Anti-igG autoantibodies and possible immune regulatory mechanisms in patients with pulmonary tuberculosis

Abstract

Setting: Anti-Ig antibodies are known to have important clinical and biological implications. Objectives: To determine naturally occurring anti-F(ab′)2γ and anti-Fcγ antibodies in patients with pulmonary tuberculosis (PTB) in relation to various clinical manifestations and human leukocyte antigen (HLA). Design: Antibodies to F(ab′)2 and Fc portions of IgG were detected in the sera of normal healthy individuals ( n = 41), patients with pulmonary tuberculosis ( n = 50) and their household family contacts ( n = 20) using an enzyme immuno assay (EIA) system. Results: As compared to controls (0.110 ± 0.01 optical density [OD]), the levels of anti-F(ab′)2γ were significantly increased in PTB patients (0.998 ± 0.08 OD, P < 0.0001) and in their contacts (0.486 ± 0.04 OD, P<0.001) suggesting that the occurrence of these autoantibodies is related to infection/exposure to Mycobacterium tuberculosis. Anti-F(ab′)2γ antibodies were significantly increased in both sputum positive and negative patients ( P<0.0001) and no deviation was observed between these two groups. The levels of these antibodies were positively correlated with disease severity assessed by chest X-ray. The drug failure patients had higher activity of anti-F(ab′)2γ than drug responders and no impact of anti-tuberculosis chemotherapy was observed. A statistically significant increase of anti-F(ab′)2γ levels (1.25 ± 0.21 OD) was observed in HLA-DR2 positive patients as compared to the DR2 negative groups (1.02 ± 0.09 OD), P<0.01. No deviation was observed in the levels of anti-Fcγ levels between controls and any group of PTB patients. Conclusion: The present data suggests that the elevated levels of anti-F(ab′)2γ antibodies in PTB patients represent an anti-idiotypic antibody response to anti- M. tuberculosis antibody caused by an immune imbalance following M. tuberculosis infection.