American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the purpose of the integrin-blocking antibody vedolizumab in ulcerative colitis treatment?

1. Induces remission

2. Blocks leukocyte trafficking

3. Enhances glucocorticoid action

4. Reduces symptoms

The correct answer is: Blocks leukocyte trafficking

Vedolizumab is an integrin-blocking antibody that is specifically designed to interfere with the process of leukocyte trafficking. In the context of ulcerative colitis, an inflammatory bowel disease, exaggerated immune responses cause inflammation in the gastrointestinal tract. The pathology involves the migration of leukocytes (white blood cells) to the gut, where they contribute to inflammation and tissue injury. Vedolizumab targets the α4β7 integrin, which is crucial for the adhesion and migration of lymphocytes into gastrointestinal tissues. By blocking this integrin, vedolizumab prevents leukocytes from entering the inflamed bowel, thereby reducing the inflammatory response. This mechanism helps control the disease's flare-ups and promotes healing by limiting the influx of these immune cells to the site of inflammation. While vedolizumab can lead to remission and alleviate symptoms as a secondary effect of reducing inflammation, its primary mechanism of action is the inhibition of leukocyte trafficking, which addresses the underlying pathological process in ulcerative colitis. Thus, the primary purpose of vedolizumab is to block the migration of leukocytes to the gut, which is essential for managing the inflammation characteristic of ulcerative colitis.