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, The right column shows some reporters expressed by immune cells. Fluorescent sensors for calcium signaling can be used to detect productive T cell contacts. An example is the Twitch-2B calcium indicator in which FRET occurs upon calcium-binding to troponin C (TnC

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, Examples of the use of intravital imaging to assess mechanisms of immunosurveillance or the effects of immunotherapies in vivo in mice

, This figure compiles time-lapse images from different studies illustrating mechanisms of intratumoral immune activity identified by intravital two-photon imaging. Images are representative of A) Immunosuppression by regulatory T cells (Tregs) forming transient contacts with antigen-presenting cells (APCs) as visualized by two-photon imaging using a dorsal skin-fold chamber

, B) A crosstalk during anti-PD-1 mAb therapy involves IL-12-producing dendritic cells and IFN-g-producing T cells as visualized by two-photon microscopy using cytokine reporter mice. Arrows highlight IL-12p40-eYFP-expressing cells. TAM, tumor-associated macrophages

, C) In vivo two-photon imaging has been used to track the fate of anti-PD-1 mAb (aPD-1) revealing rapid capture by TAM. Yellow arrows indicate sites of anti