THE ROLES OF NOVEL LECTINS IN HOST DEFENSE SYSTEM FOUND IN RABBIT SERA.

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We have found novel lectin and lectin-like proteins in rabbit and human sera. A rabbit serum lectin (RSL-I) which recognized oligosaccharide structures, blood group H type land type2 (Fuc alpha 1-2 Gal beta 1-3/4 GlcNAc beta) and N-acetyllactosamine agglutinated human red blood cells. The rabit serum lectin was purified using affinity chromatography on Synsorb H type 2 beads, gel filtration and preparative polyacrylamide gel electrophoresis. The molecular weight of the lectin was calculated to be approximate 650000 and 65000 on gel filtration and SDS-polyacrylamide gel eletrophoresis.Moreover we have isolated and purified a novel phospholipid/ganglioside-binding protein (PG-binding protein) from rabbit sera. The PG-binding protein bound to Sephacryl S gel and was easily purified by gel filtration and preparative polyacrylamide gel electrophoresis. The PG-binding protein agglutinated human red blood cells, and its hemagglutination reaction was inhibited by phospholipids (phosphatidylser … More ine and phosphatidylglycerol) and ganglioside (GM3). In order to clarify the role of this protein in body, we examined the inhibitory or control activity for bacteria. It did not have any antibacterial activity, but has agglutination activity for some Gram's negative bacterias.The protein seemed to be assembled as multimers of disulfide-bonded molecular of 86 kDa and 59 kDa subunits.The resemble PG-binding protein (antiPLHu-antibody) was found in human sera, and the protein had affinity for the same Sephacryl S gel and agglutinated rabbit red blood cells. The hemagglutination reaction was specifically inhibited by phospholipids (phosphatidylserine and phosphatidylinositol) but not any other phospholipids, gangliosides, saccharides. Furthermore, the protein was able to cause hemolysis of rabbit red blood cells with guinea pig complement.Thus these results suggest that lectin and lectin-like protein in rabbit and human sera might have important roles of the immunological protection against bacterial pathogens. Less