LTβR controls formation of the thymic DC pool for negative selection. (A) cDC1, cDC2, and pDCs in Lin⁻ thymus preparations. (B and C) CD11c⁺ DCs in ERTR5⁺ areas of indicated mice. Bars, 50 µm. Data from three experiments, n ≥ 6. (D and E) Thymic DCs in WT/Ltbr^−/− and LTβR^TEC/Foxn1^Cre mice; n = 11 from three experiments. (F) Thymic DC numbers in Wnt1^Cre2 and LTβR^MES mice; data from three experiments, n ≥ 6. (G) Numbers of total, DP, and CD4⁺ CD5⁺CD69⁺Caspase3⁺ thymocytes. Data obtained from at least two experiments where n ≥ 5 for all strains. Error bars indicate SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.