In Vivo Imaging of Immune Cells in Peyer's Patches.

Peyer's patches (PPs) are secondary lymphoid organs that coordinate the immunoglobulin A (IgA) response against commensal and pathogenic bacteria. In contrast to the immune dynamics in peripheral lymph nodes, the dynamics of immune response in PP have not been extensively characterized in vivo by two-photon microscopy, mainly due to the PP location on the anti-mesenteric side of the small intestine and the associated peristaltic movement.Here, we describe an approach based on a custom-made spring-loaded platform to immobilize PPs and allow for two-photon microscopy imaging in vivo. We also list different strategies based on fluorescent dyes, as well as Cre/Lox and Reporter-based system, that can be used to image specific immune cell populations in distinct areas of PPs.