How the innate and adaptive host immune system miscommunicate to worsen COVID-19 immunopathology has not been fully elucidated.Here,we perform single-cell deep-immune profiling of bronchoalveolar lavage (BAL) samples from 5 patients with mild and 26 with critical COVID-19 in comparison to BALs from non-COVID-19 pneumonia and normal lung.We use pseudotime inference to build T-cell and monocyte-to-macrophage trajectories and model gene expression changes along them.In mild COVID-19,CD8+ resident-memory (TRM) and CD4+ T-helper-17 (TH,7) cells undergo active (presumably antigen-driven) expansion towards the end of the trajectory,and are characterized by good effector functions,while in critical COVID-19 they remain more naive.Vice versa,CD4+ T-cells with T-helper-1 characteristics (TH,-like) and CD8+ T-cells expressing exhaustion markers (TEX-like) are enriched halfway their trajectories in mild COVID-19,where they also exhibit good effector functions,while in critical COVID-19 they show evidence of inflammation-associated stress at the end of their trajectories.Monocyte-to-macrophage trajectories show that chronic hyperinflammatory monocytes are enriched in critical COVID-19,while alveolar macrophages,otherwise characterized by anti-inflammatory and antigen-presenting characteristics,are depleted.In critical COVID-19,monocytes contribute to an ATP-purinergic signaling-inflammasome footprint that could enable COVID-19 associated fibrosis and worsen disease-severity.Finally,viral RNA-tracking reveals infected lung epithelial cells,and a significant proportion of neutrophils and macrophages that are involved in viral clearance.