Functional and molecular organisation of an antigen-specific suppressor factor from a T-cell hybridoma

Characterization of antigen-binding and MHC class II-bearing T cells with suppressive activity in response to tolerogenic stimulus

Antigen specific non-responsiveness is generally developed through clonal deletion, anergy, and suppression. The term "suppression" is being considered as a functional immune deficit that can be adoptively transferred by regulatory/suppressor T cells. Following tolerance induction protocols the aim of the present study was to characterize the T cells involved in antigen-specific suppression. After defining the immunogenic and tolerogenic protocols in vitro and in vivo, it was shown that CD90(+) cells from tolerogenic mice were able to reduce specific antibody production when adaptively transferred to immunized mice. These cells were shown to highly express CD25 and Foxp3, co-localizing with CD4 and MHC class II antigens (MHCII), while a small percentage of these cells (8-14%) was binding free antigen. Further isolation of CD90(+)MHCII(+) and CD90(+)HSA(+) from mice having received the tolerogenic treatment and adaptive transfer to immunized mice showed that CD90(+)MHCII(+) cells were able to suppress antigen-specific response only when transferred along with the second antigenic challenge, while CD90(+)HSA(+) cells were suppressive only when given along with the first antigenic challenge. The suppressive effect of these two sub-populations could also be obtained in in vitro spleen cell proliferation assays in response to the HSA antigenic stimulus. Both in vitro and in vivo tolerogenic treatments were shown to correlate with soluble MHCII production in culture supernatants or serum respectively. Increase of MHCII in the serum could only be detected upon adaptive transfer of CD90(+)HSA(+) cells, whereas transfer of CD90(+)MHCII(+) cells resulted in increased levels of IL-10 and IFN-γ in the serum. These results defined at least two different levels of suppression, one during the onset which was antigen-specific and MHC restricted, and another non-specific at the end of an immune response.

T-regulatory cells: are we re-discovering T suppressors?

Regulatory T cells are shown to originate form the thymus and their role is to maintain self-tolerance to intra-thymic as well as extra-thymic self-antigens. Their mode of action, using in vivo and in vitro systems, has led to different conclusions as to the need of cell-cell interactions or regulation upon suppressive cytokines. The more we study regulatory T cells the more we find similarities to the old notion of the suppressor T cell network. The limited knowledge in molecular technology in the early 70s and 80s discouraged investigators to further scrutinize the issue and the terms T suppressors and contra-suppressors that were coined back then have been forgotten over the years. It is now time to remember the work of these investigators and attempt to explain their findings using the current knowledge and technology.

Mode of action of monoclonal-nonspecific suppressor factor (MNSF) produced by murine hybridoma

Monoclonal-nonspecific suppressor factor (MNSF), a product of murine T cell hybridoma, suppresses antibody response to lipopolysaccharide. In an attempt to clarify the functional mechanisms in vitro, we investigated the mode of action of MNSF. This factor inhibited the antibody response by B cells (depleting T cells and Mø), thereby indicating that the lymphokine acts directly on B cells, without interaction between B and T cells or Mø. MNSF activity was absorbed by mitogen-stimulated T or B cells, but not by resting lymphocytes. Proliferative responses to T cell and B cell mitogens were inhibited dose dependently by the addition of MNSF. Kinetic studies showed that MNSF suppressed the antibody response, in all culture periods, thereby indicating that immunoglobulin secretion and proliferation were inhibited. The effect of growth factor on MNSF-mediated suppression was investigated to search for a possible suppression of MNSF action. Interleukin 2 (IL-2) remarkably inhibited MNSF activity, and the effect of IL-1 or IL-4 was less. IL-2 was most effective when added on the fourth day of culture. MNSF also inhibits division in the plasmacytoma line MOPC-31C or in thymoma EL4, but not in L929 fibroblasts. Tumor necrosis factor (TNF) inhibits cell division of various tumor cells and suppresses the pokeweed mitogen-induced antibody response, without cytotoxic action, as does MNSF. While MNSF and TNF have similar biochemical and physiochemical properties, the cross-reaction tests showed that both are antigenically discrete lymphokines. Although MNSF lacks TNF activity, the concomitant addition of both factors to L929 increases the cytotoxic action, a finding indicative of a synergistic effect.

