Sequence and expression of transcripts of the T-cell antigen receptor alpha-chain gene in a functional, antigen-specific suppressor-T-cell hybridoma

Natural killer-like nonspecific tumor cell lysis mediated by specific ligand-activated Valpha14 NKT cells

We have recently identified alpha-galactosylceramide (alpha-GalCer) as a specific ligand for an invariant Valpha14/Vbeta8.2 T cell receptor exclusively expressed on the majority of Valpha14 NKT cells, a novel subset of lymphocytes. Here, we report that alpha-GalCer selectively activates Valpha14 NKT cells resulting in prevention of tumor metastasis. The effector mechanisms of the ligand-activated Valpha14 NKT cells seem to be mediated by natural killer (NK)-like nonspecific cytotoxicity. Indeed, the cytotoxic index obtained by alpha-GalCer-activated Valpha14 NKT cells was reduced by the addition of cold target tumor cells or by treatment with concanamycin A, which inhibits activation and secretion of perforin, but not by mAbs against molecules involved in the NKT cell recognition and conventional cytotoxicity, such as CD1d, Vbeta8, NK1. 1, Ly49C, Fas, or Fas ligand. These results suggest that the ligand-activated Valpha14 NKT cells kill tumor cells directly through a CD1d/Valpha14 T cell receptor-independent, NK-like mechanism.

Requirement for Valpha14 NKT cells in IL-12-mediated rejection of tumors

A lymphocyte subpopulation, the Valpha14 natural killer T (NKT) cells, expresses both NK1.1 and a single invariant T cell receptor encoded by the Valpha14 and Jalpha281 gene segments. Mice with a deletion of the Jalpha281 gene segment were found to exclusively lack this subpopulation. The Valpha14 NKT cell-deficient mice could no longer mediate the interleukin-12 (IL-12)-induced rejection of tumors. Although the antitumor effect of IL-12 was thought to be mediated through natural killer cells and T cells, Valpha14 NKT cells were found to be an essential target of IL-12, and they mediated their cytotoxicity by an NK-like effector mechanism after activation with IL-12.

Influence of the NH2-terminal amino acid of the T cell receptor alpha chain on major histocompatibility complex (MHC) class II + peptide recognition

The alpha/beta T cell receptor (TCR) recognizes peptide fragments bound in the groove of major histocompatibility complex (MHC) molecules. We modified the TCR alpha chain from a mouse T cell hybridoma and tested its ability to reconstitute TCR expression and function in an alpha chain-deficient variant of the hybridoma. The modified alpha chain differed from wild type only in its leader peptide and mature NH2-terminal amino acid. Reconstituted cell surface TCR complexes reacted normally with anti-TCR and anti-CD3 antibodies. Although cross-linking of this TCR with an antibody to the TCR idiotype elicited vigorous T cell hybridoma activation, stimulation with its natural MHC + peptide ligand did not. We demonstrated that this phenotype could be reproduced simply by substituting the glutamic acid (E) at the mature NH2 terminus of the wild type TCR alpha chain with aspartic acid (D). The substitution also dramatically reduced the affinity of soluble alpha/beta-TCR heterodimers for soluble MHC + peptide molecules in a cell-free system, suggesting that it did not exert its effect simply by disrupting TCR interactions with accessory molecules on the hybridoma. These results demonstrate for the first time that amino acids which are not in the canonical TCR complementarity determining regions can be critical in determining how the TCR engages MHC + peptide.

Mouse CD1-specific NK1 T cells: development, specificity, and function

NK1 T cells are a specialized population of alpha/beta T cells that coexpress receptors of the NK lineage and have the unique potential to very rapidly secrete large amounts of cytokines, providing early help for effector cells and regulating the Th1 or Th2 differentiation of some immune responses. NK1 T cells express a restricted TCR repertoire made of an invariant TCR alpha chain, V alpha 14-J alpha 281, associated with polyclonal V beta 8, V beta 7, and V beta 2 TCR beta chains. NK1 T cells recognize the products of the conserved family of MHC class I-like CD1 genes, apparently in the absence of foreign antigens. Thus, this novel regulatory pathway, which straddles the innate and the adaptive immune systems, is unique in that its activation may not require associative recognition of antigen. Here, we review the specificity and function of mouse NK1 T cells, and we discuss the relationship of this lineage to mainstream T cells and NK cells.

