Sarcoidosis, atypical mycobacteriosis, and
tuberculosis are common diseases of human lung with a typical feature of formation of
granulomas. The structure of
granulomas has not been elucidated completely. We studied the expression of
tenascin-C, precursor
proteins of
collagens I and III, and the presence of myofibroblasts in
granulomas of
sarcoidosis, atypical mycobacteriosis, and
tuberculosis of human lung. Twenty-five histologic samples of lung were analyzed by immunohistochemistry using
antibodies to
tenascin-C and aminoterminal propeptides of
collagens I and III. To identify the myofibroblast-type cells in
granulomas, the sections were also stained with
antibodies against alpha-smooth muscle actin,
vimentin, and
desmin. In every case,
tenascin-C and precursor
proteins of
collagens I and III were expressed around
granulomas. Precursor
protein of
collagen I was expressed also within them. In
tuberculosis and atypical mycobacteriosis, expression of
tenascin-C and precursor
protein of
collagen I was stronger than in
sarcoidosis. The cells demarcating
granulomas and, thus, colocalizing with
tenascin-C and both
collagen precursors were positive for alpha-smooth muscle actin and
vimentin, which suggests that these cells are myofibroblasts. They were also more abundantly present in
tuberculosis and atypical mycobacteriosis, as suggested by alpha-smooth muscle actin staining. We concluded that
tenascin-C and precursor
proteins of
collagens I and III are expressed around
granulomas in
sarcoidosis, atypical mycobacteriosis, and
tuberculosis of the lung; and furthermore, their expression colocalize with the expression of myofibroblasts. Our results further point to the fact that fibrogenesis and matrix turnover is stronger in
tuberculosis and atypical mycobacteriosis than in
sarcoidosis.