Low and high dose <i>L. major</i> infection leads to comparable protection against secondary virulent challenge.

<p>C57BL/6 mice were infected with low (1×10³) or high dose (2×10⁶) <i>L. major</i> and allowed to completely resolve their lesions (>12 wks.). Healed mice and some naïve age-matched controls were challenged with 5×10⁶ (high dose challenge, A and C) or 1×10³ (low dose challenge, B and D) <i>L. major</i> in the contra-lateral footpad and delayed-type hypersensitivity (DTH) response was determined at 72 hr post-challenge (A and B). Three weeks after challenge, mice were sacrificed and parasite burden in the challenged footpads was determined by limiting dilution assay (C and D). Results presented are representative of 3 independent experiments (n = 3–4 mice/group) with similar results. **, p<0.01. ND, not detected.