Immunohistological evidence for exosome accumulation in the perilymphatic stroma of inflamed human kidneys. (a and b) Immunofluorescence of the lymphatic vessel marker podoplanin (green) and the exosome markers CD9 (a, red) or CD63 (b, red) in human renal transplant rejections (fluorescence profiles across respective vessels are plotted beneath merged images; x axis: cross-sectional distance; y axis: CD9-, CD63-, or podoplanin-specific mean immunofluorescence intensities). Cell nuclei are stained with DAPI (blue; n = 14). (c) Immunofluorescence of the lymphatic vessel marker podoplanin (green) and the exosome marker CD9 (red) in normal human kidneys (fluorescence profile across respective vessel is plotted beneath merged images; x axis: cross-sectional distance; y axis: C9- or podoplanin-specific mean immunofluorescence intensities). Cell nuclei are stained with DAPI (blue; n = 12). Bars, 10 µm. (d) Ratios of fluorescence diameters of CD9/podoplanin stainings of lymphatic vessels in normal (n = 12) and rejecting transplanted human kidneys (n = 14). Data obtained from at least two lymphatic vessels per patient sample and from six different patients who were pooled for analysis (unpaired two-tailed t test with Welch’s correction). Values represent means ± SEM.