Effect of rat intestinal glycoprotein on complement lytic activity of 32P-labelled Escherichia coli

Evidence for complement activation by an intestinal glycoprotein fraction from germfree rats is presented. The lowering effect on human serum bactericidal activity of E. coli was 28% for the intestinal glycoprotein fraction, 31% for zymosan, and 25% for inulin, while the lowering effect on conventional rat serum bactericidal activity was 65%, 53% and 21%, respectively. 32P-releasing activity of serum from germfree rats and from man on labelled E. coli amounted to 8% and 28%, respectively, of the release exerted by serum from conventional rats.