Which of the following conditions involves an abnormal immune response leading to inflammation of the intestine?

Crohn's disease is characterized by an abnormal immune response that leads to chronic inflammation of the gastrointestinal tract, which can affect any part from the mouth to the anus but most commonly impacts the ileum and the beginning of the large intestine. This inflammation can cause a variety of symptoms including abdominal pain, diarrhea, weight loss, and fatigue, and it may also lead to more serious complications such as strictures, fistulas, and nutritional deficiencies.

In contrast, appendicitis involves inflammation of the appendix due to obstruction and is not primarily an immune response. Celiac disease is also an immune condition but specifically involves an adverse reaction to gluten, leading to damage in the small intestine rather than generalized inflammation throughout the gastrointestinal tract. Gastroenteritis, while it causes inflammation, is typically due to infections (viral or bacterial) rather than an autoimmune condition. Therefore, Crohn's disease stands out as the condition that specifically involves an abnormal immune response leading to inflammation of the intestine.