Cell-surface expression of transrearranged Vgamma-cbeta T-cell receptor chains in healthy donors and in ataxia telangiectasia patients

γδ T cells: origin and fate, subsets, diseases and immunotherapy

The intricacy of diseases, shaped by intrinsic processes like immune system exhaustion and hyperactivation, highlights the potential of immune renormalization as a promising strategy in disease treatment. In recent years, our primary focus has centered on γδ T cell-based immunotherapy, particularly pioneering the use of allogeneic Vδ2+ γδ T cells for treating late-stage solid tumors and tuberculosis patients. However, we recognize untapped potential and optimization opportunities to fully harness γδ T cell effector functions in immunotherapy. This review aims to thoroughly examine γδ T cell immunology and its role in diseases. Initially, we elucidate functional differences between γδ T cells and their αβ T cell counterparts. We also provide an overview of major milestones in γδ T cell research since their discovery in 1984. Furthermore, we delve into the intricate biological processes governing their origin, development, fate decisions, and T cell receptor (TCR) rearrangement within the thymus. By examining the mechanisms underlying the anti-tumor functions of distinct γδ T cell subtypes based on γδTCR structure or cytokine release, we emphasize the importance of accurate subtyping in understanding γδ T cell function. We also explore the microenvironment-dependent functions of γδ T cell subsets, particularly in infectious diseases, autoimmune conditions, hematological malignancies, and solid tumors. Finally, we propose future strategies for utilizing allogeneic γδ T cells in tumor immunotherapy. Through this comprehensive review, we aim to provide readers with a holistic understanding of the molecular fundamentals and translational research frontiers of γδ T cells, ultimately contributing to further advancements in harnessing the therapeutic potential of γδ T cells.

Pitfalls in the characterization of circulating and tissue-resident human γδ T cells

Dissection of the role and function of human γδ T cells and their heterogeneous subsets in cancer, inflammation, and auto-immune diseases is a growing and dynamic research field of increasing interest to the scientific community. Therefore, harmonization and standardization of techniques for the characterization of peripheral and tissue-resident γδ T cells is crucial to facilitate comparability between published and emerging research. The application of commercially available reagents to classify γδ T cells, in particular the combination of multiple Abs, is not always trouble-free, posing major demands on researchers entering this field. Occasionally, even entire γδ T cell subsets may remain undetected when certain Abs are combined in flow cytometric analysis with multicolor Ab panels, or might be lost during cell isolation procedures. Here, based on the recent literature and our own experience, we provide an overview of methods commonly employed for the phenotypic and functional characterization of human γδ T cells including advanced polychromatic flow cytometry, mass cytometry, immunohistochemistry, and magnetic cell isolation. We highlight potential pitfalls and discuss how to circumvent these obstacles.

Impact of karyotype organization on interlocus recombination between T cell receptor genes in Equidae

The T cell receptor (TCR) genes (TRA, TRB, TRD and TRG) reside in 3 different chromosomal regions. During the maturation of T lymphocytes, the TCR genes are rearranged by site-specific recombination, a process that also predisposes T cells to aberrant rearrangements. Illegitimate recombination between the TCR genes occurs at a low level in healthy individuals, but this frequency may correlate with the risk of lymphoma. The aim of this work was to investigate interlocus recombination in equids. Illegitimate rearrangements were studied in peripheral blood lymphocytes by FISH with painting and BAC probes and by sequencing of PCR products, and the frequencies of recombination were assessed in horses and 4 other equids. The presence of several trans-rearrangement products between the TRA and TRG genes was verified by PCR in all investigated equids. Frequencies of trans-rearrangements in horses are higher than in humans, and colocalization of the TCR genes on the same chromosome increases the incidence of trans-rearrangements between them. The orientation of the TCR genes does not impact interlocus recombination itself but does affect the viability of cells carrying its products and consequently the number of trans-rearrangements observed in lymphocytes.

