Transmission electron micrographs of pulmonary interstitium taken at a magnification of × 3500. (A) Representative electron micrograph of untreated mice. This section shows a small arteriole/venule in the interstitium containing numerous red blood cells and plasma. Neither platelets nor neutrophils were apparent. Occasionally, solitary platelets were seen in other sections. (B) Representative electron micrograph of LPS-treated wild-type mice for 4 hours. This section shows, in addition to red blood cells and plasma, numerous platelets (arrowheads), many of which are adherent to the endothelial surface and to each other. There is no evidence of fibrin thrombus formation, and the platelets are not degranulating.