title: Letter: C3 standards.
mesh_terms: D003176:Complement C3; D003165:Complement System Proteins; D005260:Female; D006801:Humans; D007106:Immune Sera; D005779:Immunodiffusion; D008297:Male; D013997:Time Factors
chemical_list: D003176:Complement C3; D007106:Immune Sera; D003165:Complement System Proteins