Grave's Disease is classified under which type of hypersensitivity?

Graves' disease is classified as a Type II hypersensitivity reaction. This type of hypersensitivity involves the production of antibodies that target specific cells or tissues, leading to direct damage or dysfunction of those cells. In Graves' disease, the body produces autoantibodies against the thyroid-stimulating hormone (TSH) receptor on thyroid follicular cells. These antibodies mimic the action of TSH, resulting in overstimulation of the thyroid gland and excessive production of thyroid hormones, which leads to hyperthyroidism.

Type II hypersensitivity reactions are characterized by the binding of antibodies (typically IgG or IgM) to specific cell surface antigens, causing cellular damage by mechanisms such as complement activation or antibody-dependent cellular cytotoxicity. This is distinct from other types of hypersensitivities. For example, Type I hypersensitivity involves IgE antibodies and is associated with allergic reactions, Type III hypersensitivity involves immune complex deposition leading to inflammation, and Type IV hypersensitivity is mediated by T cell responses rather than antibodies. In the case of Graves' disease, the autoimmune response is specifically linked to antibody binding and the resultant dysfunction of the thyroid, confirming its classification as a Type II hypersensitivity reaction.