Fig. 4. Microvasculature changes in lungs from patients with severe COVID-19.

Haematoxylin and eosin (H&E) staining and immunostaining images showing microvasculature changes in patients with severe coronavirus disease 2019 (COVID-19). a | Arteriole filled with neutrophils that are in part adherent to the endothelium. b,c | Pulmonary microvessels (either arterioles or venules) displaying perivascular lymphocytic infiltrate. d | Immunostaining with anti-CD3 showing the vessel displayed in part c. e | Anti-CD4 staining on a serial section of the same vessel. f | Anti-CD8 staining on another serial section of the same vessel. g | Lymphocytic endothelialitis or venulitis with transmural infiltrate involving the intima; note the immediate vicinity of lymphocytes (dark blue, round nuclei) and endothelial cells (arrows). This inflammatory pattern is not frequently encountered and seems also to involve post-capillary vessels, as shown. h | Elastic-type artery (>500 μm in diameter) containing a wall-adherent, organized thrombotic lesion with endothelium-lined, cushion-like intimal fibrosis protruding into the vascular lumen.