Muromonab-CD3

OKT3 ( also called muromonab) is an immunosuppressant drug given to reduce acute rejection in transplant patients.

A major milestone in the prevention of acute allograft rejection was achieved with the development of the mAb OKT3, the first mAb to be approved for clinical use in humans. OKT3 is a murine monoclonal IgG2a antibody that reacts with the T cell receptor-CD3 complex (specifically the epsilon chain of the T lymphocyte antigen receptor) on the surface of circulating human T cells.[13] The T cell has 2 molecules on its surface which function primarily in antigen recognition. These antigen recognition structures are associated with 3 polypeptide chains (the CD-3 complex). The CD-3 complex transduces the signal for the T cell to react to the foreign antigen, proliferate, and attack the foreign matter. OKT3 is a monoclonal antibody that specifically reacts with the T-3 complex by blocking the function of T cells.

The binding of murine MAb OKT3 to CD3 can activate T cells - cytokine release syndrome - resulting in a number of side effects, including pyrexia, myalgia, nausea and diarrhoea.