Endothelial denudation and microvilli and microcolony formation due to M. suis infection. A. Aortic vessel of an infected pig with adherent blood cells and fibrin fibers attached to ECs. Scale bar = 20 μm; B. Aortic vessel from an infected pig showing activated ECs (microvilli formation) and detached ECs exposing the subendothelial layer (SEL). Leukocytes are attached to the ECs and the subcellular matrix. Scale bar = 10 μm; C. Vascular wall covered with blood clots. Scale bar = 10 μm; D. Bacterial microcolonies (BMs) attached to the vascular wall. Scale bar = 2 μm; E. M. suis coccoids of less than 100 nm. Scale bar = 2 μm; F. M. suis cells attached to RBCs and interconnected via small fibrils. Scale bar = 2 μm; G. Luminal surface of an aortic vessel from a healthy pig showing a confluent layer of ECs (overview). Scale bar = 40 μm; H. Aortic vessel from a healthy pig showing a confluent layer of ECs. Scale bar = 10 μm. Abbreviations: BM, bacterial microcolony; EC, endothelial cell; Fi, fibrinogen fibers; Leu, leukocytes; MV, microvilli; RBCs, red blood cells; F, small fibrils; SEL, subendothelial layer; and VW, vessel wall.