How a newly examined gut microbe drives the gut-lung axis

Amazing stuff!

"Their findings highlight how a little-known member of the gut microbiome reshapes the lung immune environment to have both beneficial and detrimental effects on respiratory health. ...

For their study, the researchers looked at a protozoan called Tritrichomonas musculis, or T. mu, that resides harmlessly in the gut of mice.

They found that mice colonized with T. mu had unexpectedly high levels of specific immune cells in their lungs. Importantly, the researchers showed that some of these immune cells originated from the gut and moved to the lungs, where they fine-tuned the local immune environment and changed outcomes related to respiratory illnesses and infections.

By triggering the production and migration of these immune cells from the gut to the lung, T. mu functions as "a conductor in the intestine that orchestrates the immune system to populate other regions of the body," ...

One of the study's key findings was that T. mu-driven immune changes in the lung worsened airway inflammation caused by allergic asthma but appeared to have a protective effect against respiratory infections. ..."

From the highlights and abstract:

"Highlights

• Tritrichomonas musculis (T.mu) drives trafficking of gut-derived ILC2s to the lung

• T.mu instills an ILC2, B cell, and T cell tripartite network via ICOS-OX40-IL-2

• A T.mu-triggered lung immune network promotes steady-state eosinophilia

• T.mu exacerbates asthma and boosts shielding against Mycobacterium tuberculosis (M.tb)

Summary

The underlying mechanisms used by the intestinal microbiota to shape disease outcomes of the host are poorly understood. Here, we show that the gut commensal protozoan, Tritrichomonas musculis (T.mu), remotely shapes the lung immune landscape to facilitate perivascular shielding of the airways by eosinophils. Lung-specific eosinophilia requires a tripartite immune network between gut-derived inflammatory group 2 innate lymphoid cells and lung-resident T cells and B cells. This network exacerbates the severity of allergic airway inflammation while hindering the systemic dissemination of pulmonary Mycobacterium tuberculosis. The identification of protozoan DNA sequences in the sputum of patients with severe allergic asthma further emphasizes the relevance of commensal protozoa in human disease. Collectively, these findings demonstrate that a commensal protozoan tunes pulmonary immunity via a gut-operated lung immune network, promoting both beneficial and detrimental disease outcomes in response to environmental airway allergens and pulmonary infections."

How a newly examined gut microbe drives the gut-lung axis "A team led by University of Toronto researchers has discovered a new communication pathway between the gut and lung."

U of T study uncovers how a new gut microbe drives the gut-lung axis (original news release)

A gut commensal protozoan determines respiratory disease outcomes by shaping pulmonary immunity

Graphical abstract