Analysis of the HEV network in CLL/SLL LNs. (A) Representative images showing the density and the distribution of HEV blood vessels (MECA-79⁺, green) in a reactive LN (control; left) and a CLL LN (CLL; right). Scale bar, 500 µm. (B) HEV density (number of HEVs/mm²) was quantified on control (n = 8), SLL (n = 5), and CLL (n = 13) LNs. Unpaired t test; *P < .05. (C) CLL LNs were double-stained with MECA-79 (brown) and Abs directed against Ki-67 (red). Scale bar, 100 µm. (D) Relative MECA-79⁺ area was quantified inside proliferation centers (PCs) (sum of MECA-79⁺ area inside all PC/sum of PC area × 100) and outside area (sum of MECA-79⁺ area outside all PC/overall area − sum of PC area × 100) in CLL/SLL LNs (n = 19). PCs were revealed by Ki-67 staining. Paired t test. (E) Representative image showing staining of HEV blood vessels in CLL LNs with HEV-specific Abs G72 and G152 (brown). Scale bar, 20 µm. (F) Double staining of a CLL LN section with anti-L-selectin Ab (brown) and HEV-specific Ab MECA-79 (red), showing L-selectin⁺ cells (arrows) inside, around, or at a distance from MECA-79⁺ HEVs. Scale bar, 20 µm. (G) Quantification of the percentage of L-selectin⁺ cells inside (inside HEV), around (<10 µm from HEV), or at a distance (>10 µm from HEV) from MECA-79⁺ HEVs. A total of 362 L-selectin⁺ cells were counted on 5 different sections from 2 different patients. DAPI, 4′,6 diamidino-2-phenylindole; ns, not significant.