The purification and properties of some less common allotypes of the fourth component of human complement.
Human complement component C4 is coded by two genes situated between HLA-D and HLA-B. Both genes are highly polymorphic; C4-A gene products normally carry the blood group antigen Rodgers and C4-B proteins usually carry the Chido antigen. Using a monoclonal antibody which binds Rodgers-positive and Chido-positive proteins with different affinities, we have purified a number of less common C4 allotypes and compared their properties. All C4-B allotypes tested have similar specific hemolytic activities and binding efficiencies to small molecules. All C4-A proteins tested had similar binding to small molecules and hemolytic activities except for the C4-A6 proteins from two individuals with different extended haplotypes, both of which had identical hemolytic activities and much lower ones than other C4-A allotypes. Two allotypes, C4-A1, Rodgers-negative but Chido-positive, and C4-B5, Chido-negative but probably Rodgers-positive, were found to behave as typical C4-A and C4-B proteins, respectively, apart from the switch in their antigenic properties.
D000911:Antibodies, Monoclonal; D003181:Complement C4 / Q000235:genetics / Q000302:isolation & purification*; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis; D005990:Glycerol / Q000097:blood; D005998:Glycine / Q000097:blood; D006680:HLA Antigens / Q000235:genetics; D006461:Hemolysis; D006801:Humans; D007126:Immunoglobulin Allotypes / Q000235:genetics / Q000302:isolation & purification*; D011110:Polymorphism, Genetic; D011485:Protein Binding
D000911:Antibodies, Monoclonal; D003181:Complement C4; D000939:Epitopes; D006680:HLA Antigens; D007126:Immunoglobulin Allotypes; D005990:Glycerol; D005998:Glycine