Sequence and organization of the human T cell delta chain gene

Clonal dissemination of T-lymphocytes in scid mice from familial hemophagocytic lymphohistiocytosis

BACKGROUND

Although familial hemophagocytic lymphohistiocytosis (FHL) has been considered a disorder of T-cell dysfunction, there is no evidence of the clonal origin of T-cells in this disease.

PROCEDURE

We engrafted mononuclear cells (MNCs) from five FHL patients into scid mice and examined the infiltration of human cells in mouse organs. The characterization of human cells that infiltrated in the mouse organs was then performed.

RESULTS

A diffuse infiltration of human lymphoid cells was detected in scid mice treated with 1 x 10(6) MNCs from one of the five patients. These cells were positive for HLA-DR and CD3, but negative for CD4, CD8, CD20, and CD68, suggesting the infiltration of double negative (DN) T-cells. The MNCs from the other four patients induced murine lymphoma-like disease; T-cell lymphoma in one and lymphoma of unknown origin in three. The characterization of these human DN T-cells was performed. The analysis of the Vbeta repertoire showed no preferential usage of the Vbeta family in MNCs, while the dominant expression of Vbeta13 was detected in T-cells infiltrating in the spleen and lung. A Jbeta analysis showed the restricted usage of Jbeta1.2 for Vbeta13 in these cells, and the clonality of Vbeta13-Jbeta1.2 fragment was confirmed by a single-strand confirmation polymorphism analysis. The analysis of the Valpha repertoire showed that Valpha24 was exclusively used in these DN T-cells, but no usage of JalphaQ for Valpha24 was observed.

CONCLUSIONS

A clonal expansion of T-cells was induced in scid mice by the engraftment of MNCs from an FHL patient. The infiltration of DN alphabeta T-cells bearing invariant Valpha24 T-cell receptor in mouse organs may provide a useful clue to the pathogenesis of FHL. In the patients whose MNCs induced murine lymphoma-like disease, some cytokines or unknown factors that stimulate the growth and the tumorigenicity of murine lymphocytes might be produced by the MNCs engrafted in scid mice. Further study is needed to confirm the validity of our experimental approach and the findings observed in scid mice by using more FHL samples.

Non-Hodgkin's lymphomas in Mexico. A clinicopathological and molecular analysis

It is now well established that the clinical and histopathological characteristics of non-Hodgkin's lymphomas may vary significantly throughout the world. However, only a few reports have been published in Latin American countries. In this work, the clinical and pathologic findings of 264 patients with non-Hodgkin's lymphomas in Mexico City were analyzed. Diffuse large (14%) and diffuse mixed cell types (20%) predominated among nodal lymphomas. Within the group of patients with high grade malignancies, immunoblastic sarcomas were the most common (40/48). It is important to mention that follicular lymphomas were sporadic (4.5%). Among extranodal lymphomas the most commonly involved site was the gastrointestinal tract (11.3%), followed by the midline (6%). Molecular analysis of 65 cases with immunoglobulin and T-cell receptor gene probes showed that most lymphomas were of B-cell lineage (66%). The remaining group was composed of T-cell (25%) and bigenotypic malignancies (9%). All attempts to establish a correlation between the clinical stage and histopathological types with the genetic findings were not successful. However, pre-B and bigenotypic lymphomas were observed mainly in patients over 60 years of age. This study highlights some relevant characteristics of non-Hodgkin's lymphomas in Mexico.

Phosphoantigen activation induces surface translocation of intracellular CD94/NKG2A class I receptor on CD94- peripheral Vgamma9 Vdelta2 T cells but not on CD94- thymic or mature gammadelta T cell clones

Most adult peripheral blood gammadelta T cells express Vgamma9/Vdelta2-encoded TCR that recognize a restricted set of nonpeptidic phosphorylated compounds, referred to as phosphoantigens. They also express various MHC class I-specific inhibitory receptors (IR), in particular CD94/ NKG2-A heterodimers, which participate in the fine tuning of their TCR-mediated activation threshold. Most mature Vgamma9/Vdelta2 T cells express surface CD94 receptors, unlike cord blood or thymus-derived Vgamma9/Vdelta2 clones, thus suggesting a role for the microenvironment in IR expression. In the present study we show that most CD94- Vgamma9Vdelta2 PBL ex vivo express an intracellular pool of CD94/NKG2-A receptors that is translocated to the cell surface upon activation by phosphoantigens or IL-2. In stark contrast, intracellular CD94/NKG2-A complexes are undetectable in CD94- thymus or PBL-derived mature Vdelta2 T cell clones, and no surface induction is observed following phosphoantigen activation of T cell clones. Altogether these results provide new insights into the regulation of CD94/NKG2-A expression on T lymphocytes and suggest the existence of distinct mechanisms controlling in vivo and in vitro induction of IR on these cells.

Molecular analysis of childhood acute lymphoblastic leukemia in Israel

Ninety-two Israeli children with acute lymphoblastic leukemia (ALL) (67 B-lineage and 25 T-lineage) were analyzed for the immunological antigen receptor gene configuration. Thirty-nine of the patients (27 B-lineage and 12 T-lineage) relapsed. The incidence of the identified rearrangements within the immunoglobulin heavy chain (IgH) and T-cell receptor (TCR)beta, gamma and delta genes, at diagnosis, was in accordance with previous studies from other countries. Furthermore, the clinical relevance of bi/oligoclonal status, at diagnosis, and clonal selection was determined in this long-term follow-up study (median 112 months). A similar relapse rate was observed among the B-lineage patients with bi/oligoclonal and monoclonal patterns indicated by IgH gene rearrangement. Based on our results, we suggest that bi/oligoclonality has no prognostic significance (P=0.8533). Clonal variations between diagnosis and subsequent relapses were detected in 60% (12/20) of the patients; 64% (7/11) B-lineage and 55% (5/9) T-lineage. Clonal selection significantly correlated with shorter duration of remission and earlier recurrence (P=0.0025).

T-stem cell leukemia/lymphoma with both myeloid lineage conversion and T-specific delta recombination

We evaluated retrospectively the clinical and biological characteristics of six patients with CD7+ early T-acute lymphoblastic leukemia and lymphoma (T-ALL/LBL) originating from prothymocyte stage I (pro-T I) or II cells. Patients exhibited mediastinal mass (five of six) and lymphoadenopathy (five of six) but without leukocytosis and circulating blast cells (six of six). All patients achieved a complete remission. All but one had a relapse with a transformation to the mixed type (triphenotype--three cases, biphenotype-two cases) including myeloid features in three patients. The altered phenotypes were myeloperoxidase (MPO)+ (three of five), CD13+ (four of five), CD33+ (three of five) and CD19+ (three of five). The difference for MPO-positivity were observed between the bone marrow (BM)- and lymph node (LN)-blast cells (three of three). On cytogenetic analysis, there is no common abnormality in these patients. Immunomolecular analysis revealed T-cell lineage specific delta gene rearrangements [D delta 2-J delta 1 (five of six) and V delta 1-J delta 1 (one of six)] in all cases. Furthermore, D delta 2-J delta 1 occurred even in the cases with the pro-T I phenotype. Rearrangements of TCR beta, gamma or immunoglobulin heavy chain genes occurred in three patients. The same rearranged band(s) appeared at both diagnosis and relapse, indicating the same originality of the pro-T leukemic cell clone (three of three). We suggest that this type of CD7+ early T-ALL/LBL was transformed from a pro-T I or II cell, such as T-stem cell leukemia/lymphoma, which is a subtype of CD7+ stem cell leukemia as defined by Kurtzberg et al. This study reveals that pro-T I and II cells might be capable of myeloid, T- and B-lymphoid differentiation, and T-cell lineage specific TCR delta recombination occurs.

