In B16-OVA melanoma grafts in C57BL/6 mice, anti-PD-1 and combined anti-CTLA-4/anti-PD-1 treatments produced larger and more numerous TLS with distinct T- and B-cell zones; TLS presence, number, and size correlated with a reduced tumor burden and improved response to checkpoint blockade [61,99,100]. The gene discussed is PDCD1; the disease is melanoma.