CD4 and neoplasm: It has also been shown that ERK pathway activation was involved in IL‐17A‐producing Th subset polarization,21, 22 to verify whether similar mechanisms might be involved in the induction of IL‐17A‐producing Th subset by neutrophils in GC, purified peripheral CD4+ T cells were first pre‐treated with U0126, the inhibitor of ERK pathway, and co‐cultured them with tumor‐infiltrating neutrophils and TTCS‐conditioned neutrophils for 4 days.