Ultraviolet-induced suppressor T cells and factor(s) in murine contact photosensitivity. I. Biological and immunochemical characterization of factor(s) extracted from suppressor T cells

Murine contact photosensitivity (CPS) to 3,3',4',5-tetrachlorosalicylanilide (TCSA) is a highly specific, T-cell-mediated delayed-type hypersensitivity (DTH). Preexposure of the photosensitizing site to low doses of ultraviolet B(UVB) rendered mice unresponsive to challenge reaction. This unresponsiveness was associated with the generation of antigen-specific, afferent limb-acting, Lyt-1+2-,L3T4+ suppressor T cells (Ts-cps) in the spleen, thymus, and lymph node. Cell-free extract(s) obtained by freezing and thawing of these cells contained T-cell-suppressor factor (TsF) that inhibited the development of the induction phase of the CPS response to TCSA in vivo in an antigen-specific fashion. The treatments of TsF both with immunoadsorbent columns and with reduction and alkylation showed that the factor bore photoantigen-binding site(s), was reactive with monoclonal anti-I-Jd, anti-I-E alpha but not anti-I-Ad, and behaved as a single-chain factor containing both photoantigen binding and I-J molecules. By gel chromatography the majority of the suppressive activity was eluted in the fractions corresponding to molecular weights of 60-80 and 100-200 kDa. Our present study demonstrated clearly that UVB-induced unresponsiveness in the DTH reaction was mediated by a soluble suppressive factor derived from T cells.

Production of T suppressor factor specific for the hapten picryl chloride requires both T suppressor cells and an antigen-specific, genetically restricted second signal

We investigated the requirement for activation of T suppressor cells specific for the hapten picryl chloride and the release of hapten-specific T suppressor factor. Using an in vivo experimental system, we report that activation of T suppressor cells and the consequent release of T suppressor factor required two signals: one was provided by primed T suppressor cells, i.e. spleen cells from mice injected with the tolerogen picrylsulphonic acid, and the other was provided by the specific antigen in the context of H-2 gene products. Mechanisms by which the interaction between these two signals led to activation of T suppressor cells and the production of T suppressor factor, as well as a comparison with other antigen-specific suppressor systems, are discussed.

Soluble factors in tolerance and contact sensitivity to DNFB in mice. VII. Characterization of a monoclonal, efferent-acting suppressor factor with specificity for DNP/H-2Kd

To study further soluble factors which regulate contact sensitivity (CS) to 2,4-dinitrofluorobenzene (DNFB), hapten-primed spleen cells from BALB/c mice were used to make T-cell hybridomas. A hybrid constitutively producing a suppressor factor was identified and cloned (clone 3-10). Incubation of BALB/c DNFB immune lymph node cells (LNC) in the 3-10 supernatant suppressed the ability of the immune cells to transfer CS to DNFB. The passive transfer of CS to oxazalone or to 2,4,6-trinitrochlorobenzene (TNCB) was not suppressed by the 3-10 factor. The hapten specificity of the 3-10 factor further was demonstrated by the ability of DNFB immune LNC but not LNC from unsensitized or from TNCB-sensitized mice to absorb the factor. The 3-10 factor also was adsorbed by DNFB-immune LNC from mice that were syngeneic with BALB/c mice at the K locus of the MHC (e.g., B10.D2 and D2.GD). Pretreatment of DNFB-immune LNC with monoclonal anti-Kd antibody or with anti-DNP antibodies blocked the ability to adsorb the factor. These results indicated that the 3-10 suppressor factor binds to DNP/H-2Kd complexes on immune LNC. Nylon wool-purified T cells (83% Thy-1.2+) from DNFB-immune LNC were able to adsorb the factor as well as unseparated immune LNC. Furthermore, treatment of immune LNC with anti-Thy-1.2 plus C' abrogated the ability of the cells to adsorb the factor, indicating that the cellular target of the 3-10 factor is a T cell. In addition, treatment of the immune LNC with an autoantiidiotypic antiserum (CS 231) plus C', which depletes DNP-specific delayed-type hypersensitivity effector T (TDH) cells, also abrogated the ability of the cells to adsorb the factor. Finally, the suppressor factor was adsorbed and eluted from DNP affinity columns but was not adsorbed by TNP affinity columns. Collectively, these results indicate that although the monoclonal 3-10 suppressor factor has affinity for DNP, focusing of the factor on the TDH cells requires recognition of DNP in the context of the appropriate MHC determinant, Kd.

