APOE and COVID-19: We also identified alveolar macrophage subsets in our participants with non-COVID-19 associated AHRF that are distinct from other diseases such as BAL Cluster 2, which we refer to as “Intermediate Monocyte-Macrophages.” Intermediate Monocyte-Macrophages were characterized by high expression of genes associated with mature macrophages such as FBP1 and APOE, but also low expression of other genes that are highly expressed in mature macrophages such as FABP4 and IFI278,17.