# Percentage of CD56+ monocytes at neutrophil engraftment is associated with the incidence of acute graft-versus-host disease

## TL;DR

A specific type of monocyte, marked by CD56, is linked to the risk of acute graft-versus-host disease after stem cell transplants.

## Contribution

Identifies CD56+ monocytes as a novel predictive biomarker for acute graft-versus-host disease.

## Key findings

- CD56+ monocytes transiently increase at neutrophil engraftment in patients.
- Lower CD56+ monocyte frequency correlates with reduced acute GVHD incidence.
- CD56+ monocytes show pro-inflammatory gene expression patterns.

## Abstract

Acute graft-versus-host disease (GVHD) is one of the serious complications following allogeneic hematopoietic stem cell transplantation (HSCT) that leads to non-relapse mortality. Although several biomarkers for acute GVHD have been proposed, no definitive predictive markers are clinically available. Recent studies have shown that a specific subset of peripheral blood monocytes expresses CD56 (neural cell adhesion molecule [NCAM]), particularly under inflammatory conditions; however, their role in allogeneic HSCT remains unclear. Single-cell RNA sequencing of peripheral blood mononuclear cells from patients with acute GVHD identified a unique monocyte subset characterized by an NCAM signature. Prospective multicolor flow cytometry analysis of peripheral blood samples revealed a transient increase in CD56⁺ monocytes at the time of neutrophil engraftment. Gene set enrichment analysis demonstrated pro-inflammatory transcriptome signatures of the CD56+ monocyte fraction. Notably, a reduced frequency of CD56⁺ monocytes was significantly associated with a lower incidence of acute GVHD, suggesting their potential as novel predictive cellular biomarkers of acute GVHD.

The online version contains supplementary material available at 10.1007/s00277-026-06897-2.