V alpha 14+ NK T cells: a novel lymphoid cell lineage with regulatory function

A novel lymphoid lineage, NK T cells, was recently found. The NK T cells are the major population in the periphery comprising 5% of splenic T cells and 40% of bone marrow T cells. They express a unique TCR composed of invariant V alpha 14J alpha 281 and V beta 8.2 together with NK receptor (NKRPI). Surprisingly, the invariant V alpha 14+ TCR is exclusively expressed on NK T cells but not on conventional T cells. As the selective decrease in V alpha 14+ NK T cell population in the periphery is tightly correlated with autoimmune disease development, V alpha 14+ NK T cells control development of autoimmune diseases. We also found that V alpha 14 TCR gene rearrangement and transcripts were detected at an early embryogenesis (d9.5) before the thymus formation. Therefore NK T cells are in the distinct category from conventional T cells. The target of NK T cells is found to be CD1 (class 1b, monomorphic class I MHC-like molecule) present on bone marrow-derived cells and is killed by Fas-FasL interaction or perforin-mediated mechanisms. These results indicate that NK T cells consist of an immunoregulatory system different from defense system in terms of homogeneous repertoire, extrathymic development in early stage of gestation, and their regulatory functional role.

Characterization of the mouse Tcra-V22 gene subfamily

T-cell receptors (Tcrs) of higher organisms play a key role in the specific recognition of self and non-self molecules in the immune system. The large number of Tcr variable (V) genes have been organized into V gene subfamilies according to their sequence similarity at the nucleotide and amino acid level. We cloned and characterized four new members of the Tcra-V22 gene subfamily at the genomic level using a simple and sensitive technique that can rapidly clone members of any multi-member gene family. Sequence analysis reveals that the four Tcra-V22 gene subfamily members have more than 98% sequence similarity in their coding regions, at the nucleotide and amino acid levels. However, the intron between the leader and the coding region varies up to 7% between members of the Tcra-V22 gene subfamily. Comparison of the multi-member Tcra-V22 gene subfamily with other multi-member Tcra-V gene subfamilies (V2, V8, and V11), shows that Tcra-V22 is unique in that it has multiple members with nearly identical amino acid sequence and which are not inherently pseudogenes. Sequence similarity analysis of the Tcra-V22 subfamily with the prototypes of all other Tcra-V subfamilies revealed that the Tcra-V22 subfamily has the closest sequence similarity to that of Tcra-V18 (77% at the nucleotide level and 71% at the amino acid level).

Essential requirement of an invariant V alpha 14 T cell antigen receptor expression in the development of natural killer T cells

NK1.1+ T [natural killer (NK) T] cells express an invariant T cell antigen receptor alpha chain (TCR alpha) encoded by V alpha 14 and J alpha 281 segments in association with a limited number of V betas, predominantly V beta 8.2. Expression of the invariant V alpha 14/J alpha 281, but not V alpha 1, TCR in transgenic mice lacking endogenous TCR alpha expression blocks the development of conventional T alpha beta cells and leads to the preferential development of V alpha 14 NK T cells, suggesting a prerequisite role of invariant V alpha 14 TCR in NK T cell development. In V beta 8.2 but not B beta 3 transgenic mice, two NK T cells with different CD3 epsilon expressions, CD3 epsilon(dim) and CD3 epsilon(high), can be identified. CD3 epsilon(high) NK T cells express surface V alpha 14/V beta 8 TCR, indicating a mature cell type, whereas CD3 epsilon(dim) NK T cells express V beta 8 without V alpha 14 TCR and no significant CD3 epsilon expression (CD3 epsilon(dim)) on the cell surface. However, the latter are positive for recombination activating gene (RAG-1 and RAG-2) mRNA, which are only expressed in the precursor or immature T cell lineage, and also possess CD3 epsilon mRNA in their cytoplasm, suggesting that CD3 epsilon(dim) NK T cells are the precursor of V alpha 14 NK T cells.

