GPVI down-regulation through ectodomain shedding. Wild-type (•) or FcRγ^−/− (○) mice received 20 μg biotinylated JAQ1 intravenously and (A) platelet counts were determined. (B) Surface-bound JAQ1 was detected by flow cytometric measurement of streptavidin^FITC binding after 10 minutes (black line) and 30 minutes (dotted line). The shaded area represents maximal binding (t = 0 minutes) as determined after in vitro incubation of platelets with 20 μg/mL JAQ1^biotin followed by streptavidin^FITC. (C) Detection of sGPVI/JAQ1^biotin complex in plasma of wild-type (•) or FcRγ^−/− (○) mice at the indicated time points after antibody injection. (D) Western blot analysis of platelets at the indicated time points. (A,C) Results are expressed as the mean platelet count ± SD for groups of 6 mice each. (B,D) The results are representative of 3 individual experiments.