CD8 cells make TCR:MHCI-dependent interactions with CD11c⁺ donor hematopoietic cells. (A) Experimental design. Irradiated 129 mice were reconstituted with B6 RFP⁺ CD8 cells, unlabeled B6 CD4 cells, and 1:1 mix of CD11c-YFP/β2M^−/− BM and wt B6 BM or CD11c-YFP BM and B6 β2M^−/− BM. (B) Representative images from videos with wt (left column) or β2M^−/− (right column) CD11c-YFP BM. The upper row depicts original videos; the lower row has been rendered to show the YFP⁺ surface (blue) with red spheres fit into CD8 cells (supplemental Videos 3-6). (C) Cumulative interaction times between CD8 cells and the YFP⁺ surface of CD8 cells that ever contact the YFP surface. P = .0001 comparing contacts with wt and β2M^−/− YFP⁺ cells in panel B. (D) Percentage of CD8 cells that ever have contacted the YFP⁺ surface that stayed in continuous contact for at least 30 minutes. P = .0064.