Tomograms of closed and open CD20 tetramers. Tomograms showing 1 example each of a closed (A and C) and open (B and D) conformation CD20 tetramer on Ramos RA1 cells. In the color-annotated tomograms (A and B), the parts of the tomogram representing the mAbs are shown in blue and the parts representing the CD20 multimers are shown in red. The approximate borders of individual CD20 entities within the tetramers are indicated by black lines. In the rotated views in panels C and D, the center of each CD20 molecule is marked with a red circle. Black lines connect the centers of the CD20 entities of a tetramer.