CD3 (Cluster of differentiation 3), originally known as T3, is one of the first groups of human T lymphocyte surface antigens recognized by monoclonal antibodies. It has been reported that antibodies against CD3 could either stimulate T cells to divide or inhibit the progress of effector functions according to the conditions used. It plays an important role in T cell and the CD3 T-cell co-receptor helps to activate the cytotoxic T-Cell and T helper cells. The CD3 molecule is composed of a protein complex and consists of four distinct chains. The complex of mammals contains a CD3γ chain, a CD3δ chain, and two CD3ε chains. All these chains associate with T-cell receptor and the ζ-chain to generate an activation signal in T lymphocytes. EGFR (Epidermal growth factor receptor, also known as ErbB1, ErbB or HER1) is a type I transmembrane glycoprotein involved in normal growth. It belongs to a member of the receptor tyrosine kinase superfamily and makes up the ErbB family with HER2/neu (ErbB-2), HER3 (ErbB-3) and HER4 (ErbB-4). The EGFR gene is encoded on chromosome 7p11.2 and activated by binding to specific protein ligands, such as epidermal growth factor (EGF) and transforming growth factor α (TGF-α). Ligand binding induces EGFR dimerizations resulting in protein-tyrosine kinase activation and cellular signaling. EGFR also plays a role in carcinogenic responses and the increased expression of it in most cases is predictive of tumor progression.