Cluster of differentiation 3 (CD3) is a multimeric protein complex that is essential for T cell activation and antigen recognition. It consists of five different polypeptide chains (γ, δ, ε, ζ, and η) that are noncovalently associated with the T cell receptor (TCR). The TCR is responsible for recognizing antigens presented by antigen-presenting cells (APCs), while CD3 transduces the activation signal into the T cell and activates helper T-cells and cytotoxic T-cells ^[1-2]. The CD3-TCR complex is expressed on the surface of all mature T cells, and its assembly is required for T cell development and function. CD3 plays a crucial role in stabilizing the TCR and facilitating its interaction with antigens. It also recruits signaling molecules to the TCR, which initiates a cascade of events that leads to T cell activation. CD3 is a highly specific T cell marker, and its expression is increased upon T cell activation. This makes it a valuable tool for identifying and characterizing T cells in tissues and blood samples. CD3 staining is also used to diagnose T-cell lymphomas and leukemias. Due to its essential role in T cell activation, CD3 is a promising target for immunosuppressive therapy. Several anti-CD3 monoclonal antibodies have been developed and are being tested in clinical trials for the treatment of autoimmune diseases, such as type 1 diabetes and rheumatoid arthritis ^[3].

The TNFRSF17 gene, also known as BCMA, encodes a protein belonging to the tumor necrosis factor receptor superfamily. This protein is predominantly expressed in mature B lymphocytes, particularly plasma cells, with lower expression in early B cells and non-B cells ^[4-5]. As a type III transmembrane glycoprotein, TNFRSF17 plays a critical role in B cell survival and differentiation, acting as a key regulator of B cell maturation ^[5]. Functionally, TNFRSF17 primarily acts as a receptor for the B cell-activating factor (BAFF). Upon BAFF binding, it activates both the classical NF-κB pathway and the non-classical MAPK8/JNK pathway, subsequently regulating downstream gene expression to promote B cell survival, proliferation, and antibody secretion. Furthermore, TNFRSF17 can interact with TNFR-associated factors (TRAFs) 1, 2, and 3, further mediating physiological processes related to cell differentiation and growth ^[4-5]. Multiple studies have demonstrated that the TNFRSF17 gene and its protein are associated with various B cell-related diseases. Notably, this gene exhibits abnormally high expression in diseases such as multiple myeloma and systemic lupus erythematosus, rendering it a potential therapeutic target for these conditions ^[6-7].

The B6-hCD3/hBCMA mouse is a dual-gene humanized model generated by crossing B6-hCD3 mice (Catalog No.: C001325) with B6-hBCMA (TNFRSF17) mice (Catalog No.: C001630). This model can be used for researching the pathological mechanisms and therapeutic approaches of diseases such as autoimmune diseases and multiple myeloma, as well as for the development of CD3/BCMA-targeted drugs.