Figure 6. Immunohistochemical detection of CD3. CD3 positive cells are not apparent in the canine glaucomatous retina (left). In contrast, CD3 positive cells can easily be detected in optic nerve sections of a canine patient with optic neuritis (positive control). Note labeled cells in the perivascular space of the optic nerve (arrows). ONL-outer nuclear layer, INL-inner nuclear layer, NFL – nerve fiber layer.