Analysis of circulating immune complexes (CICs) in childhood tuberculosis:levels of specific antibodies to glycolipid antigens and relationship withserum antibodies

BACKGROUND: The presence of specific antiglycolipid antibodies in serum and circulating immune complexes (CIC) in children with tuberculosis was detec ted in order to evaluate their contribution to the value of serodiagnosis o f tuberculosis, as has already been shown in adults. METHODS: ELISAs using the three glycolipids LOS, DAT and PGLTb1 were perfor med in whole serum and immune complexes from 20 children with tuberculous d isease or infection, in seven child contacts, and in 26 children with non-t uberculous disease. The contribution of complexed IgG antibody to the diagn ostic values was established for each group. RESULTS: The antibody levels in free serum were higher (P < 0.01) in childr en with tuberculous disease or infection and in contacts than in controls. By contrast, except for PGLTb1, the IgG antibody levels were higher (P < 0. 02) in children with tuberculous disease than in the other groups. The high est contribution of IgG antibody against LOS to the predictive values was s hown in children with pulmonary tuberculosis (positive predictive value 100 0, negative predictive value 1000). In paucibacillary tuberculosis (extra-p ulmonary and tuberculous infection) and in contacts, the IgG antibody did n ot contribute to the sensitivity of the serodiagnosis, where the combinatio n of antigens tested in serum increased the diagnostic yield. The very low levels of Ige antibody in these settings may indicate a different B cell re sponse. CONCLUSION: The detection of immune complexes and IgG antibodies against th e three glycolipid antigens is useful as a complementary technique for the serodiagnosis of children with a high probability of pulmonary tuberculosis .