International Immunology Advance Access published online on July 2, 2007
International Immunology, doi:10.1093/intimm/dxm059
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Specific and high-affinity binding of tetramerized PD-L1 extracellular domain to PD-1-expressing cells: possible application to enhance T cell function
1 Department of Immunology and Genomic Medicine, Graduate School of Medicine and
2 Laboratory of Immunology and Cell Biology, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe, Sakyo-Ku, Kyoto 606-8501, Japan
3 Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
4 Tsukuba Research Institute, Ono Pharmaceutical Co., Ltd, Tsukuba, Ibaraki 300-4247, Japan
5 21st Century Center of Excellent Program, Graduate School of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-Ku, Kyoto 606-8501, Japan
6 Laboratory of Food Quality Design and Development, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
7 Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, 12441 Parklawn Drive, Rockville, MD 20852, USA
Correspondence to: Correspondence to: N. Minato; E-mail: minato{at}imm.med.kyoto-u.ac.jp
The negative co-stimulatory receptor, programmed cell death 1 (PD-1), is induced on activated T cells and delivers inhibitory signals upon engagement with its ligands PD-L1 and PD-L2, which are expressed on various somatic cells and certain cancers. Accumulating evidence suggests that interfering with the PD-1–PD-L1 interaction may result in the restoration of defective T cell functions in cancer and chronic viral infection. Herein, we established procedures to produce large amounts of renatured recombinant extracellular domain proteins of mouse PD-1 (mPD-1) and PD-L1. While monomeric mPD-1 and mouse PD-L1 (mPD-L1) only marginally interacted with the cells expressing their counterpart proteins, their tetramerization markedly enhanced the affinity with the Kd of mPD-L1 tetramer being nearly 100-fold lower than that of the corresponding monomer. The affinity of mPD-L1 tetramer was even higher than a high-affinity anti-PD-1 mAb, and it efficiently inhibited the binding of mPD-L1/Fc-chimeric protein to mPD-1+ cells. Functionally, mPD-L1 tetramer significantly enhanced the proliferative responses as well as the cytotoxic activity of T cells against specific target cells in vitro. The results suggest that oligomeric PD-L1 extracellular domains may provide a potential means to restore T cell functions in cancer and viral infection in humans.
Keywords: affinity, cancer, immunoreceptor, infection, tetramer
Transmitting editor: K. Okumura