ALDH1-positive head and neck squamous cell carcinoma cells inhibited T-cell proliferation more efficiently than ALDH1-negative cells, and inhibited cytokine, interferon γ (IFN-γ), Interleukin-2 (IL-2) and tumor necrosis factor α (TNF-α) [120]. Here, IL2 is linked to head and neck squamous cell carcinoma.