Virus-induced immunosuppression

Infection with a variety of viruses results in the suppression of the host's immune system. Several mechanisms thought to be responsible for this effect are discussed: infection and alteration of lymphocytes and macrophages, production of soluble suppressor factors, and the induction of suppressor cells. The clinical significance of virus-induced immunosuppression is also discussed.

Idiotype-specific T suppressor factor alternatively interacts with a nonspecific T-acceptor-like cell to mediate immune suppression

The ability of the idiotype (Id)-specific second-order T suppressor factor (TsF2) to interact with a final effector Ts cell type other than the previously reported third-order Ts (Ts3) subset was studied in the phenyltrimethylamino (TMA) hapten system. Hence, mice were primed with unrelated heterologous haptens to induce the nonspecific T acceptor (Tacc) cells following published procedures. When enriched T cell populations containing these nonspecific Ts were briefly incubated in vitro with TMA-TsF2, they produced suppression upon adoptive transfer into cyclophosphamide-treated mice which had been previously immunized for TMA-specific delayed-type hypersensitivity. Despite the fact that the effector population studied in this report also required Id-binding TsF2 for its function, it differs markedly from the Ts3 subset studied previously in the TMA system. First, the cell type studied herein could be easily generated with noncrossreacting heterologous chemically reactive haptens when applied directly to the skin of mice. Furthermore, these Ts effector cells had no detectable intrinsic receptors for homologous haptens and most importantly, unlike Ts3, this population had no affinity for the TMA hapten. Nevertheless, the nonspecifically induced Ts once activated by TsF2 suppresses TMA-directed, but not similar immune responses specific for heterologous haptens. Thus the results indicate that TsF2 can functionally interact with a final effector Ts subset (very similar to the Tacc) other than the well described Ts3 population. The ramifications of these findings are discussed with reference to a generalized view of the cellular basis of terminal phases of immune suppression.

Regulation of herpes simplex virus-specific cell-mediated immunity by a specific suppressor factor

Our study was designed to investigate the nature of an antigen-specific suppressor factor generated by antigen-stimulated herpes simplex virus (HSV)-immune splenocytes. Factor SF-200, a 90,000- to 100,000-dalton fraction obtained after Sephacryl gel filtration, suppressed the generation of HSV-specific cytotoxic T-lymphocyte and lymphoproliferative responses. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis of SF-200 indicated that it contained an I-J+, anti-idiotypic protein. It was possible to adsorb the suppressor activity of SF-200 to an anti-I-J immunoaffinity column. The suppressor activity could be eluted from the immunoaffinity column with a low-pH buffer. The acid-eluted material was determined to be both I-J+ and reactive with anti-HSV antiserum by Western blot analysis. Both SF-200 and the I-J+ suppressor activity suppressed only HSV-specific cell-mediated immunity responses. However, it was possible to generate nonspecific suppressor activity by incubating the I-J+ suppressor factor with Lyt 1+ splenocytes from HSV-immune mice. The implication of these results with respect to the model for a suppressor cell circuit regulating HSV-specific cell-mediated immunity responses is discussed.

Cell mediated immunity to liver fluke antigens during experimental Fasciola hepatica infection of cattle

Cell mediated immunity (CMI) to Fasciola hepatica antigens was detected by lymphocyte proliferation and interleukin-2 (IL-2) production tests in cattle during the first 4 weeks following liver fluke infection. From the fifth week of infection onwards peripheral blood lymphocytes were unresponsive to fluke antigens by these in vitro tests. Investigations into the cause of this unresponsiveness found no evidence to suggest a selective loss of the IL-2 producing lymphocyte sub-population or that macrophages were responsible for the suppression or that antigen responsive cells were being sequestered in the spleen and mesenteric lymph nodes. Tests carried out on culture supernatants demonstrated the production during this unresponsive period of factors capable of suppressing in vitro responses to PHA. Although further tests failed to show antigen specific suppressor factors the presence of MHC restricted suppressor factors could not be ruled out. The early and transient appearance of CMI during F. hepatica infection of cattle indicates that delayed type hypersensitivity is unlikely to be important in protective immunity in cattle.

