TNF and neoplasm: This was further demonstrated by studies showing that IFN-γ and TNF-α released by activated Vγ9Vδ2+ T cells can induce cyclooxygenase-2 (COX2) expression and prostaglandin E2 (PGE2) release by both macrophages (Figure 2) and tumor cells, and this downregulates the cytotoxic response of γδ T cells (269, 270) and plays a major role in tumor immune escape (271, 272).