Consistent B Cell Receptor Immunoglobulin Features Between Siblings in Familial Chronic Lymphocytic Leukemia.

Key processes in the onset and evolution of chronic lymphocytic leukemia (CLL) are thought to include chronic (antigenic) activation of mature B cells through the B cell receptor (BcR), signals from the microenvironment, and acquisition of genetic alterations. Here we describe three families in which two or more siblings were affected by CLL. We investigated whether there are immunogenetic similarities in the leukemia-specific immunoglobulin heavy (IGH) and light (IGL/IGK) chain gene rearrangements of the siblings in each family. Furthermore, we performed array analysis to study if similarities in CLL-associated chromosomal aberrations are present within each family and screened for somatic mutations using paired tumor/normal whole-genome sequencing (WGS). In two families a consistent IGHV gene mutational status (one IGHV-unmutated, one IGHV-mutated) was observed. Intriguingly, the third family with four affected siblings was characterized by usage of the lambda IGLV3-21 gene, with the hallmark R110 mutation of the recently described clinically aggressive IGLV3-21R110 subset. In this family, the CLL-specific rearrangements in two siblings could be assigned to either stereotyped subset #2 or the immunogenetically related subset #169, both of which belong to the broader IGLV3-21R110 subgroup. Consistent patterns of cytogenetic aberrations were encountered in all three families. Furthermore, the CLL clones carried somatic mutations previously associated with IGHV mutational status, cytogenetic aberrations and stereotyped subsets, respectively. From these findings, we conclude that similarities in immunogenetic characteristics in familial CLL, in combination with genetic aberrations acquired, point towards shared underlying mechanisms behind CLL development within each family.

The presence of CLL-associated stereotypic B cell receptors in the normal BCR repertoire from healthy individuals increases with age.

BACKGROUND: Aging is known to induce immunosenescence, resulting in alterations in both the innate and adaptive immune system. Here we evaluated the effects of aging on B cell subsets in peripheral blood of 155 immunologically healthy individuals in four age categories (range 20-95y) via multi-parameter flow cytometry. Furthermore, we studied the naive and antigen-experienced B cell receptor (BCR) repertoire of different age groups and compared it to the clonal BCR repertoire of chronic lymphocytic leukemia (CLL), a disease typically presenting in elderly individuals. RESULTS: Total numbers and relative frequencies of B cells were found to decline upon aging, with reductions in transitional B cells, memory cell types, and plasma blasts in the 70 + y group. The BCR repertoire of naive mature B cells and antigen-experienced B cells did not clearly alter until age 70y. Clear changes in IGHV gene usage were observed in naive mature B cells of 70 + y individuals, with a transitional pattern in the 50-70y group. IGHV gene usage of naive mature B cells of the 50-70y, but not the 70 + y, age group resembled that of both younger (50-70y) and older (70 + y) CLL patients. Additionally, CLL-associated stereotypic BCR were found as part of the healthy control BCR repertoire, with an age-associated increase in frequency of several stereotypic BCR (particularly subsets #2 and #5). CONCLUSION: Composition of the peripheral B cell compartment changes with ageing, with clear reductions in non-switched and CD27 + IgG+ switched memory B cells and plasma blasts in especially the 70 + y group. The BCR repertoire is relatively stable until 70y, whereafter differences in IGHV gene usage are seen. Upon ageing, an increasing trend in the occurrence of particular CLL-associated stereotypic BCR is observed.

Next-Generation Sequencing Analysis of the Human TCRγδ+ T-Cell Repertoire Reveals Shifts in Vγ- and Vδ-Usage in Memory Populations upon Aging.