Illegitimate recombination between T cell receptor genes in humans and pigs (Sus scrofa domestica)

T cell receptor (TCR) genes (TRA/TRD, TRB and TRG) reside in three regions on human chromosomes (14q11.2, 7q34 and 7p14, respectively) and pig chromosomes (7q15.3-q21, 18q11.3-q12 and 9q21-22, respectively). During the maturation of T cells, TCR genes are rearranged by site-specific recombination. Occasionally, interlocus recombination of different TCR genes takes place, resulting in chromosome rearrangements. It has been suggested that the absolute number of these "innocent" trans-rearrangements correlates with the risk of lymphoma. The aims of this work were to assess the frequencies of rearrangements with breakpoints in TCR genes in domestic pig lymphocytes and to compare these with the frequencies of corresponding rearrangements in human lymphocytes by using fluorescence in situ hybridization with chromosome painting probes. We show that frequencies of trans-rearrangements involving TRA/TRD locus in pigs are significantly higher than the frequency of translocations with breakpoints in TRB and TRG genes in pigs and the frequencies of corresponding trans-rearrangements involving TRA/TRD locus in humans. Complex structure of the pig TRA/TRD locus with high number of potential V(D)J rearrangements compared to the human locus may account for the observed differences. Furthermore, we demonstrated that trans-rearrangements involving pig TRA/TRD locus occur at lower frequencies in γδ T cells than in αβ T lymphocytes. The decrease of the frequencies in γδ T cells is probably caused by the absence of TRA recombination during maturation of this T cell lineage. High numbers of innocent trans-rearrangements in pigs may indicate a higher risk of T-cell lymphoma than in humans.

A girl with an atypical form of ataxia telangiectasia and an additional de novo 3.14 Mb microduplication in region 19q12

A 9-year-old girl born to healthy parents showed manifestations suggestive of ataxia telangiectasia (AT), such as short stature, sudden short bouts of horizontal and rotary nystagmus, a weak and dysarthric voice, rolling gait, unstable posture, and atactic movements. She did not show several cardinal features typical of AT such as frequent, severe infections of the respiratory tract. In contrast, she showed symptoms not generally related to AT, including microcephaly, profound motor and mental retardation, small hands and feet, severely and progressively reduced muscle tone with slackly protruding abdomen and undue drooling, excess fat on her upper arms, and severe oligoarthritis. A cranial MRI showed no cerebellar hypoplasia and other abnormalities. In peripheral blood samples she carried a de novo duplication of 3.14 Mb in chromosomal region 19q12 containing six annotated genes, UQCRFS1, VSTM2B, POP4, PLEKHF1, CCNE1, and ZNF536, and a de novo mosaic inversion 14q11q32 (96% of metaphases). In a saliva-derived DNA sample only the duplication in 19q12 was detected, suggesting that the rearrangements in blood lymphocytes were acquired. These findings reinforced the suspicion that she had AT. AT was confirmed by strongly elevated serum AFP levels, cellular radiosensitivity and two inherited mutations in the ATM gene (c.510_511delGT; paternal origin and c.2922-50_2940del69; maternal origin). This case suggest that a defective ATM-dependent DNA damage response may entail additional stochastic genomic rearrangements. Screening for genomic rearrangements appears indicated in patients suspected of defective DNA damage responses.

TCR trans-rearrangements: biological significance in antigen recognition vs the role as lymphoma biomarker

V(D)J rearrangements occur within loci of TCR and BCR genes, thus generating the diversity of the AgR repertoire. In addition, interlocus V(D)J rearrangements occur, giving rise to so-called "trans-rearrangements." Such trans-rearrangements increase the diversity of the immune receptor repertoire and can be expressed as functional chimeric TCR proteins on the surface of T cells. Although chimeric receptors are not pathogenic per se, the frequency of AgR trans-rearrangements correlates with the level of genetic instability and thus could be used as a predictive biomarker for lymphoma risk.

Deficiencies in CD4+ and CD8+ T cell subsets in ataxia telangiectasia

Chronic sinopulmonary infections that are associated with immunodeficiency are one of the leading causes of death in the multi-systemic disease ataxia telangiectasia (AT). Immunological investigations of AT patients revealed a broad spectrum of defects in the humoral and the cellular immune system. Based on their important role in host defence the aim of our study was an extensive analysis of cell distribution and function of CD4+ and CD8+ T lymphocytes and NK cells. We found that naive (CD45RA+) CD4+ lymphocytes, as well as CD8+/CD45RA+ lymphocytes, are decreased, whereas NK cells (CD3-/CD16+CD56+) are significantly elevated in AT patients. In our culture system proliferation and cytokine production was normal in purified memory (CD45RO+) lymphocytes after stimulation with phorbol-12,13-dibutyrate (PBu2) and after PHA activation, indicating that differences in proliferation and cytokine production are due solely to reduced numbers of CD45RA+ lymphocytes. However, activation, and especially intracellular interferon production of AT lymphocytes, seem to follow different kinetics compared to controls. In contrast to polyclonal activation, stimulation via the T cell receptor results consistently in a reduced immune response. Taken together, our results suggest that deficiency of immunocompetent cells and an intrinsic immune activation defect are responsible for the immunodeficiency in AT.

