Scientifically Speaking | Your appendix might not be useless
In recent years, studies have shown that the appendix might be a storehouse for good bacteria. And it isn’t the only part of the body that is undergoing a radical rethink in recent years.
In school, we came across the word “vestigial” describing the appendix, implying that it is useless. The appendix is a small organ attached to the colon. Most people are oblivious that they have one, unless it becomes inflamed, in which case, it requires surgical removal. Because the appendix can be removed without no detectable deterioration in health, for most of medical history, it’s been assumed that the appendix is an organ past its evolutionary expiry date.
The appendix is a small organ attached to the colon. Most people are oblivious that they have one, unless it becomes inflamed, in which case, it requires surgical removal. (HT Illustration: Shrikrishna Patkar)
But in 2015 in a research article published in Nature Immunology, Gabrielle Belz at Walter and Eliza Hall Institute in Melbourne, Australia, and her colleagues reported that the appendix might be a storehouse for good bacteria. These bacteria normally inhabit the gut, and they help to prevent infections. The team showed that a class of white blood cells in the appendix have a role in the immune response of the body.
Later, Heather Smith at Midwestern University in Arizona and her team found that the appendix evolved independently over 30 times in different animals. And once the appendix had shown up, it rarely disappeared in an animal lineage, suggesting that it served a biological purpose. This observation lends credence to the notion that some animals have an appendix for a good reason. Smith looked at animals that have an appendix and also found that they have a high concentration of immune tissues in that part of the body. While correlation certainly isn’t causation, taken with the other data, the evidence that the appendix has a function as a storehouse of good microbes.
The appendix isn’t the only part of the body that is undergoing a radical rethink in recent years. The study of good microbes in the body has led to a new understanding of what it means to be human.
When we think of microbes, we think of harmful disease-causing organisms. But we also have microbes on our skin, in our mouth, and in our gut, without which we could not live. These microbes colonise our bodies shortly after we are born and together with their genetic material are called the microbiome.
Picture yourself. What you imagine are features of your body made of human cells. But what you do not see, and what children do not read about in school yet, is that there is an essential, invisible part of the body called the microbiome. And the microbiome is no less integral to the body than organs or tissues. In fact, the microbiome influences health from birth until death.
The microbes that make up the microbiome are tiny, but they outnumber human cells. That’s right. A human body is made up of around 30 trillion human cells and anywhere from 40-100 trillion microbial cells. There are more microbial cells than human cells inside us!
The microbiome in the mouth is different from the microbiome in the gut, even though they are both parts of the same digestive system. The organisms that occupy each microbiome are different in the same way that the ecosystem in the Andamans can be thought of as different from that of the Eastern Himalayas.
The first paradigm in clinical microbiology was to treat microbes as the enemy, and this thought process served us well. By using antibiotics, better sanitation and hygiene, and routine vaccinations average lifespan has increased around the world.
But nearly 20 years ago, a remarkable review article in the New England Journal of Medicine highlighted an unintended but likely fallout from the war on microbes. As the incidence of infectious diseases fell worldwide, there was a rise in immune disorders such as asthma, multiple sclerosis, and Crohn’s disease. Were these the effects of neglecting our good germs?
Multiple lines of evidence have since strengthened this unknown association between microbes and health. The current paradigm is to treat microbes not only as disease-causing pathogens. Some microbes are also beneficial. We’ve since discovered that these microbes help the normal function of the immune system. They also act as tiny factories that break down food that we can’t digest ourselves.
The gut microbiome also prevents metabolic disorders, protects the heart and cardiovascular system, and helps to regulate mood and brain function. Some microbes even prevent other microbes from infecting us and making us sick.
We have probably not heard the last word about what the appendix does inside the human body. But coupled with our recent understanding of the microbiome, it certainly makes sense for the appendix to be able to serve as a way for the body to reboot the gut with good germs.
Anirban Mahapatra, a scientist by training, is the author of COVID-19: Separating Fact from Fiction
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