Studies on pharmacological activation of human serum IgG by chemical modification and active subfragments. I. Induction of anti-ulcerogenic activity by chemical cleavage of interchain disulfide bonds in human IgG and properties of active subfragments.

Commercially available human IgG (native IgG) was passed through a DEAE cellulose column. Two fractions (Fr. I and Fr. II), responding equally against the anti-human IgG antibody were obtained. The carboxamide-methylated H and L chains from both fractions showed remarkable inhibitory activities on both the gastric ulceration and the gastric juice secretion in pylorus-ligated rats. The carboxamide-methylated L chain of rat IgG was also effective, while none of the human native IgG, Fr. I or Fr. II showed any effect. The reduction and the following alkylation of the interchain disulfide bonds were necessary for the induction of the biological activities of human IgG. Sulfonation of human IgG failed to induce the activities. Although the gastric acid secretion was clearly reduced by the administration of Fr. I-L (alkylated L chain of Fr. I), the gastric mucosal blood flow was not affected.