Assessing diversity: immune reconstitution and T-cell receptor BV spectratype analysis following stem cell transplantation

T Cell Receptor Repertoire Analysis Reveals Signatures of T Cell Responses to Human Mycobacterium tuberculosis

Characterization of T cell receptor (TCR) repertoires is essential for understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection involving T cell adaptive immunity. The characteristics of TCR sequences and distinctive signatures of T cell subsets in tuberculous patients are still unclear. By combining single-cell TCR sequencing (sc-TCR seq) with single-cell RNA sequencing (sc-RNA seq) and flow cytometry to characterize T cells in tuberculous pleural effusions (TPEs), we identified 41,718 CD3⁺ T cells in TPEs and paired blood samples, including 30,515 CD4⁺ T cells and 11,203 CD8⁺ T cells. Compared with controls, no differences in length and profile of length distribution were observed in complementarity determining region 3 (CDR3) in both CD4⁺ and CD8⁺ T cells in TPE. Altered hydrophobicity was demonstrated in CDR3 in CD8⁺ T cells and a significant imbalance in the TCR usage pattern of T cells with preferential expression of TRBV4-1 in TPE. A significant increase in clonality was observed in TCR repertoires in CD4⁺ T cells, but not in CD8⁺ T cells, although both enriched CD4⁺ and CD8⁺ T cells showed T_H1 and cytotoxic signatures. Furthermore, we identified a new subset of polyfunctional CD4⁺ T cells with CD1-restricted, T_H1, and cytotoxic characteristics, and this subset might provide protective immunity against Mtb.

Cytometry of Reaction Rate Constant: Measuring Reaction Rate Constant in Individual Cells To Facilitate Robust and Accurate Analysis of Cell-Population Heterogeneity

Robust and accurate analysis of cell-population heterogeneity is challenging but required in many areas of biology and medicine. In particular, it is pivotal to the development of reliable cancer biomarkers. Here, we prove that cytometry of reaction rate constant (CRRC) can facilitate such analysis when the kinetic mechanism of a reaction associated with the heterogeneity is known. In CRRC, the cells are loaded with a reaction substrate, and its conversion into a product is followed by time-lapse fluorescence microscopy at the single-cell level. A reaction rate constant is determined for every cell, and a kinetic histogram "number of cells versus the rate constant" is used to determine quantitative parameters of reaction-based cell-population heterogeneity. Such parameters include, for example, the number and sizes of subpopulations. In this work, we applied CRRC to a reaction of substrate extrusion from cells by ATP-binding cassette (ABC) transporters. This reaction is viewed as a potential basis for predictive biomarkers of chemoresistance in cancer. CRRC proved to be robust (insensitive to variations in experimental settings) and accurate for finding quantitative parameters of cell-population heterogeneity. In contrast, a typical nonkinetic analysis, performed on the same data sets, proved to be both nonrobust and inaccurate. Our results suggest that CRRC can potentially facilitate the development of reliable cancer biomarkers on the basis of quantitative parameters of cell-population heterogeneity. A plausible implementation scenario of CRRC-based development, validation, and clinical use of a predictor of ovarian cancer chemoresistance to its frontline therapy is presented.

Immune dysregulation in immunodeficiency disorders: The role of T-cell receptor sequencing

Immune dysregulation is a prominent feature of primary immunodeficiency disorders, which commonly manifested as autoimmunity, cytopenias and inflammatory bowel disease. In partial T-cell immunodeficiency disorders, it has been proposed that the imbalance between effector and regulatory T-cells drives the breakdown of peripheral tolerance. While there is no robust test for immune dysregulation, the T-cell receptor repertoire is used as a surrogate marker, and has been shown to be perturbed in a number of immunodeficiency disorders featuring immune dysregulation including Omenn's Syndrome, Wiskott-Aldrich Syndrome, and common variable immunodeficiency. This review discusses how recent advances in TCR next-generation sequencing and bioinformatics have led to the in-depth characterization of CDR3 sequences and an exponential growth in examinable parameters. Specifically, we highlight the use of junctional diversity as a means to differentiate intrinsic T-cell defects from secondary causes of repertoire perturbation in primary immunodeficiency disorders. However, key questions, such as the identity of antigenic targets for large, expanded T-cell clonotypes, remain unanswered despite the fact that such clones are likely to play a pathogenic role in driving immune dysregulation and autoimmunity. Finally, we discuss a number of emerging technologies such as in silico reconstruction, high-throughput pairwise αβ sequencing and single-cell RNAseq that offer the potential to define the antigenic epitope and function of a given T-cell, thereby enhancing our understanding in this field.

