More Blood Monocytes May Mean Greater Risk for Lung Abnormalities

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by Margarida Maia PhD |

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The more monocyte immune cells that circulate in a person’s bloodstream, the greater the odds that lung abnormalities, such as those linked to pulmonary fibrosis, will show up on a CT imaging scan, a study found.

Researchers also observed that a higher monocyte count increased the odds of lung abnormalities worsening over time.

The findings shed light on what may cause interstitial lung disease (ILD), an umbrella term for lung disorders marked by inflammation and fibrosis, or scarring. They also offer doctors a potential way to identify people who may be at risk of developing idiopathic pulmonary fibrosis (IPF), or other types of interstitial lung disease.

“Previous studies have shown that certain immune cells, including monocytes, may have a critical role in the development of interstitial lung disease and have largely focused on humans who already have disease,” John S. Kim, MD, an assistant professor in the department of medicine at the University of Virginia and the study’s first author, said in a university press release.

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“We found that higher levels of monocytes in the blood is strongly linked to early signs of injury and scarring on lung imaging among community-dwelling adults,” said Kim, also a specialist in pulmonary and critical care at UVA Health.

The findings were reported in “Associations of monocyte count and other immune cell types with interstitial lung abnormalities,” published in the American Journal of Respiratory and Critical Care Medicine.

When activated, monocytes travel through the bloodstream to sites of inflammation in the body, where they turn into another type of immune cell called macrophages, which can engulf and destroy potentially harmful substances.

“Higher blood monocyte counts are associated with worse survival in adults with clinically diagnosed pulmonary fibrosis,” the researchers wrote.

To better understand the role of monocytes in interstitial lung diseases, the team looked at data from more than 7,000 people who had taken part in four different studies.

These included 484 people from the Multi-Ethnic Study of Atherosclerosis (MESA), 646 from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-points (ECLIPSE), 3,547 from the Age/Gene Environment Susceptibility Study (AGES-Reykjavik), and 2,719 from the Genetic Epidemiology of COPD (COPDGene).

When researchers looked for a relationship between blood monocyte counts and CT scans, they found that having a higher number of monocytes increased the risk of lung abnormalities by 20% among participants in  ECLIPSE and AGES-Reykjavik. Among those who participated in MESA and COPDGene, odds were increased by 30%.

In the MESA study, there was a higher proportion of activated monocytes among people with lung abnormalities than in those without.

Moreover, lung abnormalities were 20% more likely to progress over five years in people from the AGES-Reykjavik study who had a higher monocyte count.

Researchers also found that patients from the MESA and COPDGene studies who had a higher monocyte count were more likely to have reduced forced vital capacity (FVC), an indication of poorer lung function.

“Higher blood monocyte counts were associated with the presence and progression of interstitial lung abnormalities and lower FVC,” the researchers wrote.

“With further research and collaboration with other researchers, we may gain a better understanding of how monocytes contribute to the earlier stages of interstitial lung disease that can lead to future tests and therapies,” Kim said.

“It is our ultimate hope to be able to identify individuals who are at higher risk of developing this condition and intervene quickly with treatments that can prevent this devastating disease,” Kim added.