Figure 5.

Maturation of medullary thymic epithelial cells (mTECs) in wild-type (WT), Lig4 ^R/R, and Rag1 ^S/S mice. Mature mTECs from WT mice express claudin-4 (Cld4), Ulex europaeus agglutinin 1 (UEA-1) and Aire (upper panels). Insets highlight fully mature mTECs showing immunoreactivity (IR) for Cld4 and the characteristic granular dot-like Aire positivity in the nuclei. Thymuses from Lig4 ^R/R mice show residual presence of mTECs that reach full maturation with positivity for UEA-1, Cld4, and Aire expression (middle panels). Loss of corticomedullary demarcation (CMD) with impaired maturation of mTECs was observed in the thymuses from the Rag1 ^S/S mice in which only rare UEA-1 IR cells but no mature Cld4⁺ and Aire⁺ cells were found (lower panels). IR staining: brown. All panels are from 20× original magnification; insets are from 40× original magnification. One representative example of five mice analyzed per each strain.