High and low dose infections preferentially expand CD4⁺ and CD8⁺ T cells, respectively.

<p>C57BL/6 mice were infected with low (1×10³) or high (2×10⁶) dose <i>L. major</i> promastigotes in their right hind footpad, sacrificed after 7 days and the draining lymph-node cells were labelled with CFSE dye and co-cultured with <i>L. major</i>-infected bone marrow-derived dendritic cells (BMDC) at a DC: lymph node cell ratio of 1∶100. After 4 days, the percentages of proliferating (CFSE^lo) CD4⁺ and CD8⁺ T cells (A and B) were assessed by flow cytometry. (A) is a representative histogram plots of individual animals while B represents the mean +/− SE of proliferating cells of all the animals (6 mice) within the group. Proliferating (CFSE^lo) IFN-γ (upper panels) and TNF (lower panels) -producing CD4⁺ (C and D) and CD8⁺ (E and F) T cells were also determined by flow cytometry. C and E are representative dot plots of individual animals within the group while D and F represent the mean +/− SE of proliferating cytokine-producing cells of all the animals (6 mice) within the group. The lymph nodes draining the infected feet were collected and digested with collagenase and the cells were then stained with different fluorochrome-conjugated antibodies against different DC subsets and the absolute numbers (upper panel) and percentage (lower panel) of CD11c⁺MHCII⁺ (G) and CD11c⁺CD103⁺CD8α⁺ (H) dendritic cells were determined by flow cytometry. Live cells were first gated on CD11c⁺ cells and further analyzed for MHC class II, CD103 and CD8α expression. Results are representative of 2 independent experiments (n = 6 mice/group) with similar results. *, p<0.05; **, p<0.01; ***, p<0.001.