Fibrocyte subsets in lung tissue of patients with systemic sclerosis-interstitial lung disease. Fixed, paraffin-embedded lung tissue sections from normal adults and adults with systemic sclerosis-interstitial lung disease (SSc-ILD) were stained for CD34, CD45, C-X-C chemokine receptor type 4 (CXCR4) and collagen I (ColI). Nuclei were stained with 4',6-diamidino-2-phenylindole (DAPI) (blue). Left: low-magnification images. Right: high-magnification images. The portion of the low-magnification image that is presented at high magnification is boxed. (A) CXCR4 (red)/ColI (green). (B) CD45 (red)/ColI (green). (C) CD34 (red)/ColI (green). (D) The number of double-labeled cells per field was determined from images of sections obtained from seven SSc-ILD patients and four normal subjects, with six randomly chosen fields per sectio. *P < 0.05. CXCR4 expression was evaluated by performing Western blot analysis on extracts of three normal lung samples and four SSc-ILD lung samples (E) and then quantifying them densitometrically (F) using actin as a loading control. Bars = 10 μm.