Thymic epithelial defect in RAG2^R229Q mice. (A) Macroscopic aspect of representative 5-week-old RAG2^+/+ and RAG2^R229Q thymus. (B) Thymic cellularity in RAG2^+/+ (n = 22) and RAG2^R229Q (n = 33) mice; ***P < .0001. (C) Representative H&E staining of thymus from a 5-week-old RAG2^+/+ and RAG2^R229Q mouse (original magnification, ×20) and graphic representation of the M/C in the indicated mice (n = 8); ***P < .0001. (D) CK5, CK8, UEA-1, and AIRE immunohistochemistry of 5-week-old RAG2^+/+ and RAG2^R229Q thymus (original magnification, ×20). (E left) FACS analysis of thymic stromal compartment: CD45⁻ fraction, obtained after enzymatic digestion was stained with MHCII and Ly51 Abs to identify the 3 different epithelial subsets. Numbers represent the percentage within the indicated regions. (Right) Absolute number of the different epithelial subpopulations obtained after enzymatic digestion of RAG2^+/+ and RAG2^R229Q thymi (n = 5); **P = .0025. (F) Real-time analysis of AIRE and indicated TRA transcripts on RNA extracted from total thymus of RAG2^+/+ (n = 4) and RAG2^R229Q mice (n = 4). Quantitative RT-PCR was run in triplicate (results are representative of 3 independent experiments); ***P = .0007.