Abstract
INTRODUCTION: Novel anticancer therapies include anti-programmed cell death protein-1 (PD-1) and anti-programmed death ligand-1 (PD-L1) drugs. These novel medications have side effects in different organs, including the kidney. The most common adverse effect in the kidney is acute interstitial nephritis (AIN). No diagnostic criteria are available to distinguish AIN associated with anti-PD-1 therapy from other AINs. METHODS: Kidney biopsy specimens from patients on anti-PD-1 therapy were stained with antibodies to PD-1 and PD-L1. Herein we report morphologic and immunohistochemical findings in 15 patients who received anti-PD-1 therapy and developed acute kidney injury requiring a kidney biopsy. RESULTS: Among these patients, 9 had AIN and 6 had no AIN but showed acute tubular necrosis (ATN). Immunohistochemistry with antibodies to PD-1 and PD-L1 was performed on all of these biopsy specimens and on 9 randomly selected biopsy specimens with AIN from patients who did not receive anti-PD-1 medications, as well as 9 patients with lupus nephritis and active-appearing interstitial inflammation. There was weak staining for PD-1 in T cells in all patients with AIN and lupus; however, tubular epithelial cell membrane staining for PD-L1 was seen only in patients with anti-PD-1 therapy-associated AIN, and not in patients with anti-PD-1 therapy-associated ATN, and not in those with AIN secondary to other medications, or patients with lupus nephritis. CONCLUSION: We propose that immunohistochemistry with PD-L1 could be a useful tool to differentiate AIN associated with anti-PD-1 therapy from other AINs.