Short-limb dwarfism and hypertrophic cardiomyopathy in a patient with paternal isodisomy 14: 45,XY,idic(14)(p11)

Uniparental disomy (UPD) has been shown to result in specific disorders either due to imprinting and/or homozygosity of mutant alleles. Here we present the findings in a child with paternal UPD14. Ultrasound evaluation was performed at 30 weeks of gestation because of abnormally large uterine size. Pertinent ultrasound findings included polyhydramnios, short limbs, abnormal position of hands, small thorax, and nonvisualization of the fetal stomach. Post-natally the infant was found to have a low birth weight, short birth length, contractures, short limbs, and a small thorax with upslanting ribs. Assisted ventilation and gastrostomy were required. At age 6 months, the infant required hospitalization for hypertrophic cardiomyopathy which responded to Atenolol. Initial cytogenetic studies demonstrated an apparently balanced de novo Robertsonian translocation involving chromosomes 14 and a karyotype designation of 45,XY,t(14q14q). No indication of mosaicism for trisomy 14 was observed in metaphase spreads prepared from peripheral blood lymphocytes or skin-derived fibroblasts. C-band and fluorescence in situ hybridization results demonstrated that the chromosome was dicentric. DNA analyses showed paternal uniparental isodisomy for chromosome 14. Based on the cytogenetic and DNA results a final karyotype designation of 45,XY,idic(14)(p11) was assigned to this infant with paternal isodisomy of chromosome 14.

Differences in T-cell-receptor gene rearrangement and transcription in nasal lymphomas of natural killer and T-cell types: implications on cellular origin

Although nasal lymphomas showing midfacial destructive lesions had been classified as T-cell lymphomas, their exact cellular origin is still unclear. Although they usually express a restricted number of T-cell-related antigens, namely, CD2, CD43, and CD45RO, other pan-T or subset-T-lineage antigens, such as CD3 (membrane), CD5, CD4, CD8, and CD7, are frequently absent. Conversely, they often express a natural killer (NK) cell-associated antigen, CD56, but lack other mature NK markets. To study their cellular origin further, the authors analyzed T-cell receptor (TCR) gene transcription in three cases of nasal lymphomas and correlated the findings with the phenotype and gene rearrangement data. Two cases of nasal lymphomas with CD2+CD3(Leu4)-CD19-CD56+ phenotype were shown to express truncated 1.0-kb Tbeta and multiple unrearranged Tdelta transcripts with germline TCR beta, gamma, delta, and immunoglobulin heavy-chain joining region (JH) genes, consistent with NK cell lineage. In contrast, one case of nasal lymphoma with CD2+CD3(Leu4)+CD8+CD19-CD56+ phenotype expressed full-length Talpha, Tbeta, and Tgamma transcripts rearranged TCR beta, gamma, and deleted TCR delta genes, indicating T-lineage, These results support the view that nasal lymphomas can separated into NK-cell and T-cell neoplasms, based on differences genotypic characteristics. The possibility of these tumors being derived from a putative common precursor cell merits further investigation.

TCR gene polymorphisms and autoimmune disease

Autoimmunity may result from abnormal regulation within the immune system. As the T cell is the principal regulator of the immune system and its normal function depends on immune recognition or self/non-self discrimination, abnormalities of the idiotypic T-cell receptor (TCR) may be one cause of autoimmune disease. The TCR is a clonally distributed, cell-surface heterodimer which binds peptide antigen when complexed with HLA molecules. In order to recognize the variety of antigens it may possibly encounter, the TCR, by necessity, is a diverse structure. As with immunoglobulin, it is the variable domain of the TCR which interacts with antigen and exhibits the greatest amount of amino acid variability. The underlying genetic basis for this structural diversity is similar to that described for immunoglobulin, with TCR diversity relying on the somatic recombination, in a randomly imprecise manner, of smaller gene segments to form a functional gene. There are a large number of gene segments to choose from (particularly the TCRAV, TCRAJ and TCRBV gene segments) and some of these also exhibit allelic variation. Finally, polymorphisms in non-coding regions of TCR genes, leading to biased recombination or expression, are also beginning to be recognized. All these factors contribute to the polymorphic nature of the TCR, in terms of both structure and repertoire formation. It follows that inherited abnormalities in either coding or regulatory regions of TCR genes may predispose to aberrant T-cell function and autoimmune disease. This review will outline the genomic organization of the TCR genes, the genetic mechanisms responsible for the generation of diversity, and the results of investigations into the association between germline polymorphisms and autoimmune disease.

Partial cloning and sequencing of the gene encoding the porcine T-cell receptor delta-chain constant region

The polymerase chain reaction (PCR) was utilized to clone the pig T-cell receptor (TCR) delta-chain constant region-encoding gene (C delta). A cDNA was generated from total RNA preparations of normal pig peripheral blood lymphocytes (PBLs) and a miniature pig peripheral blood cell line (PBLCL 62.G4). The cDNA was used to amplify the porcine TCR C delta gene by PCR using primers chosen by comparing other known C delta sequences for sequence identity. Clones were sequenced and used to determine the primary structure of the porcine TCR C delta chain. A comparison of the nucleotide and deduced amino acid (aa) sequences with the known human, mouse, sheep and cattle sequences revealed that the primary structure of the pig TCR C delta chain has been highly conserved. The immunoglobulin (Ig) domain has two conserved Cys residues and contains a high degree of sequence identity, whereas the hinge region is marked by a high level of diversity. The transmembrane and cytoplasmic regions are also highly conserved, including the presence of the two basic aa, Arg and Lys, in the transmembrane domain. Southern blot analysis has confirmed the presence of one TCR C delta gene in the porcine genome, consistent with similar findings in other species. Thus, the successful cloning and sequencing of the porcine TCR C delta gene should facilitate our understanding of the role of gamma delta T-lymphocytes in the swine immune system.

Isolation and characterization of gamma delta T lymphocyte cell lines from Sinclair swine peripheral blood

Sinclair miniature swine represent a breed of miniature swine which display a significant incidence of inheritable melanoma which undergo a developmentally regulated spontaneous regression. In an attempt to characterize the host cellular immune response to the melanoma, lymphocyte cell lines have been generated from peripheral blood and designated as peripheral blood lymphocyte cell lines (PBLCLs). The cell lines were expanded in vitro without the addition of exogenous mediators, cloned by limiting dilution, and characterized by flow microfluorimetry, Western, and Northern blot analysis. The cell lines were shown to be CD2-, CD4-, CD8-, and slg-, a phenotype consistent with a null cell population described in swine. The null cell population in swine has been reported to consist of a subpopulation of cells which express the gamma delta T cell receptor (TCR) heterodimer, swine gamma delta T lymphocytes. The PBLCLs were further analyzed by flow microfluorimetry and observed to express the IL-2R, swine MHC Class II antigens, and the endothelial lymphocyte adhesion marker (CD44), which can function as a homing receptor for the skin. In addition, the PBLCLs were observed to express the antigen which is recognized by mAb 86D, an antibody that has been reported to recognize an external epitope on a subset of gamma delta TCR bearing swine T lymphocytes. Western blot analysis of Triton X-114 phase fractions of a PBLCL revealed a protein recognized by the W6 antibody, an antibody which recognizes a conserved region of the C delta chain. Furthermore, Southern and Northern blot analysis indicated that the PBLCL have rearranged the TCR gamma chain gene and express mRNA from the TCR gamma and delta chain genes prior to and following treatment with ionomycin or Concanavalin A. Therefore, the data indicates that the PBLCLs represent swine gamma delta T lymphocyte cell lines which should enable us to enhance our understanding of the role of gamma delta T lymphocytes in the porcine immune system.

