A Human In Vitro T Cell Exhaustion Model for Assessing Immuno-Oncology Therapies

T cell exhaustion is central in the pathology of cancer and chronic viral infections. This chapter describes an in vitro method to generate human exhausted T cells. Chronic T cell activation is reconstructed by repeated stimulation with CD3-/CD28-targeting antibodies that results in sustained upregulation of several phenotypic hallmarks of exhaustion including co-expression of PD-1, LAG-3, TIM-3, CTLA-4, and the transcription factor TOX. This phenotype was associated with gradual functional impairment that was characterized by diminished cytokine production, proliferative capacity, and cytotoxic potential. PD-1 blockade could partially restore the functionality of the cells, but not to the levels observed in non-exhausted T cells. This model effectively emulates the T cells of the tumor microenvironment and is applicable for the assessment of various targeted therapeutics including bispecific molecules and combination therapies.