Binding of rifampicin-dependent antibodies to platelets and CHO βIX cells.

The platelets or CHO αβIX cells were labeled with primary antibody (patient serum or AB serum) in the presence or absence of rifampicin, followed by an FITC-conjugated secondary antibody (rabbit anti-human IgG), and examined by flow cytometry. The AB serum did not bind to the platelets in the presence or absence of the drug (A). A similar result was observed when the CHO αβIX cells were labeled with AB serum in the presence or absence of rifampicin (not shown). The patient serum bound to the platelets (B) and the CHO αβIX cells (C) in the presence of the drug. The shaded peak in each graph represents the binding of the serum in the absence of the drug. Pt indicates patient.