title: Regulating MHC expression for cellular therapeutics.
abstract: BACKGROUND
  In the past decade, regenerative medicine and cell-based therapies have emerged as new science and technology, with the main goal of repairing, replacing, or regenerating new tissues. A critical issue in this field is the high polymorphism of HLA, which compromises immune acceptance. The lentivirus-mediated delivery of short-hairpin RNAs (shRNAs) has proved to be an efficient method to inhibit the translation of a specific gene.
  
  
  METHODS
  A lentiviral-based vector system was used for drug-inducible expression of shRNA sequences that target either beta2-microglobulin (beta2m) or HLA heavy-chain transcripts.
  
  
  RESULTS
  The transduction of inducible RNA interference cassettes containing the sequences for shRNAs targeting beta2m or HLA heavy chain suppressed HLA class I expression by up to 90 percent in HeLa and B-lymphocyte cell lines as well as in peripheral blood monocytes. The expression of HLA class I antigens was fully restored in these cells after the drug had been discontinued. It was demonstrated that HLA class I knockdown was effective in preventing antibody-mediated cell lysis and CD8+ T-cell response. The residual HLA expression in HLA-silenced cells may provide sufficient protection against natural killer cell-mediated lysis.
  
  
  CONCLUSIONS
  These data demonstrate the feasibility of controlling HLA expression by genetically modifying cell-based therapeutics to overcome the limitations of immune rejection, bringing cellular therapies closer to reality.
authors.affiliation: Institute for Transfusion Medicine, Hanover Medical School, Hanover, Germany.
authors.forename: Constança
authors.initials: C
authors.lastname: Figueiredo
authors.forename: Peter A
authors.initials: PA
authors.lastname: Horn
authors.forename: Rainer
authors.initials: R
authors.lastname: Blasczyk
authors.forename: Axel
authors.initials: A
authors.lastname: Seltsam
mesh_terms: D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D002461:Cell Line, Transformed; D049109:Cell Proliferation; D003165:Complement System Proteins / Q000276:immunology; D003601:Cytotoxicity Tests, Immunologic; D005240:Feasibility Studies; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006084:Graft Rejection / Q000517:prevention & control; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology; D016086:Lentivirus / Q000235:genetics; D009000:Monocytes / Q000276:immunology; D034622:RNA Interference; D033581:Stem Cell Transplantation / Q000379:methods*
chemical_list: D015395:Histocompatibility Antigens Class I; D003165:Complement System Proteins