Diversity and organization of human T cell receptor delta variable gene segments

cDNA cloning of a novel cdc2+/CDC28-related protein kinase from rice

A cDNA clone, named R2, has been isolated by screening a rice cell cDNA library with a redundant oligonucleotide probe derived from the conserved ATP binding site of cdc2+/CDC28 protein kinases. The cDNA contained the entire coding sequence for a 424 amino acid polypeptide with a molecular mass of 47.6 kDa. The R2 mRNA, 2.1 kb in size, was expressed in both cultured rice cells and rice seedlings at similar levels. The predicted R2 protein has canonical motifs for ATP binding and catalysis, and is significantly homologous (up to 47%) to members of the cdc2+/CDC28 subfamily of serine/threonine protein kinase. The R2 protein is a novel member of the subfamily.

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.

Regulated expression and structure of T cell receptor gamma/delta transcripts in human thymic ontogeny

Gamma delta (gamma delta) T cells have been found in all vertebrates examined, yet their function in vivo remains unknown. Because gamma delta T cell receptors are related to immunoglobulin, and because they are encoded by rearranging, multi-gene families, the receptors are thought to be antigen recognition molecules. However, a capacity to recognize naturally diverse antigens has not yet been shown. In this work, the expression and structure of human gamma delta transcripts have been examined in the fetal and early post-natal thymus. The data indicate that many gamma and delta genes are rearranged and expressed throughout ontogeny, but that as ontogeny proceeds, quite dramatic changes occur in the patterns of gene expression and rearrangement. In particular, receptors encoded by early to mid-gestation fetal thymic transcripts would be of quite restricted diversity. Only later in ontogeny can receptors of substantial diversity be generated. These properties are very similar to the patterns of gamma delta gene activation in the mouse, and they serve to reiterate similarities both in gene rearrangement and in gamma delta across vertebrate species.

T cell receptor delta diversity of freshly isolated T lymphocytes in rheumatoid synovitis

In some patients with rheumatoid synovitis the distribution of V delta gene families used by freshly isolated T lymphocytes from the synovial fluid and peripheral blood is different: peripheral blood T lymphocytes preferentially use the V delta 2 gene segment, whereas the majority of synovial fluid T lymphocytes use the V delta 1. The antigenic diversity of T cell receptor gamma/delta is mainly dependent upon base sequences in the V-J junction. In the present study we investigated whether the synovial fluid T lymphocytes expressing the V delta 1 gene segment were derived from a polyclonal or monoclonal expansion. The sequences encoding the V-J junctions of 11 cDNA clones derived from the synovium of two patients with chronic arthritis were determined. Our data demonstrate that the V delta 1 cDNA clones have different V-J junction sequences. This indicates that the V delta 1-expressing T cells found in the synovial compartment are polyclonally expanded.

Use of oligonucleotide probes directed against T cell antigen receptor gamma delta variable-(diversity)-joining junctional sequences as a general method for detecting minimal residual disease in acute lymphoblastic leukemias

To provide a sensitive and generally applicable method to detect clonal cells in acute lymphoblastic leukemias (ALL), we have designed a new strategy based on the polymerase chain reaction (PCR) amplification of the T cell receptor gamma delta gene rearrangements found in most T and B lineage ALLs. PCR allows rapid sequencing of variable-(diversity)-joining (V-[D]-J) junctions from tumor DNA and construction of anti-junctional oligonucleotides (AJOs) used as probes to detect clonal cells in the same patient. We have defined oligonucleotides suitable for all T cell receptor (TCR) rearrangements involving functional V gamma segments. Oligonucleotides corresponding to preferential TCR delta rearrangements in T and B lineage ALLs were also used. By analysis of the nucleotide sequence of 52 V gamma-V gamma junctions from 30 cases of B and T ALLs, we demonstrate that V-J junctional sequences are clone specific in both lineages and at all stages of differentiation examined despite the frequent presence of the recently described P nucleotides. Experiments performed with TCR gamma delta AJOs on DNA from tumor cells and polyclonal T cells show that AJOs can be used to differentiate clonal cells from polyclonal T cells, distinguish between different T cell clones, and detect residual clonal populations at 10(-4)/10(-5) dilution. AJOs were also used to detect residual disease in samples from patients in clinical and morphological complete remission. Finally, rearrangement patterns were studied by classical Southern analysis in selected cases at both presentation and subsequent relapse showing absence of clonal evolution in most cases. V-(D)-J nucleotide sequences of rearrangements with an identical pattern of rearrangement at presentation and relapse were identical in all cases analyzed. We therefore describe a new, specific, and clinically useful strategy for the detection of minor clonal populations applicable in the majority of cases of ALL.

