title: [The defense mechanism and its weakening: significance of antigen mutation--antigenic shift and drift of influenza viruses].
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000276:immunology*; D006801:Humans; D009975:Orthomyxoviridae / Q000145:classification / Q000235:genetics / Q000276:immunology*; D012703:Serotyping
chemical_list: D000956:Antigens, Viral