title: Letter: C4 levels and classification of bronchial asthma.
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001249:Asthma / Q000145:classification* / Q000276:immunology; D003165:Complement System Proteins; D006801:Humans; D005779:Immunodiffusion; D008875:Middle Aged; D011485:Protein Binding; D012882:Skin Tests
chemical_list: D003165:Complement System Proteins