Extended Data Fig. 1. B cells in the thymus.

(a) Gating strategy of Thy1-depleted wild-type thymus for FACS-sorting of thymic epithelial cells (TECs, live CD45^–EpCAM⁺), thymic B cells (live CD45⁺EpCAM^–CD19⁺), and thymic dendritic cells (live CD45⁺EpCAM^–CD19^–CD11c⁺MHC-II^high). (b) Representative EpCAM immunostaining in wild-type thymus samples (n = 3 independent experiments, scale bar left 500 µm and right 50 µm). (c) CD19⁺ B cells (red) in relation to EpCAM-expressing cells (white) in wild-type (leftmost columns) and Aqp4^–/– thymus (right column). Middle row: EpCAM-expressing areas (red outlines) and CD19⁺ B cells (white outlines) are detected in DAPI-stained (blue) wild-type (left columns) and Aqp4^–/– thymi (right column). Bottom row: The density of B cells is depicted as a 5-colour heatmap within a radius of 50 μm around CD19⁺ cells and overlayed on the area of EpCAM-expressing cells. n = 2 independent experiments.