Development of Valpha4+ NK T cells in the early stages of embryogenesis

The majority of T lymphocytes start to develop at around day 15 of gestation (d15)-d17 in the thymus and comprise the peripheral repertoire characterized by the expression of polymorphic T-cell antigen receptors (TCRs). Contrary to these conventional T cells, a subset of T cells, called natural killer (NK) T cells (most of them expressing an invariant TCR encoded by the Valpha14Jalpha281 gene with a 1-nt N-region), preferentially differentiates extrathymically and dominates the peripheral T-cell population at a high frequency (5% in splenic T cells and 40% in bone marrow T cells). Here, we investigated the development of NK T cells and found that the invariant Valpha14+ TCR transcripts and the circular DNA created by Valpha14 and Jalpha281 gene rearrangements can be detected in the embryo body at d9.5 of gestation and in the yolk sac and the fetal liver at d11.5-d13.5 of gestation, but not in the thymus, whereas T cells with Valpha1+ TCR expression, a major population in the thymus, were not observed at these early stages of gestation. Fluorescence-activated cell sorter analysis also demonstrated that there exist CD3+ alpha beta+ T cells, almost all of which are Valpha14/Vbeta8+ NK+ T cells, during early embryogenesis. To our knowledge, this demonstrates for the first time that a T lymphocyte subset develops in extrathymic tissues during the early stages of embryogenesis.

Antigen-specific suppressor factor: missing pieces in the puzzle

Few areas of immunologic research have endured such strident criticism or engendered such fainthearted support as the study of antigen-specific suppression of the immune response. Although enjoying a modest resurgence as a means of promoting or maintaining peripheral tolerance to autoantigens, the study of antigen-specific suppression is not mainstream immunology. The field of immune regulation has, in fact, shifted focus toward explaining the data in terms of the Th1/Th2 paradigm. Indeed, the term suppression has been coopted, by those willing to use it, to describe the bioactivity of conventional cytokines, such as IL-4, IL-10 or TGF beta, which can be inhibitory in certain experimental models. In a very real sense, those who performed much of the early work in the field bear responsibility for the outcast status of suppression. With the increasing number of soluble mediators and cascades of interacting T cells, which populated reviews of the subject in the 1980s, the concept of antigen-specific suppression and suppressor factors simply became too complicated and was dismissed as artifact. Several laboratories have in the past few years made significant advances in the molecular characterization of antigen-specific TsF. Their work, as well as that of our own laboratory have established certain minimal molecular requirements for the expression of TsF bioactivity.

Immunoregulatory activity of a T-cell receptor alpha chain demonstrated by in vitro transcription and translation

Previous studies from our laboratory and those of others suggested the possibility that the T-cell antigen receptor alpha (TCR alpha) chain from some T cells can be released in a soluble form and can have antigen-specific immunoregulatory activity. We have analyzed this phenomenon by in vitro transcription and translation (IVTT) of a cDNA encoding a TCR alpha chain (A1.1 TCR alpha) suspected of having such activity. We found that TCR alpha, but not TCR beta, protein produced in this way showed antigen-specific regulatory activity in an in vitro immune-response assay. Protein derived from truncated forms of the A1.1 TCR alpha cDNA had activity providing that, in addition to the variable (V) and joining (J) regions of the alpha chain (VJ alpha), at least the first 25 amino acids of the alpha chain of the constant (C) region (C alpha) were present. Addition of an irrelevant protein sequence to the VJ alpha failed to impart activity to the molecule, suggesting that the C alpha requirement is not simply for stabilization of the resulting protein. These results are discussed in the context of other recent studies on the immunoregulatory activity of soluble TCR alpha molecules, and the possible physiological relevance of these observations is considered.

An invariant T cell receptor alpha chain is used by a unique subset of major histocompatibility complex class I-specific CD4+ and CD4-8- T cells in mice and humans

