{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"CTLA-4 or CTLA4 (cytotoxic T-lymphocyte-associated protein 4), also known as CD152, is a protein receptor that functions as an immune checkpoint which downregulates the immune system. CTLA-4 is a member of the immunoglobulin superfamily and is similar to the T-cell co-stimulatory protein, CD28. Both molecules bind to CD80 and CD86, also called B7-1 and B7-2 respectively, on antigen-presenting cells. CTLA-4 transmits an inhibitory signal to T cells, whereas CD28 transmits a stimulatory signal. Intracellular CTLA4 is also found in regulatory T cells and may be important to their function. Mutations in the CTLA4 gene have been associated with insulin-dependent diabetes mellitus, Graves’ disease, Hashimoto’s thyroiditis, celiac disease, systemic lupus erythematosus, thyroid-associated orbitopathy, primary biliary cirrhosis and other autoimmune diseases. Polymorphisms of the CTLA-4 gene are associated with autoimmune diseases such as autoimmune thyroid disease and multiple sclerosis, though this association is often weak."}]}]}