F_cγR chain-dependent collagen-induced pulmonary embolism. (A) The number of thrombi in the lungs of F_cγR^+/+ or F_cγR^-/- mice at the time of sacrifice 3 minutes after injection of 25 μg collagen was determined. Data are presented as mean ± SEM. (B) The absolute decrement in the platelet count from baseline of F_cγR^+/+ or F_cγR^-/- mice one minute after injection of 25 μg collagen was determined.