Development of monoclonal antibodies against human IRF-5 and their use in identifying the binding of IRF-5 to nuclear import proteins karyopherin-alpha1 and -beta1.

Purpose: IRF-5 is a direct transducer of virus-mediated and TLR-mediated signaling pathways for the expression of cytokines and chemokines which form homodimers or heterodimers with IRF-7. However, direct IRF-5-specific monoclonal antibodies (mAbs) are not available at present. These could be used to further evaluate the functions of IRF-5. In this study, we produced and characterized three mouse mAbs to human IRF-5. The binding of IRF-5 to nuclear import proteins was first identified using a mAb. Materials and Methods: Histagged human IRF-5 protein spanning amino acid residues 193257 was used as an antigen and three mAbs were produced. The mAbs were tested with ELISA, Western blot analysis (WB), immunofluorescent staining (117), and immunoprecipitation (IP). In addition, the nuclear import protein which carried phosphorylated IRF-5 was identified using one of these mAbs. Results: MAbs 5IRF8, 5IRF10 and 5IRF24 which reacted with the recombinant His-IRF-5(193-257) protein were produced. All mAbs bound to human IRF-5, but not to IRF-3 or IRF-7. They could be used for WB, IF, and IP studies. The binding of phosphorylated IRF-5 to karyopherin-alpha 1 and -beta 1 was also identified. Conclusion: Human IRF-5-specific mAbs are produced for studying the immunologic roles related to IRF-5. Phosphorylated IRF-5 is transported to the nucleus by binding to nuclear import proteins karyopherin-alpha 1 and -beta 1.