Single-cell RNAseq analysis (10X Genomics Chromium) of residual bronchoalveolar lavage fluids in healthy, fumer and COPD patients

Rationale: Alveolar macrophages (AM) are functionally important innate cells involved in lung homeostasis and immunity. However, it remains unclear whether ontogenically and functionally distinct subpopulations of AM can be found in healthy human airways, and to what extent conditions like smoking or chronic obstructive pulmonary disease (COPD) trigger changes in the AM compartment. Objective: To explore the phenotypical, ontological, transcriptional and functional diversity of human AM isolated from healthy non-smokers, healthy smokers and COPD patients. Methods: We analyzed bronchoalveolar lavage fluid (BALF) cells by flow cytometry, bulk and single-cell(sc) RNA-sequencing (RNA-seq). Main Results: We found that BALF CD206 + macrophage subpopulations could be distinguished based on their level of auto-fluorescence. CD206 + autofluorescent high (AF hi ) AM were identified as classical self-proliferative AM, while autofluorescent low (AF lo ) AM originated from monocytes and were expressing both monocyte- and classical AM-related genes. Of note, monocyte-derived AF lo AM were equally represented in each category of subjects and exhibited a functionally distinct immunoregulatory profile, including the ability to secrete the immunosuppressive cytokine interleukin-10 (IL-10). Finally, we provide evidence that the monocyte-associated marker CCR2 can be used by flow cytometry to distinguish AM according to their origin. Overall design: Analysis of bronchoalveolar lavage fluid (BALF) cells from 3 groups of patients: healthy non-smokers, healthy smokers and COPD patients.