ABSTRACT
The immune response of vertebrates has evolved as a mechanism to eradicate infectious agents that succeed in penetrating natural anti-infectious barriers. However, in some instances the immune response can be the cause of disease, both as an undesirable effect of an immune response directed against an exogenous antigen, or as a consequence of an autoimmune reaction. These undesirable immune responses define what is known as hypersensitivity, that is, as an abnormal state of immune reactivity that has deleterious effects on the host. A patient with hypersensitivity to a given compound suffers pathologic reactions as a consequence of exposure to the antigen to which one is hypersensitive. The term “allergy” is often used to designate a pathological condition resulting from hypersensitivity, particularly when the symptoms occur shortly after exposure.
