MHCs, or major histocompatibility complexes, are molecules present on the surface of immune cells. HLA-DR is a type of MHC molecule. HLA-DR is a highly heterogeneous molecule in humans, and has many numerical variants, one of which is HLA-DR3.
Presence of HLA-DR3 in patients is associated with the development of many autoimmune diseases. The exact mechanism underlying this association is unknown, but the link between certain HLA molecules and autoimmune disease development is strong.
The HLA-DR3 gene is associated with type 1 diabetes, which is an autoimmune disease which attacks insulin producing cells in the pancreas. Patients with HLA-DR3 have about a six-fold increase in the risk of the development of type 1 diabetes.
Systemic Lupus Erythematosus (SLE) is associated with HLA-DR3. This disease has an association with with not only HLA-DR3, but HLA-DR2 as well. SLE is a complex, multisystem disease that typically involves arthralgias, photo-sensitivity, and low blood counts.
Hashimoto's thyroiditis is linked to HLA-DR3 as well as DR5. This disease is the result of self-active T-cells that target and destroy thyroid peroxidase. This disease presents as hypothyroidism.
The presence of HLA-DR3 increases the likelihood for the development of Graves' disease. As with other autoimmune diseases and disorders associated with HLA-DR3, the exact mechanism underlying the association is unknown. This disease presents as hyperthyroidism.
Addison’s Disease, or Primary Adrenal Insufficiency, is associated with the presence of HLA-DR3. This disease is the result of an autoimmune attack on the cells of the adrenal cortex. Patients present with fatigue, orthostatic hypotension, and/or electrolyte abnormalities.
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