CARD9 and inflammatory bowel disease: In this study, Card9 variant rs4077515 known to create substitution S12N was established as a risk factor in the development of ileal CD, which initiated an innate immune response to peptidoglycan, a bacterial cell wall macromolecule.6 In 2018, another variant Card9 rs10781499 was confirmed to be a high IBD genetic risk factor, which altered the composition of the gut microbiota in patients with IBD.7