Expression of novel transmembrane proteins in human platelets. (A-D) Flow cytometric detection of the novel transmembrane proteins was carried out in platelet-rich plasma (i) or in permeabilized platelets (ii). Binding of individual antibodies to human platelets measured as fluorescence intensity is indicated by solid lines and matched preimmune serum by dotted lines. Expression of each protein in human platelet lysates was analyzed by Western blot. Molecular weight markers are indicated on each blot in kilodaltons. Bands of 67, 27, 85, and 40/43 kDa were detected, corresponding to ANTXR2, BAMBI, DCBLD2, and ESAM proteins, respectively. The presence of LRRC32 in platelets using similar detection procedures has already been reported.²