Kidney Injury Molecule-1 (KIM-1) Antibody Can Identify Acute Tubular Injury in Autopsy Kidneys Despite Autolysis

Document Type

Conference Proceeding

Publication Date

3-2026

Publication Title

Laboratory Investigation

Abstract

Background: Our previous study using a lab-made kidney injury molecule-1 (KIM-1) antibody (AKG7) demonstrated that KIM-1 staining identified acute tubular injury (ATI) in autopsy kidneys despite autolysis (Am J Physiol Renal Physiol 315: F1637-F1643, 2018). However, the lab-made KIM-1 antibody has limited use in other labs due to its dilution of 1:5 to 1:8 for immunostaining. Recently, a commercially available KIM-1 antibody from R&D Systems can be diluted to 1:1000 for equivalent immunostaining in native renal biopsies (validated in 28 negative and positive biopsies). The goal of this study was to evaluate the use of the new KIM-1 antibody in identifying ATI by analyzing the percentage of ATI in autopsy kidneys. The convoluted proximal tubules (CPT) in the S1 segment, and the straight proximal tubules (SPT) in the S2 segment of the medullary rays and the S3 segment below the accurate arteries were analyzed to determine the percentage of AKI. Design: Eighteen adult cases were selected from the past year, and their medical histories and premortem serum creatinine levels (sCr) were obtained. The autopsy kidney blocks were pulled and stained with the new KIM-1 antibody (R&D Monoclonal Rabbit IgG, clone #2389F, at 1:1000 dilution). The membranous staining of injured proximal tubules was graded from 0 to 3+, and the percentage of positive KIM-1 staining was estimated at S1 (cortical blood supply) and S2/S3 segments (medullary blood supply). Results: The age of the sample population ranged from 47 to 82 years old, and there were mixed male and female numbers (Table 1, n=18). Most of the cases had a moderate-to-severe degree of ATI, with all three segments showing similar density and percent staining for KIM-1. Dominant KIM-1 staining of the S2/S3 segments with weak staining in S1 implied ischemic insult to the kidneys (Figure1B-1C),whiledominantKIM-1staining inS1 segments most likely resulted from toxic tubular injury (Table 1). A small percentage of patients (2/18 cases) showed mild KIM-1 staining, implying minor premortem ATI. The sCr levels generally correlated withKIM1 staining in the proximal tubules despite some autolysis present. Conclusions: Our data indicates that the new KIM-1 antibody can be used to identify premortem ATI in autopsy kidneys, implying that KIM-1 is a stable protein in injured proximal tubules regardless of the extent of autolysis. The commercially available KIM-1 antibody can be easily adapted by many pathology labs to identify ATI in autopsy kidneys.

Volume

106

Issue

3 Suppl 1

First Page

104287

Comments

USCAP (United States and Canadian Academy of Pathology) 115th Annual Meeting, March 21-26, 2026, San Antonio, TX

Last Page

104287

DOI

10.1016/j.labinv.2025.104287

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