Comparison of microglia and infiltrating CD11c+ cells as antigen presenting cells for T cell proliferation and cytokine response

Agnieszka Wlodarczyk,Morten Løbner,Trevor Owens,Oriane Cédile

doi:10.1186/1742-2094-11-57

Abstract

BackgroundTissue-resident antigen-presenting cells (APC) exert a major influence on the local immune environment. Microglia are resident myeloid cells in the central nervous system (CNS), deriving from early post-embryonic precursors, distinct from adult hematopoietic lineages. Dendritic cells (DC) and macrophages infiltrate the CNS during experimental autoimmune encephalomyelitis (EAE). Microglia are not considered to be as effective APC as DC or macrophages.MethodsIn this work we compared the antigen presenting capacity of CD11c+ and CD11c− microglia subsets with infiltrating CD11c+ APC, which include DC. The microglial subpopulations (CD11c− CD45dim CD11b+ and CD11c+ CD45dim CD11b+) as well as infiltrating CD11c+ CD45high cells were sorted from CNS of C57BL/6 mice with EAE. Sorted cells were characterised by flow cytometry for surface phenotype and by quantitative real-time PCR for cytokine expression. They were co-cultured with primed T cells to measure induction of T cell proliferation and cytokine response.ResultsThe number of CD11c+ microglia cells increased dramatically in EAE. They expressed equivalent levels of major histocompatibility complex and co-stimulatory ligands CD80 and CD86 as those expressed by CD11c+ cells infiltrating from blood. CD11c+ microglia differed significantly from blood-derived CD11c+ cells in their cytokine profile, expressing no detectable IL-6, IL-12 or IL-23, and low levels of IL-1β. By contrast, CD11c− microglia expressed low but detectable levels of all these cytokines. Transforming growth factor β expression was similar in all three populations. Although CNS-resident and blood-derived CD11c+ cells showed equivalent ability to induce proliferation of myelin oligodendrocyte glycoprotein-immunised CD4+ T cells, CD11c+ microglia induced lower levels of T helper (Th)1 and Th17 cytokines, and did not induce Th2 cytokines.ConclusionsOur findings show distinct subtypes of APC in the inflamed CNS, with a hierarchy of functional competence for induction of CD4+ T cell responses.

Highlights

Tissue-resident antigen-presenting cells (APC) exert a major influence on the local immune environment
Activation of CD4+ T cells is a multistep process initiated by the appropriate binding of the T-cell receptor to its cognate antigenic peptide presented by major histocompatibility complex (MHC) class II molecules and subsequent stimulation by co-stimulatory molecules such as CD80 and CD86 on the antigen presenting cells
We demonstrate that infiltrating CD11c+ cells that include Dendritic cells (DC), and central nervous system (CNS)-resident CD11c+ microglia sorted from the CNS during EAE and studied directly ex vivo, express similar levels of the MHC class I and II molecules, CD80 and CD86

Summary

Introduction

Tissue-resident antigen-presenting cells (APC) exert a major influence on the local immune environment. Dendritic cells (DC) and macrophages infiltrate the CNS during experimental autoimmune encephalomyelitis (EAE). Methods: In this work we compared the antigen presenting capacity of CD11c+ and CD11c− microglia subsets with infiltrating CD11c+ APC, which include DC. Sorted cells were characterised by flow cytometry for surface phenotype and by quantitative real-time PCR for cytokine expression. They were co-cultured with primed T cells to measure induction of T cell proliferation and cytokine response. Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are characterised by infiltration to the central nervous system (CNS) of autoantigen-specific T cells, and recruitment of myeloid cells, including dendritic cells (DC) and macrophages, leading to development of inflammatory lesions, demyelination and axonal damage [1,2]. Regulatory T cells, that exert an anti-inflammatory effect, are directed by TGF-β in the absence of other Th17-inducing signals, or by IL-10 [1]

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