The past, present, and future of immune repertoire biology - the rise of next-generation repertoire analysis

T and B cell repertoires are collections of lymphocytes, each characterized by its antigen-specific receptor. We review here classical technologies and analysis strategies developed to assess immunoglobulin (IG) and T cell receptor (TR) repertoire diversity, and describe recent advances in the field. First, we describe the broad range of available methodological tools developed in the past decades, each of which answering different questions and showing complementarity for progressive identification of the level of repertoire alterations: global overview of the diversity by flow cytometry, IG repertoire descriptions at the protein level for the identification of IG reactivities, IG/TR CDR3 spectratyping strategies, and related molecular quantification or dynamics of T/B cell differentiation. Additionally, we introduce the recent technological advances in molecular biology tools allowing deeper analysis of IG/TR diversity by next-generation sequencing (NGS), offering systematic and comprehensive sequencing of IG/TR transcripts in a short amount of time. NGS provides several angles of analysis such as clonotype frequency, CDR3 diversity, CDR3 sequence analysis, V allele identification with a quantitative dimension, therefore requiring high-throughput analysis tools development. In this line, we discuss the recent efforts made for nomenclature standardization and ontology development. We then present the variety of available statistical analysis and modeling approaches developed with regards to the various levels of diversity analysis, and reveal the increasing sophistication of those modeling approaches. To conclude, we provide some examples of recent mathematical modeling strategies and perspectives that illustrate the active rise of a "next-generation" of repertoire analysis.

BCR CDR3 length distributions differ between blood and spleen and between old and young patients, and TCR distributions can be used to detect myelodysplastic syndrome

Complementarity-determining region 3 (CDR3) is the most hyper-variable region in B cell receptor (BCR) and T cell receptor (TCR) genes, and the most critical structure in antigen recognition and thereby in determining the fates of developing and responding lymphocytes. There are millions of different TCR Vβ chain or BCR heavy chain CDR3 sequences in human blood. Even now, when high-throughput sequencing becomes widely used, CDR3 length distributions (also called spectratypes) are still a much quicker and cheaper method of assessing repertoire diversity. However, distribution complexity and the large amount of information per sample (e.g. 32 distributions of the TCRα chain, and 24 of TCRβ) calls for the use of machine learning tools for full exploration. We have examined the ability of supervised machine learning, which uses computational models to find hidden patterns in predefined biological groups, to analyze CDR3 length distributions from various sources, and distinguish between experimental groups. We found that (a) splenic BCR CDR3 length distributions are characterized by low standard deviations and few local maxima, compared to peripheral blood distributions; (b) healthy elderly people's BCR CDR3 length distributions can be distinguished from those of the young; and (c) a machine learning model based on TCR CDR3 distribution features can detect myelodysplastic syndrome with approximately 93% accuracy. Overall, we demonstrate that using supervised machine learning methods can contribute to our understanding of lymphocyte repertoire diversity.

Quantification of total T-cell receptor diversity by flow cytometry and spectratyping

BACKGROUND

T-cell receptor diversity correlates with immune competency and is of particular interest in patients undergoing immune reconstitution. Spectratyping generates data about T-cell receptor CDR3 length distribution for each BV gene but is technically complex. Flow cytometry can also be used to generate data about T-cell receptor BV gene usage, but its utility has not been compared to or tested in combination with spectratyping.

RESULTS

Using flow cytometry and spectratype data, we have defined a divergence metric that quantifies the deviation from normal of T-cell receptor repertoire. We have shown that the sample size is a sensitive parameter in the predicted flow divergence values, but not in the spectratype divergence values. We have derived two ways to correct for the measurement bias using mathematical and statistical approaches and have predicted a lower bound in the number of lymphocytes needed when using the divergence as a substitute for diversity.

