CD8A and neoplasm: Unresponsive, immunologically ‘cold’, tumors include: (1) ‘immune desert’ tumors that lack TILs; and (2) ‘T cell-excluded’ tumors that stimulate CD8+ cytotoxic T lymphocytes (CTLs) but prevent their entry into the tumor so that they align along the tumor margins (Hegde et al, 2016; Herbst et al, 2014) (Fig. 1B).