The thick yellowish, first milk produced by the female after she gives birth (parturition) is called colostrum. Colostrum as a special milk secreted within first 2-5 days. (Darragh and Lönnerdal, 2011).
It is easily digestible and nutritious. (Kuralkar, P & Kuralkar, S. 2010). The infant intestinal immune system is relatively mature as compared with other parts of the immune system. Infants respond the signals actively from immune constituents in breast milk (Jones et al., 2002a). Few studies has shown that breast milk can affect intestinal immunity. It may have long-term health consequences. (Horta and Victora, 2013).
At the closing of John Steinbeck’s classic, a woman whose new born baby had just died. She saved a man dying of starvation by breast-feeding him. It was one of the most highly charged moment . This act of woman recharged his immune system. The substance transferred to that man was colostrum. . A rich source of nutrients, antibodies, and growth factors for the suckling. Colostrum is richer in growth factors and antibodies. (Uruakpa et al. 2002)
Colostrum as Immune Booster
Colostrum is the most potent natural immune booster rich in immunological components. Which include secretory IgA, lactoferrin, a variety of growth factors, immune cells. Some vitamins do not cross the placental barrier. Colostrum is the primary source of these nutrients for the suckling after birth. (Kobata et al., 2008).
A variety of immune cells are present in human colostrum which include macrophages, lymphocytes, T cells, and stem cells. Over 80% of the cells present in early milk are called breast milk macrophages. These are emerging as peripheral blood monocytes. That exit the bloodstream and migrate into milk through the mammary epithelium (Ballard and Morrow, 2013). These monocytes transform into potent cells which possess unique functional features. Monocytes has the ability to differentiate into dendritic cells that stimulate infant T-cell activity (Yagi et al., 2010).
Stem cells are also found in colostrum. The exact functions of these are not well known yet (Indumathi et al., 2013).
Several cytokines and other immunoreactivity substances have been identified in human milk and colostrum (Garofalo, 2010). Certain immune factors like sCD14, TGF-β, HGF are present in more concentration in colostrum (Kobata et al., 2008).
1.IFN-γ as Immune Factor
Levels of IFN-γ are higher in colostrum (Prokesova et al., 2006). They are secreted actively. Plays important role in infant immune defence and development.
TGF-β can promote IgA production (Ogawa et al., 2004). It may actively process immune unresponsiveness in infants (Strobel, 2002).
3. CD14 as Immune Factor
CD14 which exists in 2 forms, membrane bound and soluble. Mainly expressed by monocytes or macrophages. It plays an important role in innate immunity as a component of the complex with endotoxin (Landmann et al., 2000). The levels of CD14 on monocytes and macrophages and sCD14 are very low in the neonate. High levels of them in breast milk may compensate for this relative deficiency.
Exosomes are small, 30–100 nm membrane vesicles. That are released extracellularly after fusion of multivesicular endosomes with the cell membrane of mammalian cells. The mechanism of action of exosomes within the immune system is not fully understood. They can be secreted by various cells types (dendritic cells, mast cells, epithelial cells, B-cells, T-cells).
Those secreted by mast cells, can induce dendritic cell maturation (Skokos et al., 2003). Mast cell exosomes can transport functional mRNA to recipient cells (Lotvall and Valadi, 2007).
Exosomes and Colostrum
Exosomes have been identified in colostrum. Expressing MHC class II, CD86, and the tetraspanin proteins CD63 and CD81. These milk exosome complexes inhibit anti-CD3-induced cytokine production from PBMC and increase the number of Foxp3+CD4+CD25+ T regulatory cells. These findings suggest that exosomes in human breast milk can have a significant influence on immune ontogeny. Risks of atopic and other immune mediated diseases (Admyre et al., 2007b).
Colostrum and mature breast milk secrete immunoglobulins actively and these are identical to those found in blood or secretions. They are a family of bioactive protective proteins. Divided into several classes including IgM, IgA, IgG, IgE, and IgD (Mix et al., 2006). IgG, IgA and IgM are the major immunoglobulin classes in mammal animal secretions (Huang et al., 2008).
Immunoglobulins are found in colostrum in high concentration (Bachour et al., 2012). IgA is the major immunoglobulin class (88-90% of total immunoglobulin). The content of IgG in human colostrum is of little consequence. (Hurley and Theil, 2011).