Immunochemical characterization of saline-extracted antigens of Mycobacterium tuberculosis H37Ra

The saline extract (SE) of Mycobacterium tuberculosis H37Ra yielded four major fractions on Sephadex G-100, with average molecular weights of 48,000 (fraction I, FI), 32,000 (fraction II, FII), 15,000 (fraction III, FIII) and 5,000 (fraction IV, FIV). FI and FII gave single bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, showed complete immunological cross-reactivity with each other and were more potent in reacting with antibodies in patients’ (tuberculosis) sera than sonicate, SE, purified protein derivative, FIII and FIV when tested in a competition enzyme-linked immunosorbent assay.