Triggering of CD99 on monocytes by a specific monoclonal antibody regulates T cell activation

• Main Authors: Witida Laopajon, Supansa Pata, Nuchjira Takheaw, Sirirat Surinkaew, Saichit Khummuang, Watchara Kasinrerk
• Format: Journal
• Published: 2018
• Subjects: Immunology and Microbiology
• Online Access: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85055908810&origin=inward; http://cmuir.cmu.ac.th/jspui/handle/6653943832/62745
• Institution: Chiang Mai University

© 2018 Elsevier Inc. CD99, a leukocyte surface glycoprotein, has been implicated in many cellular processes including cell adhesion, cell migration and T cell activation. Our previous study demonstrated the anti-CD99 monoclonal antibody (mAb) clone MT99/3 inhibited T cell activation; however, the mechanism is unclear. In this study, we demonstrated that CD99 expressed on monocytes played a role in the inhibition of T cell activation. Anti-CD99 mAb MT99/3 downregulated the expression of costimulatory molecule CD86, but upregulated IL-6, IL-10 and TNF-α production by monocytes. The inhibitory effect of mAb MT99/3 required cell to cell contact between monocytes and lymphocytes. The soluble mediators produced by monocytes alone were insufficient to induce hypo-function of T lymphocytes. In summary, we demonstrated that ligation of CD99 on monocytes by anti-CD99 mAb MT99/3 could mediate T cell hypo-responsiveness. These findings provide the first evidence of the role of CD99 on monocytes that contributes to T cell activation.