Flow cytometry analyses of unstimulated and calcium ionophore–treated platelets from control and affected dogs labeled to detect platelet membrane GPIIIa.
Dot plots depict platelet suspensions from a healthy dog (control) and an affected GSD labeled with CD61-FITC, a fluorescein-conjugated monoclonal antibody directed against the β3 subunit of GPIIb/IIIa. Unstimulated platelet suspensions (A,B) and calcium ionophore–treated suspensions (C,D) were stirred in a buffer containing 2 mM CaCl2 in the absence or presence of 3 μM A23187. Control and GSD platelets demonstrate high-intensity labeling; however, only control platelets developed a marked decrease in forward scatter in response to ionophore treatment. Arrows indicate increasing forward light scatter intensity and increasing green fluourescence intensity. Data were collected without gating. The horizontal quadrant marker is set at the lower boundary of forward scatter for unstimulated platelets, and the vertical marker is set at the upper boundary of fluorescence for 95% of the isotype control–labeled particles (indicating nonspecific fluorescence). Particles in the lower left quadrant of each plot represent debris and machine noise. These plots correspond to a single analysis, representative of results obtained from ionophore treatment of all 5 affected GSDs.