The mouse thymus contains a mature T cell subset that is distinguishable from the mainstream thymocytes by several characteristics. It is restricted in its usage of T cell receptor (TCR) V beta genes to V beta 8, V beta 7, and V beta 2. Its surface phenotype is that of activated/memory cells. It carries the natural killer NK1.1 surface marker. Furthermore, though it consists entirely of CD4+ and CD4-8- cells, its selection in the thymus depends solely upon major histocompatibility complex (MHC) class I expression by cells of hematopoietic origin. Forced persistence of CD8, in fact, imparts negative selection. Here, we have studied the TCR repertoire of this subset and found that, whereas the beta chain V-D-J junctions are quite variable, a single invariant alpha chain V alpha 14-J281 is used by a majority of the TCRs. This surprisingly restricted usage of the V alpha 14-J281 alpha chain is dependent on MHC class I expression, but independent of the MHC haplotype. In humans, a similar unusual population including CD4-8- cells can also be found that uses a strikingly homologous, invariant alpha chain V alpha 24-JQ. Thus, this unique V alpha-J alpha combination has been conserved in both species, conferring specificity to some shared nonpolymorphic MHC class I/peptide self-ligand(s). This implies that the T cell subset that it defines has a specialized and important role, perhaps related to its unique ability to secrete a large set of lymphokines including interleukin 4, upon primary stimulation in vitro and in vivo.

Extrathymic differentiation of a T cell bearing invariant V alpha 14J alpha 281 TCR

We found that a homogenous CD4-/CD8- T cell bearing an invariant TCR encoded by V alpha 14J alpha 281 with a one-base N-region is highly dominant in the periphery (2-3% in spleen). Surprisingly, the high expression of this invariant V alpha 14 TCR is a general phenomenon in all laboratory strains irrespective of MHC haplotype and in some wild mouse subspecies. The majority of V alpha 14+ TCR is associated with J alpha other than J alpha 281 during the neonatal stage, after which the frequency of invariant V alpha 14J alpha 281 TCR expression increases with time reaching a maximum at around 5-8 weeks after birth. The dominant expression of V alpha 14J alpha 281 TCR is found in both euthymic and athymic mice. These results indicate that homogenous V alpha 14J alpha 281 T cells are positively selected in the periphery without thymic influence and that their VJ junction is important for positive selection. We also demonstrate that V alpha 14+ TCR gene rearrangements take place at extrathymic sites, such as bone marrow, liver, and intestine, since frequent nonproductive V alpha 14 TCR products and V alpha 14-J alpha 281 gene mediated signal sequences in circular DNA are detected as a result of TCR rearrangements in extrathymic tissues rather than in the thymus. This indicates the extrathymic development of V alpha 14J alpha 281 T cells. Furthermore, the biological roles of homogenous T cells bearing V alpha 14J alpha 281 TCR and the human counterpart of this invariant TCR are also discussed.

Molecular cloning of porcine T cell receptor alpha, beta, gamma and delta chains using polymerase chain reaction fragments of the constant regions

Fragments of the constant regions of porcine alpha, beta, delta and two types of gamma T cell receptor (TcR) chains were obtained by reverse transcription and polymerase chain reaction (PCR). Screening of a porcine peripheral T cell cDNA library with these PCR fragments led to the isolation of porcine TcR alpha, beta, gamma and delta chain clones. Sequence analysis of these clones and the respective PCR fragments demonstrated the existence of one alpha, one beta, three gamma and one delta chain isotype. Comparisons of the deduced amino acid sequences of the constant region with other species revealed a significant homology. For two of the three identified porcine gamma chain insertions of 38 and 40 amino acids were found within the hinge region. In addition, our sequence data demonstrate a high variability in the cytoplasmic C gamma domain among the three porcine TcR gamma isotypes as well as between species, which might be of structural and/or functional significance. Comparison with biochemical data indicate the existence of four porcine TcR gamma isotypes.

T cell receptor selection by and recognition of two class I major histocompatibility complex-restricted antigenic peptides that differ at a single position

Peptides derived from HLA-Cw3 and HLA-A24 within region 170-179 differ by a single substitution, at position 173, and are both presented by the class I major histocompatibility complex molecule H-2Kd for recognition by murine cytolytic T lymphocytes (CTLs). As a first approach to understand the way T cell receptors (TCRs) intact with the HLA peptides, we have analyzed the TCR selection by, and recognition of, the two HLA antigenic sites. First, we have compared the TCR repertoires selected by HLA-Cw3 and HLA-A24, not only by sequencing the TCRs carried by CTL clones isolated and grown in vitro, but also by analyzing the TCRs expressed in vivo by peritoneal exudate lymphocytes from immune animals. Second, we have compared the TCR crossrecognition of HLA-A24 by CTLs selected by HLA-Cw3 with that of HLA-Cw3 by CTLs selected by HLA-A24. The combined analysis of TCR selection by and recognition of these two related HLA antigenic sites provides evidence that the TCR beta junctional regions interact with the amino-terminal part of the HLA peptides.

