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. TROP2 (Trophoblast cell surface antigen 2) is a 36-kDa type I transmembrane glycoprotein encoded by gene TACSTD2 and originally identified in human trophoblast cell lines. It is also known as TACSTD2 (Tumor-associated calcium signal transducer 2), GA7331 (Gastrointestinal tumor-associated antigen, GA733-1/GA733 (Pancreatic carcinoma marker protein), M1S1 (Membrane component chromosome 1 surface marker 1), EGP-1 (Epithelial glycoprotein-1) and so on. Trop2 has been implicated in many intracellular signaling pathways and serves as a calcium signal transducer. Trop-2 has differential expression in certain normal tissues, while it is highly expressed in solid tumor (e.g. gastric cancer, nasopharyngeal carcinoma, gallbladder cancer, etc.) and exerts dual functional roles as an oncogene and tumor suppressor. Trop-2 pays a key role in driving tumor growth and involved in cancer cell proliferation, migration, invasion and survival.