Evaluation of matricellular proteins in systemic and local immune response to Mycobacterium tuberculosis infection

Matricellular proteins such as osteopontin (OPN), galectin‐9 (Gal‐9), and tenascin‐C (TN‐C) are expressed not only under normal physiological conditions, but also during infection, inflammation and tumorigenesis. Plasma concentrations of matricellular proteins were studied to determine their diagnostic value as potential markers of tuberculosis (TB) activity. It was found that concentrations of OPN and TN‐C were higher in patients with active TB than in healthy controls and individuals with latent infection. Moreover, LTBI patients had higher concentrations of OPN than did healthy controls. Gal‐9 concentrations did not differ significantly between groups. Concentrations of matricellular proteins were higher in pleural fluid than in the plasma of patients with TB. Expression of matricellular proteins was also investigated in TB granulomas and other granulomatous diseases. Positive OPN and Gal‐9 staining was observed in TB and sarcoidosis granulomas, but not in Crohn disease granulomas. The fibrotic ring around granulomas stained positive for TN‐C in TB and sarcoidosis, but not in Crohn disease. Of the three matricellular proteins studied, OPN and TN‐C may serve as reliable plasma markers for monitoring TB activity, whereas Gal‐9 seems to be expressed more at the site of infection than in the systemic circulation.