A T15-idiotype-positive T suppressor hybridoma does not use the T15 VH gene segment

Suppressor T cells, immunoglobulin and Igh restriction

Why do some T cell express idiotypes that are serologically similar to those of the B cells, since it is now well established that T cells do not use Ig genes for their antigen specific receptors? In this review article, we have summarized some the evidence for the influence of Igh linked genes on the Suppressor T cell repertoire, using anti-u treated mice as a model system. We investigated whether B cells and Ig molecules play a role in the generation of Ts repertoire. While our results clearly confirmed that B cells and Ig are important in the establishment of Ts repertoire, our experiments failed to resolve the fundamental question - 'what dictates the Igh restriction specificity of Ts?' Ts cells from anti-u treated mice did not lose all Igh restriction specificity. Instead, they expressed an altered restriction specificity. These results suggest that there are at least two independent mechanisms responsible for the generation of the suppressor T cell repertoire. A pre-selected germ line one, which is Ig independent, and a mature one, which is Ig dependent. The precise mechanisms responsible for the generation of germ line Ts repertoire remain to be determined.

Sequence analysis of a cDNA clone of a gene encoding a component of a putative phosphorylcholine-specific T suppressor factor and functional property of its gene product

We have isolated a putative phosphorylcholine (PC)-T cell suppressor factor (TsF) cDNA clone, p6-5, from a cDNA library of a T hybridoma which constitutively secretes a PC-TsF in vitro [8]. In the present study, we determined the nucleotide sequence of the p6-5 gene and found that the p6-5 sequence is 86% homologous to rat preproelastase 1 gene, one of the serine protease genes. An oligopeptide (14 mer, TsF14) deduced from the p6-5 sequence was synthesized and antisera against TsF14 were prepared in rabbits. Anti-TsF14-conjugated Sepharose 4B specifically absorbed the PC-TsF activity from the culture supernatant of PC-TsF-secreting T hybridomas. In contrast, the binding molecule eluted from the anti-TsF14-conjugated Sepharose suppressed the antibody response PC specifically. These results indicated that the p6-5 polypeptide is a component of the PC-TsF molecule.

Antigen-specific T cell suppressor factor (TsF): isolation of a cDNA clone encoding for a functional polypeptide chain of phosphorylcholine-specific TsF

A cDNA library of phosphorylcholine (PC)-specific suppressor T hybridoma, 29-C-6, was constructed. By differential colony hybridization, 68 colonies were selected which hybridized with mRNA probes of two PC-specific suppressor T hybridomas, 29-C-6 and 09-M-24-8, but not with those of BW5147. A hybridization translation assay revealed that only one combination of translation products of cDNA clones, p6-1 and p6-5, showed strong PC-T cell suppressor factor (TsF) activity. Sequence analysis showed that p6-5 contained a specific cDNA sequence of about 800 base pairs (bp) while p6-1 had a 190 bp poly(A) sequence insert. When total poly(A) + RNA of 29-C-6 was hybridized with p6-1 filter alone the recovered mRNA was capable of producing PC-TsF. However, when the total poly-(A) + RNA was hybridized with a p6-1 filter combined with a p6-5 filter, the mRNA eluted from the p6-1 filter was not able to produce PC-TsF, suggesting that the depletion of p6-5 specific mRNA from p6-1-binding poly(A) + RNA led to a complete abolishment of the capability to produce PC-TsF. Furthermore, p6-5 hybridizing mRNA could successfully restore the p6-1-binding poly(A) + RNA depleted of p6-5-specific mRNA, and translation products of both RNA mixtures showed strong PC-TsF activity. These results suggest that PC-TsF is not a single polypeptide chain, but is composed of at least two distinct polypeptide chains, and also that p6-5 contains a cDNA sequence encoding for one of the polypeptide chains composing the PC-TsF molecule.

