Immunological profile of lung tissue of patients with hypersensitivity pneumonitis

<bold>Background:</bold> Hypersensitivity pneumonitis (HP) is an interstitial lung disease characterized by bronchoalveolar inflammation after the inhalation of allergenic compounds in genetically predisposed individuals. The aim of this study was to determine the role of the innate and adaptive immune responses that lead to pulmonary fibrosis in patients with advanced HP. <bold>Methods:</bold> Cross-sectional study conducted in 19 patients diagnosed with fibrotic HP and 10 patients diagnosed with idiopathic pulmonary fibrosis (IPF) who underwent lung transplantation. Healthy donors (n = 8) were included as a control group. Cytokines with a Th1, Th2 and Th17 profile and other cytokines were determined in lung tissue homogenate supernatant samples. <bold>Results:</bold> Fibrotic HP and IPF patients had higher levels of GM-CSF, IL-7, IL-13 and IL-23 than healthy controls. Fifty per cent of patients with fibrotic HP had a more pronounced Th2 profile, with higher levels of IL-5 and IL-6. Th2-high profile HP patients had also increased levels of IL-1β, IL-8, G-CSF and MCP-1 than HP patients with a Th2-low profile. Causal agents of Th2-high profile patients were found to be mainly avian, while in Th2-low profile patients only one case was due to avian exposure. <bold>Conclusions:</bold> The results suggest that there are two phenotypes of the disease (Th2-high and Th2-low profiles). Exposure to birds appears to be the main cause of a Th2-high cytokine profile. The immunological response in Th2-high profile patients seems to indicate a more pronounced activation of the adaptive immune response with high production of cytokines involved in the recruitment of granulocytes. Funded by Instituto de Salud Carlos III (PI18/00345), CIBERES, FEDER and FUCAP.