CD7+ stem cell leukemia/lymphoma. Features of a subgroup without circulating blast cells

Recent advances in immunology have clarified the cellular origin of hematopoietic neoplasms. Blast cells with a CD7+ CD4- CD8- phenotype are demonstrated to originate from malignant pluripotent hematopoietic stem cells. In this article, the authors describe three rare cases, designated as a lymphoma type of CD7+ stem cell leukemia/lymphoma, with clinical features described below. All three patients were admitted with non-Hodgkin lymphoma with a 2-month to 4-month history of lymphadenopathy. Histologic examination of lymph nodes showed lymphoblastic lymphoma (LBL) in all patients. Bone marrow blast cells had an immunophenotype consistent with CD7+ CD4- CD8- acute leukemia, although abnormal cells were not observed in the peripheral blood during the course of the disease. One patient had a recurrence in the bone marrow, with myeloperoxidase-positive blast cells expressing myeloid differentiation antigens. Chromosomal analysis detected a common abnormal karyotype initially and at relapse. Furthermore, the same T-cell receptor gene rearrangement was found initially and at relapse, suggesting that these blast cells originated from the same pluripotent leukemic clone. Additional studies on more patients are required to determine the clinical significance of this group, including the difference from CD7+ stem cell leukemia/lymphoma with circulating blast cells (leukemic type) or LBL.

Detection of human T cell receptor cDNAs (alpha, beta, gamma and delta) by ligation of a universal adaptor to variable region

The study of T cell receptor (TCR) genes has been hampered by their large repertoires and elusive methods for gene amplification. We have developed a new method for amplification of all human TCR genes (alpha, beta, gamma, and delta) with the ligation of a universal adaptor to the leader sequence of variable (V) regions, which permitted effective and reproducible amplification of all four types of TCR genes. cDNA sequencing of TCR-gamma, -delta, -alpha, -beta was carried out in respectively 15, 13, 28, and 26 T cell clones from human peripheral blood T cells using a newly developed universal adaptor and these methods. TCR-gamma V-II (V gamma 9) was a major population, and V-I (V gamma 2 and 3) and V-III (V gamma 10) were next major populations among TCR-gamma subfamilies, and confirmed the previous observations determined using mAbs specific to TCR-gamma. All five clones of TCR-gamma V-II and three of five clones of TCR-gamma V-I subfamilies had in-frame V-N-J junctions. In contrast, sequences from both TCR-gamma V-III (4/4 clones) and V-IV (1/1 clones) subfamilies had intron-like regions that caused out-of-frame cDNA, suggesting that most of TCR-gamma V-III and V-IV in PBL are not functional. V delta 2 was a major population and V delta 1 was a next predominant population among TCR-delta subfamilies, also confirming the previous observations determined using mAbs to TCR-delta. With regards to TCR-alpha and -beta, this new method randomly amplified TCR cDNAs. In addition, the sequences of 5' portions of three TCR-V-alpha and one TCR-V beta were extended. Two new TCR-alpha subfamilies and one new TCR-beta family were also identified. In summary, this new method will provide a scientific tool for understanding structures of the human TCR genes involved in specific immune responses.

Alternatively spliced T cell receptor transcripts expressed in human T lymphocytes

We used the anchored-polymerase chain reaction (A-PCR) procedure to study human TCR transcripts derived from a variety of polyclonal T cell populations. In this series of experiments, 31 'unusual' cDNAs, which do not include exclusively V-J-C, J-C or 5'C genomic sequences, were identified. Ten of these were found to represent distinct types of alternatively spliced TCR alpha transcripts whose structure is derived from unusual splicing of one, two or even three intervening intronic sequences. The splicing events led to either conservation of a novel exon in the mRNA structure (designated aE1 alpha-aE5 alpha) between the V-J and C segments or to deletion of the 3' V region-J segment. In three cases, the alternatively spliced exons (aE1 alpha-aE3 alpha) interrupt the open translational reading frame of the corresponding V-J alpha segment. Nineteen and two cDNA represent sterile C beta or C delta transcripts, respectively. Their structures are derived from the conservation of a non-translatable exon, aE1 beta or aE1 delta, which is precisely spliced at the 5' end of the corresponding C exon sequences. Interestingly, the 3' region of the aE1 beta sequence is homologous to the murine C beta 0 exon. Together, these results led to the characterization of nine novel exons in the TCR alpha, beta and delta loci.

T cell receptor heterogeneity in gamma delta T cell clones from intestinal biopsies of patients with celiac disease

In celiac disease large numbers of gamma delta T lymphocytes infiltrate the intestinal epithelia. We have isolated intestinal gamma delta T cell clones from patients with celiac disease and have analyzed their T cell receptor repertoire. T cell lines and clones were obtained from jejunal biopsies of 14 celiac patients and 12 individuals without celiac disease. These were analyzed by staining with monoclonal antibodies against CD3, alpha beta and gamma delta T cell receptor, by Southern blot with gamma- and delta-specific probes and by polymerase chain reaction using V delta-specific oligonucleotides. Intestinal gamma delta cells from patients with celiac disease differed from those of controls with normal jejunal histology in that V delta 1+ cells and V delta 1-V delta 2- cells were significantly increased. There was no evidence of the expansion of one or more clones expressing particular types of gamma delta T cell receptor.

A third tal-1 promoter is specifically used in human T cell leukemias

A common feature of T cell acute lymphoblastic leukemias (T-ALLs) is the presence of structural alteration of the 5' part of the tal-1 locus, localized on chromosomal band 1p32. These alterations consist of either a t(1;14)(p32;q11) chromosomal translocation (3% of T-ALLs) or tald submicroscopic deletion (12-25% additional T-ALLs). We have characterized a case of T-ALL with t(1;14)(p32;q11) in which, unlike the majority of t(1;14), the recombination with the T cell receptor delta elements affected the 3' side of the tal-1 locus. In this case, tal-1 transcription is initiated from a promoter located within the fourth exon similarly to the DU 528 cell line. In a T-ALL bearing a t(1;14) affecting the 5' part of tal-1, two types of tal-1 transcripts were observed, namely those probably initiated from the D delta region juxtaposed to tal-1 by the translocation, and those from the exon 4 promoter. It is interesting that this exon 4 promotion was also found in leukemic T cell lines and T-ALL samples without apparent tal-1 genomic alteration. In contrast, no transcript initiated from the exon 4 promoter was found in T-ALL with tald1 or tald2 deletion. In these cells, tal-1 is expressed via SIL-tal-1 fused transcripts. Finally, this exon 4 initiation was detected neither in normal bone marrow, nor in malignant cells from the erythroid/megakaryocytic lineages. Taken as a whole, these data suggest that the exon 4 promoter is specifically active in T cell lineage.

Molecular analysis of an ataxia telangiectasia T-cell clone with a chromosomal translocation t(14;18)--evidence for a breakpoint in the T-cell receptor delta-chain gene

We established a clonal T-cell line with a reciprocal chromosomal translocation t(14;18)(q11;q23) from a patient with ataxia telangiectasia (AT) and T-cell chronic lymphocytic leukemia (T-CLL). The tumor cells and the derived T-cell line were compared with respect to phenotype, karyotype, and rearrangement pattern. Restriction fragment analyses of the T-cell receptor (TCR)-delta gene, which is located within the TCR-alpha gene on chromosome 14q11, indicated that the breakpoint is located within the TCR-delta locus, splitting the TCR-delta gene between the variable and joining segments. This specific chromosomal translocation was only detected in the derived T-cell line and may be involved in the genesis of T-cell malignancies in AT.

T cell receptor diversity and activation markers in the V delta 1 subset of rheumatoid synovial fluid and peripheral blood T lymphocytes

In the present study we have characterized the gamma/delta T cell receptor (TcR) population in synovial fluid (SF) and peripheral blood (PB) of patients with chronic inflammatory arthritis. By double staining we have shown that (a) synovial V delta 1+ cells have a high expression of activation markers CD45R0 ("memory cells") and HLA-DR as compared to PB, indicating a preactivated population of V delta 1-carrying T cells in vivo and (b) interleukin 2-induced expansion of synovial cells yields a high proportion of gamma/delta in most samples expressing predominantly the V delta 1 TcR. Junctional sequence analysis of the TcR delta chain from interleukin 2-expanded PB cell lines demonstrated a polyclonal V delta 1 population in three out of three samples. In SF cell lines three out of four samples were polyclonally expanded. In SF from one patient, however, a limited repertoire of expressed V delta 1 genes was found. Altogether, our data demonstrate the presence of preactivated V delta 1-expressing cells in the synovial compartment. This V delta 1 population is predominantly polyclonal, except in one patient where oligoclonally expanded V delta 1 cells were detected.

