Lineage-specific chimerism analysis in nucleated cells, T cells and natural killer cells after myeloablative allogeneic hematopoietic stem cell transplantation

Comparison of Three CD3-Specific Separation Methods Leading to Labeled and Label-Free T Cells

T cells are an essential part of the immune system. They determine the specificity of the immune response to foreign substances and, thus, help to protect the body from infections and cancer. Recently, T cells have gained much attention as promising tools in adoptive T cell transfer for cancer treatment. However, it is crucial not only for medical purposes but also for research to obtain T cells in large quantities, of high purity and functionality. To fulfill these criteria, efficient and robust isolation methods are needed. We used three different isolation methods to separate CD3-specific T cells from leukocyte concentrates (buffy coats) and Ficoll purified PBMCs. To catch the target cells, the Traceless Affinity Cell Selection (TACS^®) method, based on immune affinity chromatography, uses CD-specific low affinity Fab-fragments; while the classical Magnetic Activated Cell Sorting (MACS^®) method relies on magnetic beads coated with specific high affinity monoclonal antibodies. The REAlease^® system also works with magnetic beads but, in contrast to MACS^®, low-affinity antibody fragments are used. The target cells separated by TACS^® and REAlease^® are “label-free”, while cells isolated by MACS^® still carry the cell specific label. The time required to isolate T cells from buffy coat by TACS^® and MACS^® amounted to 90 min and 50 min, respectively, while it took 150 min to isolate T cells from PBMCs by TACS^® and 110 min by REAlease^®. All methods used are well suited to obtain T cells in large quantities of high viability (>92%) and purity (>98%). Only the median CD4:CD8 ratio of approximately 6.8 after REAlease^® separation differed greatly from the physiological conditions. MACS^® separation was found to induce proliferation and cytokine secretion. However, independent of the isolation methods used, stimulation of T cells by anti CD3/CD28 resulted in similar rates of proliferation and cytokine production, verifying the functional activity of the isolated cells.

Chimerism Monitoring Techniques after Hematopoietic Stem Cell Transplantation: An Overview of the Last 15 Years of Innovations

Chimerism analysis is a well-established method for monitoring the state of hematopoietic stem cell transplantation (HSCT) over time by analyzing peripheral blood or bone marrow samples of the recipient in several malignant and non-malignant hematologic diseases. From a clinical point of view, a continuous monitoring is fundamental for an effective early therapeutic intervention. This paper provides a comparative overview of the main molecular biology techniques which can be used to study chimerism after bone marrow transplantation, focusing on their advantages and disadvantages. According to the examined literature, short tandem repeats (STR) analysis through simple PCR coupled with capillary electrophoresis (STR-PCR) is the most powerful method which guarantees a high power of differentiation between different individuals. However, other methods such as real-time quantitative PCR (qPCR), digital PCR (dPCR), and next-generation sequencing (NGS) technology were developed to overcome the technical limits of STR-PCR. In particular, these other techniques guarantee a higher sensitivity, which allows for the detection of chimerism at an earlier stage, hence expanding the window for therapeutic intervention. After a comparative evaluation of the various techniques, it seems clear that STR-PCR still remains the gold standard option for chimerism study, even if it is likely that both dPCR and NGS could supplement or even replace the common methods of STR analysis.

The Relationship between STR-PCR Chimerism Analysis and Chronic GvHD Following Hematopoietic Stem Cell Transplantation

Background: The study attempts to assess the relationship between chimerism analysis using polymerase chain reaction of short tandem repeat (STR) and the incidence of chronic graft versus host disease (GvHD) as well as survival. Subjects and Methods: The retrospective cohort included all patients who received allo-HSCT during 2005-2013. Data collected by day +100 were reviewed in terms of the incidence of chronic GvHD and survival. Chimerism was evaluated for whole blood, T-cell and PMN cells on days 15, 30 and 60, respectively using polymerase chain reaction of short tandem repeat (STR). Results: Forty (69%) patients developed chronic GvHD, 11 (19%) relapsed and 22 (39.7%) expired during the study. There was a significant relationship between chronic GvHD and chimerism analysis including whole blood on day 60 (p=0.001), Polymorphonuclear neutrophil (PMN) on day 60 (p=0.05), T-cell on days 15 (p=0.028), 30 (p=0.01) and 60 (p=0.004). Patients with chronic GvHD showed a long-term survival as compared with those without chronic GvHD (p=0.0013). Conclusion: Conducting continuous analysis of chimerism provides an opportunity to initiate immediate measures in order to prevent complications.

Is there a role for B lymphocyte chimerism in the monitoring of B-acute lymphoblastic leukemia patients receiving allogeneic stem cell transplantation?

OBJECTIVE

To determine the sensitivity and significance of B-cell chimerism for the detection of early engraftment, transplant rejection, and disease relapse.

METHODS

The dynamic monitoring of lineage-specific cell subtypes (B, T, and NK cells) was made in 20 B-cell acute lymphoblastic leukemia (B-ALL) patients following allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the early period after allo-HSCT, the latest establishment of B-cell complete chimerism (CC) was observed in a majority of patients.

RESULTS

The percentage of donor cells of B-cell lineage was lower than the percent of T-cell lineage in most of the mixed chimerism (MC) patients. During graft rejection, the frequency of patients with decreasing MC of B-, T- and NK-cell lineage were 5/5, 2/5, and 2/5. When disease relapsed, five patients showed a faster decrease of the donor percent of B-cells than of T- or NK-cells. Only one patient displayed a more rapid decrease in NK-cells than in T- or B-cells.

CONCLUSION

Monitoring of B-cell chimerism after HSCT seems to be valuable for insuring complete engraftment, anticipating graft rejection, and relapse in B-ALL patients.