Production of interferon-gamma and tumour necrosis factor-alpha by human T-cell clones expressing different forms of the gamma delta receptor

Panels of human T-cell clones bearing the gamma delta T-cell receptor (TcR) were obtained from peripheral blood and decidual tissue and maintained in the presence of interleukin-2 (IL-2). TcR V gamma and V delta gene expression was determined in 40 TcR delta 1+ clones using the gamma delta T-cell subset markers Ti gamma A and delta TCS1, in conjunction with Southern blot analysis using TcR J gamma and J delta probes. gamma delta T-cell clones, together with control alpha beta T-cell clones derived from the same lymphocyte populations, were stimulated with phytohaemagglutinin (PHA) and their ability to produce interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) tested using specific ELISA. Many clones representative of the major peripheral V gamma 9/V delta 2J1 subset produced high amounts of both cytokines and mean levels were not significantly different from those produced by alpha beta T-cell clones. Panels of clones expressing V gamma 9 and V delta 2J1 produced significantly higher levels of TNF-alpha than clones not expressing V delta 2J1 and those expressing V delta 1J1. There was no relationship between levels of IFN-gamma and TNF-alpha produced by individual gamma delta T-cell clones and also no relationship between their non-major histocompatibility complex (MHC)-restricted cytotoxic activity and levels of either cytokine. There was a significant tendency for gamma delta T-cell clones to produce more TNF-alpha than IFN-gamma in comparison to alpha beta T-cell clones. The significance of these findings is discussed in the light of the reported differences in distribution in vivo of V delta 1J1+ and V delta 2J1+ cells.

Recognition by human V gamma 9/V delta 2 T cells of a GroEL homolog on Daudi Burkitt's lymphoma cells

All human gamma delta T cells coexpressing the products of the variable (V) region T cell receptor (TCR) gene segments V gamma 9 and V delta 2 recognize antigens from mycobacterial extracts and Daudi cells. Exogenous and endogenous ligands on the cell surface, homologous to the groEL heat shock family, induced reactivities that resembled superantigen responses in this major subset of human peripheral blood gamma delta T cells. Stimulation of human V gamma 9/V delta 2 T cells is not restricted by human leukocyte antigens (HLA), including nonpolymorphic beta 2-microglobulin (beta 2M)-associated class Ib molecules. These data may be important for understanding the role of gamma delta T cells in autoimmunity and in responses to microorganisms and tumors.

Analysis of early fetal T-cell receptor delta chain in humans

In the mouse it has been found that a number of T-cell receptor (Tcr) gd phenotypes are generated during fetal thymic development. To examine whether such "waves" of Tcrgd phenotypes can be found in man, we studied the V-region usage and junctional diversity of the T-cell receptor delta chain in human fetal and post-partum thymocytes and peripheral blood T cells. Using the polymerase chain reaction (PCR)-amplification technique it was found that in fetal thymocytes of 15-17 weeks of gestation the Tcrd-V3 gene segment was mainly employed, whereas in post-partum thymocytes the Tcrd-V1 gene segment was preferentially used. These Tcrd-V3 transcripts contained only a single D element (D delta 3) and a limited random nucleotide insertion. The D delta 3 element was also present in Tcrd-V3-containing transcripts derived from peripheral blood gamma delta Tcr+ clones. These data suggest that a wave of Tcr gamma delta might exist early in human fetal development that preferentially use the Tcrd-V3 gene segment.