Variable gene usage of T cell receptor gamma- and delta-chain transcripts expressed in synovia and peripheral blood of patients with rheumatoid arthritis

The synovial tissue and fluid of patients with rheumatoid arthritis (RA) contain activated T cells that probably have a central role in the disease process which leads to joint destruction. A subset of T cells, gamma delta T cells detected at the site of inflammation, may be important in the pathogenesis of the disease. This study investigated variable (V) gene usage of gamma delta T cell receptors (TcRs) expressed in synovia and peripheral blood of patients with RA by using the polymerase chain reaction (PCR) to amplify TcR gamma- and delta-chain transcripts. Most patients showed no restriction in V gamma gene usage since synovial mononuclear cells (SMC) expressed TcR gamma-chain transcripts which used the same set of V gamma genes as peripheral blood mononuclear cells (PBMC). In contrast, the majority of patients expressed a restricted SMC V delta-chain repertoire biased towards V delta 1, but V delta 2 mRNA transcripts were also detected, albeit at low levels in some patients. The TcR delta-chain repertoires of PBMC from healthy control subjects were also characterized. There was variation in the TcR delta-chain repertoires of PBMC from patients when compared with controls, particularly with respect to expression of V delta 4. V delta 4 mRNA transcripts were expressed in PBMC of only two of seven RA patients in contrast with eight of the nine controls (P = 0.03). These findings are compatible with reports that gamma delta T cells in the rheumatoid synovium are reactive to Mycobacterium tuberculosis and that response to M. tuberculosis is restricted to V gamma 9/V delta 2-bearing T cells, if a superantigen is involved in the pathogenesis of RA.

Acute undifferentiated leukemia with CD7+ and CD13+ immunophenotype. Lack of molecular lineage commitment and association with poor prognostic features

The authors studied six adult patients with acute leukemia with these unusual characteristics: unclassifiable morphology and undifferentiated cytochemistry by French-American-British (FAB) criteria; concurrent expression of CD13 (and CD33) myeloid and early T-cell CD7 immune markers; no evidence of T-cell lineage commitment as determined by T-cell receptor beta (beta), gamma (gamma), and delta (delta) chain gene rearrangement study and cytoplasmic CD3 epsilon expression; and no evidence of myeloid cell lineage commitment, as shown by absent myeloid-specific c-fms proto-oncogene expression and negative myeloperoxidase ultrastructural staining (one case). Clinically, these diagnostic features matched with a poor prognosis, being associated with refractoriness to treatment, relapse and progression of disease, antecedent hematologic abnormality, and other malignancy. These cases may represent a distinct stem cell leukemia syndrome deserving immediate recognition and a nonconventional chemotherapeutic approach.

Differential regulation of gamma and delta T cell antigen receptor gene expression by phorbol esters and Ca2+ ionophores in the acute lymphocyte leukemia DND41 cell line

We have investigated the role of two signal transduction pathways on the regulation of the gamma and delta T cell antigen receptor (TcR) gene expression, in the acute lymphocytic leukemic cell line DND41. Protein kinase C (PKC) activation, and intracellular free Ca2+ mobilization, initiated by phorbol esters and calcium ionophores, respectively, not only acted independently but, more interestingly, their effects were antagonistic, suggesting a role for these signals during T cell differentiation. The Ca2+ ionophore, ionomycin, increased the levels of intracellular free Ca2+ and induced the expression of the gamma and delta chains of the T cell antigen receptor in a concentration-dependent manner. The phorbol ester 12-myristate 13-acetate down-regulated the basal gamma TcR expression with marginal effect on delta TcR mRNA, but diminished the induction of both gamma and delta TcR, initiated by the Ca2+ ionophore. These antagonistic effects of the two arms of the phospholipase C-mediated signal transduction pathways, i.e. PKC activation and increased intracellular free Ca2+, were specific to the regulation of the gamma and delta TcR, since the same signals exerted a synergistic effect on the mRNA levels of interleukin 2 receptor. These data confirm our hypothesis that the antagonistic regulation on the gamma and delta TcR gene expression by phorbol esters and calcium ionophores occurs in the same cell, and stresses the biological significance of PKC activation and intracellular free calcium mobilization during intrathymic differentiation and selection.

Use of variable human V delta genes to create functional T cell receptor alpha chain transcripts

Previous studies of the human T cell receptor delta genes identified five commonly used V delta segments distinct from any of the known V alpha genes. To define better the relationship between the T cell receptor delta and alpha repertoires we amplified cDNA obtained by polyclonally activated lymphocytes with a common 3' antisense C alpha-specific primer and with five different 5' sense V delta family-specific primers. Amplified products were detected in staphylococcal enterotoxin C2, staphylococcal enterotoxin E, phytohemagglutinin, concanavalin A, anti-CD3 and anti-V beta 8-activated cells, although each cell population expressed a selective pattern of V delta genes. Sequence analysis revealed that each of the known V delta genes can productively rearrange to J alpha segments to produce functional V delta-J alpha-C alpha transcripts. These results argue strongly against the notion that the human V delta and V alpha repertoires are distinct. They further suggest that the restricted delta repertoire observed in many gamma/delta clones results from selection rather than from controlled rearrangements at the T cell receptor alpha/delta locus.

Recombinative events of the T cell antigen receptor delta gene in peripheral T cell lymphomas

Recombinative events of the T cell antigen receptor (TCR) delta-chain gene were studied in 37 cases of peripheral T cell lymphoma (PTCL) and related to their clinical presentation and the expression of the alpha beta or gamma delta heterodimers as determined by immunostaining of frozen tissue samples. There were 22 cases of alpha beta, 5 cases of gamma delta, and 10 cases of silent TCR expressing neither the alpha beta nor gamma delta TCR. 5 different probes were used to examine the delta locus. The 22 cases of alpha beta PTCL displayed biallelic and monoallelic deletions; a monoallelic V delta 1 J delta 1 rearrangement was observed in 1 case and a monoallelic germ line configuration in 7 cases. The 5 cases of gamma delta PTCL displayed biallelic rearrangements: the productive rearrangements could be ascribed to V delta 1J delta 1 joining in 3 cases and VJ delta 1 joining in 2 cases according to the combined pattern of DNA hybridization with the appropriate probes and of cell reactivity with the TCR delta-1, delta TCS-1, and anti-V delta 2 monoclonal antibodies. In the VJ delta 1 joining, the rearranged V segments were located between V delta 1 and V delta 2. Interestingly, in the third group of 10 cases of silent PTCL, 5 cases were found to have a TCR gene configuration identical to that in the TCR alpha beta PTCL, as demonstrated by biallelic delta gene deletion. These 5 cases were CD3 positive. The 5 remaining cases showed a monoallelic delta gene rearrangement with a monoallelic germ line configuration in 4 and a monoallelic deletion in 1. Four of these cases were CD3 negative, which was consistent with an immature genotype the TCR commitent of which could not be ascertained. Finally, TCR gamma delta PTCL consisted of a distinct clinical morphological and molecular entity whereas TCR alpha beta and silent PTCL had a similar presentation.