CONCLUSIONS

Using both flow cytometry and spectratyping of T-cells, we have defined the divergence measure as an indirect measure of T-cell receptor diversity. We have shown the dependence of the divergence measure on the sample size before it can be used to make predictions regarding the diversity of the T-cell receptor repertoire.

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.

TRBV kinetics and its association with HLA disparity and aGVHD following allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The relative expression of T cell receptor (TCR) beta variable (TRBV) and TCR diversity was compared between recipients receiving human leukocyte antigen (HLA)-mismatched transplants and those receiving HLA-matched transplants, using granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells and bone marrow as grafts.

METHODS

The kinetics of the relative expression of TRBV family members were analyzed using real-time quantitative PCR. Additionally, the association of TRBV clonotype with acute graft-versus-host disease (aGVHD) was determined by cloning and sequence analysis of the CDR3 region.

RESULTS

The TCR diversity in recipients receiving HLA-mismatched transplants was significantly lower than in those receiving HLA-matched transplants at 1 month and 2 months after hematopoietic stem cell transplantation (HSCT) (both P < 0.05). However, these differences disappeared 3 months after transplantation. The relative expression of TRBV27 (n = 7 recipients) at the onset of aGVHD was higher than in corresponding donors (P = 0.025), but no significant differences were observed between recipients lacking aGVHD and their donors at serial time points after HSCT.

CONCLUSION

Our results suggest that HLA disparity may affect the relative expression of TRBV in the early phase after transplantation, and TRBV27 may be associated with the onset of aGVHD.

Quantitative analysis of T cell receptor diversity in clinical samples of human peripheral blood

The analysis of T cell receptor diversity provides a clinically relevant and sensitive marker of repertoire loss, gain, or skewing. Spectratyping is a broadly utilized technique to measure global TCR diversity by the analysis of the lengths of CDR3 fragments in each Vβ family. However the common use of large numbers of T cells to obtain a global view of TCR Vβ CDR3 diversity has restricted spectratyping analyses when limited T-cell numbers are available in clinical setting, such as following transplant regimens. We here demonstrate that one hundred thousand T cells are sufficient to obtain a robust, highly reproducible measure of the global TCR Vβ repertoire diversity among twenty Vβ families in human peripheral blood. We also show that use of lower cell number results not in a dwindling of observed diversity but rather in non-reproducible patterns in replicate spectratypes. Finally, we report here a simple to use but sensitive method to quantify repertoire divergence in patient samples by comparison to a standard repertoire profile we generated from fifteen normal donors. We provide examples using this method to statistically evaluate the changes in the global TCR Vβ repertoire diversity that may take place during T subset immune reconstitution after hematopoietic stem cell transplantation or after immune modulating therapies.

High throughput sequencing reveals a complex pattern of dynamic interrelationships among human T cell subsets

Developing T cells face a series of cell fate choices in the thymus and in the periphery. The role of the individual T cell receptor (TCR) in determining decisions of cell fate remains unresolved. The stochastic/selection model postulates that the initial fate of the cell is independent of TCR specificity, with survival dependent on additional TCR/coreceptor "rescue" signals. The "instructive" model holds that cell fate is initiated by the interaction of the TCR with a cognate peptide-MHC complex. T cells are then segregated on the basis of TCR specificity with the aid of critical coreceptors and signal modulators [Chan S, Correia-Neves M, Benoist C, Mathis (1998) Immunol Rev 165: 195-207]. The former would predict a random representation of individual TCR across divergent T cell lineages whereas the latter would predict minimal overlap between divergent T cell subsets. To address this issue, we have used high-throughput sequencing to evaluate the TCR distribution among key T cell developmental and effector subsets from a single donor. We found numerous examples of individual subsets sharing identical TCR sequence, supporting a model of a stochastic process of cell fate determination coupled with dynamic patterns of clonal expansion of T cells bearing the same TCR sequence among both CD4(+) and CD8+ populations.