Diversity of T-cell receptor alpha gene transcripts in the newborn and adult periphery

Recent studies have demonstrated that the diversity of T-cell receptor alpha (Tcra) gene expression may be confined by a developmental program for gene rearrangement. To examine the effect of age on Tcra gene usage in peripheral tissues, a comparison of Tcr transcripts from newborn and adult mouse splenocytes was made. RNA was first isolated from the spleens of newborn (within five days from birth) and adult B10.BR mice. The polymerase chain reaction was then used to assess the presence of Tcra-V1, Tcra-V2, and Tcra-V3 gene sequences within the two RNA pools. The Tcra-V2 transcript was frequent in both newborn and adult populations and was therefore selected for sequencing analyses, by which V-gene family member and J gene usage could be delineated. Forty-one sequences were obtained, demonstrating Tcra-V2 gene family structure in the B10.BR mouse. Six family members were identified, of which four were new. Although there were differences in gene usage between newborn and adult animals, some junctional diversity added to the repertoire of both populations. A striking feature of V-J joining, as illustrated by this study, was the restriction of combinations based on the J gene location within the Tcra locus. The Tcra-V2 gene of dominant expression in the newborn (B10.BR.6) rearranged exclusively with the 30 most 5' Tcra-J genes. The Tcra-V2 gene of dominant expression at the adult stage (B10.BR.1) rearranged exclusively with the 21 most 3' Tcra-J genes in the locus. Thus, V-J combinatorial diversity was restricted in both newborn and adult mice, yielding a trend from 5'-3' Tcra-J gene usage with age. Inherent restrictions in V-J combinations should now be considered with regard to antigen responsiveness, particularly in the young animal. Qualitative restrictions in Tcr repertoire, compounding low T-cell numbers in peripheral tissues, may well contribute to functional voids and immunodeficiencies in early life.

Subgroups of Tcr alpha chains and correlation with T-cell function

T-cell receptor (Tcr) alpha chains are classified into four subgroups (I, II, III, and miscellaneous) based on the amino acid residues at positions 61 and 62. Subgroup I has Gly Phe at these positions, subgroup II has Arg Phe, subgroup III has Arg Leu, and subgroup miscellaneous has several other combinations. Variability plots for subgroups I, II, and III sequences show higher values around positions 93-103, 105, 108, 111, 113, and 115, suggesting that these positions may interact with the processed antigen molecules. Smaller peaks are present at various other regions which may bind the major histocompatibility complex class I or II molecules. The patterns of variability within one subgroup are similar for all species, for human alone, and for mouse alone. These subgroup patterns appear much less complicated than patterns for sequences in all subgroups taken together, implying that subgroups may be related to Tcr functions. Among 83 mouse chains, 15 are from cytotoxic cells and 40 from helper cells. Of the 15 from cytotoxic cells, 11, 2, 0, and 2 are in subgroups I, II, III, and miscellaneous; and of the 40 from helper cells, 9, 16, 12, and 3 are in subgroups I, II, III, and miscellaneous, respectively. Thus, a correlation between sequence and function of Tcr alpha chains seems possible.

Immunoregulatory activity of the T-cell receptor alpha chain demonstrated by retroviral gene transfer

We have previously described an antigen-specific I-Ad-restricted T-cell hybridoma, A1.1, that constitutively releases an antigen-specific immunoregulatory activity into supernatants. Using retrovirally mediated gene transfer, we have found that transfer of the T-cell receptor alpha chain (TCR alpha) gene from A1.1 to a number of other T-cell hybridomas effectively transferred the ability to produce the activity. Gene transfer of the TCR beta chain (TCR beta), however, did not transfer this ability. The regulatory activity from cells expressing the A1.1 TCR alpha bound to and was eluted from an anti-TCR alpha monoclonal antibody and displayed fine antigenic specificity identical to that of supernatants from A1.1. The possibility that this activity represents a secreted form of the TCR alpha (as opposed to shed cell-surface TCR) was examined in BW1100 cells, lacking TCR alpha and TCR beta, which produced the antigen-specific activity after gene transfer of the A1.1 TCR alpha gene. The expression of the immunoregulatory activity in supernatants correlated with a direct antigen-binding activity as detected by ELISA, thus raising the possibility that antigen binding is relevant to the mechanism of action of the soluble TCR alpha. We discuss these observations and our earlier studies suggesting an immunoregulatory role for soluble TCR alpha.

