FOXP3 and non-small cell lung carcinoma: To determine whether regulatory T (Treg) cells would produce IL-9 in the lung of patients with NSCLC, we performed double immunohistochemistry for IL-9 and Foxp3 in tissue array slides (Figures 2A, B). Here, we found an increased number of double positive cells for Foxp3 and IL-9 in the tumoral region compared to the control region of the lung of NSCLC patients suggesting that lung Treg cells may produce IL-9 in NSCLC.