Formation of large aggregates is suppressed in platelets from FcR γ-chain–deficient mice.

(A) Platelets from wild-type or FcR γ-chain–deficient mice were challenged with 1 U/mL thrombin (i), 10 ng/mL convulxin (ii), or 6 μg/mL botrocetin (iii), respectively. In the case of thrombin, washed platelets were used instead of platelet-rich plasma (PRP). The aggregation was evaluated for 5 minutes by the light transmission method. The arrows show the time points for the addition of the reagents. (B) PRPs from wild-type (■) or FcR γ-chain–deficient mice (▴) were stimulated with increasing amounts of botrocetin for 5 minutes. The maximal light transmission of platelet aggregation induced by 12 μg/mL was set as 100%. The ordinate represents the percentage maximal magnitude of platelet aggregation induced by various concentrations of botrocetin. The data are expressed as means ± SEM (n = 3). (C) The formation of small and large aggregates was assessed by a light-scattering method, as described in “Materials and methods.” ■, platelet aggregate formation from wild-type mice (n = 7); ▪, FcR γ-chain–deficient mice (n = 5). The data are expressed as means ± SEM. NS indicates not significant; SA, small aggregates; LA, large aggregates.