Background: T-cell exhaustion can occur during chronic infection and cancer due to the persistence of antigen and inflammation in local tissues. When T-cells are repeatedly stimulated, negative feedback loops limit inflammation, an event known as T-cell exhaustion. These tolerogenic feedback loops are required for normal, healthy function of T-cell activation; preventing T-cells from becoming overstimulated and damaging healthy tissues (e.g. auto-immune disorders). Blockade of immune checkpoint receptors, such as the PD-1/PD-L1 pathway, can ameliorate or partially reverse T-cell exhaustion and improve immune responses. These assays can also be utilized to explore the efficacy of new checkpoint drug candidates in development.
Principle: In this assay, lymphocytes (PBMCs) are stimulated for several days to exhaust T-cells. The cells are then re-stimulated in the presence of a checkpoint inhibitor or other immunomodulatory article to observe if T-cell exhaustion can be rerouted. Lymphocyte response (proliferation, activation, cytokines, etc.) are measured to assess the effect caused by therapeutic intervention.
There are many variations on Checkpoint inhibitor (CI) assays, where the method of T-cell activation and CI addition differs with immunological mechanism of interest: