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

Anti-Ig antibodies are known to have important clinical and biological implications.

To determine naturally occurring anti-F(ab')2 gamma and anti-Fc gamma antibodies in patients with pulmonary tuberculosis (PTB) in relation to various clinical manifestations and human leukocyte antigen (HLA).

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.

As compared to controls (0.110 +/- 0.01 optical density [OD]), the levels of anti-F(ab')2 gamma 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')2 gamma 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')2 gamma than drug responders and no impact of anti-tuberculosis chemotherapy was observed. A statistically significant increase of anti-F(ab')2 gamma 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-Fc gamma levels between controls and any group of PTB patients.

The present data suggests that the elevated levels of anti-F(ab')2 gamma antibodies in PTB patients represent an anti-idiotypic antibody response to anti-M. tuberculosis antibody caused by an immune imbalance following M. tuberculosis infection.