Preparation of precipitating antigens by coupling oligosaccharides to polylysine

Oligosaccharides isolated from human milk when coupled to polylysine by a mixed anhydride procedure are effective precipitating antigens. The lacto-N-fucopentaose II conjugate specifically precipitates antibody directed against the human Le^a blood group antigen while the lacto-N-difucohexaose I conjugate specifically precipitates antibody directed against the human Le^b blood group antigen. The derivatives were used to define the specificity of a human anti-I cold agglutinin.