T-cell receptor alpha chain plays a critical role in antigen-specific suppressor cell function

Antigen-specific suppressor T-cell hybridomas release soluble suppressor factors (TsF) in the supernatant that modulate both in vivo delayed-type hypersensitivity and in vitro plaque-forming cell responses in an antigen-specific manner. To study the relationship between the T-cell receptor (TcR) and TsF, we developed a series of TcR alpha- or TcR beta- expression variants from suppressor T-cell hybridomas that expressed the CD3-TcR alpha/beta complex. We demonstrate that loss of TcR alpha but not TcR beta mRNA was accompanied by the concomitant loss of suppressor bioactivity. Homologous transfection of TcR alpha cDNA into a TcR alpha- beta+ clone reconstituted both CD3-TcR expression and suppressor function. Furthermore, suppressor activity from TcR beta- variants was specifically absorbed by antigen and anti-TcR alpha antibodies, but not by anti-CD3 or anti-TcR beta affinity columns. These data directly establish a role for the TcR alpha chain in suppressor T-cell function and suggest that the TcR alpha chain is part of the antigen-specific TsF molecule.

Dominant expression of a distinctive V14+ T-cell antigen receptor alpha chain in mice

A distinctive variable region 14-positive (V14+) alpha chain (V alpha 14+) of the T-cell antigen receptor is predominantly expressed in multiple mouse subspecies. The V alpha 14 family has two members, V alpha 14.1 and V alpha 14.2, which differ by only three amino acids at positions 50-52. Based on the EcoRI restriction fragment length polymorphism of the gene encoding V alpha 14, mice can be divided into three groups: type I with an 11.2-kilobase (kb) fragment, type II with a 2.0-kb fragment, and type III with the 2.0-kb and 11.2-kb fragments. Usage of V alpha 14-J alpha 281, where J alpha 281 is an alpha-chain joining segment, with a one-base N region dominates at the level of 0.02-1.5% of alpha chains in all laboratory strains, Mus musculus castaneus, and Mus musculus domesticus but not in Mus musculus molossinus, Mus musculus musculus, and Mus spicilegus samples. The preferential V alpha 14-J alpha 281 expression seems to be due to positive selection because the V-J junctional region is always glycine, despite the ability of the V alpha 14 gene to associate with J alpha other than J alpha 281. As V alpha 14-J alpha 281 expression is independent of known major histocompatibility complex antigens, including H-2, TLA, Qa, and HMT, the selecting ligand must be a monomorphic molecule of the mouse, expressed in a subspecies-specific manner. Additional observations, such as the expression of homogeneous V alpha 14-J alpha 281 in athymic mice, suggest that the positive selection of V alpha 14+ T cells occurs extrathymically.

Studies on the human T cell receptor alpha/beta variable region genes. I. Identification of 7 additional V alpha subfamilies and 14 J alpha gene segments

The anchored-polymerase chain reaction has been used to study further the diversity of the human T cell receptor alpha chain. The analysis of 308 cDNA transcripts from human peripheral lymphocytes hybridizing with a C alpha probe led to the identification of a series of additional V alpha and J alpha gene segments. The sequences of seven V alpha gene segments which individually define a novel V alpha subfamily (termed V alpha w23 to V alpha w29) are reported. The sequences of some previously described V alpha 1, V alpha 2, V alpha 5, V alpha 7 and V alpha 22 gene segments are also extended. In addition, we report 14 novel J alpha gene segment sequences. Taken together, these data indicate that the contribution of the alpha chain combinatorial diversity to the human T cell receptor alpha/beta variability has not yet been fully appreciated.

