The cellular composition of lung infiltrates in patients with COVID-19 pneumonia changes with the progression of disease. Infiltrates in patients with moderate pneumonia include mainly lymphoid and dendritic cells; whereas, severe forms of disease are characterised by massive infiltration of macrophages and neutrophils.15 In patients with COVID-19, expression of T-cell chemoattractants (eg, CXCL9, CXCL10) and their receptors (eg, CXCR3) precedes expression of monocyte and neutrophil chemoattractants (eg, CCL2, CCL3, CCL4, CCL7, CXCL8) and their corresponding receptors (eg, CCR1, CXCR2).15 The composition and phenotypes of lung macrophages also change with disease severity. Resident alveolar (A-FABP4+) macrophages, which show scavenger and lipid metabolic functions typical of anti-inflammatory or resolving M2-like cells (eg, macrophage receptor MARCO, PPAR-γ, Apo-CI), predominate in mild and moderate forms, whereas CD14+ monocyte-derived macrophages (FCN1high) and chemoattractant (FCN1lowSPP-1+) macrophages, which show highly inflammatory M1-like profiles (eg, nuclear factor-kappa B [NF-κB], CCL2, CCL3), dominate tissue specimens from patients with severe forms of COVID-19 and who are critically ill.15