Since the exact role of IL12B for IBD susceptibility in the German population and IBD phenotype behaviour remains unclear, we aimed to perform a detailed genotype-phenotype analysis in a large IBD cohort and an analysis for potential epistatic interactions with other gene variants involved in IL-12 and IL-23 signaling and implicated in IBD susceptibility such as IL23R and STAT4[3], [40] which encodes the major IL-12-induced downstream transcription factor STAT4. The gene discussed is IL23R; the disease is inflammatory bowel disease.