Definition

A humanized monoclonal antibody directed against the human immunosuppressive molecule CD200 (OX-2) with potential immunomodulating and antineoplastic activities. Samalizumab binds to CD200, blocking the binding of CD200 to its receptor, CD200R, present on cells of the macrophage lineage. Inhibition of CD200 may augment the cytotoxic T-lymphocyte (CTL) mediated immune response against CD200-expressing tumor cells. CD200 is a type 1a transmembrane protein, related to the B7 family of co-stimulatory receptors, and is upregulated on the surface of multiple hematologic malignant cells; this transmembrane protein appears to be involved in the downregulation of a Th1 (helper T cell) immune response.