Raja, Alamelu and Uma Devi, K R and Ramalingam, B and Brennan, P J
(2002)
Immunoglobulin G, A, and M Responses in Serum and Circulating
Immune Complexes Elicited by the 16-Kilodalton Antigen of
Mycobacterium tuberculosis.
Clinical and Diagnostic Laboratory Immunology, 9 (2).
pp. 308-312.
ISSN Print: 1556-6811; Online: 1556-679X
Abstract
The 16-kDa cytosolic antigen of M. tuberculosis was purified to homogeneity by molecular sieving chromatography,
and the diagnostic potential of the antigen was evaluated in various categories of patients by
enzyme-linked immunosorbent assay (ELISA). The immunoglobulin G (IgG), IgA, and IgM antibody levels to
16-kDa antigen were estimated in the two polar groups, namely, smear- and culture-positive pulmonary
tuberculosis (S�C�) patients and healthy subjects (HS). Sensitivities of 62, 52 and 11% with specificities of
100, 97, and 95% were obtained for the three isotypes, respectively. The total number of positives by a
combination of the three isotypes was analyzed in the polar groups, and the sensitivity improved to 83% with
a specificity of 93%. Even when a combination of IgG and IgA alone was considered, the sensitivity was 82%
with a specificity of 97%. Polyethylene glycol precipitation of the circulating immune complex (CIC) in sera was
carried out. The CIC-bound antibodies to 16-kDa antigen were assessed by ELISA in the S�C�, S�C�, and
S�C� categories of patients. Measuring the IgG-IgA-IgM combination positivities of the CIC-bound antibodies
gave sensitivities of 97.5, 100, and 45.3%, respectively. The specificity of the assay with these combinations was
maintained at 95.4%.
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