title: Discrete monoclonal antibodies define functionally important epitopes in the CD200 molecule responsible for immunosuppression function.
abstract: BACKGROUND
  Both murine and human CD200 fusion proteins (CD200Fc) act as immunosuppressants after engagement of cell-bound receptors (CD200R). Anti-CD200 monoclonal antibodies (mAbs) augment activity in mixed leukocyte cultures (MLCs) (increased cytotoxic T lymphocyte/cytokine production) after neutralization of endogenous CD200 activity. Previous studies documented critical regions in the N-terminal domains of both CD200 and CD200R1 for ligand:receptor binding and defined a number of synthetic CD200 and CD200R peptides that antagonize that interaction.
  
  
  METHODS
  We used a panel of mAbs to mouse and human CD200Fc to compare the rank activities of antibodies for binding (flow cytometric analysis [FACS] or enzyme-linked immunoadsorbent assay [ELISA]) to CD200 with their abilities to augment immune reactivity in MLCs.
  
  
  RESULTS
  Only mAbs defining epitopes in the N-terminal domain could augment MLC reactivity (or block immunosuppression by soluble CD200Fc), whereas mAbs targeting C-domain epitopes, although reactive in ELISA or FACS (targeting cell surface CD200), were inactive in MLCs.
  
  
  CONCLUSIONS
  In addition to defining the importance of N-terminal epitopes for CD200 function, rank comparison of mAbs for FACS staining of CD200 expressed on various cell types indicates heterogeneity in expressed CD200.
authors.affiliation: The Toronto Hospital, University Health Network, Toronto, Canada.
authors.forename: Dang-Xiao
authors.initials: DX
authors.lastname: Chen
authors.forename: Reginald M
authors.initials: RM
authors.lastname: Gorczynski
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015703:Antigens, CD; D000954:Antigens, Surface / Q000276:immunology*; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D016207:Cytokines / Q000032:analysis / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000032:analysis; D006801:Humans; D007165:Immunosuppression Therapy / Q000379:methods; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D013154:Spleen / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000954:Antigens, Surface; D016207:Cytokines; D000939:Epitopes; D008070:Lipopolysaccharides; D010446:Peptide Fragments; C042739:antigens, CD200