Immunological aging remodels the immune system at several levels. This has been documented in particular for the T-cell receptor (TCR)αß+ T-cell compartment, showing reduced naive T-cell outputs and an accumulation of terminally differentiated clonally expanding effector T-cells, leading to increased proneness to autoimmunity and cancer development at older age. Even though TCRαß+ and TCRγδ+ T-cells follow similar paths of development involving V(D)J-recombination of TCR genes in the thymus, TCRγδ+ T-cells tend to be more subjected to peripheral rather than central selection. However, the impact of aging in shaping of the peripheral TRG/TRD repertoire remains largely elusive. Next-generation sequencing analysis methods were optimized based on a spike-in method using plasmid vector DNA-samples for accurate TRG/TRD receptor diversity quantification, resulting in optimally defined primer concentrations, annealing temperatures and cycle numbers. Next, TRG/TRD repertoire diversity was evaluated during TCRγδ+ T-cell ontogeny, showing a broad, diverse repertoire in thymic and cord blood samples with Gaussian CDR3-length distributions, in contrast to the more skewed repertoire in mature circulating TCRγδ+ T-cells in adult peripheral blood. During aging the naive repertoire maintained its diversity with Gaussian CDR3-length distributions, while in the central and effector memory populations a clear shift from young (Vγ9/Vδ2 dominance) to elderly (Vγ2/Vδ1 dominance) was observed. Together with less clear Gaussian CDR3-length distributions, this would be highly suggestive of differentially heavily selected repertoires. Despite the apparent age-related shift from Vγ9/Vδ2 to Vγ2/Vδ1, no clear aging effect was observed on the Vδ2 invariant T nucleotide and canonical Vγ9-Jγ1.2 selection determinants. A more detailed look into the healthy TRG/TRD repertoire revealed known cytomegalovirus-specific TRG/TRD clonotypes in a few donors, albeit without a significant aging-effect, while Mycobacterium tuberculosis-specific clonotypes were absent. Notably, in effector subsets of elderly individuals, we could identify reported TRG and TRD receptor chains from TCRγδ+ T-cell large granular lymphocyte leukemia proliferations, which typically present in the elderly population. Collectively, our results point to relatively subtle age-related changes in the human TRG/TRD repertoire, with a clear shift in Vγ/Vδ usage in memory cells upon aging.

Identification of checkpoints in human T-cell development using severe combined immunodeficiency stem cells.

BACKGROUND: Severe combined immunodeficiency (SCID) represents congenital disorders characterized by a deficiency of T cells caused by arrested development in the thymus. Yet the nature of these developmental blocks has remained elusive because of the difficulty of taking thymic biopsy specimens from affected children. OBJECTIVE: We sought to identify the stages of arrest in human T-cell development caused by various major types of SCID. METHODS: We performed transplantation of SCID CD34(+) bone marrow stem/progenitor cells into an optimized NSG xenograft mouse model, followed by detailed phenotypic and molecular characterization using flow cytometry, immunoglobulin and T-cell receptor spectratyping, and deep sequencing of immunoglobulin heavy chain (IGH) and T-cell receptor δ (TRD) loci. RESULTS: Arrests in T-cell development caused by mutations in IL-7 receptor α (IL7RA) and IL-2 receptor γ (IL2RG) were observed at the most immature thymocytes much earlier than expected based on gene expression profiling of human thymocyte subsets and studies with corresponding mouse mutants. T-cell receptor rearrangements were functionally required at the CD4(-)CD8(-)CD7(+)CD5(+) stage given the developmental block and extent of rearrangements in mice transplanted with Artemis-SCID cells. The xenograft model used is not informative for adenosine deaminase-SCID, whereas hypomorphic mutations lead to less severe arrests in development. CONCLUSION: Transplanting CD34(+) stem cells from patients with SCID into a xenograft mouse model provides previously unattainable insight into human T-cell development and functionally identifies the arrest in thymic development caused by several SCID mutations.

End stage renal disease patients have a skewed T cell receptor Vß repertoire.

BACKGROUND: End stage renal disease (ESRD) is associated with defective T-cell mediated immunity. A diverse T-cell receptor (TCR) Vß repertoire is central to effective T-cell mediated immune responses to foreign antigens. In this study, the effect of ESRD on TCR Vß repertoire was assessed. RESULTS: A higher proportion of ESRD patients (68.9 %) had a skewed TCR Vß repertoire compared to age and cytomegalovirus (CMV) - IgG serostatus matched healthy individuals (31.4 %, P < 0.001). Age, CMV serostatus and ESRD were independently associated with an increase in shifting of the TCR Vß repertoire. More differentiated CD8(+) T cells were observed in young ESRD patients with a shifted TCR Vß repertoire. CD31-expressing naive T cells and relative telomere length of T cells were not significantly related to TCR Vß skewing. CONCLUSIONS: ESRD significantly skewed the TCR Vß repertoire particularly in the elderly population, which may contribute to the uremia-associated defect in T-cell mediated immunity.

Development of a diverse human T-cell repertoire despite stringent restriction of hematopoietic clonality in the thymus.

