CD11c+ antigen presenting cells from the alveolar space, lung parenchyma and spleen differ in their phenotype and capabilities to activate naïve and antigen-primed T cells

Kapilan Kugathasan,Elizabeth K Roediger,Zhou Xing,Sarah Mccormick,Cherrie-Lee Small,Pingchang Yang

doi:10.1186/1471-2172-9-48

Abstract

BackgroundThe lung is divided into two major compartments: the alveolar space and the parenchyma. The alveolar macrophages are the first line of leukocytes in the lung taking up incoming microbes or microbial antigens whereas the parenchymal dendritic cells (DCs) are believed to be the sole potent antigen presenting cells (APCs) in the lung. Both resting alveolar macrophages and parenchymal DCs express CD11c. Several important questions remain to be elucidated: 1] to which extent the alveolar space and lung parenchymal CD11c+ APCs differ in their phenotype and ability to activate naïve T cells; 2] whether they differ in their ability to activate antigen-experienced or -primed T cells; and 3] whether these lung CD11c+ APC populations differ from the splenic CD11c+ APCs which have been commonly used for understanding APC biology.ResultsCD11c+ APCs from the alveolar space, lung parenchyma, and the spleen display differential co-stimulatory molecule expression and cytokine responsiveness upon stimulation. Alveolar space APCs are weak activators of naïve T cells compared to lung parenchymal and splenic CD11c+ APC populations. However, alveolar space APCs are able to potently activate the in vivo microbial antigen-primed T cells to a similar extent as lung parenchymal and splenic APCs.ConclusionTogether our findings indicate that alveolar CD11c+ APCs have a specialized T cell-activating function, capable of activating antigen-primed, but not naïve, T cells whereas lung CD11c+ APCs are capable of activating both the naïve and antigen-primed T cell populations.

Highlights

The lung is divided into two major compartments: the alveolar space and the parenchyma
Isolated CD11c+ antigen presenting cells (APCs) populations from the alveolar space, lung parenchyma, and spleen express differential levels of co-stimulatory molecules Alveolar macrophages (AMs) in the lung are well known to express the cell surface marker CD11c which is commonly expressed by murine dendritic cells (DCs) populations in other tissue sites such as the lung interstitium and spleen [22,3538], resulting in the vast majority (> 95%) of alveolar macrophages (AMs) in naïve lungs being CD11c+ [39,40]
By using this approach, we first compared the costimulatory molecule expression of CD11c+ APC populations freshly isolated by MACS purification from the alveolar space, lung parenchyma and the spleen as expression of co-stimulatory molecules on APCs is critical to T cell activation

Summary

Introduction

The lung is divided into two major compartments: the alveolar space and the parenchyma. The alveolar macrophages are the first line of leukocytes in the lung taking up incoming microbes or microbial antigens whereas the parenchymal dendritic cells (DCs) are believed to be the sole potent antigen presenting cells (APCs) in the lung. Both resting alveolar macrophages and parenchymal DCs express CD11c. BMC Immunology 2008, 9:48 http://www.biomedcentral.com/1471-2172/9/48 bronchoalveolar lavage (BAL), are alveolar macrophages (AMs), which are the first line of leukocytes in the lung taking up incoming microbes or microbial antigens [1,2,3,4]. It is the lung DCs that are deemed the most critical to transporting antigens from tissue to the local draining lymph nodes to activate naïve T cells [7,8]

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Conclusion