Humoral immune response against mycobacterial antigens in children with tuberculosis

Different clinical outcomes of tuberculosis (TB) are related to the balance between cell-mediated and humoral immunity and may depend on environmental and individual factors including age and sex. The purpose of this study was to analyze the humoral immune response to recombinant and native mycobacterial antigens in relation to clinical presentations of pulmonary TB in children. We examined 224 serum samples including 81 primary and 31 postprimary TB cases, 30 cases of latent TB infection, and 82 nontuberculosis controls. Commercially available ELISA assays detecting IgG, IgA, and IgM against antigens: 38 kDa, 16 kDa, 38 kDa, lipoarabinomannan (LAM), and A-60 were used. The results indicate that IgG production was very low in primary compared with postprimary TB (P<0.0001). IgM levels did not differ between the examined groups. Antibody levels strongly depended on the child's age. In infants aged below 1 there was no difference in the antibody level between the TB and control cases. Most positive cases were observed in children aged above 10. The influence of BCG vaccination on the antibody level was not seen. In all subgroups, person-to-person heterogeneity of antigen recognition was observed. We conclude that humoral immune response is associated with the phase of TB and is stronger in more advanced TB forms. IgG and IgA production against mycobacterial antigens is very low in young children.