Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn disease, is characterized by an abnormal mucosal immune response to normal gut microflora. Two main hypotheses explain its pathogenesis: one suggests that dysregulation of the mucosal immune system leads to excessive immune responses to gut bacteria, while the other proposes that changes in gut microbiota or epithelial barrier dysfunction trigger immune responses. The authors conclude that IBD involves an abnormal mucosal immune response, with microbial and epithelial factors contributing to this response. IBD is a chronic, relapsing condition that affects the gastrointestinal tract. It is associated with excessive production of cytokines such as IL-12, IL-23, and IFN-γ in Crohn disease, and IL-13 in ulcerative colitis. These cytokines drive inflammation, leading to symptoms like abdominal pain, diarrhea, and rectal bleeding. Treatment options include corticosteroids, immunosuppressants, and newer biologic therapies targeting specific cytokines like TNF-α. However, these treatments have limitations, including reduced efficacy and side effects. Genetic factors, such as mutations in the NOD2 gene, play a significant role in IBD susceptibility. NOD2 is involved in recognizing bacterial components like muramyl dipeptide (MDP), and mutations in NOD2 can lead to impaired immune responses, increasing the risk of Crohn disease. Studies in mouse models have shown that NOD2 deficiency can lead to increased inflammation when exposed to specific antigens, highlighting the role of immune defects in IBD. Additionally, abnormalities in the gut microbiota and epithelial barrier function may contribute to IBD. Defects in epithelial barrier function, such as reduced production of α-defensins, can allow increased bacterial exposure, leading to immune activation. However, the exact mechanisms by which these factors contribute to IBD are still being investigated. In conclusion, IBD is caused by a combination of genetic and environmental factors that lead to an abnormal immune response to gut microflora. Understanding these mechanisms is crucial for developing more effective treatments. Current research focuses on targeting specific immune pathways and restoring immune balance to manage IBD.Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn disease, is characterized by an abnormal mucosal immune response to normal gut microflora. Two main hypotheses explain its pathogenesis: one suggests that dysregulation of the mucosal immune system leads to excessive immune responses to gut bacteria, while the other proposes that changes in gut microbiota or epithelial barrier dysfunction trigger immune responses. The authors conclude that IBD involves an abnormal mucosal immune response, with microbial and epithelial factors contributing to this response. IBD is a chronic, relapsing condition that affects the gastrointestinal tract. It is associated with excessive production of cytokines such as IL-12, IL-23, and IFN-γ in Crohn disease, and IL-13 in ulcerative colitis. These cytokines drive inflammation, leading to symptoms like abdominal pain, diarrhea, and rectal bleeding. Treatment options include corticosteroids, immunosuppressants, and newer biologic therapies targeting specific cytokines like TNF-α. However, these treatments have limitations, including reduced efficacy and side effects. Genetic factors, such as mutations in the NOD2 gene, play a significant role in IBD susceptibility. NOD2 is involved in recognizing bacterial components like muramyl dipeptide (MDP), and mutations in NOD2 can lead to impaired immune responses, increasing the risk of Crohn disease. Studies in mouse models have shown that NOD2 deficiency can lead to increased inflammation when exposed to specific antigens, highlighting the role of immune defects in IBD. Additionally, abnormalities in the gut microbiota and epithelial barrier function may contribute to IBD. Defects in epithelial barrier function, such as reduced production of α-defensins, can allow increased bacterial exposure, leading to immune activation. However, the exact mechanisms by which these factors contribute to IBD are still being investigated. In conclusion, IBD is caused by a combination of genetic and environmental factors that lead to an abnormal immune response to gut microflora. Understanding these mechanisms is crucial for developing more effective treatments. Current research focuses on targeting specific immune pathways and restoring immune balance to manage IBD.