Genotypic and cytogenetic study of acute myelocytic leukemia and chronic myelocytic leukemia in blast crisis: specific delta rearrangement pattern does not involve J delta gene locus

We have analysed the configuration of immunoassociated genes and the karyotypes of 30 patients with acute myelocytic leukemia (AML) and 10 with chronic myelocytic leukemia in blast crisis (CML-BC). In AML, the frequencies of T-cell receptor (TcR) beta, gamma, and delta chain and immunoglobulin heavy and light chain gene rearrangements were 4.2%, 19%, 8%, 10.7% and 10.5%, respectively. In CML-BC, they were 10%, 20%, 40%, 50% and 0%, respectively. Nine patients had abnormalities in chromosome 2, 7 or 14, upon which immunoassociated genes are located. There seems to be no apparent relationship between these chromosome abnormalities and gene rearrangements. In all patients but one (5/6), the delta rearrangement was accompanied by other immunoassociated gene rearrangements. Molecular size analysis revealed specific delta rearranged band(s) (19.5 kb-BamHI and/or 6.9 kb-EcoRI), as commonly detected in B-acute lymphocytic leukemia (ALL). All the patients with the delta rearranged band, however, had a germline configuration of J delta gene loci, suggesting a DD or V(D)D (probably V delta 2(D)D) pattern. This study also indicates that the delta rearrangement is specific in AML or CML-BC and distinct from that in early T leukemia/lymphoma.

In vitro expansion of CD3/TCR- human thymocyte populations that selectively lack CD3 delta gene expression: a phenotypic and functional analysis

Highly purified CD1-3-4-8- human thymocytes were obtained by panning techniques combined with cell depletion with antibody-coated magnetic beads. Most of these cells expressed cytoplasmic CD3 antigen, as assessed by mAbs known to react with the CD3 epsilon chain. After culture with low doses of PMA (0.5 ng/ml) and subsequent addition (at 24 h) of recombinant interleukin 2 (rIL-2; 100 U/ml) cells underwent extensive proliferation (40-60-fold of the initial cell input after 2 wk). The majority of the proliferating cells were CD3-TCR-. The remaining cells (5-40%) were represented by CD3+ TCR gamma/delta+ (BB3- A13+) cells. Further removal of CD3+ TCR-gamma/delta+ cells resulted in highly purified CD3- populations that further proliferated in culture with no substantial phenotypic changes. When CD3+ thymocytes were cultured under the same experimental conditions, only CD3+ TCR-alpha/beta+ cells could be detected, thus indicating that PMA did not affect the surface expression of the CD3/TCR complex, but rather induced preferential growth of CD3- thymocytes. Surface marker analysis of cultured CD3- thymocytes showed that they were homogeneously CD7+, whereas low proportions of cells expressed CD2 and CD8 antigens. Among the natural killer (NK) cell markers, CD56 was highly expressed by all cells, whereas CD16, CD57, CD11b, NKH2, and GL183 were absent. Importantly, these cells were different from peripheral NK cells, as 80-95% of them expressed cytoplasmic CD3 antigen. Functional analysis revealed a strong cytolytic activity against both NK-sensitive (K562) and NK-resistant (M14, Daudi) human target cells. In a redirected killing assay against the Fc gamma R+ P815 cells, mAbs specific for triggering molecules including CD3, CD2, and CD16 failed to augment target cell lysis, while a strong cytolytic effect was induced by PHA. In addition, PHA alone or in combination with PMA induced tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) (but not IL-2) production by CD3- thymocytes. Cloning of fresh CD1-3-4-8-thymocytes in the presence of PMA and rIL-2 resulted in CD3-CD56+ clones that displayed a pattern of cytolytic activity and lymphokine production similar to that of the polyclonal populations. Northern blot analysis of transcripts coding for CD3/TCR molecules revealed the presence of CD3 zeta, epsilon, and gamma transcripts, while CD3 delta was undetectable. Mature transcripts for both gamma and delta TCR chains could be detected, whereas no TCR-alpha mRNA and only a truncated (1.0 kb) form of TCR-beta mRNA were revealed.(ABSTRACT TRUNCATED AT 400 WORDS)

Genotypic and immunophenotypic analysis of anaplastic large cell lymphoma (Ki-1 lymphoma)

Genotypic and immunological analysis was performed in 10 patients with anaplastic large cell lymphoma (Ki-1 lymphoma), 4 were male and 6 female. Immunophenotypically, 9 of these patients expressed some T cell markers; CD 2 in 9, CD 4 in 9, CD 3 in 6, CD 8 in 4, and UCHL-1 in 8. For B cell markers, 4 patients expressed B 1 and one expressed L 26; these patients also expressed T cell markers. In genotypic analysis, 9 of 10 cases displayed some incidence of T cell receptor gene (TCR) rearrangement or deletion, which was found in 3 patients for C beta 1, 7 for C beta 2, 8 for J gamma, 5 for C gamma (Hind III), 5 for C gamma (EcoRI), 3 for J delta 1 (Hind III), 3 for J delta 1 (BamHI), 3 for J delta 2, and 2 for C delta. One patient with rearrangement of TCR also showed rearrangement of immunoglobulin heavy chain. Another patient exhibited rearrangement of both TCR and immunoglobulin chain. These results indicate a common T cell lineage for this type of lymphoma.

Aggressive natural killer cell leukaemia/lymphoma: report of four cases and review of the literature. Possible existence of a new clinical entity originating from the third lineage of lymphoid cells

The morphologic, immunologic, genotypic and functional properties of peripheral blood and bone marrow cells or cultured cells from four patients with a clinically aggressive non-T, non-B natural killer cell leukaemia/lymphoma (ANKL/L) are described. The leukaemic cells possessed medium to large granules in the cytoplasm, antigens against CD38, CD2, OKIa 1 and NKH-1 CD56) monoclonal antibodies on their cell-surface, and also showed natural killer (NK) activity. In addition, these ANKL/L belonged to neither T- nor B-cell lineage, proved by studying clonal gene rearrangement for the T beta, T gamma and T delta receptors, and immunoglobulin. After comparing them with the seven cases of ANKL/L reported in other institutions, with regard to immunophenotype, genotype and function, we conclude that ANKL/L originating from a third lineage of lymphoid cells is a distinct clinical entity.

Two distinct mechanisms for the SCL gene activation in the t(1;14) translocation of T-cell leukemias

Molecular study of a t(1;14)(p32;q11) translocation found in an acute T-cell leukemia (Kd cells) with a relatively mature phenotype is reported. Complex DNA rearrangements were characterized in the TCR alpha/delta locus. Besides a productive V alpha/J alpha assembly found on the normal allele, two deletions within the J alpha cluster were identified in the translocated allele. The translocation breakpoints involved the TCR delta gene on chromosome 14 and the SCL locus on chromosome band Ip32 that was recently shown to be activated by the t(1;14) translocation of the DU 528 leukemic cell line. Significantly, both Kd and DU 528 translocation breakpoints were located at the boundaries of D delta or J delta segments and were clustered in a 10 kb genomic fragment of the SCL gene. The presence of recombination signal motifs (heptamer-12/23 bp spacer-nonamer) on both normal chromosome partners, and N nucleotide addition on both derivative chromosomes involved the recombinase system in the translocation event. The SCL locus was highly expressed as a 5 kb transcript in Kd cells and, as already reported, as a 2 kb transcript in DU 528 cells. Importantly, a 5 kb SCL transcript was also detected in immature nonlymphoid hematopoietic cells but not in normal mature T cells, suggesting that it might correspond to the normal SCL transcript. Taken together, our data support the notion that the involvement of the SCL gene in the leukemogenic process may occur through overexpression of an apparently normal transcript (Kd cells) or expression of a truncated RNA (DU 528 cells).

Rearrangement of the T-cell receptor alpha, beta and gamma chain genes in chronic lymphocytic leukemia

Simultaneous expression of mature B-cell and T-cell markers and subsequent abrogation of expression of the T-cell surface markers by cytotoxic chemotherapy was reported earlier in a patient (TG) with chronic lymphocytic leukemia (CLL). In addition to rearrangements of the immunoglobulin (Ig) gene loci correlating with phenotypic data, the T-cell receptor (TCR) alpha, beta and gamma chain genes also displayed clonal rearrangements in peripheral blood lymphocyte DNA of TG. The present case shows that in CLL cells not only the expression of B-cell and T-cell specific differentiation antigens but also the rearrangement of Ig as well as TCR alpha, beta and gamma genes may occur simultaneously.