Abnormalities of the alphabeta T-cell receptor repertoire in advanced myelodysplastic syndrome

OBJECTIVE

Analysis of the alphabeta T-cell receptor (TCR) repertoire in patients with myelodysplastic syndrome (MDS) using the technique of TCR beta-chain spectratyping has provided valuable insight into the pathophysiology of cytopenias in a subset of patients with this heterogeneous disorder. TCR beta-chain spectratypes are complex data sets, however, and statistical tools for their comprehensive analysis are limited. The objective of the present work was to develop a method to enable quantitative evaluation and global comparison of spectratype data from different individuals and to study the prevalence of TCR beta repertoire abnormalities in MDS patients.

MATERIALS AND METHODS

We developed a robust statistical method based on k-means clustering analysis, and applied this method to analysis of the alphabeta TCR repertoires in 50 MDS patients and 23 age-matched healthy controls.

RESULTS

Cluster analysis identified a subset of 11 MDS patients with profoundly abnormal alphabeta TCR repertoires. This group of patients was characterized by advanced disease by International Prognostic Scoring System and World Health Organization criteria, increased expression of the Wilms' tumor-1 oncogene, increased bone marrow myeloblast count, and older age.

CONCLUSIONS

We have developed a robust analytic algorithm that enables the comparison of alphabeta TCR repertoires between individuals and have shown that abnormal alphabeta TCR repertoire is a feature of a subset of patients with advanced MDS.

Characterization of T-cell population in children with prolonged fetal exposure to dexamethasone for anti-Ro/SS-A antibodies associated congenital heart block

The objectives of the study were to characterize the production, function and survival of T lymphocytes of children with prolonged fetal exposure to dexamethasone for anti-Ro/SS-A antibodies associated congenital complete heart block. The analysis of thymic function, studied by measuring the level of T-cell receptor excision circles, was performed by real time PCR, the composition of T-cell subpopulation was evaluated by flow cytometry and the T-cell diversity was assayed by heteroduplex analysis. T-cell competence was gauged at two functional levels by determining the proliferation and the number of T-cell divisions and by measuring gamma-interferon production after mitogenic stimulation. We observed that the thymic output, distribution of T-cell subsets, thymidine incorporation, number of T-cell divisions, and y-interferon production were comparable to those of age-matched control. On the contrary, heteroduplex analysis demonstrated the presence of both polyclonal and oligoclonal peripheral T-cell repertoires. In conclusion, the analysis of the T-cell compartment in children with prolonged intrauterine exposure to high dose dexamethasone did not disclose any relevant abnormality, except a restriction of T-cell receptor diversity in some patients.

Standardized analysis for the quantification of Vbeta CDR3 T-cell receptor diversity

Assessment of the diversity of the T-cell receptor (TCR) repertoire is often determined by measuring the frequency and distribution of individually rearranged TCRs in a population of T cells. Spectratyping is a common method used to measure TCR repertoire diversity, which examines genetic variation in the third complementarity-determining region (CDR3) region of the TCR Vbeta chain using RT-PCR length-distribution analysis. A variety of methods are currently used to analyze spectratype data including subjective visual measures, qualitative counting measures, and semi-quantitative measures that compare the original data to a standard, control data set. Two major limitations exist for most of these approaches: data files become very wieldy and difficult to manage, and current analytic methods generate data which are difficult to compare between laboratories and across different platforms. Here, we introduce a highly efficient method of analysis that is based upon a normal theoretical Gaussian distribution observed in cord blood and recent thymic emigrants. Using this analysis method, we demonstrate that PBMC obtained from patients with various diseases have skewed TCR repertoire profiles. Upon in vitro activation with anti-CD3 and anti-CD28 coated beads (Xcyte Dynabeads) TCR diversity was restored. Moreover, changes in the TCR repertoire were dynamic in vivo. We demonstrate that use of this streamlined method of analysis in concert with a flexible software package makes quantitative assessment of TCR repertoire diversity straightforward and reproducible, enabling reliable comparisons of diversity values between laboratories and over-time to further collaborative efforts. Analysis of TCR repertoire by such an approach may be valuable in the clinical setting, both for prognostic potential and measuring clinical responses to therapy.

