Real-time in vivo analysis of T cell activation in the central nervous system using a genetically encoded calcium indicator

Marsilius Mues et al. have overcome previous obstacles precluding the expression of genetically encoded calcium indicators (GECIs) in immune cells by developing a new fluorescence resonance energy transfer–based GECI for the functional calcium imaging of T cells in vivo. Using two-photon imaging, the group traced the real-time activation of T cells in peripheral lymph nodes after antigen application, as well as in the CNS during experimental autoimmune encephalomyelitis.