Precise Delineation and Transcriptional Characterization of Bovine Blood Dendritic-Cell and Monocyte Subsets.

Stephanie C Talker,Arnaud Baumann,Irene Keller,Rémy Bruggmann,Artur Summerfield,G Tuba Barut

doi:10.3389/fimmu.2018.02505

Stephanie C Talker, Arnaud Baumann + Show 4 more

Open Access

https://doi.org/10.3389/fimmu.2018.02505

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Abstract

A clear-cut delineation of bovine bona fide dendritic cells (DC) from monocytes has proved challenging, given the high phenotypic and functional plasticity of these innate immune cells and the marked phenotypic differences between species. Here, we demonstrate that, based on expression of Flt3, CD172a, CD13, and CD4, a precise identification of bovine blood conventional DC type 1 and 2 (cDC1, cDC2), plasmacytoid DC (pDC), and monocytes is possible with cDC1 being Flt3+CD172adimCD13+CD4−, cDC2 being Flt3+CD172a+CD13−CD4−, pDC being Flt3+CD172adimCD13−CD4+, and monocytes being Flt3−CD172ahighCD13−CD4−. The phenotype of these subsets was characterized in further detail, and a subset-specific differential expression of CD2, CD5, CD11b, CD11c, CD14, CD16, CD26, CD62L, CD71, CD163, and CD205 was found. Subset identity was confirmed by transcriptomic analysis and subset-specific transcription of conserved key genes. We also sorted monocyte subsets based on their differential expression of CD14 and CD16. Classical monocytes (CD14+CD16−) clustered clearly apart from the two CD16+ monocyte subsets probably representing intermediate and non-classical monocytes described in human. The transcriptomic data also revealed differential gene transcription for molecules involved in antigen presentation, pathogen sensing, and migration, and therefore gives insights into functional differences between bovine DC and monocyte subsets. The identification of cell-type- and subset-specific gene transcription will assist in the quest for “marker molecules” that—when targeted by flow cytometry—will greatly facilitate research on bovine DC and monocytes. Overall, species comparisons will elucidate basic principles of DC and monocyte biology and will help to translate experimental findings from one species to another.

Highlights

Dendritic (DC) and monocytic cells are bone-marrow derived innate immune cells with partly overlapping phenotypes and functions [1, 2]
Based on previous studies with bovine dendritic cells (DC) [27, 30], the CD4+CD13− subset was preliminarily defined as putative plasmacytoid DC (pDC), the CD4−CD13+ subset as putative conventional DC type 1 (cDC1), and the CD4−CD13− subset as putative cDC2
The present study provides a phenotypic definition of pDC, cDC1, and cDC2 in blood of cattle, which could be confirmed by subset-restricted transcription of key genes

Summary

Introduction

Dendritic (DC) and monocytic cells are bone-marrow derived innate immune cells with partly overlapping phenotypes and functions [1, 2]. Both cell types are well-equipped with pattern-recognition receptors [3], with which they can rapidly sense infection, become activated, and prime the adaptive immune system. Mouse studies have provided evidence that cDC1 and cDC2 each preferentially activate CD8 T cells or different subsets of CD4 T cells, according to crosspresentation capabilities and cytokine repertoire [9, 10]. The special feature of plasmacytoid DC (pDC), the third subset of DC, is the ability to rapidly produce large amounts of type I interferons upon activation [11], but pDC are able to activate T cells and to cross-present antigen [12, 13]

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