Interleukin (IL)-4, IL-13, and IL-17A differentially affect the profibrotic and proinflammatory functions of fibrocytes from asthmatic patients

What is it about?

The authors of this article isolated circulating fibrocytes from patients with allergen-exacerbated asthma, who showed the presence of fibrocytes, together with elevated concentrations of Th2 cell-derived interleukin (IL)-4 and IL-13 and slightly increased concentrations of the Th17 cell-derived IL-17A, in induced sputum. Fibrocytes stimulated with IL-4 and IL-13 produced high levels of collagenous and non-collagenous matrix components and low levels of proinflammatory cytokines. Conversely, fibrocytes stimulated with IL-17A proliferated and released proinflammatory factors that may promote neutrophil recruitment and airway hyperresponsiveness. IL-17A also indirectly increased alpha-smooth muscle actin but not collagen expression in fibrocytes.

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Why is it important?

This study provides the first evidence that IL-4, IL-13, and IL-17A differentially affect the profibrotic and proinflammatory function of fibrocytes isolated from the peripheral blood of patients with allergen-exacerbated asthma. These cells express an asthma-specific profibrotic phenotype when stimulated with IL-4 and IL-13, while they proliferate and acquire a proinflammatory phenotype, which may facilitates neutrophil recruitment and airway hyperresponsiveness, on stimulation with IL-17A. Study findings suggest that fibrocytes may be involved in the development of subepithelial fibrosis and contribute to determine the pattern of infiltrating leukocytes to various extents in asthma, depending on the relative concentrations of Th2 cell-derived cytokines and IL-17A present in the microenvironment.