title: Suppressed splenocyte proliferation following a xenogeneic skin graft due to implanted biomaterials.
abstract: BACKGROUND
  Immune system responses to antigens in the context of biomaterials are poorly understood. Biomaterial implantation results in an inflammatory reaction, which is anticipated to alter the adaptive immune response, in the case presented here, to a skin xenograft. Our earlier work showed unexpectedly low splenocyte proliferation following a xenogeneic cell implant in tandem with a biomaterial in the form of a microcapsule. Here we explore whether that effect was due to the cells or the biomaterial, and attempt to dissect the mechanism of immune deviation.
  
  
  METHODS
  We assessed the immune response of Balb/c mice to hamster skin grafts accompanied by one of three implants: encapsulated xenogeneic cells; free cells accompanied by the same encapsulation biomaterials; and the encapsulation biomaterials without cells. Cells were encapsulated in a hydroxyethyl methacrylate-methyl methacrylate copolymer then embedded in an agarose gel. Splenocyte proliferation upon re-challenge in vitro, antibody titer in serum, and Th1/2 polarization (by cytokines in splenocyte challenge supernatants and antibody isotypes in serum) were measured.
  
  
  RESULTS
  All skin grafts with encapsulation materials (even without cells) suppressed subsequent splenocyte proliferation at 10 days postimplant, although this effect disappeared by two months. In contrast, the antibody response was equal to or greater than that for a skin graft alone. Th1/2 polarization could not explain these observations because it did not correlate with the suppression of splenocyte proliferation.
  
  
  CONCLUSIONS
  Implanted biomaterials caused nonspecific, transient suppression of splenocyte responses to hamster cells following hamster skin grafts, which is potentially important in the context of tissue engineering.
authors.affiliation: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Ontario, Canada. kjones@mcmaster.ca
authors.forename: Kim S
authors.initials: KS
authors.lastname: Jones
authors.forename: Michael V
authors.initials: MV
authors.lastname: Sefton
authors.forename: Reginald M
authors.initials: RM
authors.lastname: Gorczynski
mesh_terms: D000818:Animals; D000917:Antibody Formation / Q000276:immunology; D001672:Biocompatible Materials / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D006224:Cricetinae; D016207:Cytokines / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D019736:Prostheses and Implants; D016038:Skin Transplantation / Q000276:immunology; D013154:Spleen / Q000166:cytology* / Q000187:drug effects; D014183:Transplantation, Heterologous
chemical_list: D001672:Biocompatible Materials; D016207:Cytokines