Her-2/CD3 Antibodies

Target Information

HER2, also known as ErbB2, is a member of the epidermal growth factor receptor (EGFR/ErbB) family of receptor tyrosine kinases. Unlike other family members, HER2 has no known direct ligand and functions primarily through heterodimerization with other ErbB receptors, leading to activation of downstream signaling pathways such as PI3K/AKT and MAPK that regulate cell proliferation, survival, and differentiation. HER2 is overexpressed or amplified in several cancers, most notably breast and gastric cancers, where it is associated with aggressive disease and poor prognosis. Due to its role in tumor growth and its cell surface accessibility, HER2 is an important target for monoclonal antibodies, antibody-drug conjugates, and other targeted therapies.

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.