Figure 1.

High endothelial venules (HEVs) in inflamed colonic tissue of patients with inflammatory bowel disease. Density of extrafollicular HEVs in colonic tissue (a), determined in the inflamed colonic tissue of patients with Crohn's disease (CD) and ulcerative colitis (UC) as well as in healthy controls. The density is higher in UC patients when compared to controls (P = 0·033) and there is a trend for higher densities in CD patients compared to controls (P = 0·092). Immunohistochemical staining (B1–B5). Representative photomicrographs, with a magnification of ×200, of an immunostained colonic biopsy sample from a Crohn's disease patient with MECA‐79 staining (b1), CD20 staining showing B lymphocytes (b2) and CD3 staining showing T lymphocytes (b3). HEVs are shown in closer detail in b4 (extrafollicular) and b5 (inside a follicle). Arrows in Fig. b1, b4 and b5 indicate HEVs. Red arrows indicate HEVs inside a lymphoid follicle and black arrows indicate extrafollicular HEVs. [Colour figure can be viewed at wileyonlinelibrary.com]