Phenotypic and functional analysis of human CD3- decidual leucocyte clones

CD3- leucocyte clones were generated from human first-trimester decidualized uterine endometrium in a culture system containing interleukin-2 (IL-2) and phytohaemagglutinin (PHA). All CD3- clones tested by Southern blot analysis had T-cell receptor (TcR) gamma and delta genes in germ-line configuration. Thirty-six CD3- cell clones obtained from eight decidual samples were mostly CD2+CD56+ but, unlike fresh decidual leucocytes, many were also CD16+. Morphological differences were noted between CD16+CD56+ and CD16-CD56+ clones, with the latter cells possessing granules of more variable size. All CD16+ clones expressed strong cytotoxic activity against natural killer (NK) sensitive and NK-resistant cell targets, while CD16- clones had low or negligible activity. Some CD3- clones produced high levels of interferon-gamma, tumour necrosis factor-negligible activity. Some CD3- clones produced high levels of interferon-gamma, tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) upon stimulation, but there was no relationship between specific cytokine production and cell clone phenotype or cytotoxic function. Levels of TGF-beta were generally higher than those produced by decidual CD3+ T-cell clones. Since decidual CD3- CD16- leucocytes have a low proliferative capacity in response to IL-2, and as clones with this phenotype invariably possess low NK cell activity, it is suggested that the NK cell activity of fresh decidual leucocyte populations is mediated largely by the small numbers of CD3- CD16+ cells present.

Maturation or differentiation of human thymocyte precursors in vitro?

The differentiation or maturation potential of human thymocyte precursors has been studied by using a population of CD3/TCR-, CD4-, CD8- ("triple negative") thymocytes isolated by negative selection (TCR, T-cell receptor). This cell population, however, also contained 30-50% previously undescribed cells expressing very low levels of CD3/TCR gamma delta (CD3/TCR gamma delta low; approximately 60% of which expressed the variable region gene V delta 1). Correspondingly, TCR gamma and TCR delta gene rearrangements (predominantly V delta 1/joining region J delta 1) and full-length TCR gamma and TCR delta transcripts (but only immature TCR beta and no TCR alpha mRNAs) were found. These cells mobilized Ca2+ in response to ligation of CD3 but not following ligation of TCR gamma delta. When cultured in the presence of interleukin 7 or interleukin 2, these thymocytes gave rise to 30-60% CD3/TCR gamma delta medium and high cells (60-70% expressing V delta 1) seen as discrete populations. Thus, the proportion and V delta phenotype of in vitro generated CD3/TCR gamma delta cells closely resembled those of CD3/TCR gamma delta low cells in freshly isolated "thymocyte precursor" preparations. Small numbers of TCR alpha beta + cells also appeared. It is thus uncertain whether maturation, differentiation, or both account for the appearance of mature CD3/TCR+ thymocytes, although the former appears most likely.

Diversity in junctional sequences associated with the common human V gamma 9 and V delta 2 gene segments in normal blood and lung compared with the limited diversity in a granulomatous disease

The T cell receptor (TCR) junctional regions (N regions) of the common human V gamma 9 and V delta 2 gene segments were sequenced from the blood and lung of normal individuals (195 transcripts) and a group of individuals with sarcoidosis (220 transcripts), a granulomatous disease in which increased numbers of V gamma 9+ gamma/delta + T cells are often observed. In normal individuals, the vast majority (86%) of blood V gamma 9 transcripts used the J gamma P gene segment. In contrast to this restriction of J region usage, there was a large diversity of the junctional region, with less than 20% of blood V gamma 9 junctional regions showing identical sequences for any one normal individual. For the blood V delta 2 transcripts in normal individuals, there was restriction of J region usage, with 93% using J delta 1. The junctional regions were even more diverse than for V gamma 9, with a unique sequence observed in each transcript examined. Compared with blood, sequences from the normal lung showed a small increase in identical junctional regions, particularly in one individual where 46% of V gamma 9 transcripts examined were identical, suggesting a response of some gamma/delta T cells to antigens found in the lung in the normal state. In marked contrast to normals, some individuals with sarcoidosis had large numbers of V gamma 9 transcripts, as well as V delta 2 transcripts, sharing identical sequences. For V gamma 9 blood transcripts, two individuals showed 84 and 56% of junctional region sequences to be identical, respectively. Similarly, blood V delta 2 transcripts showed 43, 33, and 25% identical junctional region sequences in three individuals. In the sarcoid patient with the most striking over-representation of blood V gamma 9 junctional sequences, lung V gamma 9 transcripts showed increased (67%) use of the same junctional region sequence as in blood. This limited diversity of TCR junctional regions among some individuals with sarcoidosis suggests a response from specific stimuli, possibly antigenic, and that gamma/delta T cells may play a specific role in granuloma formation in sarcoidosis, as has been suggested in other granulomatous diseases.

