[Expression pattern of Mycobacterium tuberculosis Ag85B and its value in pathological diagnosis].

OBJECTIVE

To detect the expression of Mycobacterium tuberculosis secreted protein Ag85B in paraffin-embedded tissues by immunohistochemistry (IHC), and to evaluate its application in the pathological diagnosis of tuberculosis.

METHODS

One hundred and five tuberculosis specimens (54 pulmonary tuberculosis, 51 lymph nodal tuberculosis) and 51 specimens of other diseases (8 lung cancer, 10 pulmonary abscess, 10 bronchiectasis, 7 lymphoma, 5 necrotizing lymphadenitis, 4 reactive hyperplasia lymphoid, and 7 sarcoidosis) were collected from January 2012 to July 2013 from Beijing Chest Hospital, Capital Medical University. One-step IHC was performed on paraffin-embedded tissues using antibody directed against Ag85B.

RESULTS

IHC and Ziehl-Neelsen (ZN) acid-fast staining showed that distribution and intensity of Ag85B expression were concordant with the distribution and number of acid-fast bacilli. IHC showed significantly higher sensitivity than ZN staining (50.5%, 53/105 vs. 31.4%, 33/105; χ² = 7.877, P = 0.005). The combined sensitivity of IHC and ZN staining was 59.0%. Moreover, oil immersion was not necessary for IHC, allowing more rapid diagnosis.

CONCLUSION

IHC detection of Ag85B is a simple method with higher sensitivity than ZN staining, and demonstrated good value in the pathological diagnosis of tuberculosis.