We demonstrated that long-term antibiotic treatment promotes host dysbiosis, diminishes intestinal IL-4 and TGF-β gene expression, decreases the frequency of colonic lamina propria Th9 and Tc9 cells, increases the susceptibility to tumour development and reduces the frequency of Th9 and Tc9 cells in the tumour microenvironment. The gene discussed is IL4; the disease is neoplasm.