The fate and numbers of hematopoietic stem cells (HSC) and their progeny that seed the thymus constitute a fundamental question with important clinical implications. HSC transplantation is often complicated by limited T-cell reconstitution, especially when HSC from umbilical cord blood are used. Attempts to improve immune reconstitution have until now been unsuccessful, underscoring the need for better insight into thymic reconstitution. Here we made use of the NOD-SCID-IL-2Rγ(-/-) xenograft model and lentiviral cellular barcoding of human HSCs to study T-cell development in the thymus at a clonal level. Barcoded HSCs showed robust (>80% human chimerism) and reproducible myeloid and lymphoid engraftment, with T cells arising 12 wk after transplantation. A very limited number of HSC clones (<10) repopulated the xenografted thymus, with further restriction of the number of clones during subsequent development. Nevertheless, T-cell receptor rearrangements were polyclonal and showed a diverse repertoire, demonstrating that a multitude of T-lymphocyte clones can develop from a single HSC clone. Our data imply that intrathymic clonal fitness is important during T-cell development. As a consequence, immune incompetence after HSC transplantation is not related to the transplantation of limited numbers of HSC but to intrathymic events.

Successive B-cell lymphomas mostly reflect recurrences rather than unrelated primary lymphomas.

OBJECTIVES: To address whether successive B-cell lymphomas, diagnosed within a 5- to 15-year interval, are recurrences or unrelated primary lymphomas. METHODS: Immunoglobulin heavy and κ light chain gene rearrangements were studied using multiplex polymerase chain reaction fragment assays and sequence analysis in 61 patients. RESULTS: Clonal patterns of the multiple lymphomas from 36 patients were determined and classified accordingly: 30 recurrences, 2 possible recurrences, 2 different clones with a common origin, and 2 unrelated primary lymphomas. CONCLUSIONS: Regardless of subtype, 89% to 94% of late B-cell lymphoma relapses were recurrences of the primary tumor. Therefore, routinely investigating the possible clonal relationship between successive lymphomas may not be warranted except for specific lymphoma subtypes such as diffuse large B-cell lymphomas.

Skewed X chromosomal inactivation impacts T regulatory cell function in systemic sclerosis.

OBJECTIVES: > To investigate the role of X chromosomal inactivation (XCI) in systemic sclerosis (SSc) and its effects on forkhead box P3 (Foxp3) expression in T regulatory cells (Tregs). METHODS: 217 women with SSc and 107 healthy women (controls) were included in the study. From these subjects, DNA was isolated from total peripheral blood mononuclear cells, plasmacytoid dendritic cells, T cells, B cells, myeloid dendritic cells and monocytes after magnetic bead separation. All samples were assessed for skewed XCI patterns with the Human Androgen Receptor Assay. The outcome was assessed by linear regression. CD4+ CD25+ cells were then isolated and intracellular Foxp3 expression was assessed by flow cytometry. RESULTS: Skewing was not associated with increased age in patients with SSc, in contrast to the control population (r = 0.45, p < 0.0001). Taking this into account, a significantly higher frequency of skewed XCI was found in patients with SSc compared with controls (p = 0.001). No difference in skewing was observed between the immune cell subsets. In addition, a higher concentration of Foxp3+ cells exhibiting a lower Foxp3 mean fluorescence intensity was found in the patients with SSc, with profound XCI skewing (both p < 0.001) associated with less efficient suppressive activity (p=0.012). CONCLUSIONS: Skewed XCI plays a role in susceptibility to SSc, is not restricted and influences Foxp3 expression and the suppressive capacity of Tregs.

Unraveling the consecutive recombination events in the human IGK locus.

In addition to the classical Vkappa-Jkappa, Vkappa-kappa deleting element (Kde), and intron-Kde gene rearrangements, atypical recombinations involving Jkappa recombination signal sequence (RSS) or intronRSS elements can occur in the Igkappa (IGK) locus, as observed in human B cell malignancies. In-depth analysis revealed that atypical JkappaRSS-intronRSS, Vkappa-intronRSS, and JkappaRSS-Kde recombinations not only occur in B cell malignancies, but rather reflect physiological gene rearrangements present in normal human B cells as well. Excision circle analysis and recombination substrate assays can discriminate between single-step vs multistep rearrangements. Using this combined approach, we unraveled that the atypical Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints most probably result from ongoing recombination following an initial aberrant JkappaRSS-intronRSS signal joint formation. Based on our observations in normal and malignant human B cells, a model is presented to describe the sequential (classical and atypical) recombination events in the human IGK locus and their estimated relative frequencies (0.2-1.0 vs < 0.03). The initial JkappaRSS-intronRSS signal joint formation (except for Jkappa1RSS-intronRSS) might be a side event of an active V(D)J recombination mechanism, but the subsequent formation of Vkappa-intronRSS and JkappaRSS-Kde pseudohybrid joints can represent an alternative pathway for IGK allele inactivation and allelic exclusion, in addition to classical Ckappa deletions. Although usage of this alternative pathway is limited, it seems essential for inactivation of those IGK alleles that have undergone initial aberrant recombinations, which might otherwise hamper selection of functional Ig L chain proteins.

