A novel bacterial artificial chromosome-transgenic Podoplanin–Cre mouse targets lymphoid organ stromal cells in vivo

Lucas Onder

doi:10.3389/fimmu.2011.00050

Abstract

Stromal cells provide the structural foundation of secondary lymphoid organs (SLOs), and regulate leukocyte access and cell migration within the different compartments of spleen and lymph nodes (LNs). Furthermore, several stromal cell subsets have been implied in shaping of T cell responses through direct presentation of antigen. Despite significant gain of knowledge on the biology of different SLO-resident stromal cell subsets, their molecular and functional characterization has remained incomplete. To address this need, we have generated a bacterial artificial chromosome-transgenic mouse model that utilizes the podoplanin (pdpn) promoter to express the Cre-recombinase exclusively in stromal cells of SLOs. The characterization of the Pdpn–Cre mouse revealed transgene expression in subsets of fibroblastic reticular cells and lymphatic endothelial cells in LNs. Furthermore, the transgene facilitated the identification of a novel splenic perivascular stromal cell subpopulation that forms web-like structures around central arterioles. Assessment of the in vivo antigen expression in the genetically tagged stromal cells in Pdpn–Cre mice revealed activation of both MHC I and II-restricted TCR transgenic T cells. Taken together, stromal pdpn–Cre expression is well-suited to characterize the phenotype and to dissect the function of lymphoid organ stromal cells.

Highlights

Secondary lymphoid organs (SLOs) are characterized by a complex architecture with specialized compartments that facilitate the efficient interaction between immune cells
The present study has addressed the need to generate models that facilitate (i) genetic definition of distinct lymph node (LN) and splenic stromal cell populations, (ii) in vivo labeling and tracking of particular stromal cell subsets, and (iii) functional assessment of immune activation/tolerization processes through selective expression of model antigens
One of the three Pdpn–Cre founder lines displayed a suitable transgene expression pattern that facilitated the identification of novel stromal cell subpopulations in secondary lymphoid organ (SLO) such as the splenic perivascular stromal cell

Summary

Introduction

Secondary lymphoid organs (SLOs) are characterized by a complex architecture with specialized compartments that facilitate the efficient interaction between immune cells. The structural foundation of this compartmentalization is formed by elaborate frameworks of stromal cell elements (Junt et al, 2008; Mueller and Germain, 2009). These non-hematopoietic cells can be divided in subpopulations that are distinguished by their properties, functions, and localization. The highly plastic system of lymphatic vessels that is formed by lymphatic endothelial cells (LECs), distributes lymph fluid through the lymphoid tissues and regulates lymphocyte trafficking (Pham et al, 2010). A bridging function, in terms of junction formation between the lymphatic vasculature and the conduit network, is fulfilled by marginal reticular cells (MRCs) that form a dense web of stromal cells underlying the subcapsular

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