Fig. 5: Histological characterization of the PI16⁺ RC-underpinned subepithelial T and B cell niche.

a,b, PI16-positive cells in the subepithelial niche of tonsils from adult patients with OSA or tonsillitis. Cryosections were stained with the indicated antibodies and analyzed by confocal microscopy. c, High-resolution analysis of PI16⁺ cells shows intracellular PI16 signal in FBLN1⁺ reticular cells. Sections were stained with anti-FBLN1 and anti-PI16, and data were acquired by confocal microscopy and reconstructed in 3D. d, Morphology of the FBLN1⁺ subepithelial compartment in adult tonsils. Histological sections were stained with the indicated antibodies, and data were acquired and analyzed by confocal microscopy. The boxed area shows an FBLN1⁺ reticular network around UEA1⁺ endothelial cells at higher magnification on the right. e, High-resolution reconstruction of the adult subepithelial FBLN1⁺ FRC niche occupied by CD3⁺ and CD20⁺ lymphocytes. Sections were stained with the indicated antibodies, and data were acquired by confocal microscopy and reconstructed in 3D. f, Surface contact areas (blue) of FBLN1⁺ cells with CD20⁺ (arrows) and CD3⁺ (arrowheads) cells are shown at higher magnification. Microscopy images are representative for n = 3 adult patients with OSA and n = 3 adult patients with tonsillitis.