Detecting Chimerism after Blood and Marrow Transplantation

Abstract

This chapter discusses fundamental aspects of laboratory assessment of hematopoietic chimerism after blood and marrow transplantation. Clinical indications for chimerism testing in blood and marrow transplantation include posttransplant monitoring of engraftment kinetics and stable mixed chimerism as well as detecting relapse and graft loss. Additional applications include detecting cells engrafted from a third party and distinguishing monozygotic and dizygotic twins. Chimerism testing is routinely used after allogeneic blood and marrow transplantation to monitor the status of the allograft and to detect relapse. In the early years of bone marrow transplantation, chimerism testing was primarily limited to use for monitoring donor engraftment. In 2005, the predominant methods for chimerism testing involve amplification of short tandem repeats (STR) loci. There are many situations in which there is coexistence of donor and host hematopoietic cells, and this phenomenon is referred to as mixed chimerism. In patients with mixed chimerism, the proportion (percentage) of donor cells can change, and this condition is described as increasing mixed chimerism if the percentage of donor cells is increasing or decreasing mixed chimerism if the percentage of donor cells is decreasing. For blood and marrow transplantation, chimerism analysis has become an important component of posttransplant monitoring. In addition to the clinical indications, chimerism testing can be used to test for the presence of third-party cells derived from blood transfusions, maternal cell engraftment in immunocompromised children, and maternal cell contamination of umbilical cord blood units.