Examination of Cell Chimerism

The examination of cell chimerism has been performed in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT) since 1992 in patients of the IHBT, Department of Pediatric Hematology and Oncology, 2nd Faculty of Medicine, Charles University in Prague and Motol University Hospital, as well as other clinical users.

Chimerism is a unique state when cells from genetically different individuals coexist in one body. Allogeneic hematopoietic stem cell transplantation leads to the development of chimerism in the recipient.

DNA of each person consists of a complex of variable polymorphisms, namely short tandem repeats (STR), variable number of tandem repeats (VNTR), short deletions and insertions (indels) and single nucleotide polymorphisms (SNP) that are localized in noncoding DNA areas, which are unique for each individual. Based on the differences between the recipient´s and the donor´s DNA profiles, we can determine the origin of the cells in any case.

Analysis of individual hematopoietic chimerism at a particular point of time after transplantation is a nonspecific marker for post-transplant hematopoiesis for all diagnoses with the aim of providing a diagnostic evidence for clinical decisions.

The determination of cell chimerism allows to monitor the activity of allogeneic hematopoiesis, first signs of autologous re-population or dynamics of engraftments. The persistence of recipient hematopoiesis augments the risk of relapse. With the development of new sensitive techniques for the detection of chimerism it is possible to distinguish a relapse at a very early stage of the disease, and the subsequent quick therapeutic intervention can efficiently reduce the number of autologous cells before clinical manifestation of the disease.

For genotyping and quantification we use the following methods:

• The genotype examination of sequence polymorphisms of STR is based on single multiplex or monoplex polymerase chain reaction (PCR) of length polymorphisms, DIP polymorphisms (deletion and insertion polymorphisms) and sex specific polymorphism Amelogenin by fragment analysis.
• The genotype examination of sequence polymorphisms of SNP and indel type based on the method of quantitative real-time PCR.

The methods for an intensive monitoring of patients treated by allo-HSCT are quick, very efficient and sensitive.

The laboratory organizes External Proficiency Testing programs for this examination.