PIRB partially mediates ANGPTL2 elicited inhibition of CRP-induced activation of mouse platelets. (A) Aggregation of washed WT and PIRB-TM platelets in response to 0.25 μg/mL CRP with 0.1, 0.5, or 1 μg/mL ANGPTL2, respectively. (B) The tyrosine phosphorylation time courses of LAT, SLP76, and PLCγ2 in washed WT and PIRB-TM platelets preincubated with 0.5 μg/mL ANGPTL2 in the absence or presence of 0.25 μg/mL CRP. (C) Time course phosphorylation of Shp1 Y564 and Shp2 Y580 in washed WT and PIRB-TM platelets preincubated with 0.5 μg/mL ANGPTL2 in the absence or presence of 0.25 μg/mL CRP. GAPDH was used to verify equal loading. (D) The effects of PerCP-conjugated rat anti-mouse PIRB monoclonal antibody on Alexa 488-conjugated Flag-ANGPTL2 binding to WT mouse platelets. Rat IgG was used as a negative control. (E) A diagram of a plausible explanation for the inhibitory effects of PIRB/ANGPTL2 on platelet activation.