Effect of hirudin on laser-induced thrombus formation in wild-type and FcRγ-deficient mice. Severe (A) or moderate (B) laser-induced lesions were generated in the mesenteric arteries of wild-type (i) and FcRγ^–/– (ii) mice treated with vehicle alone or hirudin (10 mg/kg subcutaneously). Traces represent the mean surface area (± SEM) of thrombi developing over 150 seconds (severe injury: (i) WT, n = 12 vessels in 8 mice; WT + Hir, n = 5 vessels in 3 mice; (ii) FcRγ^–/–, n = 12 vessels in 7 mice; FcRγ^–/– + Hir, n = 5 vessels in 4 mice; moderate injury (i) WT, n = 19 vessels in 7 mice; WT + Hir, n = 11 vessels in 4 mice; (ii) FcRγ^–/–, n = 29 vessels in 9 mice; FcRγ^–/– + Hir, n = 7 vessels in 4 mice).