T cell receptor gamma gene status of human alpha/beta+ and gamma/delta+ T cell clones: absence of V9JP rearrangements in alpha/beta+ clones is not a result of a lack of rearrangements involving more 5' J gamma segments

T cell receptor (TCR) gamma gene rearrangements were examined in panels of human T cell clones expressing TCR alpha/beta or gamma/delta heterodimers. Over half of the alpha/beta+ clones had both chromosomes rearranged to C gamma 2 but this was the case for only 20% of the gamma/delta+ clones. While more than half of the gamma/delta+ clones showed a V9JP rearrangement, this configuration was absent from all 49 alpha/beta+ clones analysed. However, this was not a result of all rearrangements being to the more 3' J gamma genes as 11 alpha/beta+ clones had rearrangement(s) to JP1, the most 5' J gamma gene segment. Both alpha/beta+ and gamma/delta+ clones showed a similar pattern of V gamma gene usage in rearrangements to J gamma 1 or J gamma 2 with a lower proportion of the more 3' genes being rearranged to J gamma 2 than for the more 5' genes. Several alpha/beta+ and several gamma/delta+ clones had noncoordinate patterns of rearrangement involving both C gamma 1 and C gamma 2. Eleven out of fourteen CD8+ clones tested had both chromosomes rearranged to C gamma 2 whereas all clones derived from CD4-8- cells and having unconventional phenotypes (CD4-8- or CD4+8+) had at least one C gamma 1 rearrangement. Twelve out of twenty-seven CD4+ clones also had this pattern, suggesting that CD4-8+ clones had a tendency to utilize more 3' J gamma gene segments than CD4+ clones. There was some evidence for interdonor variation in the proportions of TCR gamma rearrangements to C gamma 1 or C gamma 2 in alpha/beta+ clones as well as gamma/delta+ clones. The results illustrate the unique nature of the V9JP rearrangement in gamma/delta+ clones and the possible use of a sequential mechanism of TCR gamma gene rearrangements during T cell differentiation is discussed.

Non-random expression of T cell receptor gamma and delta variable gene segments in functional T lymphocyte clones from human peripheral blood

Human T cell receptor (TcR) gamma delta displays a variety of protein forms. Disulfide-linked (type 1) or non disulfide-linked (type 2) receptors occur, with gamma chains encoded by the C gamma 1 or the C gamma 2 gene segment, respectively. Exon 2 of C gamma 2 may either be duplicated or triplicated (type 2a or 2b receptors). TcR gamma chains differ in molecular mass and charge between type 1 and type 2 receptors. The delta chains as well as the gamma chains have different structural properties between receptor types. This cannot be due to the use of different C delta gene segments, since the genome encodes only one. To understand the genetic basis of this dichotomy in gamma/delta combinations, rearrangement and expression of V gamma, J gamma, C gamma and V delta gene segments were determined in TcR gamma/delta+ clones derived randomly from peripheral blood of normal donors. Most clones used C gamma 1, a minority C gamma 2. The different protein properties of receptor types could be explained by the non-random expression of V gamma (J gamma) and V delta gene segments. Type 1 receptors preferentially used gamma chains encoded by the V gamma 9 and J gamma 1.2 gene segments together with delta chains encoded by V delta 2. In type 2a receptors, V gamma 9 was not predominant; often other V gamma gene segments were employed, but then in high frequency in coordination with V delta 1. Reactivity of the clones with monoclonal antibodies anti-Ti gamma A, BB3 and delta-TCS-1 correlated with the expression of the V gamma 9, V delta 2 and V delta 1 gene segments, respectively. Therefore, V gamma and V delta use in TcR gamma/delta+ cells from peripheral blood of eight healthy individuals, including the two donors of the clones, could be determined tentatively by double immunofluorescence. Indeed, the V gamma 9-V delta 2 combination was predominant, while the V gamma 9-V delta 1 and particularly the V gamma 9-"V delta other" combination was rare. These data indicate that the TcR gamma delta repertoire in peripheral blood of normal individuals is largely dependent on junctional diversity and suggest that selection of receptors occurs.

The t(11;14)(p15;q11) in a T-cell acute lymphoblastic leukemia cell line activates multiple transcripts, including Ttg-1, a gene encoding a potential zinc finger protein

Interchromosomal translocations within lymphoid neoplasms frequently involve the antigen receptor genes. We cloned the breakpoints of the t(11;14)(p15;q11) in a CD3-negative T-cell acute lymphoblastic leukemia cell line (RPMI 8402) in order to identify new genes potentially involved in T-cell neoplasia. An extensive comparison of both breakpoints and their germ line counterparts indicated that an inadvertant recombinase-mediated break at chromosome segment 11p15 recombined with the delta T-cell receptor at 14q11. The derivative 11 breakpoint resembles a coding joint in which 11p15 rather than a variable region was introduced 5' to a D delta 1 D delta 2 J delta 1 intermediate rearrangement. Conversely, the derivative 14 breakpoint corresponds to a signal joint between the 5' heptamer-spacer-nonamer recombinational signal of D delta 1 and an isolated heptamer at 11p15. Multiple, apparently distinct transcripts were found flanking both breakpoints of 8402. RNAs of 3.5, 4.4, 1.4, and 8.0 kilobases originating from either side of the derivative 14 breakpoint were highly expressed in 8402 compared with other cells. This suggests that this translocation deregulated multiple genes and provides the opportunity to assess any multifactorial contribution they may have to malignancy. We cloned and sequenced several cDNAs representing the 1.4-kilobase transcript (termed Ttg-1 [T-cell translocation gene 1]) from an 8402 library. The predicted protein of 156 amino acids contained two internal repeats which could potentially form zinc fingers.

The human T-cell receptor gamma (TRG) genes

The human T-cell receptor gamma (TRG) chain genes, like those encoding the T-cell receptor alpha- and beta-polypeptides, undergo rearrangements specifically in T cells. The human TRG locus, which has been completely mapped, is composed of two constant region genes (TRGC), five joining segments (TRGJ) and at least 14 variable gamma-genes (TRGV). Eight variable genes are functional and belong to four different subgroups. The product of the rearranged TRG gene is the gamma-chain which is expressed, along with the delta-chain, at the surface of a subset of T lymphocytes. Although some gamma delta + cells display a cytolytic activity, their precise function remains to be elucidated.

Dual rearrangement of immunoglobulin and T-cell receptor genes in blast crisis of CML

Dual rearrangement of immunoglobulin and T-cell antigen receptor (beta, delta) genes was demonstrated in a case of Philadelphia chromosome-positive chronic myeloid leukemia (CML) in blast crisis. The blast cells, showing L2 morphology and high activity of TdT, expressed pre-B cell (CD19+, Ia+) and myeloid (CD13+, CD34+) surface antigens but lacket T-cell antigens (CD2-, CD7-). Cytogenetic studies on bone marrow and peripheral blood revealed the Phl chromosome in all metaphases analyzed, majority of which also had the additional chromosome changes, +8, +10, +21. Furthermore, molecular analysis of the breakpoint cluster region (bcr) on chromosome 22 showed a rearrangement, confirming the CML origin of the blast cells.

