Electron micrographs of dendritic cells and macrophages pulsed with type II collagen (CII). (a,b) Macrophages and (c,d) dendritic cells were incubated in the (a,c) absence and (b,d) presence of 200 μg/ml CII for 30 minutes and analyzed by transmission electron microscopy. The arrows show fibrils of collagen aligned parallel to the plane of the section. Magnification: (a) ×8,900; (b) ×6,610; (c) ×8,900; (d) ×21,000. Bar = 1 μm. Sections through several planes of more than 50 cells were examined for each treatment.