Immunohistochemistry demonstrating T cell infiltration and immune activation in oxonic acid (OA) group (A, C, E) and oxonic acid plus uric acid (UA) group (B, D, F). (A) Kidney of OA group showing some R73+ T cells within the kidney tissue. (B) Kidney of UA group showing numerous R73+ T cells within granulomatous lesions (*). (C) Kidney of OA group showing few major histocompatibility complex (MHC) class II expressing (OX-6+) cells within the tissue. (D) Kidney of UA group showing strong MHC class II expression (OX-6+) by most cells within granulomatous lesions. (E) Kidney of OA group showing undetectable interleukin-2R (IL-2R) expression (NDS-61). (F) Kidney of UA group showing strong expression of IL-2R by many infiltrated cells in the injured tubulointerstitial area. Note that some IL-2R+ cells (arrows) are present within the damaged tubules. Magnifications: 250X (A–C), 100X (D–F).