Tumor necrosis factor (TNF)-like cytokine 1A (TL1A) is expressed on
antigen presenting cells and provides co-stimulatory signals to activated
lymphocytes that bear its functional receptor, death receptor 3 (DR3). TL1A/DR3
signaling is involved in the pathogenesis of human and experimental inflammatory
bowel disease (IBD). In the present study, we investigated the role of this
cytokine/receptor pair in acute intestinal injury/repair pathways. We
demonstrate that intact DR3 signaling protected mice from acute DSS colitis, as
DR3−/− mice showed more severe mucosal
inflammation and increased mortality. DR3−/− mice
were compromised in their ability to maintain adequate numbers of
CD4+CD25+Foxp3+ T regulatory cells (Tregs)
in response to acute mucosal damage. This defect in immune regulation led to a
non-specific upregulation of effector pro-inflammatory pathways, which was most
prominent for the Th17 immunophenotype. TL1A−/− mice
were similarly more susceptible to DSS colitis, although without mortality and
with delayed kinetics compared to DR3−/− mice, and
also displayed significantly reduced numbers of Tregs. Infection of
DR3−/− mice with Salmonella
typhimurium was associated with defective microbial clearance and
elevated bacterial load. Taken together, our findings indicate a novel
protective role for the TL1A/DR3 axis in the regulation of mucosal homeostasis
during acute intestinal injury/repair, which contrasts with its known pathogenic
function during chronic intestinal inflammation.