Allergic reactions to drugs: involvement of T cells

Drug side eVects are common. They are usually classified as type A reactions if they are related to the pharmacological activity of the drug, and type B reactions if unrelated to the pharmacological activity. Immune mediated side eVects are type B reactions and account for about one seventh of all drug related side eVects.1 Their frequency is, however, highly dependent on the type of drug. Some drugs are notorious for their allergic side eVects—for example, some antibiotics and antiepileptics— while other drugs are seldom related to allergies. The diagnosis of drug allergy is diYcult for various reasons. Firstly, the clinical manifesta-