For DKO (BALB-Rag2-/- IL2Rgc-/-) mice (4–5 weeks old) engrafted with PBMCs (0.3–0.5×107) from patients with SLE, the ratio of human CD45+ cells to total PBMCs increased from 5–10% (6–7 weeks old) to 20–80% (8–10 weeks old) (21). The gene discussed is PTPRC; the disease is systemic lupus erythematosus.