Two dual-color split signal fluorescence in situ hybridization assays to detect t(5;14) involving HOX11L2 or CSX in T-cell acute lymphoblastic leukemia.

BACKGROUND AND OBJECTIVES: The t(5;14)(q35;q32) is a novel cryptic translocation in pediatric T-cell acute lymphoblastic leukemia (T-ALL), involving HOX11L2 or CSX on 5q35. The 14q32 breakpoints are heterogeneous. Because the t(5;14)(q35;q32) is hard to detect using conventional karyotyping, it is easily missed in routine diagnostics. Here we describe the development and application of split signal fluorescence in situ hybridization (FISH) assays for both HOX11L2 and CSX, for detection of t(5;14) possibly present in T-ALL patients. DESIGN AND METHODS: We developed and validated two split signal FISH assays for metaphase and interphase detection of t(5;14) in T-ALL patients. We also investigated the involvement of IGH on 14q32. In addition, HOX11L2 and SIL-TAL1 expression was studied using reverse transcription polymerase chain reaction (RT-PCR). RESULTS: The FISH assays were validated on cell lines and T-ALL patients. We did not identify cases with a t(5;14)(q35;q32) involving CSX, but we did identify 5 cases of t(5;14) involving HOX11L2 out of 32 T-ALL cases studied; in each case the 14q32 breakpoint was found to be centromeric to the IGH region. All 5 positive cases showed HOX11L2 expression, as did 1 case without t(5;14)(q35;q32). Cases with t(5;14)(q35;q32) involving HOX11L2 did not show TAL1 abnormalities, whereas 5 HOX11L2 negative cases did. INTERPRETATION AND CONCLUSIONS: Using the newly developed and validated FISH probe sets, we identified 5 new cases of t(5;14) involving HOX11L2 both on metaphases and interphases. The incidence of the t(5;14)(q35;q32) involving CSX is probably low. RT-PCR results suggest that TAL1 and HOX11L2 expression, or TAL1 aberrations and the t(5;14)(q35;q32) involving HOX11L2 are mutually exclusive.

Molecular immunoglobulin/T- cell receptor clonality analysis in cutaneous lymphoproliferations. Experience with the BIOMED-2 standardized polymerase chain reaction protocol.

BACKGROUND AND OBJECTIVES: Molecular clonality analysis of immunoglobulin (Ig) and T-cell receptor (TCR) genes is a widely used diagnostic tool for discrimination between polyclonal, oligoclonal, and monoclonal lymphoproliferative skin lesions. We studied Ig/TCR clonality in a series of 60 patients with an initial suspicion of (primary) cutaneous B- or T-cell lymphoma (CBCL/CTCL). Clonality of Ig/TCR gene rearrangements was assessed by Southern blot (SB) and polymerase chain reaction (PCR) analysis using standardized PCR primers and protocols of the BIOMED-2 Concerted Action BMH4-CT98-3936. The obtained PCR products were subjected to heteroduplex (HD) and GeneScan (GS) analysis. We compared the data of 154 samples with the histopathologic diagnosis, based on the EORTC classification of skin lymphomas. DESIGN AND METHODS: Molecular results were largely concordant with histopathology. In 12 CBCL patients PCR analysis of Ig gene rearrangements detected clonality in 83% of cases whereas SB did so in 92%. Clonal TCR gene rearrangements were detected by SB in 68% of CTCL patients, whereas TCRG and TCRB PCR analysis detected clonality in 76% and 66% of cases, respectively. PCR GS analysis of TCR rearrangements appeared to be slightly more informative than HD analysis. Clonality assessment was particularly informative for studying involvement of extracutaneous sites, such as regional lymph nodes, peripheral blood, and bone marrow. INTERPRETATION AND CONCLUSIONS: Our study shows that the BIOMED-2 multiplex PCR analysis strategy is a reliable and useful technique in the diagnostic process of patients with an initial suspicion of (primary) CBCL/CTCL and for assessment of extracutaneous dissemination, provided that the results are interpreted in the context of clinical, histologic and immunophenotypic data.