Fig. 3: SPACECAT enables tagging of precise regions in live tissue sections.

a–d Various mouse tissue samples were sectioned live, stained with calcein NVOC, and photoactivated in arbitrary regions (within white dashed boundaries). a Small intestine (n = 3 independent fields of view; scale bar = 50 μm), b Lung (n = 3 independent fields of view; scale bar = 50 μm). c, d Representative images of mouse spleen (n = 3 independent fields of view); T cell-rich areas were selected for photo-tagging (within dashed white boundary). Left: TCRβ chain antibody (red, c) or photoactivation illumination (blue, d); left middle: calcein NVOC prior to photoactivation; right middle: calcein NVOC after photoactivation; right: calcein NVOC ΔF/F₀. Scale bar = 50 μm. e, f Flow cytometry of calcein NVOC (x-axis, marker of viability and photoactivation) vs. calcein violet (y-axis, marker of viability) in non-photoactivated (e) and photoactivated (f) splenic slices of T cell-rich areas. g, h Abundance of TCRβ-positive cells among all splenic cells (g) and photoactivated cells (h) from photoactivated splenic slices.