DNA sequence analysis of interlocus recombination between the human T-cell receptor gamma variable (GV) and beta diversity-joining (BD/BJ) sequences on chromosome 7 (inversion 7)

V(D)J recombinase-mediated recombination between the T-cell receptor (TCR) gamma variable (GV) genes at chromosome 7p15 and the TCR beta joining (BJ) genes at 7q35 leads to the formation of a hybrid TCR gene. These TCR gamma/beta interlocus rearrangements occur at classic V(D)J recombination signal sequences (RSS) and, because the loci are in an inverted orientation, result in inversion events that are detectable in the chromosome structure as inv(7)(p15;q35). Similar rearrangements involving oncogenes and either TCR or immunoglobulin genes mediated by the V(D)J recombinase are found in lymphoid malignancies. Oligonucleotide primers that allow polymerase chain reaction (PCR) amplification across the inv(7) genomic recombination junction sequence have been described. Southern blot analysis has been primarily used to confirm the GV/BJ hybrid nature of the product, with limited information on the DNA sequence of these recombinations. We have modified this PCR method using total genomic DNA from the mononuclear cells in peripheral blood samples to increase specificity and to allow direct sequencing of the translocation junction that results from the recombination between the GV1 and BJ1 families of TCR genes in 25 examples from 11 individuals (three adults, one child, six newborns, and one ataxia telangiectasia (AT) patient). We focused on samples from newborns based on previous studies indicating that the predominant hypoxanthine-guanine phosphoribosyl transferase (HPRT) mutations in newborns are V(D)J recombinase-mediated deletion events and that the frequency of these mutations decreases with increasing age. Although the dilution series-based PCR assay utilized does not yield sharply defined quantitative endpoints, results of this study strongly suggest that inv(7) recombinations in newborns occur at equal or lower frequencies than those seen in adults. Consistent with the PCR primer pairs, all sequenced products contain a GV1 and a BJ1 segment and most also contain a BD1 segment. GV1s2 and 1s4 were the most frequently found GV1 genes (8 and 9 examples, respectively) and BJ1s5 and 1s6 were the most frequently found BJ1 genes (9 and 10 examples, respectively). These results demonstrate the effectiveness of this methodology for assessing GV/BJ interlocus rearrangements mediated by V(D)J recombinase.

T-large granular lymphocyte leukaemia with natural killer cell-like cytotoxicity and expression of two different alpha- and beta-T-cell receptor chains

We describe a case of cytotoxic T-large granular lymphocyte leukaemia showing typical morphological features, expressing antigens characteristic for cytotoxic T cells and exhibiting marked natural killer-like cytotoxicity towards different target cells. Moreover, characterization of the T-cell receptors revealed simultaneous expression of two different types of beta-chains as well as alpha-chains by the malignant cell clone. The patient had an 8 year history of indolent disease, before progressing to an aggressive clinical course hardly responsive to chemotherapeutic treatment. This is the first description of a peripheral T-cell neoplasm expressing four distinct types of T-cell receptor molecules.

Identification of the T-cell receptor alpha variable (TRAV) gene(s) in T-cell malignancies

Due to the lack of a complete range of monoclonal antibodies (mAb) it is often impossible to rapidly identify by flow cytometry the T-cell receptor variable genes in patients suffering from T-cell malignancies. This applies especially to the alpha variable genes (TRAV), since only very few anti-TcR variable alpha mAb are available. We describe a very rapid method for inverse PCR amplification of the TcR alpha chain without prior purification of the double-stranded cDNA, provide the sequences for appropriate oligonucleotides, and describe a buffer system that dramatically enhances the amplification efficiency as compared to standard conditions.