CD4 and neoplasm: Guo et al. first used a full-length single-cell mRNA-seq technique, Smart-seq2, to evaluate NSCLC biopsies from treatment-naïve patients to determine the baseline landscape of tumor-infiltrating lymphocytes.134 In addition to conventional CD4+ and CD8+ T cell clusters, two novel CD8+ T cell clusters were observed and defined as “pre-exhausted” cells, which exhibited low expression of exhaustion markers.