CCL2 and neoplasm: In addition, high levels of ROS and peroxynitrite has been shown to be associated with T-cell deactivation by downregulating the TCR ζ-chain expression and chemically modifying the TCR through nitrosylation, and by excluding T-cell infiltration by nitration of CCL2 (N-CCL2), which has been found to trap T lymphocytes in the stroma that surrounds the tumour and prevent their infiltration into the tumour core [180].