What Does the Appendix Do, Anyway?

The appendix protects against recurrent infection by Clostridium difficile (C difficile) and possibly other pathogenic bacteria, according to a study published in the December issue of Clinical Gastroenterology and Hepatology.

Although the human appendix is considered to be expendable, it contains gut-associated lymphoid tissue (GALT), which processes antigen and regulates the humoral immune responses. It could therefore have an unappreciated immunomodulatory role in the gut. The presence or absence of an appendix has been associated with several intestinal disorders, and some researchers think it is an important secondary lymphatic organ that controls inflammatory and anti-inflammatory T-cell responses.

Im et al. investigated whether there was a relationship between the presence of absence of an appendix and risk of recurrent C difficile infection, based on data from 254 patients admitted to the hospital for this infection from 2005 to 2007. Using a multivariate analysis, they found that patients with an appendix were at much lower risk for recurrence of C difficile infection than those without (an adjusted relative risk of 0.40).

C difficile is a spore-forming, anaerobic, and gram-positive bacterium that causes gastrointestinal infection resulting in diarrhea and colitis; infections have been increasing in incidence and the severity over the past 10 years. C difficile is a leading cause of death from nosocomial infection, and recurrence is one of the most challenging aspects of its management—approximately 25% of patients experience recurrence despite initial successful treatment.

How might the appendix protect patients from recurring infections with pathogenic bacteria? Im et al. state that the GALT of the human appendix has a higher density of IgA- and IgG-producing B cells than the colon—these antibodies fight C difficile and other bacterial infections. Furthermore, the appendix contains abundant biofilm—adherent colonies of commensal microbes within the extracellular matrix and mucus lining of the bowel epithelium. The authors propose that the appendix serves as a storage location for commensal flora, which can re-inoculate the intestinal tract if they are overtaken by a pathogen or eliminated by an antibiotic.

In an accompanying editorial, Xi Na and Ciaran Kelly propose that biofilms in the appendix accelerate the repopulation of the colonic lumen with the commesal bacteria. The colon’s immune response to C difficile and its toxins might therefore be impaired by appendectomy, which makes the gut more vulnerable to re-infection by pathogenic bacteria (figure).

Risk factors for Clostridium difficile infection and the protective role of the appendix.

Na and Kelly state that the findings of Im et al. raise important questions about the functions of the appendix, its role as a biofilm reservoir, and as an intestinal immune organ.

Im et al. conclude that surgeons should re-assess the practice of performing incidental appendectomies during abdominal and gynecologic surgeries—these might increase patients’ risk for recurrent pathogenic infections.

More Information of Clostridium Difficile Infection:

Read the article online.
Im GY, Modayil RJ, Lin CT, et al. The appendix may protect against Clostridium difficile recurrence. Clin Gastroenterol and Hepatol 2011; 9:1072–1077.

Read the accompanying editorial.
Na X, Kelly C. The vermiform appendix and recurrent Clostridium difficile infection: a curious connection. Clin Gastroenterol and Hepatol 2011; 9:1018–1019.

About Kristine Novak, PhD, Science Editor

Dr. Kristine Novak is the science editor for Gastroenterology and Clinical Gastroenterology and Hepatology, both published by the American Gastroenterological Association. She has worked as an editor at biomedical research journals and as a science writer for more than 12 years, covering advances in gastroenterology, hepatology, cancer, immunology, biotechnology, molecular genetics, and clinical trials. She has a PhD in cell biology and an interest in all areas of medical research.
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2 Responses to What Does the Appendix Do, Anyway?

  1. There is more information about the possible function of the appendix at http://www.mydiverticulitis.co.uk “The colons little helpers” This idea predated the work at Dukes

  2. You should be a part of a contest for one of the finest sites on the internet.
    I will recommend this blog!

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