Table 1

Summary of the four types of hypersensitivity reaction

Type I Immediate hypersensitivity
Dependent on the specific triggering of IgE sensitised mast cells by antigen—for example, asthma, hay fever, urticaria, anaphylaxis
Type II
Antibody is directed against antigens on specific host cells and tissues—for example, graft rejection, autoimmuine haemolytic anaemia, myasthenia gravis
Type III
Antigen-antibody complexes are deposited in tissues—for example, rheumatoid arthritis, systemic lupus erythematosus, serum sickness, infective endocarditis, malaria
Type IV Delayed hypersensitivity
Antigen sensitisred T cells release cytokines following secondary contact with the same antigen—for example, contact dermatitis, tuberculosis, leprosy