Statistical analysis of CDR3 length distributions for the assessment of T and B cell repertoire biases

Complementarity-determining region 3 (CDR3) length distribution analysis explores the diversity of the T cell receptor (TCR) and immunoglobulin (Ig) repertoire at the transcriptome level. Studies of the CDR3, the most hypervariable part of these molecules, have been frequently used to identify recruitment of T and B cell clones involved in immunological responses. CDR3 length distribution analysis gives a clear perception of repertoire variations between individuals and over time. However, the complexity of CDR3 length distribution patterns and the high number of possible repertoire alterations per individual called for the development of robust data analysis methods. The goal of these methods is to identify, quantify and statistically assess differences between repertoires so as to offer a better diagnostic or predictive tool for pathologies involving the immune system. In this review we will explain the benefit of analyzing CDR3 length distribution for the study of immune cell diversity. We will start by describing this technology and its associated data processing, and will subsequently focus on the statistical methods used to compare CDR3 length distribution patterns. Finally, we will address the various methods for assessing CDR3 length distribution gene signatures in pathological states.

GMP production and testing of Xcellerated T Cells for the treatment of patients with CLL

BACKGROUND

Pre-clinical studies suggest Xcellerated T Cells have the potential to produce a potent anti-tumor effect, restore broad immune function and reduce the risk of infectious complications in patients with CLL. Unlike other cancer settings, T cells constitute only a small fraction of CLL patients' PBMC. To generate large numbers of Xcellerated T Cells of high purity from CLL patients' PBMC, a reproducible, streamlined and cost-effective good manufacturing process (GMP) is required.

METHODS

The 10-L volume Wave Bioreactor-based Xcellerate III Process using Xcyte Dynabeads in a single custom 20-L Cellbag container was adapted, qualified and implemented for GMP operations.

RESULTS

For n=17 CLL patients, starting with approximately 1.34 x 10(9) CD3+ T cells at 6.8+/-7.5% purity in the PBMC leukapheresis products, using the 10-L volume Wave Bioreactor-based Xcellerate III Process, it was feasible to manufacture 137.0+/-34.3 x 10(9) Xcellerated T Cells at 98.5+/-1.0% CD3+ T-cell purity. An average 400-fold clearance of malignant B cells was documented during the manufacturing process. The Xcellerated T Cells produced from the Xcellerate III Process exhibited high in vitro biologic activity and have their T-cell receptor repertoire restored to a normal diversity. In-process T-cell activation was reproducibly robust, as measured by increase in cell size, up-regulation of CD25 and CD154 expression and the secretion of IL-2, IFN-gamma and tumor necrosis factor (TNF)-alpha.

DISCUSSION

A low-volume, high-yield bioreactor-based process has been developed, qualified and implemented for the reproducible, GMP manufacture of high purity, biologically active Xcellerated T Cells for the treatment of CLL patients in clinical trials.

T-Cell Immune Reconstitution after Hematopoietic Stem Cell Transplantation for HIV-Associated Lymphoma

BACKGROUND

One of the major concern for high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT) for HIV-associated lymphoma is that posttransplant immunosuppression might worsen immune defects of HIV individuals. Since the introduction of highly active antiretroviral therapy has made HSCT possible also in these patients, we analyzed whether the immune system already compromised by HIV infection might support an efficient T-cell recovery after HSCT.

METHODS

The kinetics and the extent of T-cell reconstitution were investigated before and after HSCT in four patients with HIV-related lymphoma (one with Hodgkin's Disease and three with non-Hodgkin's lymphoma) by measuring the thymic output, the level of IL-7 and the heterogeneity of T-cell repertoire. T-cell competence was gauged at two functional levels: by determining the number of T-cell divisions and by measuring IFN-gamma production.

RESULTS

The thymus of transplanted patients can be capable of generating new T cells, but there is no relationship between increasing number of newly produced lymphocytes and modification of IL-7 level. Various T-cell subsets, expressing different T-cell receptor variable beta genes, were preferentially expanded in CD8 population and most of them showed a restricted diversity. Furthermore, CD3 lymphocytes showed heterogeneous behaviors in terms of proliferative capability and IFN-gamma production.