The t(11;14)(p15;q11) in a T-cell acute lymphoblastic leukemia cell line activates multiple transcripts, including Ttg-1, a gene encoding a potential zinc finger protein

Interchromosomal translocations within lymphoid neoplasms frequently involve the antigen receptor genes. We cloned the breakpoints of the t(11;14)(p15;q11) in a CD3-negative T-cell acute lymphoblastic leukemia cell line (RPMI 8402) in order to identify new genes potentially involved in T-cell neoplasia. An extensive comparison of both breakpoints and their germ line counterparts indicated that an inadvertant recombinase-mediated break at chromosome segment 11p15 recombined with the delta T-cell receptor at 14q11. The derivative 11 breakpoint resembles a coding joint in which 11p15 rather than a variable region was introduced 5' to a D delta 1 D delta 2 J delta 1 intermediate rearrangement. Conversely, the derivative 14 breakpoint corresponds to a signal joint between the 5' heptamer-spacer-nonamer recombinational signal of D delta 1 and an isolated heptamer at 11p15. Multiple, apparently distinct transcripts were found flanking both breakpoints of 8402. RNAs of 3.5, 4.4, 1.4, and 8.0 kilobases originating from either side of the derivative 14 breakpoint were highly expressed in 8402 compared with other cells. This suggests that this translocation deregulated multiple genes and provides the opportunity to assess any multifactorial contribution they may have to malignancy. We cloned and sequenced several cDNAs representing the 1.4-kilobase transcript (termed Ttg-1 [T-cell translocation gene 1]) from an 8402 library. The predicted protein of 156 amino acids contained two internal repeats which could potentially form zinc fingers.

Organization and orientation of a human T cell receptor delta chain V gene segment that suggests an inversion mechanism is utilized in its rearrangement

A human T cell receptor (TcR) delta chain variable region segment, V delta 3, has been mapped 2 kilobases 3' to the constant (C delta) gene. The V delta 3 gene segment is in an inverted transcriptional orientation to the diversity regions (D delta), joining regions (J delta) and C delta gene segments. Analyses of TcR delta cDNA clone, KT041, showed that V delta 3 is linked to D delta 1, D delta 2, J delta 3 and C delta and that this message encodes a potentially functional TcR delta chain. These findings indicate that a functional TcR delta gene can be constructed through a chromosomal inversion, suggesting that in human, chromosomal inversion is one of the important rearrangement mechanisms.

Chromosomal translocation in a human leukemic stem-cell line disrupts the T-cell antigen receptor delta-chain diversity region and results in a previously unreported fusion transcript

We have studied a leukemic stem-cell line, DU.528, that is able to differentiate into myeloid and lymphoid cells. The leukemic cells have a translocation between chromosomes 1 and 14, t(1;14)(p33;q11), which we have molecularly cloned and sequenced. Initial screening used joining (J)-segment probes from the T-cell receptor (TCR) alpha- and delta-chain loci. In apparent concert with the translocation, a deletion has occurred between delta-chain diversity (D)-region genes D delta 1 and D delta 2. D delta 2 was observed on derivative chromosome 1 [der(1)] and D delta 1 on der(14) with a deletion of the intervening 10 kilobases of germ-line DNA. The nature of the D delta 1-D delta 2 deletional event implicates a lymphoid recombinase in the mechanism of the translocation. As a consequence of the translocation, an unusual fusion transcript was generated. Probes from chromosome 1 detected a previously unreported transcript in RNA from both the cell line and the patient. A chromosome 14 probe identified the same transcript, thus confirming a fusion transcript derived from both chromosomes 1 and 14. This translocation may identify a gene for which we propose the name SCL (stem-cell leukemia) that is important for hemopoietic development and oncogenesis and that has been disrupted or altered in this stem-cell line.

Diversity and structure of human T cell receptor delta chain genes in peripheral blood gamma/delta-bearing T lymphocytes

We have investigated the diversity and repertoire of human TCR delta chain variable gene segments in the human peripheral blood CD4- CD8- (double-negative) population, using rearrangement and expression studies and sequence analyses. 20 TCR delta DNA clones were derived from the RNA of bulk-cultured double-negative T cells and their nucleotide sequences determined. These clones can be classified into six different V delta subfamilies. The distribution, however, was uneven in these cells, with 16 of 20 being derived from the V delta 1 (9) and V delta 2 (7) subfamilies. The remaining subfamilies, V delta 3, V delta 4, V delta 5, and V delta 6, were only represented by one clone each. The majority of these subfamilies seem to consist of a single member, in contrast with the closely linked V alpha subfamilies, which, in most cases, consist of multiple members. Our findings suggest that only a limited number of V delta genes are used in human peripheral blood double-negative T cells and that two major V delta subfamilies (V delta 1 and V delta 2) are used more frequently. Sequence comparison of our cDNA clones to V alpha clones indicates that there is no overlap in usage of V alpha and V delta gene segments, except for the V delta 4 (V alpha 6) subfamily. Comparison of the different V delta sequences suggests that the majority of the sequence diversity is concentrated in the junctions between V, D, and J segments and results from extensive N region diversity.

T cell receptors

Over the past few decades, a solid body of evidence has been built up linking certain autoimmune diseases to the presence of specific major histocompatibility complex haplotypes. Major histocompatibility complex products are used by the immune system to distinguish non-self from self and are important in the recognition of foreign antigen by T cells. T cells play a number of roles in the initiation and control of the immune response, leading to the suggestion that T cells may be important in the genesis of these diseases. T cell recognition is mediated by a heterodimeric cell surface receptor, the T cell antigen receptor. A better understanding of the molecular biology of this receptor may shed some light on the cellular and molecular processes involved in the initiation and progression of these diseases.

Human T-cell antigen receptor (TCR) delta-chain locus and elements responsible for its deletion are within the TCR alpha-chain locus

Individual T cells express the CD3 molecule in association with alternative gamma delta or alpha beta heterodimeric T-cell receptors (TCRs). T-cell precursors and occasional gamma delta-expressing T cells in humans possess an unexpected 2.0-kilobase (kb) mRNA in which a tandemly repeated motif, TEA (T early alpha), has been spliced to the constant (C alpha) region. Long-range pulsed-field gel mapping as well as molecular cloning showed that TEA is located immediately 5' to the most upstream joining (J alpha) segment of the TCR alpha-chain locus. The TCR delta-chain locus is immediately 5' to TEA, and diversity (D delta) gene segments, J delta, C delta, and TEA are linked within 35 kb. The human TCR delta locus conserves a 12/23-base-pair (bp) spacer paradigm in which J delta possesses a 12-bp and V delta a 23-bp spacer, while the D delta segments have a 12 bp-D delta-23 bp spacer motif. Considerable TCR delta diversity can be generated despite the predominant use of one V delta and one J delta segment. Two D delta segments, D delta 1 and D delta 2, are 9 and 13 bp long, are frequently recombined as D delta 1-D delta 2, and reveal exonucleolytic trimming with extensive N-segment addition. A gamma delta clonal T cell possessed an effective VDDJ delta rearrangement and an intermediate DDJ delta rearrangement, arguing that the TCR delta locus displays allelic exclusion. Specific rearranging elements that delete the delta locus, delta Rec and psi J alpha, were mapped and found to separate the delta locus from the alpha locus. The delta locus including D delta 1-D delta 2-J delta 1-C delta-TEA was deleted in mature, alpha beta-expressing T cells, whereas V delta 1 was frequently retained. The location of the delta locus within the alpha locus may necessitate an exclusive choice between delta or alpha expression.

T cell receptor delta gene rearrangements in acute lymphoblastic leukemia

Using a newly isolated cDNA clone encoding the TCR-delta gene and genomic probes, we have analyzed T cell receptor (TCR) delta gene rearrangement in 19 patients with T cell acute lymphoblastic leukemia (T-ALL) and 29 patients with B-precursor ALL. Five out of seven CD3- T-ALL and 4 of 12 CD3+ T-ALL showed bi-allelic rearrangements of the TCR-delta gene. In three CD3+ patients, a single allelic TCR-delta gene rearrangement was observed with rearrangement of the TCR-alpha gene on the other allele. In five CD3+ patients with bi-allelic rearrangements of the TCR-alpha gene, the TCR-delta gene locus was deleted. Transcription of the TCR-delta gene was also analyzed in six T-ALL. Five patients expressed TCR-delta transcripts. Only one T-ALL, presumably derived from the most immature T lineage cells, did not have TCR-delta transcripts, but expressed TCR-gamma and 1.0-kb truncated TCR-beta transcripts. In B-precursor ALL, 20 patients (69%) showed rearrangements of the TCR-delta gene. The frequency of TCR-delta gene rearrangement was higher than TCR-alpha (59%), gamma (52%), or beta (31%) genes. These findings suggest that TCR-alpha gene rearrangements may take place after rearrangements of the TCR-delta gene with concomitant deletion of rearranged TCR-delta genes in T cell differentiation. Among leukemic cells of B lineage, the TCR-delta gene is the earliest rearranging TCR gene, followed by TCR-gamma and beta gene rearrangements.

