The slan antigen identifies the prototypical non-classical CD16+-monocytes in human blood

Front Immunol. 2023 Oct 27:14:1287656. doi: 10.3389/fimmu.2023.1287656. eCollection 2023.

Abstract

Introduction: Peripheral monocytes in humans are conventionally divided into classical (CL, CD14++CD16-), intermediate (INT, CD14++CD16+) and non-classical (NC, CD14dim/-CD16++) cells, based on their expression levels of CD14 and CD16. A major fraction of the NC-monocytes has been shown to express the 6-sulfo LacNAc (slan) antigen, but whether these slan+/NC-monocytes represent the prototypical non-classical monocytes or whether they are simply a sub-fraction with identical features as the remainder of NC monocytes is still unclear.

Methods: We analyzed transcriptome (by bulk and single cell RNA-seq), proteome, cell surface markers and production of discrete cytokines by peripheral slan+/NC- and slan-/NC-monocytes, in comparison to total NC-, CL- and INT- monocytes.

Results: By bulk RNA-seq and proteomic analysis, we found that slan+/NC-monocytes express higher levels of genes and proteins specific of NC-monocytes than slan-/NC-monocytes do. Unsupervised clustering of scRNA-seq data generated one cluster of NC- and one of INT-monocytes, where all slan+/NC-monocytes were allocated to the NC-monocyte cluster, while slan-/NC-monocytes were found, in part (13.4%), within the INT-monocyte cluster. In addition, total NC- and slan-/NC-monocytes, but not slan+/NC-monocytes, were found by both bulk RNA-seq and scRNA-seq to contain a small percentage of natural killer cells.

Conclusion: In addition to comparatively characterize total NC-, slan-/NC- and slan+/NC-monocyte transcriptomes and proteomes, our data prove that slan+/NC-, but not slan-/NC-, monocytes are more representative of prototypical NC-monocytes.

Keywords: classical/non-classical monocytes; proteomics; scRNA-seq; slan+-monocytes; transcriptomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Leukocytes, Mononuclear
  • Monocytes*
  • Proteomics*

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by grants from Associazione Italiana per la Ricerca sul Cancro (AIRC, IG-27613 to MAC) and Ministero dell’Istruzione, dell’Università e della Ricerca (PRIN 20227YR8AW and PRIN 2022W839FM to MAC and NT, respectively).