Immunological activities associated with milk.

Milk contains a multitude of components that can, or may, provide immune protection to the suckling offspring and that also may promote development of neonatal immune competence. In addition, these specialized factors are essential for the protection of the mammary gland, the offspring's food source, from pathogen colonization and lactation failure. Breast milk also facilitates the establishment of a gut flora that inhibits colonization by many pathogens and stimulates the growth of beneficial microorganisms. Maternal immunity can be transferred to the infant via antibodies, primarily of the sIgA type in humans, as well as by leukocytes including effector and memory T lymphocytes. In this way, protection is provided passively against the pathogens to which the mother has been exposed. Currently, there is much interest in determining the protective efficacy of oral supplementation with immunoglobulins from the milk of lactating animals hyperimmunized against specific pathogens. An array of immunostimulatory components in milk, notably cytokines, may be protected against intestinal proteolysis, thereby providing the offspring with a prepackaged immune response system. These components may help to boost the infant's immature immune system. At the same time, anti-inflammatory factors in breast milk help to modulate cytokine responses to infection, thereby facilitating defense while minimizing tissue damage such as that which occurs in infants with necrotizing enterocolitis. Undoubtedly, the many components constituting the repertoire of immune and immunomodulating agents in milk interact synergistically to protect both the mammary gland and the offspring from invading pathogenic microorganisms.