Macrophage subsets in lung tissue of healthy controls and asthma patients

Macrophages are abundantly present in the airways of asthmatics and they can respond to allergens with different states of activation at the cost of the anti-inflammatory state. These states have not been quantified in lung tissue of asthmatics versus healthy controls yet, and it is unknown how they relate to disease severity and treatment responses. We quantified activated and anti-inflammatory macrophages in asthma patients and healthy controls and studied associations with lung function, sex and corticosteroid use. 138 bronchial biopsies from clinically well-characterized asthma patients and 50 matched healthy controls were stained for activated macrophages defined by IRF5+CD68+ or CD206+CD68+ and anti-inflammatory macrophages defined by IL-10+CD68+. Double positive cells were counted and expressed as positive cells per millimeter basement membrane. Higher numbers of IRF5+ and CD206+ macrophages were found in biopsies of asthma patients compared to healthy individuals, with males having more IRF5+ and females more CD206+ macrophages. Asthma patients had lower numbers of IL-10+ macrophages than healthy individuals, with more IL10+ macrophages in corticosteroid users than in non-users. Higher numbers of IRF5+ macrophages are associated with more severe airflow obstruction as reflected by lower FEV1 and FEV1/FVC values, while the number of IL-10+ macrophages correlated positively with FEV1/FVC ratio (Pearson r=0.18, p This study suggests that macrophages are important in asthma. Their activation state can be linked with disease severity, sex and corticosteroid treatment. Especially increasing the number of anti-inflammatory macrophages by therapeutic intervention may be a novel way of treating asthma.