A Versatile Anti-CXCR5 Monoclonal Antibody (Cx₅Mab-6) for Basic Research and Diagnosis

The G protein-coupled receptor, CXC chemokine receptor 5 (CXCR5), is predominantly expressed on B cells located in the secondary lymphoid tissues, follicular helper T cells, and lymphoma cells. Binding to its ligand, CXCL13, mediates cell migration and regulates lymphocyte trafficking. Aberrant CXCL13/CXCR5 expression and signaling have been implicated in tumor progression, autoimmune diseases, and chronic inflammatory disorders. Therefore, specific mAbs against CXCR5 are expected to be useful for diagnosis and therapeutic applications. In this study, novel anti-human CXCR5 mAbs (Cx₅Mabs) were developed through flow cytometry-based high-throughput screening. One clone, Cx₅Mab-6 (IgG_2b, κ), recognized CXCR5-overexpressed Chinese hamster ovary (CHO)-K1 cells but did not react with the other five CXCR receptors-overexpressed CHO-K1 cells in flow cytometry. Additionally, Cx₅Mab-6 recognized endogenous CXCR5 in the human Burkitt lymphoma Raji cell line. The dissociation constant (K_D) values of Cx₅Mab-6 for CHO/CXCR5 and Raji were 3.4 × 10^-9 M and 1.2 × 10^-10 M, respectively. Furthermore, Cx₅Mab-6 is useful for Western blotting and can detect CXCR5 in human lymphoma tissue by immunohistochemistry. These findings suggest that Cx₅Mab-6 is versatile for basic research and has potential applications in clinical diagnosis.