Proliferation capacity of thymic stromal cells. (A) Dot plots of MHC II versus Ki67 expression on CD45^– thymic stromal cells at various time points, with regions indicating the proportion of Ki67⁺ TECs (CD45^–/MHC II⁺) and Ki67⁺ non-TECs (CD45^–/MHC II^–). Histograms show Ki67 (solid line) and isotype control (dashed line) staining gated on TECs with markers indicating the proportion of Ki67⁺ TECs. (B) Histograms of Ki67 expression on cTECs (CD45^–/MHC II⁺/Ly51⁺) and mTECs (CD45^–/MHC II⁺/Ly51^–) from 4-week-old mice, with markers set according to isotype controls. (C) MHC II expression versus BrdU incorporated into 4-week-old CD45^– stromal cells following 3 days of constant exposure. The proportion of CD45^– cells that are BrdU⁺ TECs is indicated. All plots are representative of 3 experiments performed.