title: Letter: C3 standards.
mesh_terms: D003176:Complement C3 / Q000032:analysis*; D003165:Complement System Proteins / Q000032:analysis*; D006801:Humans; D005779:Immunodiffusion; D012685:Sepharose
chemical_list: D003176:Complement C3; D003165:Complement System Proteins; D012685:Sepharose