Current methods to identify cancer-specific CTLs rely on the IFNγ expression and production following stimulation, such as by using intracellular cytokine assay and enzyme-linked immunosorbent assay.139,143,144 Our group has recently demonstrated a certain portion of CTA-specific CTLs could be deficient in their IFNγ expression.140 This suggest that the commonly used techniques might have overlooked a great proportion of CTA-specific CTLs and could potentially lead to unintended biases in cancer-specific T cells analysis. The gene discussed is IFNG; the disease is cancer.