TNF and neoplasm: Conversely, IFN-γ and TNF-α secreted by activated Vγ9Vδ2 T cells can induce cyclooxygenase-2 (COX2) expression and prostaglandin E2 release in macrophages, which, in turn, downregulate the cytotoxic activity of γδ T cells and facilitate tumor immune evasion (52, 53).