OKT3: Brand name for muromonab-CD3, an immunosuppressant drug given intravenously to reverse acute rejection of transplanted organs, including the heart, kidneys and liver. OKT3 was the first monoclonal antibody used to treat patients.
OKT3 acts by blocking the function of T cells which play a major role in acute graft rejection. OKT3 reacts with and blocks the function of a molecule called CD3 in the membrane of T cell. The binding of OKT3 to T lymphocyte results in their early activation, which leads to cytokine release, followed by blocking T cell functions.
After OKT3 therapy is over, T cell function usually returns to normal within a week. The sides effects with OKT3 treatment are appreciable and include flu-like symptoms and sometimes more serious reactions. The full brand name is Orthoclone OKT3.