title: The I antigen of human red cell membrane.
abstract: A high-active I antigen was isolated from human red cells after papainization. Investigations on its chemical composition and its serological properties are reported. 1. The I antigen activity was clearly demonstrated by hemagglutination inhibition studies and by the immuno-double-diffusion with all available anti-I sera. 2. The I antigen did not react with other antibodies directed against red cell antigens thus proving its specificity. Any relationships to antigen activities within the Pr-1/Pr-2, MN, and ABO systems could be excluded. 3. The substance was shown to be a glycoprotein and not a glycolipid. This was confirmed by different delipidation procedures promoting always an increase of I activity. The delipidized material contained only traces of fatty acids, and did not move on thin-layer chromatography in solvent systems normally used for glycolipid development. 4. The I determinant resides on alkali-stable oligosaccharide chains. The main sugars are galactose and N-acetylglucosamine which might be involved in the immunodeterminants.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000941:Antigens; D001894:Borohydrides; D002462:Cell Membrane / Q000276:immunology*; D002849:Chromatography, Gas; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004589:Electrophoresis, Disc; D004912:Erythrocytes / Q000276:immunology*; D005227:Fatty Acids / Q000032:analysis; D006023:Glycoproteins / Q000097:blood; D006385:Hemagglutination Inhibition Tests; D006595:Hexosamines / Q000032:analysis; D006601:Hexoses / Q000032:analysis; D006801:Humans; D005779:Immunodiffusion; D010206:Papain; D010743:Phospholipids / Q000032:analysis; D011402:Pronase; D011487:Protein Conformation; D011817:Rabbits / Q000276:immunology; D012794:Sialic Acids / Q000032:analysis
chemical_list: D000596:Amino Acids; D000941:Antigens; D001894:Borohydrides; D005227:Fatty Acids; D006023:Glycoproteins; D006595:Hexosamines; D006601:Hexoses; D010743:Phospholipids; D012794:Sialic Acids; D010206:Papain; D011402:Pronase