T-cell development in HIS (BALB-Rag/γ) mice. (A) FACS profiles gated on human CD45⁺ cells showing T-cell development in the thymus (top) and established T-cell pool in the periphery of 8- to 12-week-old HIS (BALB-Rag/γ) mice (middle). Distribution of human T cells according to CD4 and CD8 expression is also shown for spleen CD45⁺CD3⁺ T cells (bottom). (B) Surface expression of the costimulatory molecule CD28 and the IL-2Rα/CD25 in the DN (CD4^-CD8^-), DP (CD4⁺CD8⁺), SP4 (CD4⁺CD8^-CD3⁺), SP8 (CD4^-CD8⁺CD3⁺) thymocytes populations, and mature T CD4⁺ and T CD8⁺ of the spleen. Percentages corresponding to quadrant areas or regions are indicated inside each plot.