Using a cohort of patients with basal cell carcinoma and squamous cell carcinoma, Wang et al. demonstrated that anti-PD-1 therapy triggered the expansion of intra-tumoral CD200+ T cells, and higher proportions of these CD200+ TIL subsets were positively associated with favorable clinical outcomes to ICB (immune checkpoint blockade) therapy. This evidence concerns the gene CD200 and squamous cell carcinoma.