Appendix - a secondary immune organ

Appendix is a small finger-like structure located on the lower right side of the abdomen which is attached to cecum. Appendicitis is a condition which occurs when appendix becomes inflamed and filled with pus. If left untreated, appendix can burst and cause serious health problems. For this reason, appendix is often removed surgically even if it does not seem to cause any problems.

In 1961 during an expedition to the Antarctic, one of the crew members developed appendicitis. Ironically he was also the only person of the crew capable of performing otherwise routine operation of removing the inflamed organ. He successfully performed an operation on himself, but since that time, prophylactic appendectomy has become standard procedure for people who might stay in isolated areas without medical assistance.

Since appendicitis can cause a lot of trouble if not treated swiftly, it became a standard procedure to remove appendix during another surgical procedure on lower abdomen (Incidental appendectomy). This makes sense as 7% of people develop acute appendicitis during their lifetime. But why do we even have in the first place? Why not just remove it when the child is born?

Herbivorous animals have long cecum and use it to digest fibrous vegetation and even break down cellulose. This is an important adaptation that helps them extract the most nutrients possible from their diet. For example, the cecum of a horse can be up to six feet long, while a cow's is typically four feet. Since appendix is attached to cecum, it is also part of the enlarged digestive organ. It has been suggested that we lost our need to digest cellulose when we started cooking our food.

Although appendix is no longer used by humans for digestive purposes it still contains a high concentration of lymphoid tissue. Lymphoid tissue is essential for the immune system and may help encourage the growth of some types of beneficial gut flora. So, although appendix may not have a clear purpose anymore, it still has an important function in our immune system.

There is also a safe-house theory which suggests that appendix might serve as a safe house for beneficial bacteria. The theory suggests that the cells of the immune system of the appendix can protect the good bacteria, since there are more of them in the appendix and their number decreases moving away from it. The use of antibiotics as well as diseases that cause severe diarrhea can rid the body of all the bacteria. The good bacteria that preserved in the appendix will then repopulate the bowel.

Given recent research into the function of the appendix, removing it as a preventive measure may not seem like a good idea, but we still have to consider the likelihood of acute appendicitis and the mortality rate if not treated promptly. Regarding its function as a haven for good bacteria, while the theory is plausible, it doesn't seem to matter in today's society. Since 1735, when the first successful appendectomy was performed, until now, no negative effects of this procedure on the immune system have been recorded.