CIRCULATING IMMUNE-COMPLEXES IN HUMAN TUBERCULOSIS SERA - DEMONSTRATION OF SPECIFIC ANTIBODIES AGAINST MYCOBACTERIUM-TUBERCULOSIS GLYCOLIPID (DAT, PGLTB1, LOS) ANTIGENS IN ISOLATED CIRCULATING IMMUNE-COMPLEXES

An enzyme-linked immunosorbent assay (ELISA) for IgG using three glyco lipid antigens from Mycobacterium tuberculosis in 65 tuberculosis (TB) patients and 50 healthy control subjects was performed. The circulati ng immune complexes (CICs) were isolated by precipitation with polyeth ylene glycol 6000 (PEG). This method associated to ELISA measured the specific antibodies present in these CICs. PEG [optical density (OD) 2 80] was shown to be significantly elevated (P <.0.001) in tuberculous samples. The concentrations of IgG antibodies complexed to the three g lycolipid antigens were shown to be higher in patient with tuberculosi s than in normal control subjects (P <0.001). No correlation was obser ved between levels of free and CIC-bound antibodies. These antibodies isolated from CICs were responsible for almost all of the false-negati ve serological results. However, great heterogeneity was noticed depen ding on the antigen used, showing a more positive ELISAs against DAT ( 77%) than against LOS (71%) or PGLTb1 (18.5%). No correlation was esta blished between the presence of specific CIC-complexed IgG and the bac teriological load or the tuberculosis localization (pulmonary vs. extr apulmonary). The sensitivity of ELISA for CIC-complexed IgG to DAT and LOS was lower in HIV-infected TB patients. From these results, we con clude that detection of complexed IgG DAT and LOS glycolipid antigen w ill be useful as a complementary technique for the serodiagnosis of tu berculosis.