IL4 and cancer: Therefore, our data strongly suggest that the type of ongoing immune response in NSCLC tumors is not only qualitatively inappropriate (Th2 instead of Th1), but also detrimental because Th2 (and Treg) cells may inhibit the anti-cancer activity of the few Th1 cells by secreting Th2-associated cytokines such as IL-4 and IL-10.