Construction of chimaeric processed immunoglobulin genes containing mouse variable and human constant region sequences

The specificity of monoclonal antibodies provides a powerful diagnostic and therapeutic tool in investigating human neoplasia. Radiological scanning and immunotherapy with mouse tumour-specific monoclonal antibodies have been applied to patients with some success, but a major problem is the neutralization of the mouse antibody induced by repeated administration of heterologous antibodies. To avoid or reduce such immune reactions, chimaeric immunoglobulins consisting of mouse variable (V) and human constant (C) regions can be synthesized. We have constructed a recombinant retrovirus DNA carrying genomic heavy-chain (H) variable-diversity joining (VH-D-JH) and C gamma 1 genes from different species and show here that the chimaeric intervening sequences are spliced out precisely. This procedure provides a useful method to construct the chimaeric mouse-human immunoglobulin gene to be expressed in Escherichia coli, yeast and animal cells. Unexpectedly, a hidden splice donor site in the 5'-flanking region of a human VH gene is used in place of the donor site of the leader sequence exon, resulting in the formation of the V region without the leader sequence.

Suppressor T-cell factor(s) display an altered pattern of Igh (immunoglobulin heavy chain locus) genetic restriction when developed in an Igh-congeneic host

Suppressor T-cell factor(s) (TsF1) inhibit the in vivo priming of azobenzenearsonate-specific cytotoxic T-cell responses. The activity of TsF1 is restricted by genes linked to Igh-1 allotypic markers. TsF1 obtained from B6.Igh-1n mice was unable to suppress the immune response in B6.Igh-1b mice and vice versa. However, TsF1 prepared from B6.Igh-1n T cells "parked" in an Igh-congeneic B6.Igh-1b environment displays an additional restriction specificity of the host. Thus, TsF1 prepared from these Igh-chimeric mice suppressed immune responses in both B6.Igh-1n (donor) and B6.Igh-1b (recipient) mice but not in mice of the unrelated strain BALB/c.Igh-1a. The results indicate that the establishment of the suppressor T-cell repertoire is dependent not only upon the genetic background of the individual T cell but also upon the influence of Igh-linked determinants present when T-cell clones are selected during the response.

Rearrangement and transcription of a T-cell receptor beta-chain gene in different T-cell subsets

The functionally defined sets of T lymphocytes--helper T cells, cytotoxic T cells, and suppressor T cells--were examined for the possible involvement of a recently identified T-cell receptor beta gene locus in receptor formation. Since gene rearrangements are required for functional gene expression, cloned T-cell lines from each of the groups were surveyed for the expression of unique gene rearrangements. In addition, cell lines that showed gene rearrangements were further tested for the expression of the mature 1.2- to 1.3-kilobase mRNA transcribed from a productive gene rearrangement. The results of such experiments show that helper and cytotoxic T cells may use a common beta chain of the receptor, whereas suppressor cells do so rarely, if at all.

Structure, expression and divergence of T-cell receptor beta-chain variable regions

Analysis of three new T-cell receptor beta-chain variable regions together with those in the literature indicates that they have both remarkable similarities and differences with those of immunoglobulin. Less than 10 V regions appear to predominate in the thymus. V beta sequences are much more heterogeneous at the amino acid level than are immunoglobulin V regions and they appear to diverge between species much more quickly, apparently the result of additional hypervariable regions. Three of these putative new hypervariable regions lie outside of the classical immunoglobulin binding site, an indication that important interactions may be occurring in these regions with polymorphic MHC determinants.

