CD68-GFP macrophage BCG infection. BCG Pasteur was administered intranasally at 4 × 10⁵ colony-forming unit to WT and CD68-GFP mice. After 4 weeks, mice were euthanized, and immunofluorescence analysis for transgene GFP expression in frozen lung tissue sections of naive (A-B) and BCG-infected (C-D) CD68-GFP and WT mice was performed. (E-F) Costaining with iNOS (red) was performed and showed strong association with endogenous GFP expression.