Anti-CD3ε mAb-mediated thymus development positively affects the selection of Rag2^R229Q T-cell progenitors (indicated as FL^R229Q). (A) Representative H&E staining of a thymus from PBS and anti-CD3ε mAb-treated chimeric mice (original magnification, ×20) and graphic representation of the M/C in the 2 groups (PBS n = 6, anti-CD3ε mAb n = 8); **P = .008. (B) Immunohistochemistry of thymi from PBS and anti-CD3ε mAb-treated mice (original magnification, ×20). In AIRE panel, the inset shows magnification of AIRE⁺ cells induced by the treatment (original magnification, ×40). (C) Quantitative analysis of thymic AIRE⁺ cells obtained as described in “Methods” in wild-type mice, chimeric mice treated with PBS (n = 6) and chimeric mice treated with anti-CD3ε mAb (n = 8); **P = .007 (D) Percentages of EM and naive cells within the donor-derived CD4⁺ and CD8⁺ populations in the 2 groups (n = 7); **P = .0028, ***P < .0001. (E left) H&E staining of skin (original magnification, ×10), lung, liver, and gut (original magnification, ×20) from PBS and anti-CD3ε mAb chimeric mice. (Right) Pie charts show global infiltration grade in each organ calculated from H&E staining as described in “Histology.” Each pie indicates tissue infiltration in individual mouse in the 2 groups.