General organization of the zebrafish GIALT. Representative deconvolved confocal images of adult zebrafish gills acquired from a transversal (A) and oblique longitudinal orientations (B). The section planes are illustrated on a dissected gill arch in (C). Images were acquired from 30 μm whole-body cryosections stained with phalloidin (actin -green) and DAPI (DNA-blue) and where T/NK cells were labeled with anti-ZAP70 antibody (red hot). Both transversally and longitudinally sectioned gills display a distribution of ZAP70 positive cells that is connected to the different morphological territories of the gills, thus revealing the segmentation of the GIALT into five sub-regions (1-5) (ILT, interlamellar region-lamellae-efferent aspect of filaments, interbranchial septum, gill arch, T/NK cell clusters at the base of filaments on each side of the gill arch). (D, E) Schematic representation of (A, B) displaying the 5 sub-regions of the GIALT. (A, B) Images are maximum intensity projections (MIP). Annotations: Aa, Afferent artery; Aaa, Afferent arch artery; Af, Afferent aspect of filaments; Bc, Branchial cavity; Bm, Basement membrane; C, Cartilage; dILT, distal Interbranchial Lymphoid Tissue; Eaa, Efferent arch artery; Ea, Efferent artery; Ef, Efferent aspect of filaments; F, Filament; Ft, Filament top; Ga, Gill arch; Gr, Gill raker; IR, Interlamellar region; La, Lamellae; P, Pharynx; pILT, proximal Interbranchial Lymphoid Tissue; S, Septum; Sm, Smooth muscles; Sw, Septum wall and Vs, Venous sinus. Scale bars: 100 μm (A, B).
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