If you’ve ever had a foodborne illness, you know how awful it is. It’s hard to even stomach a conversation about it, let alone think about the food that made you sick. But believe it or not, there’s a bright side: Your gut is smart, and it won’t let you suffer the same damage twice.
Research recently published in Cell suggests that the intestine actually “learns” from illnesses caused by pathogens such as viruses, bacteria, or parasites (known as “enteric diseases”). How? According to the study, the immune system doesn’t kill new pathogens that enter your system. Instead, it protects neurons in the gut, so they don’t die in the presence of a new infection.
If that seems a little backwards to you, you’re not alone. The researchers noted that this theory goes against what a lot of us learned in biology about immunity. However, the study helps us better understand how the gut functions, and may help explain why some people develop serious conditions like irritable bowel syndrome (IBS).
Your Second Brain
By now, you’ve probably heard that the gut is your “second brain.” The network of neurons in your gastrointestinal tract – from the lower part of your esophagus to your rectum – is known as the enteric nervous system (ENS). The ENS controls your digestive tract, processing a range of sensations, collecting information, and controlling the movement of nutrients, waste, fluid, and blood flow.
What fascinates many scientists is that the ENS doesn’t need much input from the brain; it controls the digestive tract by itself. In fact, it is the largest collection of neurons and glia outside of the brain. (Glia are non-neuronal cells that support neuron function and help transport nutrients and waste.)
Given how much the ENS does, it makes sense that the neurons in the gastrointestinal tract are vital to the functioning of your body. They may be so important, in fact, that the immune system protects them in the wake of a new pathogen, rather than simply attacking the pathogen.
Understanding the Study
Based on their previous work and other studies, the researchers knew that specialized immune system cells, known as macrophages, protect the health of neurons in the digestive system. Specifically, neurons in the gut can die in response to stress. To prevent this, macrophages produce unique molecules that protect those neurons from dying.
However, the researchers didn’t yet know whether macrophages could protect gut neurons from dying in response to an infection. To test out the idea, they infected mice with a non-lethal strain of salmonella. The mice got rid of the infection in about a week, but lost a number of neurons in the digestive tract. The research team then infected those same mice with a similar foodborne illness. Again, the mice cleared the infection, but this time, they didn’t lose any neurons.
How did the immune systems in the mice learn to protect the ENS? The researchers said that during the first infection, the neurons in the digestive tract sent signals to macrophages, effectively asking for help. Those macrophages then gathered around vulnerable neurons to protect them from future attacks. By the next infection, the neurons were well protected.
The Lasting Impact of Neuronal Loss in the Gut
The body’s effort to protect the ENS tells us just how important these neurons are to our overall health. Neuronal loss in the gastrointestinal tract is linked to a number of health issues. For instance, the researchers note that animals can eat more calories without gaining weight after losing neurons in the gut. This might sound like a positive thing, but it implies that the body is struggling to absorb important nutrients and energy to survive.
In addition, previous research suggests that IBS is linked to neuron loss and damage in the gut. If scientists learn how to protect gut neurons in IBS patients, they may be able to find an effective treatment for IBS.
Whether you have IBS or not, it’s good to know that your immune system is working to keep your digestive tract in good health after a foodborne illness! And of course, getting an infection is still never a good thing. To better protect you and your family from food poisoning, check out these tips.