Characterization of the culture filtrate-specific cytotoxic T lymphocyte response induced by bacillus Calmette-Guerin vaccination in H-2(b) mice

Although CD8(+) T cells are supposed to play an important role in protectiv e immunity to mycobacteria, cytotoxic T lymphocyte (CTL) responses in this infection remain poorly characterized. We previously demonstrated that baci llus Calmette-Guerin (BCG) immunization of H-2(b) mice induced CTL able to recognize and kill macrophages incubated with proteins from mycobacterial c ulture supernatant [culture filtrate (CF) antigens]. In the present study, we have further characterized the lytic activity of these CTL and the proce ssing pathway used for the presentation of CF proteins. We show that they u se the degranulation pathway (secretion of perforins and granzymes) as the main lytic mechanism of cytotoxicity and also secrete IFN-gamma upon incuba tion with CF-pulsed macrophages. The in vitro presentation of CF proteins t o CTL required a processing step inhibited in the cold but insensitive to B refeldin A. Transporter-associated protein (TAP)-2-deficient RMA-S cells we re efficiently recognized and killed by CF-specific CTL, demonstrating the lack of TAP requirement for this presentation. However, recognition of targ et cells by CTL was abolished when carried out in the presence of chloroqui ne. These results indicate that a non-classical MHC class I-processing path way allows the recognition of a CF protein by CTL in ace-vaccinated H-2(b) mice.