S100A9 and acute kidney injury: Testing tasquinimod or paquinimod has been suggested as a clinical strategy for patients with severe COVID‐19 since plasma calprotectin (S100A8/A9) level positively correlates with disease severity.[40, 41] In the current study, the presence of kidney S100A8/S100A9+ macrophage infiltration and the relevance of renal S100a8/a9 expression to the degree of renal tubular pathological injury, tubule cell apoptosis, and renal dysfunction were confirmed in human AKI with nephrotoxic or renal ischemic etiologies.