# Evaluation of neutrophil activation in autoimmune kidney diseases using blood heparin-binding protein: a pilot study

## TL;DR

This pilot study explores blood heparin-binding protein (HBP) as a marker for neutrophil activation in autoimmune kidney diseases, finding it to be elevated across various conditions and independent of kidney function.

## Contribution

The study introduces blood HBP as a novel, eGFR-independent marker for neutrophil activation in autoimmune kidney diseases.

## Key findings

- Blood HBP levels were significantly elevated in all autoimmune kidney diseases tested.
- HBP showed higher sensitivity than NGAL, neutrophil counts, and C-reactive protein in detecting neutrophil activation.
- HBP levels correlated with disease activity markers like hematuria and proteinuria in specific conditions.

## Abstract

Currently, there is limited understanding about the activation of neutrophils in autoimmune kidney diseases. Heparin-binding protein (HBP) is a protein in neutrophil granules and has been widely used as a marker for infectious diseases. This study aims to explore the use of blood HBP to evaluate neutrophil activation in autoimmune kidney diseases.

A total of 70 patients diagnosed with autoimmune kidney diseases were enrolled, including 20 with anti-neutrophil cytoplasmic antibodies-associated vasculitis (AAV), 17 with membranous nephropathy (MN), 17 with IgA nephropathy (IgAN), and 16 with minimal change disease (MCD)/focal segmental glomerulosclerosis (FSGS). The control group consisted of 18 patients with sepsis, 20 patients on maintenance hemodialysis, and 20 healthy volunteers. Clinical and laboratory indicators were collected, and the blood HBP were measured.

The blood HBP were significantly elevated in all kinds of autoimmune kidney disease, with the highest levels in AAV and the lowest in MCD/FSGS. Unlike blood NGAL, blood HBP was not affected by estimated glomerular filtration rate (eGFR). Blood HBP was independently correlated with blood neutrophil counts, and its sensitivity was higher than that of blood NGAL, neutrophil counts, and C-reactive protein. In AAV, blood HBP was associated with hematuria, and its levels significantly decreased after remission. In MN and MCD/FSGS, elevated HBP was associated with higher levels of proteinuria. There was a positive correlation between blood HBP and urine HBP in patients with autoimmune kidney diseases.

Blood HBP is a valuable and eGFR-independent marker of neutrophil activation. This study preliminarily reveals that neutrophil activation is widespread in various autoimmune kidney diseases and may be involved in the pathogenesis of these diseases.