PRF1 and neoplasm: Indeed, others have reported that paracrine cytokine production can enhance the anti‐tumour functions of native or even high‐affinity CD8+ T cells by increasing CD8+ T cell accumulation at the tumour site, increasing CD8+ T cell tumour killing (e.g. by up‐regulation of granzyme and perforin) and CD8+ T cell proliferation 12, 14, 16, 17.