CONCLUSIONS

High-dose therapy and HSCT in HIV patients under highly active antiretroviral therapy does not worsen the immune defects. On the contrary, in the presence of some conditions (including the type of hematologic malignancy, the therapy compliance, and the immune status before transplantation), high-dose therapy and HSCT might support the improvement of immune conditions.

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.

Direct measurement of lymphocyte receptor diversity

The ability to mount an immune defense against infectious microorganisms and their products, and against tumors is believed to be a direct function of lymphocyte diversity. Because the diversity of lymphocyte receptor genes is >1000-fold more diverse than the entire genome and varies between genetically identical individuals, measuring lymphocyte diversity has been a daunting challenge. We developed a novel technique for measuring lymphocyte diversity directly using gene chips. We reasoned and here demonstrate that the frequency of hybridization of nucleic acids coding for lymphocyte receptors to the oligonucleotides on a gene chip varies in direct proportion to diversity. We applied the technique to detect changes in lymphocyte diversity in mice with known B cell alterations and in persons with known T cell repertoire defects. This approach is the first to provide direct analysis of lymphocyte receptor diversity and should facilitate fundamental study of the adaptive immune system and clinical efforts to assess immunological diseases. In addition, this approach could be more broadly applied, for example to measure diversity of viral quasi-species.

Shared and individual specificities of immunodominant cytotoxic T-cell clones in paroxysmal nocturnal hemoglobinuria as determined by molecular analysis

OBJECTIVE

Similar immune mechanisms have been suggested to operate in aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH), and the presence of PNH clones in AA may indicate that an immune reaction directed against hematopoietic stem cells may be responsible for the immune selection pressure leading to PNH evolution. We previously described expansions of selective cytotoxic T-lymphocyte (CTL) clones in AA patients.

MATERIALS AND METHODS

We applied a molecular analysis of the T-cell receptor repertoire to study the characteristics of CTL response in patients with various forms of PNH. Immunodominant T-cell clones were detected using combined flow cytometric and molecular analysis of the variable beta (VB) chain and CDR3 representation, followed by determination of the frequency of individual CDR3 clonotypes. Clonotypic polymerase chain reaction (PCR) was performed to establish clonotypic utilization pattern.

RESULTS

In patients with a past history of AA, and when subgrouped by current blood counts as "hypoproliferative" PNH patients (in contrast to purely hemolytic form of PNH), more pronounced skewing of VB family utilization was found, consistent with T-cell responses involving several immunodominant CTL clones. Sequences of the PNH-derived clonotypes were used to design PCR-based assays for the utilization analysis of individual clones in PNH patients. The clonotypic distribution pattern established by this PCR method indicated that immunodominant T-cell specificities were shared between some patients but also may be found at low frequencies in controls.

CONCLUSION

Analysis of the CDR3 sequence pattern as a marker for expanded immunodominant clonotypes may have an application in the study of T-cell responses in PNH.

T- and B-cell immune reconstitution and clinical outcome in patients with multiple myeloma receiving T-cell-depleted, reduced-intensity allogeneic stem cell transplantation with an alemtuzumab-containing conditioning regimen followed by escalated donor ly

Immune reconstitution after conventional allogeneic transplantation is a major determinant of survival. We conducted a detailed investigation of T- and B-cell immune reconstitution and clinical outcome in 19 patients with multiple myeloma undergoing reduced-intensity stem cell transplantation using in vivo T-cell depletion with alemtuzumab. These patients experienced delayed T-cell recovery, particularly in the naïve (CD45 RA+) CD4 compartment. T-cell receptor spectratype analysis showed a reduced repertoire diversity, which improved rapidly after the administration of donor leucocyte infusions and subsequent conversion to full donor T-cell chimaerism. Post-transplant recovery of CD19+ B cells was also delayed for up to 18 months. Spectratype analysis of IgH CDR3 repertoire revealed a gradual normalization in IgM spectratype complexity by 6-12 months after transplant. There was a high incidence of viral infection, particularly cytomegalovirus reactivation, but the regimen-related mortality was low, perhaps because of the very low incidence of acute graft-versus-host disease (GVHD; grade I-II skin GVHD was seen in 5/19 patients). Over 80% of all patients have relapsed at a median of 283 (range 153-895) d after transplant, suggesting that the initially low rate of GVHD comes at a high price with regard to the desired graft-versus-myeloma effect.

