Background and objectives: Mycobacterial infections are known to induce the development of autoantibodies and a few of these antibodies are also known to be diagnostic markers for some other diseases and it is uncertain whether these autoantibodies play a role in the pathogenesis of autoimmune disorders. This study was undertaken to determine the prevalence of autoantibodies like anti-neutrophil cytoplasmic antibodies (ANCA), anti-nuclear antibodies (ANA), anti-double stranded antibodies (anti-dsDNA) and anti-histone antibodies (AHA)in pulmonary Tuberculosis.
Materials & methods: Seventy consecutive pulmonary TB patients, 30 patients of interstitial lung disease and 100 normal individuals were studied. ANCA and ANA were detected by indirect immunofluorescence test (IIF). Anti-dsDNA and AHA were tested by ELISA.
Results: ANCA was detected in 30% cases, and of these 52.4% showed perinuclear pattern (p-ANCA), 38.1% cytoplasmic (c-ANCA) and 9.5% showed an "atypical" pattern. ANCA specificities by ELISA revealed that, 47.6% had anti-Myeloperoxidase (anti-MPO), 28.6% had anti-Proteinase3 (anti-PR3) and 19.1% had anti-Lactoferrin (anti-LF) antibodies. ANA and AHA were present in 24.3% and 21.4% cases respectively whereas anti-ds DNA antibodies were absent. Normal controls showed 4% and 2% positivity for ANA and ANCA whereas disease control group of ILD showed 7% of ANA and ANCA posititivy.
Conclusion: The presence of autoantibodies in TB patients could have a multifactorial etiology. Clinically relevant is the presence of anti-PR3 antibodies. This finding along with pulmonary and renal manifestations could lead to a false diagnosis of Wegener's granulomatosis or vice versa because these autoantibodies may be present in both diseases.