Development of Anti-human T Cell Immunoreceptor with Ig and ITIM Domains (TIGIT) Monoclonal Antibodies for Flow Cytometry.

Immune checkpoint inhibitors targeting programmed cell death-ligand 1 (PD-L1), programmed cell death-1 (PD-1), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) recently made a significant survival rate improvement in cancer treatment. T cell immunoreceptor with Ig and ITIM domains (TIGIT) is expressed in T and NK cells related to their activities. It has a single extracellular immunoglobulin domain, a type 1 transmembrane domain, and a single intracellular ITIM. TIGIT binds with poliovirus receptor (PVR) or PVR2, resulting in suppressing T and NK cell activities. Some studies showed that the combined use of a TIGIT inhibitor with another immune checkpoint inhibitor enhanced antitumor activities more strongly than their single use. Therefore, TIGIT should be a new target for immunotherapy. In this study, we developed new anti-human TIGIT (hTIGIT) monoclonal antibodies (mAbs) using the Cell-Based Immunization and Screening (CBIS) method. Mice were immunized with hTIGIT-overexpressed Chinese hamster ovary (CHO)-K1 cells (CHO/hTIGIT), and hybridomas were screened by flow cytometry. One of the mAbs, TgMab-2 (IgG ₁ , kappa), specifically and sensitively detects hTIGIT in CHO/hTIGIT and NK cells. The dissociation constants ( K _D ) of TgMab-2 for CHO/hTIGIT cells were determined to be 3.5 × 10 ^-9  M. These results suggest that TgMab-2, which was developed by CBIS method, is useful for analyzing the function of hTIGIT by flow cytometry.