A murine T cell receptor gene complex: isolation, structure and rearrangement

We describe here our efforts to develop a systematic strategy for the enumeration and isolation of genes encoding T cell-specific, membrane-associated polypeptides. Of particular importance among the cDNA clones that we have isolated is one which encodes the beta chain of the murine T cell receptor for antigen. The gene product is strikingly similar to immunoglobulin in its variable (V), constant (C), joining (J), and diversity (D) - like elements and the ability of the latter three types of element to assort independently during differentiation. The genomic organization of the constant region locus which encodes this molecule consists of two tandemly arrayed units of the form JC/JC, where the J clusters consist of fourteen distinct elements, many of which may be functional. The two constant regions differ by only four amino acids and both are apparently expressed in T cells of the same phenotype, so they probably do not represent isotypes in the classical sense. The sequences flanking the V, D and J elements are also similar to the conserved heptamer and nonomer sequences of immunoglobulins thought to be important in the recombination of the specific gene segments. These similarities indicate both the common evolutionary origins of these loci and the strong selective pressure that must be operative. The T cell receptor locus differs somewhat from immunoglobulins in the large number of possible J region elements and to some extent in the hypervariable-framework regions of the V region. We and others have mapped this gene to chromosome 6 of the mouse, in the same portion of the chromosome but not closely linked the kappa locus. The significance of the predicted protein structure of the beta chain and its support of the one-receptor model of MHC-antigen recognition are discussed.

Murine T cell receptor beta chain is encoded on chromosome 6

Southern blot analysis of somatic cell hybrid lines indicates that the beta chain of the T cell receptor for antigen maps to chromosome 6 of the mouse. An experiment testing hybridization of the constant region of this gene to DNA from a hybrid cell line containing a translocation of chromosome 6 supports the localization of this gene to the proximal (centromeric) one-third of chromosome 6, in the same general region as the immunoglobulin kappa chain locus. This may be another indication of the shared evolutionary origins of the genes encoding both T and B cell antigen recognition.

Macrophage-chemotactic factor-producing T cell hybridomas reactive to phosphorylcholine in I-E-restricted manner

Macrophage-chemotactic factor (MChF)-producing T cell hybridomas were established. These hybridomas produced MChF upon the specific antigenic stimulation with phosphorylcholine (PC)-conjugated protein in the presence of I-Ed-positive antigen-presenting cells. The hybridomas also secreted MChF after co-culture with concanavalin A in the absence of antigen-presenting cells. The MChF-secreting hybridomas were positive for Kd, Dd, Lyt-1.2 but negative for I-Ad, Lyt-2.2. The molecular weight of MChF produced by the hybridomas was 43000 and the factor was focused at pH 6.6-6.8 in the chromatofocusing procedure. The MChF was protease sensitive but resistant to neuraminidase treatment, and it was stable by heating at 80 degrees C for 15 min. The MChF-producing hybridomas established in this stud did not produce macrophage migration inhibitory factor (MIF), macrophage-activating factor (MAF) or interleukin 2, suggesting molecular nonidentity between MChF and these lymphokines. The MChF-producing T cell hybridomas reactive to specific antigens (PC) will be promising tools for analysis of molecular nature of MChF as well as molecular aspects of antigen recognition mechanism of T cells.

Heterogeneity of Igh-linked allotypic determinants expressed on functional T cell subsets as detected by monoclonal antibodies

Hybridomas producing monoclonal antibodies (mAb) specific for immunoglobulin heavy chain (Igh) allotype-linked gene products expressed only on functional T cells but not on B cells and macrophages were established by fusion of allotype congenic SJL (Igh-1b) and SJA /9 (Igh-1a) B cells immunized reciprocally with partner spleen cells with a myeloma P3-X63-Ag8-653 of BALB/c origin. Nine mAb have been selected on the criteria that they can specifically block various antigen-dependent functions of known T cell subsets in in vitro immune responses of mouse strains having the corresponding Igh allotype, but not the other one. These included (a) four mAb that augment the in vitro secondary antibody response of either Igh-1a or Igh-1b strains and thus are considered to react with the Igh-linked allotypic determinant expressed on suppressor T cells, (b) one mAb that inhibits the helper T cell activity of Igh-1b but not of Igh-1a strains, (c) two mAb that inhibit the antigen-induced proliferative response of Igh-1a but not Igh-1b strains, and (d) two mAb that block the cytotoxicity of alloreactive cytotoxic T cells of Igh-1a strains. The linkage to Igh-1 allotype of the T cell products was established by testing with Igh-1-congenic strains with different backgrounds including the H-2 complex. Some of the mAb were able to react with cloned hybridomas and a continuous cell line of the given allotype and functions. Each mAb was able to block one of the known functions of T cell subsets, but not others, indicating the existence of the heterogeneity and multiplicity of the Igh allotype-linked products on T cells.

