The function of TNFSF14 (TNF superfamily member 14, ENSG00000125735) is as follows. Cytokine that binds to TNFRSF3/LTB and TNFRSF14/HVEM and plays major roles in immune system regulation (PubMed:10754304, PubMed:9462508). Upon binding to TNFRSF14/HVEM, delivers costimulatory signals to T cells, leading to T cell proliferation and IFNG production (PubMed:10754304). Binds to the decoy receptor TNFRSF6B thereby disrupts the activation signal initiated by TNFSF14, resulting in reduced T-cell activation (PubMed:25087510). {ECO:0000269|PubMed:10754304, ECO:0000269|PubMed:25087510, ECO:0000269|PubMed:9462508}.