IFNG and neoplasm: Upon encountering their cognate antigen either expressed on MHC class-II-positive tumour cells or on infiltrating APCs, Th1 CD4s release cytokines such as IL-2 that maintain the function and viability of CD8+ T cells and interferon gamma (IFNγ) and tumour necrosis factor alpha (TNFα) which can directly induce apoptosis of target cells and upregulate MHC molecules to enhance T-cell killing.