The V delta gene usage by freshly isolated T lymphocytes from synovial fluids in rheumatoid synovitis: a preliminary report

Taking advantage of the polymerase chain reaction we have studied the usage of variable delta-(V delta) region genes in freshly isolated synovial fluid T cells from patients with rheumatoid synovitis. Amplified mRNA from one patient with rheumatoid arthritis (RA) was cloned into an SmaI-cleaved pUC19 vector and colonies were screened with probes for three of the known human variable delta-gene families (V delta 1, V delta 2, V delta 3). Of 10 clones, seven used V delta 1, two V delta 2 and one V delta 3. This pattern of distribution is different from that of normal peripheral blood, where approximately 60% of T gamma delta cells are reported to use the V delta 2 gene. Furthermore, Northern blot hybridization analyses of mononuclear cells from two additional synovial fluids derived from another patient with RA and one with juvenile rheumatoid arthritis (JRA) also showed significant hybridization only with V delta 1. In summary, these preliminary results suggest a usage of V delta gene families in T gamma delta lymphocytes in synovial fluid of rheumatoid patients different to that found in normal peripheral blood.

Further analysis of the T cell receptor gamma/delta+ peripheral lymphocyte subset. The V delta 1 gene segment is expressed with either C alpha or C delta

In the present study, we have characterized the reactivity of two mAbs that are directed at the human TCR-gamma/delta. These reagents, designated anti-A13 and anti-TiV delta 2, were found to recognize antigenic determinants encoded by the TCR V delta 1 and V delta 2 gene segments, respectively. Immunofluorescence analyses performed with the antibodies confirmed that, in the TCR-gamma/delta+ cell subpopulation, the expression of V delta 2+ delta chains is largely predominant, as compared with the V delta 1+ counterparts. However, these experiments led to an apparently discrepant finding. Indeed, the total number of cells recognized by the anti-A13 plus the anti-TiV delta 2 antibodies was often greater than that detected with anti-TCR-delta 1, a reagent specific for a constant epitope of the human delta chain. Further investigation showed that the presence of a sizeable peripheral lymphocyte subset coexpressing the BMA031 and the A13 epitopes. Because the former antibody is known to recognize an invariant antigenic determinant of the TCR-alpha/beta dimer, these results suggested that the V delta 1 gene segment may be expressed with either C delta or C alpha. This hypothesis was confirmed using T2, an IL-2-dependent BMA031+ A13+ polyclonal cell line developed from peripheral blood of a healthy adult donor. Indeed, T2 cells were found to have productively rearranged the V delta 1 gene. Together, results of Northern blot analysis and cDNA cloning indicated that V delta 1 was expressed in these cells as part of a 1.6-kb full-length message including J alpha-C alpha segments.

A T cell-specific transcriptional enhancer within the human T cell receptor delta locus

The T cell antigen receptor (TCR) delta gene is located within the TCR alpha locus. A T cell-specific transcriptional enhancer, distinct from the TCR alpha enhancer, has been identified within the J delta 3-C delta intron of the human T cell receptor delta gene. This enhancer activates transcription from the V delta 1 and V delta 3 promoters as well as from heterologous promoters. Enhancer activity has been localized to a 250-bp region that contains multiple binding sites for nuclear proteins. Thus, transcriptional control of the TCR delta and TCR alpha genes is mediated by distinct regulatory elements.

