CD8A and cancer: There is ample evidence that Tyk2 is involved in immune surveillance of cancer.44–46 Tyk2 is required for IL12 production by myeloid cells, which triggers a Th1 response with enhanced IFNγ production and tumor cell killing by CD8+ T cells and NK cells.47 Therefore, we expected similar cancer phenotypes in Tyk2Δ/Δ and Tyk2ΔHem mice since both mouse models lack Tyk2 in immune cells.