title: Current progress in xenogeneic tolerance.
abstract: OBJECTIVE
  The present review updates the current status of research regarding the immunologic responses of the recipient following xenotransplantation. Additionally, we present the recent progress with attempts to induce xenogeneic tolerance induction.
  
  
  RESULTS
  There continues to be great interest in xenotransplantation. Recently, descriptions of the mechanisms responsible for attempted T-cell xenogeneic tolerance in both large and small animal models have improved xenogeneic graft survivals. Additionally, the cellular signaling mechanisms, such as those involving CD39, CD44, and CD47, are proving to be highly important. Using the mixed chimerism approach to tolerance in xenogeneic model may be encouraging, especially given the recent clarification of the role for macrophage-induced phagocytosis of xenogeneic donor cells.
  
  
  CONCLUSIONS
  Induction of tolerance to xenogeneic antigens has been accomplished only in small animals; however, graft survivals in large animal models continue to improve. Further clarification of both the adaptive and innate immune responses to xenogeneic antigens is required for success to continue.
authors.affiliation: Transplantation Biology Research Center, Massachusetts General Hospital, Boston, Massachusetts 02129, USA. kaz.yamada@tbrc.mgh.harvard.edu
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamada
authors.forename: Joseph
authors.initials: J
authors.lastname: Scalea
mesh_terms: D000818:Animals; D046528:Chimerism; D006085:Graft Survival / Q000276:immunology; D006801:Humans; D013601:T-Lymphocytes / Q000276:immunology; D023001:Transplantation Tolerance / Q000276:immunology*; D014183:Transplantation, Heterologous / Q000276:immunology*