Cytotoxic T-lymphocyte associated protein 4

Cytotoxic T-Lymphocyte Associated Protein 4 or CTLA4 is a protein-encoding gene. It is associated with autoimmunity, immunodeficiency and uncontrolled production of lymphocytes.

CD28 is an important paralog of this CTLA4.

Function
CTLA4 and PTPN22 genes play a key role in regulating B cell and T cell activation.

CTLA4 gene mutations have been associated with a variety of autoimmune and immune mediated diseases including:
 * Insulin-dependent diabetes mellitus
 * Graves' disease
 * Hashimoto's thyroiditis (hypothyroidism)
 * Celiac disease type 3
 * Systemic lupus erythematosus
 * Thyroid-associated orbitopathy

ME/CFS
Steiner et al. (2021) found that patients who developed chronic fatigue syndrome after a virus were more likely to have PTPN22 and CTLA4 gene mutations. Dr Carmen Scheibenbogen stated:

"Our finding provides evidence that ME/CFS is an autoimmune disease in the subgroup of patients whose disease is triggered by an infection. It encourages us to pursue clinical studies with IgG or immunoadsorption to target autoantibodies."

A later study did not find any link between ME/CFS and the CTLA4 and PTPN22 genes.

Notable studies

 * 2020, Autoimmunity-Related Risk Variants in PTPN22 and CTLA4 Are Associated With ME/CFS With Infectious Onset - (Full text)

Learn more

 * CTLA4 Gene - Gene cards