Representative images of checkpoint inhibitor-induced acute kidney injury

Core needle biopsy specimens (A-C) from patient 9 show "typical" features of acute tubulointerstitial nephritis; (D) from patient 2 show granulomatous acute tubulointerstitial nephritis; (E,F) from patient 8 show acute thrombotic microangiopathy.
(A) Periodic acid-Schiff stain shows diffuse interstitial inflammation and focal severe tubulitis with infiltrating lymphocytes (arrows, times 200; bar = 50 mcg).
(B) Hematoxylin and eosin stain shows diffuse interstitial infiltrates predominantly composed of lymphocytes, with several eosinophils (arrows, times 400; bar = 25 mcg).
(C) Immunohistochemistry reveals the lymphocytic infiltrates in the interstitium to be predominantly CD4b T cells (times 40; bar = 100 mcg).
(D) Periodic acid-Schiff stain shows a noncaseating granuloma with multinucleated giant cells (striped arrows), severe interstitial inflammation and tubulitis (arrows), and severe glomerulitis (dashed arrow, times 200; bar = 50 mcg).
(E) Silver stain shows diffusely wrinkled glomerular basement membranes and "onion-skin" lesion of small arteries (arrow, times 200; bar = 50 mcg).
(F) Electron microscopy shows swollen endothelium and subintimal widening filled with electron-lucent "fluffy" material (arrows, times 1400; bar = 4 mcg).