Beta-glucan calms the immune system in gut disease
Your immune system can learn from an infection and respond faster next time. That sounds helpful. But in chronic gut inflammation, the same mechanism can make the disease worse.
Beta-glucan is a substance found in the cell walls of fungi and grains. It is known as an activator of the innate immune system, the body’s first line of defence. Beta-glucan can trigger what is called trained immunity: a process by which immune cells change durably after exposure and then respond more strongly to subsequent stimuli. This is useful during infections, but potentially harmful when inflammation is chronic.
The study, published in eLife, examined what beta-glucan does in inflammatory bowel disease (IBD). In mice with experimentally induced gut inflammation, beta-glucan did not cause the expected worsening. Instead, it steered a type of white blood cell called a monocyte in a different direction. Monocytes are early immune cells that can transform into various specialised cell types. Beta-glucan changed that transformation in a way that reduced rather than increased inflammation.
Trained immunity: a mechanism with two edges
Trained immunity is the ability of innate immune cells to respond differently after a first stimulus. This is a relatively recent insight: for a long time it was thought that only the adaptive immune system, with its T and B cells, could learn. It is now clear that monocytes and other early immune cells can also develop a form of memory. This memory differs from that of T cells: it lies in how genes are switched on or off, not in the recognition of specific pathogens.
In chronic diseases like IBD, this creates a problem. An activated innate immune system can sustain inflammation even when no infection is present. The fact that beta-glucan in this case steers monocyte development toward a less inflammation-promoting state is unexpected. It suggests that the effects of trained immunity depend more heavily on context than previously thought.
What this could mean
Beta-glucan is already used as a dietary supplement and is part of discussions about immune modulation. This research provides a more concrete mechanistic picture of how it works in gut inflammation. Whether it is safe and useful in people with IBD requires clinical studies. But the finding that trained immunity can also have an anti-inflammatory outcome opens new questions about how the innate immune system can be directed.