Heterogeneity of antibody response to myobacterial antigens in different clinical manifestations of pulmonary tuberculosis.

Different clinical outcomes of tuberculosis can be related to the balance between cell-mediated and humoral immunity. In this prospective study we examined the humoral immune responses to recombinant and native mycobacterial antigens in relation to clinical presentations of pulmonary TB. Two hundred and fifteen serum samples were examined including: non-cavitary (n=120), cavitary (n=65), caseous pneumonia (n=12), and disseminated TB (n=18). ELISA tests detecting IgG, IgA, and IgM against antigens: 38 kDa and 16 kDa, 38 kDa and lipoarabinomannan (LAM) were used. Univariate and multivariate logistic regression analyses were carried out to find the association between the antibody level and demographic or clinical characteristics. The relationships among specific antibody profiles and the phase of the disease in relation to demographic (age and sex) and clinico-radiological factors were investigated by measuring serum antibody levels (IgG, IgA, and IgM) to 38 kDa and 16 kDa recombinant M. tuberculosis antigens and to LAM - native mycobacterial antigen. The results show that the radiological extent of the disease is the strongest factor associated with IgG antibody production. Patients with more extensive pulmonary TB showed higher titers of IgG antibody to M. tuberculosis antigens (P<0.0001). The highest IgG and IgA level were observed in fibro-cavernous TB. The presence of cavity was associated only with IgG anti 38+16 kDa (P<0.001). IgA level was the highest in caseous pneumonia. IgM antibody production was not associated with any clinical and radiological factor, but only with the male gender. Age was independently and inversely associated with IgG anti 38 kDa+LAM level and IgM anti 38 kDa+LAM. We conclude that the humoral immune response to mycobacterial antigens is highly heterogeneous and varies with the stage of TB. IgG antibody level is higher in most advanced and extensive forms of the disease.