Sequence relationships between putative T-cell receptor polypeptides and immunoglobulins

Comparison of the sequence of a cloned T cell-specific cDNA with those of cross-reacting cloned cDNAs isolated from a thymocyte library indicates the presence of variable, constant and joining regions remarkably similar in size and sequence to those encoding immunoglobulin proteins. Together with the evidence for somatic gene rearrangements reported in the accompanying paper, this strongly suggests that the TM86 cDNA clone encodes one chain of the T-cell receptor for antigen.

Isolation of cDNA clones encoding T cell-specific membrane-associated proteins

Of 10 distinct cloned DNA copies of mRNAs expressed in T lymphocytes but not in B lymphocytes and associated with membrane-bound polysomes, one hybridizes to a region of the genome that has rearranged in a T-cell lymphoma and several T-cell hybridomas. These characteristics suggest that it encodes one chain of the elusive antigen receptor on the surface of T lymphocytes.

Anti-hypervariable region antibody induced by a defined peptide: an approach for studying the structural correlates of idiotypes

The structural correlates of idiotypes have been sought in several antibody systems. However, the precise molecular basis of idiotypes are exceedingly difficult to define. Antibodies of predetermined specificity can be induced by immunization with synthetic peptides. In the present experiments, a synthetic peptide corresponding to a hypervariable region on a monoclonal human IgM rheumatoid factor (Sie) has been used to induce specific anti-hypervariable region antibodies. The antibodies bound to the intact Ig molecule and to its isolated heavy chains but not to other IgM paraproteins nor to pooled human IgG. The binding of the antibody to the intact IgM was inhibited specifically by the free peptide, and the antibody activity was removed by a peptide-coupled affinity column. These results clearly demonstrate that specific anti-idiotypic antibody of predefined specificity can be induced by a hypervariable region peptide. Antibodies of this class may provide a new tool for defining the structural correlates of idiotypes.

The D-JH complex is an intermediate to the complete immunoglobulin heavy-chain V-region gene

We have examined the organization of the immunoglobulin JH segments in three clones derived from a single Abelson murine leukemia virus-transformed cell. Cloning and nucleotide sequence analyses of the JH-containing fragments have revealed the rearrangement from the preformed D-JH complex to the complete VH-D-JH gene, which was accompanied by the expression of the intra-cytoplasmic mu chain. In one case a JH segment downstream to the preformed D-JH was used to create a new VH-D-JH gene. Upon the D-JH and VH-D-JH rearrangements the intervening D segments were deleted from the chromosome. One of the expressed VH genes suffered from a large deletion of the 3' portion (including the 95th cysteine residue) of the VH segment. We discuss the possible mechanism of the allelic exclusion.

Three T cell hybridomas do not contain detectable heavy chain variable gene transcripts

We attempted to determine whether T cells express any VH gene segments. cDNA libraries were constructed from one suppressor and two helper T cell hybridomas. Both the library construction and screening were designed to maximize detection of a wide range of VH gene segments. One screening method should detect about half of the sequenced VH genes, while the second should detect most of these genes. The probability of detecting a VH gene homologous to the probes and present at 10 copies per cell was 77% for one helper cell cDNA library, 88% for the second helper cell library, and greater than 99% for the suppressor cell library. No cDNA clones with VH gene segments were detected. From this result, we conclude that VH gene segments are not likely to encode the antigen-specific receptor in the cells we tested.

