With the increasing frequency of solid organ and hematopoietic stem cell transplantation (HSCT), the population of chimeric individuals is also rising. Additionally, our understanding of, and ability to detect, microchimerism further increases the pool of chimeric people. An understanding of the causes of chimerism and the clinical implications for transplantation and transfusion is needed to properly care for these chimeric patients. Chimerism poses a special challenge for transfusion of blood products because it can lead to typing discrepancies and unexpected antigens or antibodies. Additionally, blood products may need to be chosen based on compatibility with the host and the graft. Congenital or in utero acquired chimerism is often discovered due to abnormalities on ABO typing or HLA typing as part of the transplantation process. Additionally, chimerism due to intrauterine transfusions with a naïve immune system may have long term effects different than seen in transfusion in other populations. Example cases will be used to illustrate concepts such as congenital chimerism identified by typing, persistent donor chimerism post-transfusion, transfusion in ABO and Rh mismatched HSCT, transplant donor choice and passenger lymphocyte syndrome.
Describe causes of congenital and acquired macro- and microchimerism in humans
Apply concepts of chimerism to make clinical diagnoses
Use information about chimerism to predict clinical outcomes and choose between treatment options