Aging CD19-hBtk mice have large perivascular infiltrates in various organs. (A) Immunohistochemical analysis for dendritic cells (CD11c⁺, red) and B cells (B220⁺, blue; left panel) or T cells (CD3⁺, blue; right panel) of kidney tissue sections from old CD19-hBtk mice (objective 10×). (B) Proteinuria in 2 of 8 (25%) CD19-hBtk mice; albumin levels in urine samples were measured by ELISA. (C-D) Immunohistochemical analysis for dendritic cells (CD11c⁺, red) and B cells (B220⁺, blue; left panel), T cells (CD3⁺, blue; middle panel), or GC B cells (GL7⁺, red) and plasma cells (CD138⁺, blue; right panel) of lungs (C) and salivary glands (D) from old CD19-hBtk mice (objective 10×). Data are representative of 5-8 CD19-hBtk mice.