IL6 and neoplasm: But the proliferation of T cells in 4T1IL-6low tumors was recovered compared with that in 4T1NC tumors (18.30 ± 1.91 vs. 11.03 ± 0.73, P = 0.0236), which implied that IL-6 reduction in tumor microenvironment can relieve immunosuppression on T cell proliferation and function.