TCR retrogenic TB10-specific CD8⁺ T cells allow direct comparison of the 1° and 2° responses during infection.

<p><b>(a)</b> The proportion of TB10Rg3 cells (%GFP⁺Vα2⁺) among CD8⁺ T cells and their CD44 expression, 8w after vaccination of TCR Rg mice (memory) or age-matched unvaccinated TCR Rg mice (naïve). <b>(b)</b> CD62L, KLRG1, and IL-7R expression of naïve TB10Rg3 cells, and 8w after a single immunization with TB10_4-11. <b>(c)</b> Proportion (left) and absolute numbers (right) of TB10Rg3 cells in the lungs of TCRα^-/- mice 28d after adoptive transfer of 10⁵ naïve or memory TB10Rg3 CD8⁺ T cells and Mtb infection. <b>(d)</b> <i>Ex vivo</i> KLRG1 and IL-7R expression by TB10Rg3 cells (left) and IFNγ production after <i>ex vivo</i> stimulation of lung cells [from (<b>c</b>)] with TB10_4-11 peptide (right). <b>(e)</b> Lung CFU of TCRα^-/- mice 28d after transfer of naïve or memory TB10Rg3 CD8⁺ T cells and Mtb infection. <b>(f)</b> Lung CFU of sub-lethally irradiated C57BL/6 mice 21d after Mtb infection and transfer of memory TB10Rg3 (8w post-vaccination; left) or effector TB10Rg3 (1w post-vaccination; right). Numbers in quadrants or gated regions represent percent events. CFU were log₁₀-transformed before a student’s t-test or one-way ANOVA with a Bonferroni post-test. Data are representative of 2–4 independent experiments, each with 5 mice per group. * p < 0.05. n.s., not significant.