Intracellular Mtb are required for T cell activation.

<p>A) BEAS-2B cells were seeded in a 12-well tissue culture plate and a 0.4 uM pore size transwell insert. Cells in the transwell were infected with Mtb (MOI:10) for 18 hrs. Cells from both chambers were then used as APCs (10,000 cells/well) in an IFN-γ Elispot assay. Results are representative of three independent experiments. B-C) Mtb were labeled with streptavidin coated magnetic microbeads prior to infection (MOI:30). A fraction enriched for infected BEAS-2B cells was then obtained by magnetic sorting (adherent). Mtb CFUs were enumerated from each fraction (B) and cells were used as APCs (5,000 cells/well) in an IFN-γ Elispot assay (C). (N = Non-adherent, A = Adherent). Results are representative of three independent experiments. D) The T cell response to the enriched fraction of Mtb-infected BEAS-2B cells (MOI:30, 2,000 cells/well) was compared to an equal number of Mtb-infected DC (MOI:30) in an IFN-γ Elispot assay. Results are representative of two independent experiments. For all assays, error bars represent the mean and standard error from duplicate wells.