title: Allogeneic major histocompatibility complex-mismatched equine bone marrow-derived mesenchymal stem cells are targeted for death by cytotoxic anti-major histocompatibility complex antibodies.
abstract: BACKGROUND
  Allogeneic mesenchymal stem cells (MSCs) are a promising cell source for treating musculoskeletal injuries in horses. Controversy exists, however, over whether major histocompatibility complex (MHC)-mismatched MSCs are recognised by the recipient immune system and targeted for death by a cytotoxic antibody response.
  
  
  OBJECTIVE
  To determine if cytotoxic anti-MHC antibodies generated in vivo following MHC-mismatched MSC injections are capable of initiating complement-dependent cytotoxicity of MSCs.
  
  
  METHODS
  Experimental controlled study.
  
  
  METHODS
  Antisera previously collected at Days 0, 7, 14 and 21 post-injection from 4 horses injected with donor MHC-mismatched equine leucocyte antigen (ELA)-A2 haplotype MSCs and one control horse injected with donor MHC-matched ELA-A2 MSCs were utilised in this study. Antisera were incubated with ELA-A2 MSCs before adding complement in microcytotoxicity assays and cell death was analysed via eosin dye exclusion. ELA-A2 peripheral blood leucocytes (PBLs) were used in the assays as a positive control.
  
  
  RESULTS
  Antisera from all 4 horses injected with MHC-mismatched MSCs contained antibodies that caused the death of ELA-A2 haplotype MSCs in the microcytotoxicity assays. In 2 of the 4 horses, antibodies were present as early as Day 7 post-injection. MSC death was consistently equivalent to that of ELA-A2 haplotype PBL death at all time points and antisera dilutions. Antisera from the control horse that was injected with MHC-matched MSCs did not contain cytotoxic ELA-A2 antibodies at any of the time points examined.
  
  
  CONCLUSIONS
  This study examined MSC death in vitro only and utilized antisera from a small number of horses.
  
  
  CONCLUSIONS
  The cytotoxic antibody response induced in recipient horses following injection with donor MHC-mismatched MSCs is capable of killing donor MSCs in vitro. These results suggest that the use of allogeneic MHC-mismatched MSCs must be cautioned against, not only for potential adverse events, but also for reduced therapeutic efficacy due to targeted MSC death.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Berglund
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
authors.forename: L V
authors.initials: LV
authors.lastname: Schnabel
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D000917:Antibody Formation / Q000276:immunology*; D001853:Bone Marrow; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology*; D006736:Horses; D008285:Major Histocompatibility Complex / Q000276:immunology*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000276:immunology*
chemical_list: D000906:Antibodies
keywords: allogeneic; antibody response; complement-dependent cytotoxicity; horse; major histocompatibility complex-mismatched; mesenchymal stem cell