Correlation between T cell receptor gamma delta isotypic forms and cytotoxic activity: analysis with human T cell clones and lines

Three biochemically distinct isotypic forms of the human T cell receptor (TcR) gamma delta structure can be expressed at the cell membrane. This unique variation in structure of TcR, which is due to C gamma gene segments utilization, prompted us to look for isotype-association functional differences. In this regard, we have developed human T cell clones or lines from normal thymus or peripheral blood from several patients. In the present report, we have selected by phenotypic, biochemical, and TcR gene rearrangement analysis representative pairs of IL2-dependent clones or lines for each TcR gamma delta isotypic form. The results showed a lack of correlation between the TcR isotypes and the ability of the cells to proliferate in response to TcR stimulation mediated through the CD3 molecular complexes. By contrast, despite the fact that all of these representative cells exhibit an NK-like activity, as measured by their ability to kill K562, the strongest lytic activity was observed with the cells having the disulfide-bonded form of the receptor. Moreover only those latter cells were able to efficiently kill the LAK-sensitive Daudi cell line.

Molecular Structure of the Rearranged T-Cell Gamma Chain Gene in a Human Leukemia Which Expresses Its Product

The gamma gene product is a component of the second T-cell receptor. We report a new case of acute lymphoblastic leukemia bearing a CD3+ CD4- CD5+ CD7+ CD8- WT31- immunophenpotype that expresses the gamma peptide. Immunoprecipitation studies using an anti Cγ heteroantisera showed two different bands of 40 and 60 Kd. Southern analysis revealed Cγ1 utilization in the productive rearrangement. The demonstration of Vδ-Jδ1 rearrangement in this leukemia suggests that the 60 Kd band could correspond to the product of the delta gene. The utilization of the Jγ1.3 exon in this leukemia suggests that the T lymphocytes that undergo leukemic transformation are derived from a population different from the circulating γ/δ lymphocytes, that preferentially use the Jγ1.2 (JγP) exon.

Regulation of transcription of the human T cell antigen receptor delta chain gene. A T lineage-specific enhancer element is located in the J delta 3-C delta intron

We have defined transcriptional enhancing sequences inside the TCR-delta gene locus, using transient transfections with constructs containing DNA fragments cloned upstream to a reporter gene fused to a heterologous promoter. A 14-kb DNA region extending from the J delta 3 segment to 6 kb 3' to C delta was analyzed. We show the presence of positive regulatory sequences inside the J delta 3-C delta intron and have localized these sequences to two DNA fragments of approximately 300 and 258 bp. Analysis of cell specificity of the activation of such sequences demonstrates a T cell pattern for one of the two fragments. The nucleotide sequence of the T cell-specific element shows motifs sharing homology with previously described core enhancers.

Molecular analysis of human gamma/delta+ clones from thymus and peripheral blood

We analyzed the V gamma and V delta gene usage in TCR-gamma/delta-bearing T cell clones isolated from human peripheral blood and postnatal thymus using V-specific mAbs and Southern and Northern analyses. In peripheral blood most of the gamma/delta cells express the V gamma 9-JP-C gamma 1 chain paired with a delta chain bearing the V delta 2 gene product. This heterodimer is very rare in the postnatal thymus, where a different and less restricted pairing of V gamma 9 and V delta 2 chains is found. These findings indicate that physical constraints cannot explain the overrepresentation of a particular V gamma 9-JP/V delta 2 heterodimer in the peripheral blood, and we discuss alternative mechanisms that may account for this differential distribution. In addition, this analysis allowed us to map the specificity of the delta TCS1 mAb to V delta 1-J delta 1 and to identify at least five different expressed V delta genes.

The promoter regions of the T-cell receptor V9 gamma (TRGV9) and V2 delta (TRDV2) genes display short direct repeats but no TATA box

T lymphocytes expressing the T-cell gamma delta receptor have been shown to express preferentially the T-cell receptor V9 gamma (TRGV9) gene, in association with the T-cell receptor V2 delta (TRDV2) gene. In this paper, we report that the promoter regions of the TRDV2 and TRGV9 genes, which are preferentially expressed early in T-cell differentiation, display short direct repeats but no TATA box, in contrast to the V gamma genes belonging to subgroup I. The TCCTCAGT octanucleotide found 100 pb upstream of the ATG of the HD-Mar V alpha transcript, a TCR V alpha gene without a TATA box, is observed upstream of TRDV2 but not TRGV9. Of interest is the presence of a characteristic decanucleotide AGGTGGT(T)GAG in the promoter regions of both the TRDV2 and TRGV9 genes.

