ABSTRACT
The lower frequency and severity of enteric infections in breast-fed infants, particularly in developing countries, 1–3 led to research concerning the factors in human milk that protect against infectious agents. During the past 30 years, considerable evidence was found that the protection is due to a complex defense system which is adapted to operate in the aeroalimentary tract of the human infant. 4–6 That system consists of living cells, growth promoting factors for Lactobacillus bifidus, proteins that bind bacterial nutrients, oligosaccharides, and non-antibody peptides that are antibacterial, lipids that are antiviral or anti-parasitic, enzymes that are antibacterial, and immunoglobulins. 4–6 This review will be limited to one of the best characterized and more important components of the natural antimicrobial system in human milk, the immunoglobulins.
