Analysis of the CD1 Antigen Presenting System in Humanized SCID Mice

Jennifer L Lockridge,Deepika Rajesh,Jenny E Gumperz,Regan J Anderson,Ying Zhou,Drew A Roenneburg,William J Burlingham,Tan-Yun Cheng,Gavin F Painter,Sarah Gerdts,Subramanya Hegde,Xiuxu Chen,D Branch Moody,Jean Kanellopoulos

doi:10.1371/journal.pone.0021701

Jennifer L Lockridge, Deepika Rajesh + Show 12 more

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https://doi.org/10.1371/journal.pone.0021701

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Abstract

CD1 molecules are glycoproteins that present lipids and glycolipids for recognition by T cells. CD1-dependent immune activation has been implicated in a wide range of immune responses, however, our understanding of the role of this pathway in human disease remains limited because of species differences between humans and other mammals: whereas humans express five different CD1 gene products (CD1a, CD1b, CD1c, CD1d, and CD1e), muroid rodents express only one CD1 isoform (CD1d). Here we report that immune deficient mice engrafted with human fetal thymus, liver, and CD34+ hematopoietic stem cells develop a functional human CD1 compartment. CD1a, b, c, and d isoforms were highly expressed by human thymocytes, and CD1a+ cells with a dendritic morphology were present in the thymic medulla. CD1+ cells were also detected in spleen, liver, and lungs. APCs from spleen and liver were capable of presenting bacterial glycolipids to human CD1-restricted T cells. ELISpot analyses of splenocytes demonstrated the presence of CD1-reactive IFN-γ producing cells. CD1d tetramer staining directly identified human iNKT cells in spleen and liver samples from engrafted mice, and injection of the glycolipid antigen α-GalCer resulted in rapid elevation of human IFN-γ and IL-4 levels in the blood indicating that the human iNKT cells are biologically active in vivo. Together, these results demonstrate that the human CD1 system is present and functionally competent in this humanized mouse model. Thus, this system provides a new opportunity to study the role of CD1-related immune activation in infections to human-specific pathogens.

Highlights

CD1 molecules are a family of b2-microglobulin-associated transmembrane glycoproteins that have a structure resembling class I molecules of the major histocompatibility complex (MHC) [1]
Human hematopoietic cell engraftment To generate ‘humanized’ mice we followed an approach that has been described previously [30], in which 6–8 week old NOD/ Prkdcscid/ccnull (NSG) mice are sub-lethally irradiated, fragments of autologous human fetal liver and fetal thymus are implanted next to each other under the kidney capsule, and concurrently, CD34+ hematopoietic stem cells purified from the fetal liver are injected intravenously (Figure 1A)
Great progress has been made using murine model systems to understand the development and function of CD1d-restricted invariant Natural Killer T (iNKT) cells, it remains unclear whether human iNKT cells are identical to their murine counterparts

Summary

Introduction

CD1 molecules are a family of b2-microglobulin-associated transmembrane glycoproteins that have a structure resembling class I molecules of the major histocompatibility complex (MHC) [1]. There are five different CD1 isoforms, called CD1a, b, c, d and e, each of which is encoded by a distinct gene [2]. In contrast to MHC-encoded antigen presenting molecules, CD1 molecules are specialized for binding lipid-containing antigens. Antigen binding to CD1 molecules is thought to occur mainly in intracellular compartments, and since CD1a and CD1b clearly follow different intracellular trafficking routes than CD1c and CD1d, it is thought that different CD1 isoforms may access distinct types of antigens. CD1 isoforms are differentially expressed on antigen presenting cell (APC) types, with CD1d expressed broadly by myeloid APCs and B cells, and CD1a, CD1b, and CD1c showing more restricted patterns of expression [1]. As a result of these differences, different CD1 isoforms may carry out divergent antigen presenting functions

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