T and B cells that recognize the same antigen do not transcribe similar heavy chain variable region gene segments

We have attempted to determine whether T cells and B cells that have the same antigenic specificity and whose receptors share idiotypic determinants in fact express similar VH gene segments. To do this, we have obtained and characterized a cDNA clone containing the entire coding sequence for the VH gene from a glutamic acid60/alanine30/tyrosine10 (GAT)-binding immunoglobulin that carries the CGAT idiotype. The GAT-VH clone was hybridized to Northern blots of GAT-specific T cell RNAs; there was no evidence of a T cell transcript that hybridized to the GAT-VH probe. The T cells analyzed included: (a) 10 GAT-binding suppressor T cell hybridomas, 6 of which secreted factors with CGAT idiotypic determinants, (b) one GAT-specific helper T cell hybridoma, and (c) two GAT-specific helper T cell lines grown in the absence of feeder cells. The detection limit of the Northern blot analysis was 1-2 copies of a particular mRNA species per cell for the hybridomas and 5-10 copies per cell for the T cell lines. Therefore, we conclude that T and B lymphocytes responding to GAT do not utilize similar VH gene segments. Furthermore, the presence of idiotypic determinants on T lymphocytes does not necessarily imply close structural similarity between T and B cell antigen receptors.

Monoclonal suppressor T-cell factor displaying V H restriction and fine antigenic specificity

The production of stable T-cell clones is essential for the study of T-cell-derived, specific immunoregulatory products and of specific T-cell receptors. T-cell clones have been established by radiation leukaemia virus (RadLV)-induced transformation of suppressor T lymphocytes specific for hen egg white lysozyme (HEL). We report here that culture supernatant obtained from these T-cell clones can, when injected into mice, specifically suppress the anti-HEL antibody response. This monoclonal T-cell product suppresses the antibody response induced by HEL and human lysozyme, but not that induced by ring-necked pheasant egg white lysozyme (REL), thus displaying fine antigenic specificity probably restricted to an epitope involving phenylalanine at amino acid residue 3, present in the N-terminal region of HEL and shared by human lysozyme but absent in REL. The suppression induced by this monoclonal T-cell product is restricted by both H-2 and Igh-1 genes whereas anti-HEL antibodies bearing a predominant idiotype are induced in all mice strains tested, irrespective of their H-2 haplotype or Igh-1 allotype.

Quantitative of anti-NP (4-hydroxy-3-nitrophenyl)-acetyl idiotype expression on spleen and thymus cells

Direct binding of 125I-labeled rabbit anti-NPb idiotype antibodies (RaId) was used to quantitate the expression by immune spleen and thymus cells of NPbId, the characteristic Id of the lambda 1-containing antibodies made by C57BL/6 (B6) mice to the (4-hydroxy-3-nitrophenyl)acetyl (NP) group. Direct binding of RaId by B and T cell preparations reached a maximum of 12 ng RaId per 10(8) cells at 7 days after immunization. Spleen T cell preparations maintained similar levels of binding after positive selection for Thy-1.2+ cells and overnight culture. RaId binding was also demonstrated for immune B6 thymus cells and for spleen and thymus cells of immune SJL mice, which have the appropriate heavy chain allotype for NPbId expression but have only barely detectable serum Id. However, the NPbId of T and B cell preparations were indistinguishable by (a) the susceptibility of RaId binding by the cells to inhibition by hapten or by antibodies to the variable regions of lambda light chains (anti-V lambda) and by (b) the ability of anti-V lambda and of monoclonal antibodies to the constant region of lambda 1 chains (anti-C lambda 1) to immunoprecipitate antigen (NP10-bovine serum albumin)-binding proteins from detergent extracts of isotopically labeled cells. The results strongly imply that virtually all of the NPbId of T cell preparations is due to conventional NPbId antibody that is tightly bound to T cells. The results do not, however, exclude the possibility that the T cell preparations contain a trace amount (less than or equal to 1 ng/10(8) cells) of unusual NPbId-like molecules that lack lambda chains.