TLR4 and inflammatory bowel disease: Furthermore, genes that play roles in immunological cell-cell interactions and signaling, such as the tumor necrosis factor receptor 1 (TNFR1) [40], the interleukin-23 receptor (IL23R) [41], and other genes that are involved in immune response to bacteria, such as the toll-like receptor 4 (TLR4) [42,43], have been proposed to be associated with IBD.