CD4 and infection: Using an ex vivo model from Harding et al., we demonstrated that mycobacteria-infected mouse APCs rapidly present Ag85B-derived P25 epitope to BB7 CD4 T cells in vitro (4, 13, 14). Because autophagy regulates MHC-II-dependent mycobacterial antigen presentation in DCs (5), we subjected wt-DCs to siRNA-mediated beclin1 (ATG6) knockdown followed by infection with non-labeled mycobacteria and antigen presentation assays.