Effect of lectins on the hemolytic activity of complement components

We have studied the effect of several lectins that have different sugar specifications on the functional activity of purified guinea-pig and human complement components 1 to 9. We tested castor bean type II (specific for galactose and lactose), wheat germ agglutinin (specific forN-aceytl-glucosamine), lotus bean (specific for fucose), soybean and phytohemagglutinin (PHA) (specific forN-aceytl-d-galactosamine). Leucoagglutinin, a purified constituent of PHA with no known suger specificity, was also included. Soy bean, wheat germ agglutinin and PHA, when immobilized, interacted with GP or Hu C1. Only PHA affected the activity of human or guinea-pig fluid phase Cl. Castor bean type II was found to inhibit the hemolytic action of fluid phase or cell-bound Cl and C4 but inhibited C2 only in the fluid phase. Castor bean type II binds to EACH cells with only minimal impairment of the binding and hemolytic functioning of C2; however, the presence of the lectin inhibited the decay of the hemolytically effective EAC142 sites generated. Lotus bean and leucoagglutinin did not affect the activity of any of the complement components under the conditions tested. Our results suggest that specific sugar residues (e.g. glucose, mannose, lactose or galactose) may play a significant role in the functional activity of human and guinea-pig C1, C4 and C2.