Responsiveness to live M. tuberculosis, and common antigens, of sonicate-stimulated T cell lines from normal donors.

Live mycobacteria are more efficient vaccines against mycobacterial disease than killed ones. A possible explanation is the existence of important protective antigens released by live bacilli, which are not present in any significant quantity in dead ones. Conversely, internal mycobacterial antigens may be irrelevant to protection if not released by live bacilli. We show here, using T cell lines derived by limiting dilution from the peripheral blood of normal donors stimulated with sonicated BCG, that a variable percentage of sonicate responsive T cells is unable to respond to live M. tuberculosis. The possibility that such lines have an immunopathological, rather than protective role, is discussed.