Hypersensitivity Reactions

Although the function of the immune system is to protect the body, it is clear that the immune response to exogenous agents, such as infection, can also lead to tissue damage. When the immune response to an otherwise harmless antigen results in tissue damage, we can broadly refer to this as a hypersensitivity reaction. There are four types of hypersensitivity reactions, each mediated by a different class of immunoglobulins.