MELBOURNE scientists have discovered new proof that the appendix — the often-removed organ once thought to be redundant — can be crucial to digestive health.

Researchers from the Walter and Eliza Hall Institute have shown how a group of immune cells team up with the appendix to protect the gut during infection.

They work together during bouts of food poisoning and other bacterial illnesses, and also help boost the immune systems of cancer patients.

Lead researcher Professor Gabrielle Belz, a laboratory head from WEHI’s molecular immunology division, said about 70,000 Australians have their appendix removed every year — making it one of the most common surgical procedures.

“Popular belief tells us the appendix is a liability,” Prof Belz said.

“However, we may wish to rethink whether the appendix is irrelevant for our health.”

Prof Belz said surgeons no longer removed the appendix “at the first drop of a hat”, reserving surgery for more serious cases of appendicitis.

The new research, led by Prof Belz and leading French immunologist Prof Eric Vivier, has shown that innate lymphoid cells (ILCs) shield the appendix from harmful bacteria.

This allows the small organ to act as a safe haven for “good” bacteria, which could then “reseed” the intestines and restore the health of the digestive system.

Prof Belz, whose research was published today in Nature Immunology journal, said ILCs offered an added layer of immune protection for healthy people.

But they were vital in fighting bacterial infections in people with compromised immune systems, such as cancer patients, Prof Belz said.

“This is particularly important because ILCs are able to survive in the gut even during (cancer) treatments, which typically wipe out other immune cells,” she said.

Prof Belz said that ability of ILCs to withstand chemotherapy also opened up “new avenues of investigation” for cancer treatment.

Despite the new research, many patients need to have their appendix removed.

They include Millie Bode, 11, who needed emergency surgery at the Royal Children’s Hospital in September after her appendix ruptured.

The grade 5 student spent a week recovering in hospital, but is now back to full health.

EASY TO DIGEST FACTS

• The appendix sits at the junction of the small intestine and large intestine. It’s a thin tube about 10cm long. Normally, the appendix sits in the lower right abdomen. The function of the appendix is unknown.

• Blockage may occur from infection, since the appendix swells in response to any infection in the body. The classic symptoms of appendicitis include dull pain near the navel or the upper abdomen that becomes sharp as it moves to the lower right abdomen.

evonne.madden@news.com.au