It has been published that removal of the appendix appears to help stave off Ulcerative Colitis but to increase the risk of Crohn's Disease. Here is an interesting concept along those lines:
... some scientists have challenged the idea that the appendix serves no purpose. It's been clear for about a century that the structure contains a particular type of tissue belonging to the lymphatic system. This system carries the white blood cells that help fight infections. Within the last decade, research has shown that this lymphatic tissue encourages the growth of some kinds of beneficial gut bacteria.
... In 2007, Parker and his colleagues suggested that the appendix has an immunological role, acting as a "safe house" for beneficial gut bacteria. These bacteria help train the immune system and can prevent diseases by outcompeting dangerous pathogenic bacteria�but there are times when the dangerous microbes gain the upper hand and overrun the gut. The researchers reasoned that when this happens, the beneficial bacteria could retreat to the safety of the appendix, which remains unaffected. Once the immune system has beaten the infection, the beneficial bacteria emerge from the appendix to quickly recolonize the gut.
The "safe house" idea makes sense, says Indi Trehan, a pediatrician at the Institute for Public Health at Washington University in St. Louis who recently studied the importance of maintaining gut bacteria when treating people with malnutrition. "The appendix has a unique anatomical location that is out of the way," he says. "Bacteria can be kept safe there for repopulation as needed."
ScienceNOW, the daily online news service of the journal Science