Based on the observations that the anti-TIGIT: mIgG2a antibody is significantly more efficacious than an anti-TIGIT: mIgG1* antibody and the demonstration that the interaction of the anti-TIGIT:mIgG2a with FcγRIV is required for full anti-tumor activity, we set out to investigate the ability of tumors to grow in TIGIT knockout (KO) mice. Here, TIGIT is linked to neoplasm.