Immunization increases iNOS positivity in the footpad of <i>M. ulcerans</i> challenged mice.

<p>Mice were either non-immunized (A and D) or immunized with BCG (B, E, and G) or with mycolactone-negative <i>M. ulcerans</i> 5114 (C, F, and H) two months before challenge. All mice were infected in the footpad with 2 log₁₀ CFU of <i>M. ulcerans</i> 98–912. The footpads were harvested at on day 60 (A–C), day 70 (D–F), or day 100–200 (G–H and J–K) and processed for histology. Cells were stained for the presence of iNOS (red) and nuclei were stained with DAPI (blue). In footpads of non-immunized mice, scarce or no iNOS positive cells were found in the tissue (A, D). The footpads of vaccinated mice presented foci of iNOS positive cells during the initial weeks of infection (B–C and E–F). With progression of infection, iNOS positivity became sparse. Images are representative of 4 footpads per group. Original magnification: 20×.