, the mouth, the intestines, and the vagina. It is typically found in body fluids like colostrum and milk. It protects against disease by killing bacteria and viruses and thus preventing them from damaging bodily tissue and—more significant—from passing through the lining and entering the bloodstream.