Reactions of mAb 314.1 with CHO cells expressing mixed (human/rat) GPIIb/IIIa integrins. In the presence of quinine (solid histograms) mAb 314.1 reacted with cells expressing human GPIIb paired with either human (H/H) or rat (H/R) GPIIIa but failed to react with cells expressing rat GPIIb paired with either human (R/H) or rat (R/R) GPIIIa. No reactions were obtained in the absence of quinine (dashed histograms). Essentially identical reactions were obtained with mAb 314.3 (not shown).