Isolated antibodies or antigen-binding portions that bind to human TIGIT (T-cell immunoreceptor with Ig and ITIM domains) are provided. In some embodiments, the antibody or antigen-binding portion thereof has a binding affinity (KD) for human TIGIT of less than 5 nM. In some embodiments, the anti-TIGIT antibody blocks binding of CD155 and/or CD112 to TIGIT.
