Interaction of CTL with neurons in vivo. A, Representative image of the cranial window (on the left) and two-photon microscopy image of the intact (1), penumbral (2), and infarcted (3) brain area (on the right) of YFP-16 mice expressing YFP in motor and sensory neurons. B, A CMPTX-labeled CTL (red) can be seen in a nonlabeled blood vessel in close proximity to the YFP-16 mouse brain parenchyma 3 d after stroke. Scale bar, 10 μm. C, CMTPX-labeled CD8+ T cells (red) were found in the brain parenchyma 6 d after stroke. Neurons (YFP, yellow) and blood vessels (FITC, miscolored in turquoise) can be seen. Scale bar, 10 μm. D, CMTPX-labeled CD8+ T cells (red, arrow) were in close proximity to neurons (yellow, dashed line) at 5 d after MCAO. These neurons were no longer detectable by YFP signal on day 7. Scale bars, 10 μm.