PRF1 and neoplasm: To further investigate whether the absence of JAK1 affects T-cell cytotoxicity, tumor-specific OT-I T-cells were co-cultured with B16/OVA or B16/OVA-JAK1−/− cells and the expression of the cytotoxicity-related effector molecules tumor necrosis factor (TNF)-α, granzyme B, and perforin was analyzed.