Disulfide-linked surface molecules of monoclonal antigen-specific suppressor T cells: evidence for T cell receptor structures

By two-dimensional polyacrylamide gel electrophoresis analysis under nonreducing/reducing conditions, five proteins with interchain disulfide bridges are revealed on the surface of the suppressor T cell lymphoma line LH8-105 obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme-specific suppressor T lymphocytes. Two disulfide-linked surface proteins expressed by LH8-105 cells have been positively identified by immunoprecipitation with specific antisera. The major labeled membrane protein of LH8-105 cells is the murine leukemia virus env glycoprotein gp70. The second disulfide-linked molecule identified on LH8-105 cells has a molecular mass of 84 kDa under nonreducing conditions and 42 kDa after reduction, and is immunoprecipitated by an antiserum which recognizes the T cell receptor for antigen. A disulfide-linked molecule of a similar molecular mass is also immunoprecipitated from surface-labeled LH8-105 cells by a rabbit antiserum directed against a synthetic peptide predicted from the nucleotide sequence of a cDNA clone encoding the beta chain constant region of a helper T cell hybridoma. Therefore, a dimeric structure comparable to the T cell receptor expressed by cytotoxic and helper T cells is present on the cell surface of these monoclonal antigen-specific suppressor T cells.

An Ia-positive mouse T-cell clone is functional in presenting antigen to other T cells

In this report we present data demonstrating the endogenous expression of I-region associated (Ia) antigens on a cloned line of mouse T cells, CTLL, as well as transcription of the invariant chain gene in these cells. We demonstrate further that this Ia-bearing T-cell clone, CTLL, can utilize the expressed Ia molecules to present antigen to Ia-restricted antigen-specific T cells.

T-cell subsets regulating anti-acetylcholine-receptor-antibody formation in myasthenia gravis and characterization of suppressor T-cell factors involved

The in vitro generation of anti-acetylcholine-receptor (AChR)-antibody-forming cells from B cells of myasthenia gravis (MG) patients occurred only in the presence of OKT4+ cells. Anti-AChR-antibody formation by lymphocytes from MG patients was suppressed by normal T cells, and the requirement of both OKT4+ and OKT8+ cells was suggested for this suppression. Culture supernatant from normal T cells stimulated with excess doses of AChR antigen, but not T cells from patients, suppressed anti-AChR-antibody formation by lymphocytes from patients. The fraction of the culture supernatant with molecular weight of 45,000 to 67,000 seemed to contain an AChR-antigen-specific and antigen-binding suppressor factor with some allogeneic barrier, while the fraction with a molecular weight of 10,000 to 28,000 contained the antigen-nonspecific factor.

T3-Ti receptor triggering of T8+ suppressor T cells leads to unresponsiveness to interleukin-2

T3-associated disulphide linked heterodimers (Tin) comprised of clonally unique alpha-chains of molecular weight (MW) 49,000-54,000 and beta chains of MW 43,000 have been identified as the antigen receptors on human cytotoxic effector and inducer T-lymphocytes. Crosslinking of Ti molecules by either the appropriate nominal antigen/MHC specificity or anti-clonotypic monoclonal antibody results in clonal expansion of such cells via induction of IL-2 receptor expression, endogenous IL-2 release and IL-2-IL-2 receptor interaction. To determine whether analogous antigen receptor molecules and autocrine growth mechanisms are utilized by suppressor T-cells, we produced an anti-clonotypic monoclonal antibody against a non-cytotoxic T8+ suppressor T-cell, T8AC6, which defines a T3-associated disulphide-linked heterodimer of similar molecular weight to the above clonotypes. We find that Te-Ti triggering of suppressor clones (T8AC6, T8AC7 or T8RW) does not result in IL-2 production or T-cell proliferation and in contrast to inducer clones, also leads to a transient IL-2 unresponsive state. We suggest that such T3-Ti receptor mediated autoregulation of suppressor T-cell growth is necessary in the facilitation of initial inducer T-cell activation following antigenic perturbation.

