TL1A

TL1A (TNF-like ligand 1A, TNFSF15, also VEGI) is a TNF family cytokine expressed predominantly by endothelial cells, monocytes, macrophages, dendritic cells and activated T cells, upregulated by inflammatory stimuli. TL1A exists as both a membrane-bound type II protein and a soluble homotrimer, and binds its functional receptor DR3 (TNFRSF25) with high affinity while also engaging the decoy receptor DcR3. Through DR3, TL1A provides co-stimulatory signals that selectively expand effector T cells, Th1, Th17 and Th9 populations, enhance cytokine production and promote T-cell survival; it simultaneously boosts group 2 and 3 innate lymphoid cell responses. TL1A is a central amplifier of mucosal inflammation: it is strongly associated with inflammatory bowel disease (both Crohn's and ulcerative colitis), where genetic variants and increased TL1A levels correlate with disease risk and severity, and it also drives rheumatoid arthritis, psoriasis and asthmatic inflammation. Anti-TL1A antibodies such as PF-06480605 and anti-DR3 strategies have entered clinical trials for IBD and autoimmune disease.