Aggregation of transfected CHO cells.

Cells not transfected (NT) or expressing the Duv^a− or Duv^a+ allelic forms of the GP IIb-IIIa were treated by 10 mM DTT (+DTT) for 20 minutes at room temperature to activate the complex prior to being incubated with 100 μg/mL fibrinogen in the presence of 2 mM calcium with gentle shaking for 20 minutes. Only Duv^a− and Duv^a+ cells aggregated in the presence of fibrinogen when treated by DTT. No significant aggregation was observed for nontreated cells (−DTT) or nontransfected cells treated or not. The specimens were examined with a Leica-Orthoplan fluorescence microscope (Leica, Wetzlar, Germany) using a ×40 oil immersion objective. Microphotographs were taken using Ilford HP5 400 films (ILFORD Imaging, Mobberley, Cheshire, United Kingdom).