IL-10 Protein Reduces Pulmonary Fibrosis Risk

For a long time, physicians and scientists believed our lungs were sterile (germ-free). But modern science indicates otherwise. Now we know they contain allergens, bacteria or viruses we inhale, such as influenza or SARS-COV-2, the virus that causes COVID-19. When those contaminants combine with inflammation, it can lead to chronic lung disease.

UIC researchers have discovered that a small protein called IL-10 is critical for preventing lung inflammation and associated diseases like pulmonary fibrosis and bronchiolitis. Their work appears in the journal Immunity.

Every human body has a microbiome: a community of tiny living organisms like bacteria that help our bodies digest (in the gut), secrete moisture (in our skin), and carry out other functions. These microorganisms are in constant communication with our immune systems to maintain balance.

"Our immune system needs to be strong enough to fight off threats without triggering excessive inflammation or over-the-top immune responses," said the study's lead author, Kiwook Kim, an assistant professor of pharmacology and regenerative medicine at the UIC College of Medicine.

Previous research has shown that interstitial macrophages, white blood cells nestled in our lung tissue, help keep lungs healthy by clearing out dead cells and unwanted microorganisms. Kim said they're also vital for resolving respiratory diseases, but researchers aren't entirely sure how.

Kim and his colleagues found that interstitial macrophages produce an interleukin-10, or the IL-10 protein receptor, which sends anti-inflammatory signals to immune cells. In mouse models without IL-10 signaling, the researchers observed spontaneous lung inflammation.

When IL-10 signaling was absent, the researchers noticed two bacteria initiating lung inflammation: Delftia acidovorans and Rhodoccus erthropolis.

"It's the perfect storm," said Teruyuki Sano, a co-author and assistant professor of microbiology and immunology in the College of Medicine. "When the bacteria are present and IL-10 signaling is absent, inflammation and resulting diseases are more likely to occur."

The researchers said understanding these micro-operations inside the lung is crucial for catching and treating pulmonary diseases, like pulmonary fibrosis, follicular bronchiolitis and COPD.