Extended Data Fig. 8: T_PEX cells interact with cDC1 in the paracortical T cell zones of lymph nodes.

(a–f) Naïve P14 CD8⁺ T cells, which ubiquitously express tdTomato (ref. ⁷¹) were adoptively transferred into naïve Xcr1^Venus reporter mice (ref. ⁷²), which were subsequently infected with LCMV-Docile. Lymph nodes (LN) were harvested on d25 p.i., fixed and imaged using confocal microscopy. (a) Representative confocal micrograph and quantification showing the distribution of B220⁺, TCF1⁺, CD11c⁺ CD68⁺ and P14 cells. (b) Analysis and (c) quantification showing the spatial distribution of T_PEX (tdTomato⁺TCF1⁺) and T_EX (tdTomato⁺TCF1⁻) cells within different anatomical regions of a LN (Follicular areas: n = 10; Paracortical TCZ: n = 9; Medullary regions: n = 7). (d) Representative confocal micrograph and (e) quantification showing the distribution of XCR1⁺ dendritic cells within different regions of the LN (Follicular areas: n = 10; Paracortical TCZ: n = 9; Medullary regions: n = 7). (f) Representative confocal micrographs and quantification showing the expression of CD11c in XCR1⁺ dendritic cells found within different anatomical regions of the LN (TCZ: n = 40; non-TCZ: n = 59). (g–j) Mixed bone marrow chimeric mice containing Ccr7^−/− and Xcr1^DTR (ref. ⁷²) haematopoietic cells were infected with LCMV-Docile before the administering of Diphtheria toxin (DTX) starting on d18 p.i. P14 cells in the spleen and LN were analysed using flow cytometry on d25 p.i. (g) Representative flow cytometry plots and (h) quantification showing the frequencies of XCR1⁺ cells in spleen and LN in untreated or DTX treated mice (n = 8). (i) Quantification showing absolute numbers of P14 T_PEX and T_EX cell subsets in the presence and absence of cDC1 depletion in the spleen and LN (n = 9). (j) Representative flow cytometry plots and corresponding quantification showing the frequencies of Ly108^intCX3CR1⁺ cells among P14 cells in the presence and absence of cDC1 depletion in the spleen and LN (n = 9). Dots in graphs represent (b, e) individual manually defined regions of interest, (f) individual cells, or individual mice (h–j), and bars represent median, and bars represent median. Quantification and statistics derive from unpaired two-tailed t tests (f) and one-way ANOVA (c, e, h–j) and based on all data points across at least two independent experiments.