Development of multiorgan lymphoid infiltrates in Il12rb2 KO mice. (A) Liver from a 15-month-old Il12rb2 KO mouse shows periarteriolar lymphoid cuff (Ai). At the age of 18 months, the ectopic lymphoid infiltrate appears arranged in follicle-like structures (Aii). Magnification, × 400; H&E staining. (B) Ectopic lymphoid infiltrates in the kidney from a 18-month-old mouse (Bi-iv). These infiltrates are mostly composed of B220⁺ (Bi), CD43⁺ (Bii), and PCNA⁺ (Biii) cells and compress the glomeruli and tubules. Lymphoid aggregates can invade epithelial structures (lymphoepithelial lesions indicated by arrows in Biv). Magnification, × 400. (C) Lymphocytic infiltration develops in the submandibular gland of a 15-month-old mouse (Ci). The centroblastic-centrocytic follicular infiltrate (Ci, arrows) is predominantly composed of B220⁺ B cells (Cii), bordered by small mature lymphoid cells (Ci, arrowheads) displaying a CD3⁺ T-cell phenotype (Ciii), with intermingled FDC-M2⁺ cells (Civ). This ectopic lymphoid infiltrate organizes close to PNAd⁺ vessels (inset in Civ). Magnification, × 400.