Microchimerism
This chapter focuses on transfusion-associated microchimeism (TA-MC). Chimerism is the presence of more than one genetically distinct population of cells in a single organism that originated from more than one zygote and microchimerism occurs when the non-host cells represent only 5% of the cells of an individual and can be a consequence of pregnancy, organ transplantation and transfusion. Blood transfusion can result in a stable persistent minor population of allogeneic cells within the recipient and it is termed TA-MC. Transfusion-associated microchimerism is the presence of transfused donor leukocytes constituting up to 5% of the recipient's peripheral blood leukocytes, which can remain for long periods of time. For the diagnosis of TA-MC, it requires the selection of optimal genetic difference between donor and recipient DNA, and the capability to detect the small amount of donor DNA amongst a large amount of host DNA. A technique to detect TA-MC is real-time polymerase chain reaction (PCR) and a limitation to the testing techniques is the difficulty to detect TC-MC in the sample volume and sampling error.
