Until recently the presence of Cytokines in colostrum was unsuspected but it has been now clarified that normally there are at least four Cytokines in colostrum: initially IL ß, followed by I1-2, were determined as being part of the colostral factors that stimulate resistance to infections. IL-6, tissue necrosis factor (TNF) and biologically active gamma interferon are thought to immunostimulate the oropharyngeal and intestinal lymphoid tissues in the newborn, and contribute to the development and maturation of the immune system (1,6,7,8,10). Other factors, like Transforming Growth Factor Beta (TGFß) are present in colostrum and milk (9).

Colostrum of mothers of pre-term babies was found to have a higher concentration of IgA lisozime and lactoferrin, and higher macrophage counts when compared to that of mothers of term babies. Other substance found to have a significantly greater activity in pre-term colostrum is a phagocytosis-promoting factor, which not only increases the number of phagocytic cells, but also stimulates the phagocytic activity of the individual cell (11).

The fact that colostrum of mothers of pre-term babies shows a higher nutritional and immunological value is not surprising if we consider the greater need for protection of pre-term babies. The protective effect of breast-feeding against diarrhea has been extensively studied. It is well known that the incidence of diarrhea in third world countries is inversely related to the prevalence of breast-feeding in the community (12,13).

COLOSTRUM FROM ANIMALS

Bovine colostrum contains a glucose tolerance-promoting factor, which consists of a chromium-based complex, with a molecular weight around 1500. This complex was shown to participate in glucose metabolism closely related to insulin. The authors of this study hypothesize this complex could be useful to enhance glucose metabolism in adult diabetic patients (14). The presence of a Gonadotrophin Releasing Hormone (GRH)-related peptide, presumably synthesized in the mammary gland has also been demonstrated (15). There is evidence of IgE transference by colostrum to calves during the first 12 weeks of life, and this is assumed to generate protection against intestinal parasites. IgG, IgA, and IgM are also present in bovine colostrum showing the capacity of neutralizing human, simian and bovine rotavirus (16).

The polymorphonuclear granulocytes (PMN's) found in colostrum show a greater phagocytic activity against at least two breeds of S. Aureus than the PMN's from peripheral blood. This was demonstrated using both the rosette and phagocytosis tests (17).

Ovine and porcine colostrum enhances intestinal protein synthesis to a greater level than the synthesis induced by milk or lactose in their respective newborns. These findings support the idea that colostrum is an important factor for tissue maturation in newborns (18, 19, 20).

Proline-Rich-Polypeptide (PRP), a polypeptide with a clear immunomodulating activity is present in ovine colostrum. PRP acts both in vivo and in vitro, and is not species specific. PRP increases skin permeability and causes differentiation of murine thymocytes into functionally active T cells. The effects of PRP resemble the effects of thymic hormones on autoimmunity and T cell maturation. PRP has a molecular weight of approximately 6000. It is interesting to note that fractions with a molecular weight of approximately 1000 show the same spectrum of activity of the original molecule, apparently indicating that a three amino acid sequence is responsible for the immunological effect of the peptide (21, 22, 23).