Differential expression of ubiquitin and PU.1 in granulomatous lesions of tuberculosis and sarcoidosis

Backgrounds: Ubiquitin is used for protein degradation and recycling via proteasome. Tuberculosis and sarcoidosis show slightly different granuloma. Studies for ubiquitination in two diseases are still very few. we studied ubiquitin expression patterns in two diseases to define the differences of metabolism in macrophages. Methods: Thirteen sarcoidosis and 29 tuberculosis tissue samples were used for immunohistochemistry(IHC) for CD68, CD163, PU.1 and ubiquitin. The intensity and percentage of staining were semi-quantified and multiplied into scores. Results: The expression of ubiquitin and PU.1 showed similarity between sarcoidosis and tuberculosis. Statistical correlation between PU.1 and ubiquitin was shown in tuberculosis and sarcoidosis. PU.1 was markedly located within nuclei of macrophages in tuberculosis, but positive both cytoplasm and nuclei of macrophages in sarcoidois. Ubiquitin expression showed clear macrophagic nuclei in sarcoidosis but diffuse stain in tuberculosis. These seemed to be correlated with caseation necrosis, which may suggest the role of ubiquitination. Conclusion: Taken together, the characteristic expressional difference and mutual correlation between ubiquitin and PU.1 in the granuloma of tuberculosis and sarcoidosis may partly explain the mechanism of caseation necrosis and formation of granuloma in two diseases. We hope ubiquitin-related studies may contribute to define the etiology and pathogenesis in macrophage-involved granulomatous diseases.