title: Blood group chimerism.
abstract: OBJECTIVE
  With improved methods for detecting chimeras and growing numbers of stem cell transplantations, blood group and other forms of chimerism are observed with increasing frequency. This review will focus on the state of science and new insights into the multifaceted subject of blood group chimerism.
  
  
  RESULTS
  Recognition that the immune system tolerates chimeric cells under certain conditions has led to efforts to elucidate related immune-modulating processes. The chimeric state following transplantation of hematopoietic stem cells, as well as after solid organ transplantation, is of special interest. Also, chimerism is considered to be a potential trigger for certain autoimmune diseases. Natural chimerism is more frequent than previously recognized. Using improved laboratory techniques, investigators can often trace chimeric tissues to their origin. New therapeutic strategies have been applied after stem cell transplantation depending on the chimeric state. Also, recent research has resulted in methods for determining chimerism in maternal peripheral blood that reflect fetal blood type and certain congenital diseases.
  
  
  CONCLUSIONS
  The subject of human chimerism has evolved from a curiosity of nature to an important field of research and, potentially, holds the key to advancing our understanding of the fundamental mechanisms of immune tolerance.
authors.affiliation: Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Camilla
authors.initials: C
authors.lastname: Drexler
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
mesh_terms: D001788:Blood Grouping and Crossmatching / Q000379:methods*; D046528:Chimerism; D006801:Humans; D007108:Immune Tolerance; D025202:Molecular Diagnostic Techniques; D033581:Stem Cell Transplantation; D018183:Transplantation Chimera / Q000097:blood* / Q000235:genetics / Q000276:immunology; D014184:Transplantation, Homologous / Q000276:immunology*