Peptides accompanying chicken egg yolk IgY--alternative methods of isolation and immunoregulatory activity.

In the hen immune system the egg content plays as significant a role in the development of the chick as colostrum does in newborn mammals. One of the most important proteins in this system seems to be the main yolk immunoglobulin IgY. It has been shown that IgY is accompanied by an immunostimulatory polypeptide complex named yolkin. In this report the biological activities of yolkin separated by means of four different procedures are presented. It was shown that yolkin acts as an inducer rather than a modulator of cytokine and nitric oxide release, and does not participate in the protection of cells against destructive effects of reactive oxygen species. However, using the perchloric acid procedure it is possible to obtain a peptide fraction with higher inducing activity, stronger antioxidant properties and ability to decrease the NO level induced by lipopolysaccharide. The results obtained show that it is feasible to select one of the presented methods of yolkin isolation that yields a product of particular activity. The properties of yolk peptides not only indicate their roles in the development of chicks, but can also be useful for the regulation of some immunological disturbances.