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

Abstract

IntroductionPeripheral 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.MethodsWe 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.ResultsBy 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.ConclusionIn 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.

Target Role of Monocytes as Key Cells of Innate Immunity in Rheumatoid Arthritis

“…Hyperexpressed allograft inflammatory factor-1 participates in the proliferation of inflammatory macrophages and activated T lymphocytes in the RA synovium [51]. Moreover, 50-60% of CD14 + CD16 ++ non-classical monocytes have been shown to express the 6-sulfo LacNAc (SLAN) antigen, which is an O-linked glycosylated variant of P-selectin glycoprotein ligand-1 recognized by specific monoclonal antibodies, including macrophage-derived chemokine 8 and anti-D-dimers 1 and 2 [52,53]. In clinical studies, Hofer Th.P.…”