In CF all measured cytokines, with the except of IL-2, were positively correlated with increasing leucocyte count per high power field: IFN-γ (r = 0.358, p = 0.011); IL-4 (r = 0.382, p = 0.006); IL-10 (r = 0.331, p = 0.019); IL-12 (r = 0.373, p −0.008); IL-13 (r = 0.299, p = 0.035); IL-1β (r = 0.334, p = 0.009); IL-6 (r = 0.276, p = 0.05); IL-8 (r = 0.346, p = 0.019) and TNF-α (r = 0.302, p = 0.033). This evidence concerns the gene IL13 and cystic fibrosis.