An Anti-CD3 monoclonal antibody is one that binds to CD3 on the surface of T cell

T cell

T cells or T lymphocytes belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocytes, such as B cells and natural killer cells , by the presence of a T cell receptor on the cell surface. They are...

s. They are immunosuppresive drugs.

The first to be approved was muromonab-CD3 in 1986, to treat transplant rejection

Transplant rejection

Transplant rejection occurs when transplanted tissue is rejected by the recipient's immune system, which destroys the transplanted tissue. Transplant rejection can be lessened by determining the molecular similitude between donor and recipient and by use of immunosuppressant drugs after...

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Newer monoclonal antibodies with the same mechanism of action include otelixizumab

Otelixizumab

Otelixizumab, also known as TRX4, is a monoclonal antibody, which is being developed for the treatment of type 1 diabetes and other autoimmune diseases. The antibody is being developed by Tolerx, Inc...

, teplizumab

Teplizumab

Teplizumab is a monoclonal antibody which is used as an immunosuppressive drug.Teplizumab is a humanized Fc-engineered monoclonal antibody also known as MGA031 and hOKT3γ1....

 and visilizumab

Visilizumab

Visilizumab is a humanized monoclonal antibody. It is being investigated for use as an immunosuppressive drug in patients with ulcerative colitis and Crohn's disease. Visilizumab binds to the CD3 receptor on certain activated T cells without affecting resting T cells...

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They are being investigated for the treatment of other conditions like Crohn's disease

Crohn's disease

Crohn's disease, also known as regional enteritis, is a type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms...

, ulcerative colitis

Ulcerative colitis

Ulcerative colitis is a form of inflammatory bowel disease . Ulcerative colitis is a form of colitis, a disease of the colon , that includes characteristic ulcers, or open sores. The main symptom of active disease is usually constant diarrhea mixed with blood, of gradual onset...

 and type 1 diabetes,
and for inducing immune tolerance

Immune tolerance

Immune tolerance or immunological tolerance is the process by which the immune system does not attack an antigen. It can be either 'natural' or 'self tolerance', in which the body does not mount an immune response to self antigens, or 'induced tolerance', in which tolerance to external antigens can...

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