BLOCKING OF HOG INTRINSIC FACTOR BY HUMAN GASTRIC JUICE AND CERTAIN MUCOPOLYSACCHARIDES, INCLUDING BLOOD GROUP SUBSTANCE*

Abstract

The enhancing effect of hog intrinsic factor concentrate (HIFC) on Co60-B12 uptake by rat liver homogenate receptors may be reduced ("blocked") by blood group substance, degraded blood group substance ("P-l fractions"), type XIV pneumococcus polysaccharide, human gastric juice (from A, B, or O subjects, undegraded, dialyzed, or heated), and to a lesser extent by other polysaccharides. Blocking is Ca++-dependent and EDTA-reversible, as is the effect of intrinsic factor. In accordance with the concept of molecular complementarity as the basis of specificity, it is suggested that intrinsic factor may have terminal B-galactosyl groups which link to receptors on liver (or small intestine), and that various mucopolysaccharides are effective as blockers of this linkage in proportion to the similarity of their end-group conformation to that of intrinsic factor. Human refractoriness to HIFC may be partly due to cross reaction with antibody to P-l fractions or type XIV pneumococcus polysaccharide.