Two-photon imaging of immune cells in neural tissue.

To develop new therapeutic strategies for many central nervous system (CNS) diseases, it is essential to observe the motility and function of immune cells within neural tissue. Two-photon laser-scanning microscopy is an outstanding technique for imaging these phenomena under in vivo-like conditions. To gain deeper insight into the pathological phenomena that occur during chronic neuroinflammation of the CNS, we use it to view acute murine hippocampal slices cocultured with different subpopulations of immune cells and to view in vivo the brain stem of anesthetized transgenic mice affected by experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. This protocol describes the preparation of cocultures of acute hippocampal slices with antigen-specific T helper 17 (Th17) cells migrating into the parenchyma, and the preparation of anesthetized mice for imaging the brain stem. We also discuss technical aspects of dual-color, two-photon laser-scanning microscopy that is used to image these samples and that allows for greater flexibility in the choice of fluorophores.