A novel human V delta gene expressed predominantly in the Ti gamma A fraction of gamma/delta+ peripheral lymphocytes

We have characterized a functional T cell receptor (TcR) delta transcript in a Ti gamma A+ human cloned cell line derived from peripheral blood. This cDNA includes a novel V gene (V-AB12), whose expression was initially studied in a series of TcR gamma/delta+ clones. Nine Ti gamma A+ clones derived independently from distinct donors have been tested: each of them was found to possess a unique V-AB12/J-IDP2 5.5-kb Eco RI rearrangement, which was constantly transcribed. Surface expression of the protein encoded by this unique rearranged gene was demonstrated by immunoprecipitations performed on three Ti gamma A+ polyclonal cell lines using a specific rabbit heteroantiserum. Further analysis strongly suggested that a monoclonal antibody (mAb), designated anti-BB3, detects a V-AB12-encoded antigenic determinant on the cell surface. Double-color immunofluorescence analysis of peripheral blood lymphocytes from ten donors indicated that most BB3+ cells are recognized by anti-Ti gamma A mAb. In previous studies, we have shown that a majority of TcR gamma/delta+ peripheral T cells expresses a gamma chain including V9 (Ti gamma A) and most frequently JP-encoded peptides. Given the present results on the delta chain, it can be concluded that, in many individuals, a predominant fraction (V gamma 9+/V-AB12+) of circulating CD3+ TcR alpha/beta- T lymphocytes expresses a receptor with little, if any, combinatorial diversity.

Cloned CD3+ TcR alpha/beta- Ti gamma A- peripheral blood lymphocytes compared to the Ti gamma A+ counterparts: structural differences of the gamma/delta receptor and functional heterogeneity

We have assessed the organization of T cell gamma rearranging genes (TRG) in circulating TcR gamma/delta+ lymphocytes which do not express V gamma 9-encoded Ti gamma A+ gamma chain. Following purification of the minor TcR gamma/delta+ Ti gamma A- fraction, cloned cell lines were developed from peripheral blood of 5 individuals. Out of the 26 clones studied, only 3 TcR gamma/delta+ Ti gamma A- cells were found to express a disulfide-linked C1-encoded gamma chain. The remaining 23 Ti gamma A- clones with a C2-encoded nondisulfide-linked receptor were found to display rearrangements of various V genes to J2 segments on both chromosomes; there was no predominance of a unique rearrangement even though the TRG-V3 and -V4 genes belonging to subgroup I were frequently employed. Together, these findings further strengthen the hypothesis that lymphocytes with a C gamma 1 encoded chain are produced earlier in T cell ontogeny than the C gamma 2 counterparts. The "non-major histocompatibility complex (MHC) requiring" (i.e., "natural killer-like") cytotoxicity mediated by many TcR gamma/delta+ Ti gamma A- cells appeared to be very low as compared to that of Ti gamma A+ clones. Yet, treatment by the OKT3 monoclonal antibody revealed a strong lytic potential in the Ti gamma A- lymphocytes with little, if any, natural killer-like activity. Thus, with respect to the latter function, a substantial heterogeneity is found in cells expressing distinct gamma chains. In an attempt to characterize undefined specificities of Ti gamma A- lymphocytes, they were screened against a panel of Epstein-Barr virus-transformed B cell lines homozygous for HLA-DR1 to DR10 determinants; one of the clones was found to recognize DR7. In light of reports from other groups describing class I-related specificities, it is apparent that TcR gamma/delta+ lymphocytes are able, like the TcR alpha/beta+, to recognize and kill target cells through either an MHC-dependent (with involvement of either class I or class II gene products) or a non-MHC-requiring pathway.

Genomic organization of the human T-cell antigen-receptor alpha/delta locus

Two clusters of overlapping cosmid clones comprising about 100 kilobases (kb) at the human T-cell antigen-receptor alpha/delta locus were isolated from a genomic library. The structure of the germ-line V delta 1 variable gene segment was determined. V delta 1 is located 8.5 kb downstream of the V alpha 13.1 gene segment, and both V segments are arranged in the same transcriptional orientation. The V alpha 17.1 segment is located between V delta 1 and the D delta, J delta, C delta region (containing the diversity, joining, and constant gene segments). Thus, V delta and V alpha segments are interspersed along the chromosome. The germ-line organization of the D delta 2, J delta 1, and J delta 2 segments was determined. Linkage of C delta to the J alpha region was established by identification of J alpha segments within 20 kb downstream of C delta. The organization of the locus was also analyzed by field-inversion gel electrophoresis. The unrearranged V delta 1 and D delta, J delta, C delta regions are quite distant from each other, apparently separated by a minimum of 175-180 kb.

Structure of the gamma/delta T cell receptor of a human thymocyte clone

The CD3+, IL-2-dependent normal human thymocyte clone, CII, expresses on its surface a CD3-associated gamma/delta TCR. We have further elucidated the structure of this receptor from the nucleotide sequence of cDNA and genomic clones from CII that encode functional TCR-gamma and -delta chains. We find that the CII line expresses a C gamma 2 constant region that is a polymorphic form lacking a copy of an internal exon; the sequence of this constant region accounts for the size of the gamma chain and noncovalent linkage of gamma and delta chains in the CII TCR. The V gamma region used for the CII TCR is identical to the several previously characterized expressed human V gamma segments. Possible implications of this finding are discussed.

The V gamma locus of the human T cell receptor gamma gene. Repertoire polymorphism of the first variable gene segment subgroup

Southern blot analysis using a genomic probe of the human TCR-gamma chain first variable gene subgroup (V gamma I) was performed on DNA samples from both parents of 36 healthy Caucasian families. Two types of polymorphisms were found in these 72 unrelated DNA samples: three repertoire polymorphisms and two restriction fragment length polymorphisms (RFLP). In all cases, Mendelian inheritance of these polymorphisms was demonstrated. The most frequent repertoire polymorphism consists in the lack of the V gamma 4 and V gamma 5 segments. In 16% of chromosomes, the Eco RI and Taq I restriction fragments corresponding to V gamma 4 and V gamma 5 were lacking, with no additional bands. In these cases, a decrease of 10 kb was observed in the Bam HI fragment containing all V gamma I segments as compared with samples containing V gamma 4-V gamma 5 segments. To better understand this polymorphism, which takes place in a previously incompletely defined region, the central part of the V gamma I region, including the polymorphic V gamma 4-V gamma 5 segments, was cloned. This allowed us to localize precisely the V gamma 5 segment and thus complete the description of the V gamma I region. A striking homology of DNA and deduced amino acid sequences is present between V gamma 2 and V gamma 4 and between V gamma 3 and V gamma 5, much higher than that observed between V gamma 2 and V gamma 3 and between V gamma 4 and V gamma 5. The differences in nucleotide sequence occur mainly in the intron and three hypervariable regions. These results strongly suggest a gene duplication relationship between the segments V gamma 2-V gamma 3 and the segments V gamma 4-V gamma 5. The most frequent RFLP documented in this study is due to the combined absence of the Eco RI and the Taq I sites located in the noncoding region between V gamma 3 and V gamma 4. The haplotypic frequence of this RFLP is 6.9% of the general population. As the gamma/delta receptor may play an important role in immunological response, the biological relevance of the high degree of polymorphism occurring in the V gamma I region, as well as its possible association with some immune disturbances, should be further explored.