Clinical and experimental study on therapeutic effect of umbilical cord blood transplantation on severe viral hepatitis

AIM: To investigate the therapeutic effect of umbilical cord blood transplantation (UCBT) on patients with severe viral hepatitis and on liver lesions in rats.

METHODS: One hundred and fifty three patients with severe viral hepatitis were included in the study between April 1990 and July 2002. The patients were treated with adult plasma transfusion (control), UCBT, plasma exchange (PE) and UCBT combined with PE (UCBT+PE) respectively. The therapeutic effectiveness was evaluated by serial determinations of liver function, lipids and immune function in all patients before and after the treatment. The model of experimental hepatic failure was constructed in SD rats by injecting carbon tetrachloride. Then, the rats were given normal saline, adult plasma or neonate cord blood intraperitoneally. After detection of liver function, the rats were killed and morphological changes of the liver were microscopically observed.

RESULTS: UCBT group and UCBT+PE group had much better improvement in liver and immune functions than control group and PE group. The patients in UCBT+PE group had the best clinical efficacy. UCBT was safe and had no side effects. The animal experiment showed significant improvements in liver function and survival rate in neonate cord blood group as compared with adult plasma group. The histopathology of rat’s liver indicated that neonate cord blood application could decrease the liver injury and increase hepatocellular regeneration.

CONCLUSION: UCBT demonstrated a good therapeutic effect on severe viral hepatitis and no obvious side effects. Umbilical cord blood can attenuate the liver lesions and reproduce hepatocyte. The treatment of UCBT combined with PE was much better than that of single plasma exchange, thus UCBT can enhance the therapeutic effect of plasma exchange on severe viral hepatitis.

Application of the molecular analysis of the T-cell receptor repertoire in the study of immune-mediated hematologic diseases

The basis for the vast recognition spectrum of the T-cell receptor (TCR) can be determined by the rearrangement and recombination of the variable, diversity and joining regions of the variable portions of beta (B) and alpha (A) chains as well as their recombination and modification. Analysis of the TCR rearrangement has been routinely used to detect clonality for the diagnosis of lymphoid malignancies. However, molecular analysis of the TCR repertoire can be a powerful tool in the study of T-cell responses to pathogens and in autoimmune diseases. The concept of the oligoclonality in the context of cellular immune responses is based on the presence of immunodominant T-cell clones within distinct T-cell subpopulations used for analysis. Under normal circumstances, a limited number of clones undergo periodic expansions in reaction to foreign antigens. Under pathologic conditions, though, the derailment of immune regulation allows expansions of specific and potentially pathogenic T-cell clones. For example, large granular lymphocyte (LGL) leukemia illustrates an extreme expansion of a single T-cell clone associated with a distinct autoimmune pathology, which suggests an exaggerated clonal response to a specific antigenic target. In immune-mediated bone marrow failure syndromes, clonal rearrangement of the TCR cannot be detected in unseparated blood or marrow. Nevertheless, individual T-cell clones can significantly expand and may allow for demonstration of oligoclonality in selected T-cell populations. These subpopulations are defined, for example, by a specific beta (B)-chain usage or other phenotypic markers. Given the diversity of the TCR recognition spectrum, the task of identifying immunodominant clonotypes derived from unique complementarity determining region-3 (CDR3) sequences is very complex. However, expanded T-cell clones likely represent immunodominant responses which can be detected on the molecular level using analysis of the individual TCR VB-chain representation, CDR3 size fragment skewing, and determination of the frequency of individual clonotypic sequences. In the future, TCR VB clonotypes may be applied as a diagnostic tool, analogous to serologic markers. As an investigative tool in hematology, molecular analysis of the TCR utilization pattern and the detection of immunodominant clonotypes represents a novel approach in the study of immune-mediated hematologic diseases, such as aplastic anemia (AA), some forms of myelodysplasia (MDS), anti-leukemic immune surveillance, graft-versus-leukemia effects and graft-versus-host disease (GvHD).