Establishment of mouse lymphokine-activated killer cell clones and their properties

To assess the properties of lymphokine-activated killer (LAK) cells, we established mouse LAK cell clones from LAK cell lines induced from C57BL/6 mouse spleen cells. Although these clones expressed similar phenotypes to the parent LAK cells, Lyt-2 was expressed in a restricted portion of the clones. All clones were found to express T3 CD2 and T cell receptor (TcR) alpha beta on their cell surface. Rearrangement patterns of TcR beta were the same among the clones derived from the same parent cell line but differed in those from different cell lines as determined by using C beta 1 and J beta 2 probes. The molecules responsible for LAK-target cell binding were examined by using a monoclonal antibody (mAb) against lymphocyte function associated antigen 1 (LFA-1). This mAb (termed KBA) showed inhibitory effects on both LAK-target cell binding and cytolytic activity of LAK cell clones, indicating a principal role of LFA-1 in LAK cell clones. The magnitude of perforin mRNA expression in LAK cell clones was unrelated to their cytolytic activities.

Homogenous junctional sequence of the V14+ T-cell antigen receptor alpha chain expanded in unprimed mice

Nucleotide sequences of VJ (variable-joining) junctional regions of V14+ alpha-chain T-cell receptor genes show that most V alpha 14+ T cells use one alpha chain (V alpha 14J alpha 281 with a one-nucleotide N region, which is frequently used in keyhole limpet hemocyanin-specific suppressor T-cell hybridomas) in unprimed mice. Moreover, the frequency of this alpha-chain expression was greater than 1.5% of the total alpha chains found in laboratory strains, including B10 congenic mice. This is about 10(4) times higher than was expected. The V14J281 alpha-chain expression was relatively low but was significant in CD4+/CD8+ immature thymocytes and became quite high in mature single-positive T cells, implying that this alpha chain is selected during T-cell maturation. V14J281 expression increased with time after birth and reached a maximum at around 5 weeks of age. The ligand seems to be a self molecule and to be present in laboratory strains but to be absent in a wild mouse, Mus musculus molossinus, because bone marrow chimeras clearly showed that bone marrow cells derived from Mus musculus molossinus negative for this alpha chain raised V14J281-positive T cells in a C57BL/6 environment. The above results suggest that there are some selection mechanisms for this cell type other than those for conventional alpha beta T cells and also that the homogenous VJ junction of the V14J281 alpha chain plays a pivotal role in the selection of the T cell and its ligand reactivity.

Regulation of IgG production by suppressor Fc gamma RII+ T hybridomas

In this work, we analyzed the immunoglobulin heavy (H) and light (L) chain production by two variant B hybridomas, UN2.C3 and UN2.C17.K1 co-cultured with cells from a Fc gamma RII+, IgG-binding factor (IgG-BF)-producer T hybridoma (T2D4.C1) or with cells of a Fc gamma RII-, IgG-BF-nonproducer variant (D10C5). We showed that only the Fc gamma RII+ hybridoma directly inhibits the IgG secretion by UN2.C3 through a soluble mediator. This inhibition affects the H and L chain synthesis as well as the H and L chain-encoding mRNA steady state. No apparent cytotoxic effect could be detected. In contrast, the production of kappa chain by an H chain-negative variant (UN2.C17.K1) was unaffected. This indicates that a complete IgG molecule is required to observe the inhibitory effect induced by T2D4.C1. The pattern of effector/target cell interactions observed in our work suggests that the soluble factor involved in the suppression of IgG production is IgG-BF, able to transiently modify the IgG gene expression in target cells.

Specific inhibition of cell-surface T-cell receptor expression by antisense oligodeoxynucleotides and its effect on the production of an antigen-specific regulatory T-cell factor

We have used antisense oligodeoxynucleotides corresponding to genes encoding the variable (V) region of the T-cell receptor (TCR) alpha and beta chains (V alpha and V beta) to control TCR expression in T-cell hybridomas. Two hybridomas, A1.1 and B1.1, recognize a synthetic polypeptide antigen designated poly 18 (poly[Glu-Tyr-Lys-(Glu-Tyr-Ala)5]) together with I-Ad. We have found that TCR function (production of lymphokines in response to antigen) and T3 expression were removed after protease treatment of the cells and were fully recovered 48 hr later. However, when antisense oligodeoxynucleotides corresponding to the appropriate TCR V genes were present after protease treatment, little or no recovery of TCR function or T3 expression was observed. This effect was specific for the TCR V genes utilized by the T cell: antisense oligodeoxynucleotides corresponding to the TCR V regions of A1.1 had no effect on TCR expression in B1.1 and vice versa. Thus, antisense oligodeoxynucleotides can be used to temporarily block expression of a TCR gene in a T-cell hybridoma. This technique was then applied to a paradoxical phenomenon in A1.1 cells. We had observed previously that A1.1 releases an antigen-specific immunoregulatory activity that shows the same antigenic fine specificity as is displayed by the TCR of A1.1. We now report that antisense oligodeoxynucleotides corresponding to the A1.1 V alpha gene blocked the production of this soluble antigen-specific activity by the cell. Antisense oligodeoxynucleotides corresponding to A1.1 V beta, on the other hand, had no effect on the production of this antigen-specific activity. We discuss these observations in the context of recent findings on the nature of T cell-derived antigen-specific regulatory factors.

