Antigen presenting cells are key players in the immune response. They are involved in priming naove and effector cells and are critical for orchestrating a response to infection as well as responses to self- antigens (autoimmunity). Among antigen presenting cells, B cells are uniquely capable of presenting small amounts of antigen, which they capture and take up through surface immunoglobulin (Ig). Based on our preliminary findings, we hypothesize that HLA-DM is a key player in enhancing presentation of antigen taken up through Ig on the surface of the B cell by bringing Ig in close proximity to MHC II and facilitating antigen release from Ig. Here, we propose to assess the functional outcome of the DM/Ig interaction in cells. We will engineer a B cell line to express a GAD65 specific immunoglobulin as well as a mutant DM that does not interact with Ig but does interact with MHC II. Mutant and wild type DM will be compared for their ability to enhance presentation of GAD65 in T cell proliferation assays, across a range of B cell numbers and antigen doses. We also propose to localize the site of the HLA-DM/Ig interaction in cells by using proximity ligation assays and fluorescence microscopy. Although we focus here on surface immunoglobulin as an antigen receptor in B cells, our results will have implications for the function of other antigen presenting cell types, such as macrophages and dendritic cells, that take up immune complexes via surface Fc receptors (FcR). These antigen/antibody complexes are also targeted to the endosomal pathway, where they encounter HLA-DM.
In health, the immune system responds to foreign antigens and mounts a response to infection. In autoimmune disease, the immune system mounts a response against the body's own (self) antigens. Antigen presenting cells mediate a critical initiating role in the development of an effective immune response by presenting self and foreign antigens to responder cells of the immune system. This project investigates a newly discovered interaction between molecules involved in antigen processing and presentation, a process that is key in shaping the immune response against foreign and self antigens with consequences for infectious as well as autoimmune diseases. The experimental system employed uses proteins of relevance to type 1 diabetes in humans.
|Jiang, Wei; Strohman, Michael J; Somasundaram, Sriram et al. (2015) pH-susceptibility of HLA-DO tunes DO/DM ratios to regulate HLA-DM catalytic activity. Sci Rep 5:17333|
|Macmillan, Henriette; Strohman, Michael J; Ayyangar, Sashi et al. (2014) The MHC class II cofactor HLA-DM interacts with Ig in B cells. J Immunol 193:2641-2650|
|Sathiyamoorthy, Karthik; Jiang, Jiansen; Hu, Yao Xiong et al. (2014) Assembly and architecture of the EBV B cell entry triggering complex. PLoS Pathog 10:e1004309|
|Mellins, Elizabeth D; Stern, Lawrence J (2014) HLA-DM and HLA-DO, key regulators of MHC-II processing and presentation. Curr Opin Immunol 26:115-22|
|Yin, Liusong; Trenh, Peter; Guce, Abigail et al. (2014) Susceptibility to HLA-DM protein is determined by a dynamic conformation of major histocompatibility complex class II molecule bound with peptide. J Biol Chem 289:23449-64|
|De la Herrán-Arita, Alberto K; Kornum, Birgitte Rahbek; Mahlios, Josh et al. (2013) CD4+ T cell autoimmunity to hypocretin/orexin and cross-reactivity to a 2009 H1N1 influenza A epitope in narcolepsy. Sci Transl Med 5:216ra176|
|Hou, Tieying; Rinderknecht, Cornelia H; Hadjinicolaou, Andreas V et al. (2013) Pulse-chase analysis for studies of MHC class II biosynthesis, maturation, and peptide loading. Methods Mol Biol 960:411-432|
|Guce, Abigail I; Mortimer, Sarah E; Yoon, Taejin et al. (2013) HLA-DO acts as a substrate mimic to inhibit HLA-DM by a competitive mechanism. Nat Struct Mol Biol 20:90-8|
|Yoon, Taejin; Macmillan, Henriette; Mortimer, Sarah E et al. (2012) Mapping the HLA-DO/HLA-DM complex by FRET and mutagenesis. Proc Natl Acad Sci U S A 109:11276-81|
|Busch, Robert; De Riva, Alessandra; Hadjinicolaou, Andreas V et al. (2012) On the perils of poor editing: regulation of peptide loading by HLA-DQ and H2-A molecules associated with celiac disease and type 1 diabetes. Expert Rev Mol Med 14:e15|