Characterization of the ECM niche in the BM from patients with FL. (A) Soluble matrix protein levels measured in the BM plasma from patients with FL (n = 11) and HDs (n = 12) using Luminex assay. Statistical significance was determined using the Mann-Whitney nonparametric U test. ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. (B) Immunofluorescence on FL BM sections for PAX5 (cyan) and collagen VI (ColVI; green). Nuclei were counterstained with DAPI (4′,6-diamidino-2-phenylindole). Scale bar, 200 μm. Boxes indicate 2 PAX5^hi areas magnified in right panels for ColVI and PAX5 staining (scale bars, 50 μm). (C) Immunofluorescence on FL BM sections for PAX5 (cyan) and LOX (red). Nuclei were counterstained with DAPI. Scale bar, 500 μm. Boxes indicate areas magnified in right panels in which scale bars represent 50 μm. Each box illustrates a category of PAX5 expression area: (1) PAX5^hi area, (2) PAX5^med area, and (3) PAX5^lo area. (D) Quantification of LOX signal intensity in HD (n = 5) vs patients with FL (n = 12). Each dot corresponds to the quantification of the whole slide for 1 sample (HD or FL). Statistical significance was determined using the Mann-Whitney nonparametric U test. ∗P < .05. (E) Quantification of LOX signal intensity in the 3 categories of PAX5 frequency areas in patients with FL (n = 12). Each symbol represents a different patient with FL. The green dotted line represents LOX intensity level in HDs. Statistical significance was determined using the Friedman test with Wilcoxon matched-pairs comparisons. ∗∗∗P < .001. hi, high; lo, low; med, medium; MFI, mean fluorescence intensity.