Analysis of the CD1 Antigen Presenting System in Humanized SCID Mice Jennifer L. Lockridge1., Xiuxu Chen1.¤a, Ying Zhou 2 , Deepika Rajesh2¤b, Drew A. Roenneburg2, Subramanya Hegde1, Sarah Gerdts1¤c, Tan-Yun Cheng3, Regan J. Anderson4, Gavin F. Painter4, D. Branch Moody3, William J. Burlingham2, Jenny E. Gumperz1* 1 Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America, 2 Department of Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States of America, 3 Division of Rheumatology, Immunology and Allergy, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America, 4 Carbohydrate Chemistry Team, Industrial Research Ltd, Lower Hutt, New Zealand 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-c producing cells. CD1d tetramer staining directly identified human iNKT cells in spleen and liver samples from engrafted mice, and injection of the glycolipid antigen a-GalCer resulted in rapid elevation of human IFN-c 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. Citation: Lockridge JL, Chen X, Zhou Y, Rajesh D, Roenneburg DA, et al. (2011) Analysis of the CD1 Antigen Presenting System in Humanized SCID Mice. PLoS ONE 6(6): e21701. doi:10.1371/journal.pone.0021701 Editor: Jean Kanellopoulos, University Paris Sud, France Received April 21, 2011; Accepted June 5, 2011; Published June 30, 2011 Copyright: 2011 Lockridge et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Major funding for this work was from an award to JEG from the Pew Scholars Program in the Biomedical Sciences and from NIH grants R01AI060777 and R21AI076707 to JEG, and by a grant from the Medical Education and Research Committee of the Wisconsin Partnership Program to WJB. GFP and RJA are employees of Industrial Research Ltd., which is a limited liability company fully owned by the government of New Zealand. The role these authors played in this study was to prepare the synthetic glycolipid a-GalCer and to formulate it for injection into mice. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: Gavin Painter and Regan Anderson are employees of Industrial Research Ltd., which is a limited liability company fully owned by the government of New Zealand. This affiliation does not alter adherence to the PLoS ONE policies on sharing data and materials. None of the other authors have competing interests to declare. * E-mail: jegumperz@wisc.edu . These authors contributed equally to this work. ¤a Current address: Department of Pathology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America ¤b Current address: Cellular Dynamics International, Madison, Wisconsin, United States of America ¤c Current address: Department of Epidemiology, University of Washington School of Public Health, Seattle, Washington, United States of America 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]. Of these, CD1a-d have been shown to present antigens at the cell surface for recognition by T cells, while CD1e is expressed intracellularly and contributes to antigen loading and processing [3]. 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. Additionally, 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. T cells that are restricted by CD1a, CD1b, or CD1c have been implicated in human immune responses to mycobacterial infections (M. tuberculosis and M. leprae) [4,5,6,7,8], and have been shown to recognize specific mycobacterial antigens including the lipid mycolic acid [9], glycolipids such as lipoarabinomannan, glucose monomycolate, and mannosyl-b-1-phosphomycoketides PLoS ONE | www.plosone.org 1 June 2011 | Volume 6 | Issue 6 | e21701