Figure 1.

T‐bet fate mapping identifies a population of peripheral naïve‐like CD4⁺ T cells that have experienced T‐bet expression. (A) Representative flow plots from two independent experiments showing YFP expression in different splenic immune cells populations (n = 7 except for CD4⁺ T cells where n = 3). (B) Quantification of the mean proportions of YFP⁺ cells for each cell type shown in A (n = 7 except for CD4⁺ T cells where n = 3). (C) Representative flow plots from two independent experiments showing YFP expression in the naïve‐like (CD62L⁺ CD44^– CD28⁺ CD27⁺), T_CM (CD62L⁺ CD44⁺ CD28⁺ CD27⁺), and T_EM (CD62L^– CD44⁺ CD28⁺ CD27^–) compartments in the thymus, spleen, colon, mesenteric lymph nodes, peripheral lymph nodes, and liver (n = 3 for thymus, colon, and pLN, n = 7 for mLN and liver, and n = 11 for spleen). (D) Mean proportions of YFP⁺ cells in the naïve, effector memory, and central memory CD4⁺ T‐cell populations shown in C (n = 3 for thymus, colon, and pLN, n = 7 for mLN and liver, and n = 11 for spleen). (E) Representative histograms from three independent experiments showing surface marker expression of CXCR3, CD122, CD49d in YFP^– versus YFP⁺ naïve‐like (live CD3⁺ CD4⁺ CD62L⁺ CD44^–) and effector memory (live CD3⁺ CD4⁺ CD62L^– CD44⁺) CD4⁺ T cells from the spleen. Percentages of YFP⁺ naïve CD4⁺ T cells positive for each marker are shown (n = 16). (F) Representative flow plots from three independent experiments showing YFP expression by conventional naïve‐like CD4⁺ T cells (CD62L⁺ CD44^– CD28⁺ CD27⁺ CD127⁺ CD122^– CD95^–) compared with T_SCM (CD62L⁺ CD44^– CD28⁺ CD27⁺ CD127⁺ CD122⁺ CD95⁺) from the spleen (n = 16). (G) Representative flow plots from three independent experiments showing YFP expression in splenic CD28⁺ CD27⁺ T‐cell populations divided by CD62L, CD44, CXCR3, and CD49d expression. Naïve (CD62L⁺ CD44^– CXCR3^– CD49d^–), T_MNP (CD62L⁺ CD44^– CXCR3⁺ CD49d⁺), T_H1‐like MP (CD62L^– CD44⁺ CD49d⁺ CXCR3⁺), and VM (CD62L^– CD44⁺ CD49d^– CXCR3⁺) T‐cell populations are labeled (n = 16). (H) Representative histograms and mean proportions of CD5^hi expressing cells from naïve‐like YFP⁺ CD4⁺ T cells (live CD3⁺ CD4⁺ CD62L⁺ CD44^–) and naïve YFP^– CD4⁺ T cells in the spleen, mLN, colon, and liver from two independent experiments (n = 6 for spleen and mLN, n = 10 for colon, n = 4 for liver). Percentages shown for YFP⁺ naïve‐like CD4⁺ T cells. *p < 0.05, **p < 0.01, ***p < 0.005 (Mann–Whitney U‐test).