The T-cell receptor V delta genes predominantly used by human peripheral gamma/delta+ T lymphocytes are not rearranged in CD3- natural killer cells

We have analyzed, in 19 CD3- natural killer cell clones, the genomic organization of the T-cell receptor delta locus with two distinct V delta probes, V delta 1 and V delta 2. These two V delta genes code for surface proteins expressed in more than 90% of peripheral blood T-cell receptor gamma/delta+ lymphocytes, as shown by double color immunofluorescence analysis with anti-TCR delta 1, anti-BB3, and anti-delta TCS1 monoclonal antibodies. The V delta 1 and V delta 2 genes were found to be in germline position in all these clones, which are distinct phenotypically and represent a variety of the corresponding peripheral natural killer cell populations. We also studied in these cloned cell lines the transcriptional activity of the T-cell receptor delta locus with a C delta probe: short transcripts (1.7 and 0.8 kb) were found exclusively. These experiments further suggest that CD3- natural killer peripheral cells are likely to constitute a unique lineage distinct from T lymphocytes.

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.

cDNA cloning of functional T cell receptor gamma/delta chains expressed in human peripheral blood lymphocytes

We have identified in earlier studies two V delta rearrangements corresponding to a 4.5-kb Eco RI fragment detected with a V delta1 probe and to a 7-kb Eco RI band detected with a V delta2 probe. These rearrangements have been found in two human T cell clones, F6C7 and G6, displaying surface phenotypes unfrequent in human peripheral blood, namely Ti gamma A+ BB3- (F6C7) and Ti gamma A- BB3+ (G6). Herein, we report the sequences of the functional transcripts encoded by these rearranged genes and show that the 4.5- and the 7-kb Eco RI fragments correspond to V1/D3/J delta 3 and to V2/D3/J delta 3 recombinations, respectively. In addition, we have sequenced the V2/D3/J1/C delta transcripts expressed in two clones, AB12 and VTC, which have a Ti gamma A+ BB3+ surface phenotype corresponding to that of most gamma/delta peripheral lymphocytes. Analyses of the delta transcripts expressed by these four cells further strengthen the hypothesis that anti-BB3 and anti-delta-TCS-1 monoclonal antibodies recognize a V delta 2- and a V1/(D)/J delta 1-encoded epitope, respectively. Sequence of the gamma transcripts expressed by AB12 and F6C7 cells shows that they encode a V9/JP/C gamma 1 chain. Finally, we confirm that non-combinatorial diversity in the gamma and delta proteins is generated by both junctional flexibility and N-region addition without any somatic mutation.

T-cell receptor delta-chain can substitute for alpha to form a beta delta heterodimer

Specific monoclonal antibodies have made possible the identification of two T-cell antigen receptor (TCR) heterodimers, alpha beta TCR and gamma delta TCR. Formation of these receptors is largely separated by the preferential pairing of alpha-TCR with beta and gamma-TCR with delta, the sequential rearrangement and expression of the TCR loci during thymic development and the deletion of the delta-loci either prior to or concomitant with alpha-rearrangement in alpha beta TCR cells. Here we show that delta-TCR can substitute for alpha in pairing with beta to form a beta delta heterodimer. This receptor is expressed on the cell surface of the T-leukaemia cell line DND41 as analysed with beta- and delta-specific monoclonal antibodies. We suggest that a variety of factors including, for example, the deletion of the delta-TCR loci, can now be understood as exclusion mechanisms operating to prevent not only the formation of gamma delta receptors, but also of beta delta T-cell receptors, thereby promoting the numerically dominant alpha beta TCR lineage. Nevertheless, some developing T-cells that do not rearrange the alpha-loci may express the beta delta TCR as described here.

Subpopulations of human peripheral T gamma delta lymphocytes

In the search for the genes encoding the alpha and beta chains of the T-cell receptor, Tonegawa et al. discovered a third class of rearranging T-cell specific genes. This finding led them to postulate the existence of additional forms of T-cell receptors. In this article, Frédéric Tribel and Thierry Hercend briefly discuss recent results, which may help in the delineation of human peripheral blood gamma delta+ subsets based on the molecular structure of this receptor.