Evaluation of CD163 expression on alveolar macrophages from BAL of patients with Fibrotic Lung Diseases

Abstract

The role of pulmonary macrophages in the pathogenesis of Idiopathic Pulmonary Fibrosis (IPF) remains poorly understood. CD163 a scavenger receptor expressed on monocyte/macrophage cells, increases during resolution of inflammation and has been proposed as a marker of anti-inflammatory (M2) macrophages. It is suggested that the alveolar macrophage population in IPF is complex and adopts a pro-fibrotic phenotype. A recent study performed on lung biopsies demonstrated increased CD163 positive macrophages in ILDs in comparison with controls, and higher CD163 expression in other fibrotic lung diseases compared with IPF.

In this study we analysed fresh BAL cells of patients at the time of diagnosis. Patients with IPF (n=33) and other ILDs (n=17), as well as control subjects (n=12) were included. Patients’ characteristics were analysed, including pulmonary function tests and smoking history. CD163 expression was analysed in alveolar macrophages identified as FSC^highSSC^highCD45⁺CD11c⁺ cells by flow cytometry. Furthermore, we analysed the correlation between CD163 percentage and pulmonary function (FVC, DLco) at the time of diagnosis as well as during follow-up period.

CD163 positive macrophages were significantly higher in IPF (62.4±20.4%) relative to controls (40.8±18.3%) while there was no significant difference among fibrotic ILDs. The percentage of CD163 did not show significant correlation with pulmonary function parameters.

Our results showed elevated expression of CD163 on alveolar macrophages in the BAL in fibrotic lung diseases, however the heterogeneity of the alveolar macrophages warrants further evaluation in order to clarify the subtypes and activation of ILD macrophages.