# Integrated Functional and scRNA-Seq Analyses Reveal Convergence of M-CSF– and GM-CSF–Derived Macrophages Following IL-27 Polarization

## TL;DR

This study shows that IL-27 can reprogram two types of macrophages into a similar state, suggesting a key role for IL-27 in macrophage plasticity.

## Contribution

The study reveals that IL-27 induces a convergent phenotype in M-CSF- and GM-CSF-derived macrophages.

## Key findings

- IL-27-polarized M-Mac and GM-Mac show similar transcriptional and functional profiles.
- IL-27 treatment suppresses HIV replication and enhances CD38 expression and autophagy in macrophages.
- Phagocytic activity is reduced in IL-27-polarized macrophages compared to controls.

## Abstract

What are the main findings?
Two distinct macrophage subsets—M-CSF– and GM-CSF–differentiated monocyte-derived macrophages (MDMs)—are reprogrammed by IL-27 into a convergent phenotype

Two distinct macrophage subsets—M-CSF– and GM-CSF–differentiated monocyte-derived macrophages (MDMs)—are reprogrammed by IL-27 into a convergent phenotype

What are the implications of the main findings?
IL-27 functions as a convergent polarization cytokine.IL-27 may play a central role in regulating macrophage plasticity.

IL-27 functions as a convergent polarization cytokine.

IL-27 may play a central role in regulating macrophage plasticity.

Macrophages differentiated with macrophage colony-stimulating factor (M-CSF) (M-Mac) are widely used as an experimental model. Interleukin 27 (IL-27)-polarized M-Mac (27M-Mac) suppresses HIV replication; however, the effects of IL-27 polarization on granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced macrophages (GM-Mac) remain less investigation. Here, we compare multiple functional properties and gene expression profiles of 27M-Mac and IL-27-polarized GM-Mac (27GM-Mac). M-Mac and GM-Mac were generated from monocytes of healthy donors and subsequently treated with IL-27 for three days. HIV replication in 27M-Mac, GM-Mac, and 27GM-Mac was suppressed to nearly 10% of that in M-Mac; however, single-cell RNA sequencing showed that M-Mac clustered with GM-Mac, and 27M-Mac clustered with 27GM-Mac. Expression of CD38 and secretion of CXCL9 and C1q were significantly increased in 27M-Mac and 27GM-Mac compared with M-Mac and GM-Mac. Although CD16 and CD64 expression increased in 27M-Mac and 27GM-Mac relative to their respective controls, phagocytic activity in 27M-Mac and 27GM-Mac was 30% of that in M-Mac. Autophagy was promoted 3.7-fold more strongly in 27M-Mac than in M-Mac, reaching levels comparable to those in GM-Mac and 27GM-Mac. Collectively, these findings indicate that IL-27 polarizes M-Mac and GM-Mac toward transcriptionally and functionally similar subtypes, providing insight into the role of IL-27 in macrophage polarization and plasticity.