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 |