Increased inflammation in the pulmonary arteries in fatal asthma

MedWire News: A post-mortem study of individuals who died of asthma has shown increased inflammation in the periarterial region of the small pulmonary arteries.

The study revealed the presence of mast cells, eosinophils, and neutrophils, but not lymphocytes, in the adventitial layer of the pulmonary artery.

Discussing the existing data in the Journal of Clinical and Experimental Allergy, Thais Mauad (Sao Paulo University Medical School, Brazil) and colleagues note that in human asthma, much of the knowledge on vascular changes is based on analyses of vessels involved in bronchial circulation.

The pulmonary arteries are not sampled in bronchial biopsies, and as a result less in known about their changes in human asthma.

In this study of 22 individuals who died of asthma, the researchers quantified the different inflammatory cell types in the periarterial region of small pulmonary arteries using immunohistochemistry and image analysis.

Compared with healthy controls, there was a statistically significant increase in mast cells, eosinophils, and neutrophils in the periarterial space among those who died of asthma. For example, the cell density of mast cells was 271.8 cells/mm² among those who died of asthma compared with 177.0 cells/mm² in healthy controls.

Among the different mast cells, chymase/tryptase-positive mast cells were more common that tryptase mast cells in the perivascular arterial space in both asthma patients and controls.

"This information is of relevance because airway chymase-positive mast cells have been associated with angiogenesis and are thought to play a protective role with respect to hyperresponsiveness in asthma," report the researchers.

There were no significant differences among controls or fatal-asthma patients regarding B and T lymphocytes, findings that are in line with other studies.

"Our results contribute to the understanding of distal lung alterations in severe and fatal asthma, reinforcing the role of these major effector cells at this lung level," conclude Mauad and colleagues.

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