Changes in the pattern of TCR V beta repertoire expression after bone marrow transplant is linked to the HLA haplotype in humans

T-cell receptor repertoire usage in hematologic malignancies

Over the last few years several studies have addressed the possible influence of different immune mechanisms on the evolution of hematologic malignancies. More specifically, a fundamental role of reactive T-cells has now been demonstrated in the pathogenesis of many of these disorders as well as in the typical immunological milieu observed after stem cell transplantation in patients affected by these malignancies. In this context the study of the T-cell receptor (TCR) repertoire performed by different techniques, such as for instance flow cytometry and spectratyping, has undoubtedly provided a fundamental contribution. More recently, these seminal observations have even opened new potential therapeutic avenues based on the employment of adoptive T-cells somehow engineered toward potential neoplastic targets. This review will run through the most relevant studies which have tried to dissect the TCR repertoire usage in patients with different hematologic malignancies, especially focusing on the possible pathogenetic and therapeutic implications.

Distribution and evolution of T-cell receptor Vbeta repertoire on peripheral blood lymphocytes of newborn infants of human immunodeficiency virus (HIV)-infected mothers: differential display on CD4 and CD8 T cells and effect of HIV infection

Neonatal human peripheral blood mononuclear cells from 12 human immunodeficiency virus (HIV)-infected and 84 uninfected children were assessed for their distribution of T-cell receptors (TCRs) by flow cytometry employing monoclonal antibodies to 14 Vbeta types. Vbeta 2, 5c, and 13 were the most commonly found on CD4 cells (in that order). There was a bimodal distribution of Vbeta 2, being most common in 48% of individuals but in limiting frequency (<2% of CD4) in 21%. Vbeta 2, 3, 8b, and 13 were most commonly expressed on CD8 cells at similar frequencies. There was little difference in the pattern displayed among the infected compared to that of the uninfected. The variation of the distribution over time was studied in 12 infants (7 infected). Only a single HIV-infected child had a significant difference in the interquartile range; none of the HIV-negative patients showed a significant difference. In conclusion, newborns demonstrate different distributions of TCR Vbeta types on CD4 and CD8 cells. HIV infection produces no change in neonatal TCR and little change over the course of 2 years compared to that seen in the uninfected.

Molecular TCR diagnostics can be used to identify shared clonotypes after allogeneic hematopoietic stem cell transplantation

OBJECTIVE

In allogeneic hematopoietic stem cell (HSCT) transplantation, recovery of the T cell receptor (TCR) repertoire depends upon the composition of the graft and is modulated by peri-transplant immunosuppression, viral infections, and graft-vs-host disease (GVHD). We hypothesized that after allogeneic HSCT, molecular analysis of the TCR repertoire can be used to identify and quantitate immunodominant T cell clones that may play a role in GVHD or other clinical events.

METHODS

We utilized a rational strategy for the analysis of the expanded CTL clones. First, we studied the VB spectrum in a cohort of patients who had received either matched sibling or unrelated donor grafts. The CDR3 sequences of immunodominant clones were identified and clonotypic PCR and sequencing was applied to determine the level of clonotype sharing.

RESULTS

Significant expansions of VB families were observed following transplantations; 61% were oligo/monoclonal. Immunodeficiency was reflected by depletion of multiple VB families from both the CD8 and CD4 repertoires. The level of sharing varied between clonotypes, suggesting that some antigens have a more "public" spectrum while others are restricted to specific patients. Immunodominant CDR3 sequences common to allogeneic HSCT, healthy controls, and other conditions were identified.

CONCLUSION

The clonotypes of expanded CTL clones may reflect responses to alloantigens (e.g., in correlation with clinical GVHD) or pathogens. In the future, molecular T cell diagnostics may become a powerful clinical tool in transplantation to monitor disease and to direct treatment.

Improving the outcome of unrelated donor stem cell transplantation by molecular matching

Volunteer unrelated donor (VUD) stem cell transplantation is now a well-established procedure in the treatment for many haematological and other disorders. The improved success of this modality of treatment is related, in part, to the existence of large volunteer donor registries (with well characterized tissue typing), as well as to the improved understanding of the molecular factors that have an influence on transplantation outcome. It is clear that close attention to human leukocyte antigen (HLA) matching is essential in ensuring a satisfactory transplant outcome, however the extent to which donor-recipient pairs need to be matched is not yet clear. There is also an increased understanding that factors other than HLA do affect clinical outcome. The ability to perform high resolution molecular typing techniques has allowed researchers to begin assessing the significance of mismatches at particular loci against an otherwise matched background, and in this way highlight the effects of individual genetic factors on transplantation outcome.