Microbial signals and lymphotoxin drive TNF-independent death of A20 and ABIN-1 deficient epithelium

ABSTRACT Anti-TNF antibodies are effective for treating patients with inflammatory bowel disease (IBD), but many patients fail to respond to anti-TNF therapy, highlighting the importance of TNF-independent disease. We previously demonstrated that acute deletion of two IBD susceptibility genes, A20 ( Tnfaip3 ) and Abin-1 ( Tnip1 ), in intestinal epithelial cells (IECs) sensitizes mice to both TNF-dependent and TNF-independent death. Here we show that TNF-independent IEC death after A20 and Abin-1 deletion is rescued by germ-free derivation or deletion of MyD88 , while deletion of Trif provides only partial protection. Combined deletion of Ripk3 and Casp8 , which inhibits both apoptotic and necroptotic death, completely protects against death after acute deletion of A20 and Abin-1 in IECs. A20 and Abin-1 -deficient IECs are sensitized to TNF-independent, TNFR-1-mediated death in response to lymphotoxin alpha (LTα) homotrimers. Blockade of LTα in vivo reduces weight loss and improves survival when combined with partial deletion of MyD88 . These data show that microbial signals, MyD88 , and LTα all contribute to TNF-independent intestinal injury. SUMMARY Here we show that germ-free derivation, MyD88 deletion, combined Ripk3 and Casp8 deletion, or anti-LTα, all reduce TNF-independent intestinal injury after A20 and Abin-1 deletion.