CD33/CD3 Antibodies

Target Information

CD33 is a transmembrane protein of the sialic acid-binding immunoglobulin-like lectin (Siglec) family. It belongs to the immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing molecules able of recruiting protein tyrosine phosphatases SHP-1 and SHP-2 to signal assemblies, and these ITIMs are also used for ubiquitin-mediated removal of the receptor from the cell surface. CD33 is expressed on cells of myelomonocytic lineage, binds sialic acid residues in N- and O-glycans on cell surfaces, and is a therapeutic target for acute myeloid leukemia. Further, CD33 is found on granulocyte and macrophage precursors in the bone marrow, but is not on pluripotent stem cells. CD33 is also expressed on, and is a useful marker for, peripheral monocytes. CD33 is useful for distinguishing myelogenous leukemia cells from lymphoid or erythroid leukemias. Diseases associated with CD43 dysfunction include gallbladder lymphoma and extracutaneous mastocytoma.

The CD3 complex, composed of gamma, delta, epsilon, and zeta subunits, is essential for the assembly, trafficking, and surface expression of the T cell receptor (TCR) complex. These subunits are structurally related members of the immunoglobulin superfamily and are encoded by closely linked genes on human chromosome 11. CD3 is expressed by thymocytes in a developmentally regulated manner and by all mature T cells, but not on B or NK cells. The CD3 subunits play a crucial role in transducing antigen-recognition signals into the cytoplasm of T cells. The cytoplasmic tails of CD3 subunits contain a double tyrosine-based motif that associates with cytoplasmic signal transduction molecules, mediating T cell activation through the TCR. Crosslinking of the TCR initiates intracellular biochemical pathways that result in cellular activation, proliferation, and potentially growth arrest and cell survival. CD3 is present on 68-82% of normal peripheral blood lymphocytes, 65-85% of thymocytes, and Purkinje cells in the cerebellum. Decreased percentages of T lymphocytes may be observed in some autoimmune diseases. Defects in the CD3 gene are associated with CD3 immunodeficiency, highlighting its importance in immune function and regulation.