CD68-positive mononuclear cells are present in fibrotic lesions. (A) Colonic tissue specimens from CD patients with active disease feature a large amount of collagen fibers indicative for fibrosis as visualized by van-Gieson staining. (B) Same area as in (A) features strong expression of CD68, a marker of activated monocytes/macrophages. (C) Fibrotic regions in the intestine of CD patients feature strong expression of CD68. (D) Enlarged section from (C) featuring CD68-positive mononuclear cells. (E) Representative section from (C) visualizing collagen fibers by van-Gieson staining. Magnification: 10-fold or 40-fold, respectively. All analysed patient samples showed comparable staining characteristics when compared to samples from non-affected controls.