Expression of CD3-associated antigen-binding receptors on suppressor T cells

Three suppressor T (Ts)-cell hybridomas specific for 4-hydroxy-3-nitrophenyl acetyl (NP) hapten were selected for surface expression of cluster determinant 3 (CD3) by using antibody (anti-CD3) or antigen (NP-bovine serum albumin) panning procedures followed by cloning at limiting dilution. The CD3-selected Ts hybridomas showed a 1-2 logarithmic enrichment in suppressor activity when compared to the parent lines; they also specifically bound NP-coupled sheep red blood cells in rosette assays. This antigen-binding ability could be down-modulated by anti-CD3 antibody. Similarly, surface expression of CD3 was specifically down-modulated by preincubation of these hybridomas with antigen. Anti-CD3 monoclonal antibody under reducing conditions coprecipitated a broad band of 38-50 kDa associated with two CD3 (25 and 16 kDa) bands. T-cell receptor, anti-alpha-specific monoclonal antibody also immunoprecipitated a broad band in the 41 to 49-kDa region. The combined results suggest that, like helper and cytotoxic T lymphocytes, Ts cells also bear antigen-specific receptors associated with CD3 molecules.

Biochemical purification of various receptor molecules involved in human T lymphocyte activation. Separation of 9.3 antigen from the T cell receptor for antigen

The now classical major histocompatibility complex (MHC)-restricted receptor for antigen on human T lymphocytes has been identified as a 90 kDa disulphide-linked heterodimer composed of two glycoproteins termed alpha and beta. More recently, another type of T cell receptor for antigen has been described, which seems to mediate killing of target cells without any obvious requirement for MHC recognition. This T cell receptor for antigen is also a heterodimer composed of gamma, delta chains non-covalently associated with the three mon morphic CD3 subunits. Another disulphide-linked dimer capable of triggering T lymphocytes has been defined recently by a monoclonal antibody: the anti-human 9.3 antigen. In order to generate monoclonal or polyclonal reagents against variable and constant regions of the T cell receptor chains and against new epitopes of the 9.3 antigen, we have developed a biochemical method of purification of T lymphocyte disulphide-linked dimers. Our method relies on two biochemical properties of the 9.3 surface molecule and the T cell receptor for antigen. (1) They are disulphide-linked dimers and thus can be separated from the vast majority of the cell surface molecules by two-dimensional (non-reduced versus reduced) sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). (2) T cell receptor chains are less hydrophobic than the 9.3 antigen, and thus can be isolated from it on reverse-phase high-performance liquid chromatography (HPLC) at a lower concentration of acetonitrile. Microsomal preparations from T cell clones and leukaemia lines were prepared by nitrocavitation and lysed in sodium deoxycholate. After concentration, this lysate was electrophoresed on SDS-PAGE in non-reducing conditions. The gel slice corresponding to the molecular weight of the T cell receptor was cut out and run in reducing conditions in the second dimension. The T cell receptor spots were easily located on the gel by autoradiography as the microsomal lysate had been mixed with iodinated glycoproteins. The T cell receptor was eluted from the gel with about 85% yield. At this stage, the T cell receptor preparations also contained the 9.3 antigen, another disulphide-linked dimer. The separation of this antigen from the T cell receptor chains had been achieved on reverse-phase HPLC. This procedure allows the purification and separation of two disulphide-linked dimers which are both involved in T cell activation. The obtention of antibodies against new epitopes of these important molecules would be extremely useful for analysing their role in T cell function and ontogeny.