Mucins require P-selectin on platelets but not on endothelial cells to generate microthrombi in vivo. Transplantation of bone marrow into lethally irradiated mice was used to generate mice lacking P-selectin in platelets or in endothelial cells. (A) Representative images of lung sections prepared 5 minutes after intravenous injection of mucins or saline. (B) Quantification of CD41-positive pixels in lung sections. The data represent the mean ± SEM, n = 5-6 for each group. *P < .001.