Development of non-allergic peptide preparation having mucosal immunostimulatory ability

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Results obtained in the present investigation were summarized as follows:1) Dietary casein phosphopeptides reduced atopic dermatitis in NC mice via the enhancement of mucosal IgA levels and the reduction of serum IgE levels specific to allergens.2) The immunoregulatory activity of casen phosphopeptides was confirmed to be attributable to the sequence SerP-X-SerP.3) SerP-SerP-SerP obviously reacted with an antibody specific to phosphoserine-rich region of casein phosphopeptides whereas SerP-Leu-SeP was inert. These results suggested that SerP-X-SerP (X is not SerP) was non-allergic IgA-stimulatory peptide.4) Bovine casein was digested with 14 kinds of proteases, which are permitted to use as food supplements, and casein phosphopeptides were recovered from the digests. Casein phosphopeptides preparation obtained from caseins digested with proteases from Aspergillus oryzae had high stimulatory effect on IgA production and little reactivity with the antibody specific to phosphoserine-rich region of casein phosphopeptides. These facts suggested that the casein phosphopeptide preparation obtained from caseins digested with proteases from Aspergillus oryzae was non-allergic IgA-stimulatory peptide.5) In general, a dextrin consisting of 15 to 16 glucoses is considered to be non-allergic. On the other hand two phosphate groups is essential to display IgA-stimulatory effect of casein phosphopeptides. Hence, dextrins covalently coupled with 5 to 7 phosphate groups were prepared. The phosphorylated dextrin sitmulated IgA production in mouse spleen cell cultures. Moreover, the intestinal IgA level to pathogenic bacteria orally ingested was increased significantly when mice were given a diet containing phosphorylated dextrin for 35 days. These results suggest that phosphorylated dextrin is another non-allereic lgA-stimulatorv substance.