PDCD1 and non-small cell lung carcinoma: A recent large-scale study in patients with NSCLC further demonstrated that the co-expression of exhaustion markers on CD8+T cells—including PD-1, T cell immunoreceptor with Ig and ITIM domains(TIGIT), LAG-3, and TIM-3—serves as an independent predictive factor for the occurrence of primary resistance to ICI (38).