Immunoregulation of lysozyme-specific suppression. II. Hen egg-white lysozyme-specific monoclonal suppressor T cell factor suppresses the afferent phase of delayed-type hypersensitivity and induces second-order suppressor T cells

Culture supernatant from a monoclonal T cell lymphoma line (LH8-105) obtained by radiation leukemia virus-induced transformation of hen egg-white lysozyme (HEL)-specific suppressor T lymphocytes is able, when injected into mice, to specifically suppress the delayed-type hypersensitivity (DTH) reaction induced by HEL. The suppressor T cell factor (TsF) exhibits fine antigenic specificity since it suppresses the DTH response induced by HEL without affecting the DTH response induced by ring-necked pheasant egg-white lysozyme (REL), a lysozyme closely related to HEL. Conversely, LH8-105 TsF is able to suppress the DTH response induced by human lysozyme, distantly related to HEL but sharing a common epitope critical for induction of suppressive activity. The fine antigenic specificity of LH8-105 TsF for a restricted epitope on the HEL molecule is confirmed by binding to HEL but not to REL immunosorbents. This TsF also bears I-J determinants, as demonstrated by binding to monoclonal anti-I-J immunosorbents, and it suppresses the afferent but not the efferent phase of the DTH response to HEL. The afferent suppression is controlled by genes apparently mapping in the I-J subregion of the H-2 complex since I-J-incompatible mice are not suppressed by LH8-105 TsF injection. This inducer-type TsF induces second-order effector suppressor T cells only in HEL-primed mice indicating the primary role of antigen, in association with H-2 (I-J) products, in the afferent portion of this suppressive circuit.

Composition of a suppressor factor that inhibits the immune response to lactate dehydrogenase B

Hybridomas obtained by fusion of lactate dehydrogenase B (LDHB)-activated suppressor T (Ts) cells with the BW5147 thymoma produce a suppressor factor (TsF) that inhibits the proliferation of LDHB-activated helper T (Th) cells. A similar factor (TsE) is contained in the extract of suppressor hybridomas. Both TsF and TsE are specifically retained by LDHB-immunoadsorbent columns. Both consist of two components, an antigen-binding component (ABC) and possibly a major histocompatibility complex (MHC) component. The latter reacts with certain monoclonal antibodies specific for MHC determinants. The two components are covalently associated in the TsF and noncovalently associated in TsE. Mixing of the two components reconstitutes the activity of the TsF or TsE. Disruption of the ABC's tertiary structure results in its inability to reconstitute suppressive activity on mixing with the MHC components. The ABC may contain an intrachain disulphide bond(s). Suppression is obtained when Th cells are incubated first with the ABC and then with the MHC component or vice versa, provided that the incubation period is at least 4 h. The MHC component is also produced by nonsuppressor hybridomas but not by mitogen-stimulated blasts or by the parental thymoma. The TsF is a glycoprotein with a molecular weight of about 120,000 to 160,000. The molecular weight of the ABC is about 76,000-86,000 and of the MHC component about 30,000-37,000.

T suppressor factor activity is due to two separate molecules. The Lyt-1(-)2+I-J+ cells of mice primed with antigen make an antigen binding molecule which is only active when complemented by cofactor made by Lyt-1+2(-)I-J+ cells

Mice primed with picrylsulfonic acid (PSA) and then painted on the skin with picryl chloride produce antigen-specific T suppressor factor (TsF). In contrast unpainted primed mice fail to produce active TsF. This is not due to the absence of the antigen binding part of TsF but to the absence of a cofactor. This cofactor is (a) antigen nonspecific and occurs in potassium chloride extract of normal spleen cells. It also occurs in the 24 hr supernatant of normal cells modified by haptenisation with picryl or the unrelated NP antigen (4-hydroxy-3-nitrophenylacetyl), and in preparations of conventional TsF (PSA/PCl) from painted PSA-primed mice; (b) bears I-J determinants; and (c) is produced by Lyt-1+2(-)I-J+ cells. The antigen binding molecule occurs alone in the supernatant of PSA-primed mice. It lacks I-J determinants and has a molecular weight around 35,000 and 75,000. It is produced by Lyt-1(-)2+I-J+ cells and is only active when complemented by cofactor. However, the complementation is genetically restricted and the restriction maps to the I-J subregion of the MHC.

Two-chain structure of T-suppressor factor: antigen-specific T-suppressor factor occurs as a single molecule and as separate antigen-binding and I-J+ parts, both of which are required for biological activity

Antigen-specific T-suppressor factor (TsF), which acts at the expression stage of the contract sensitivity reaction, was produced by culturing the lymphoid cells of mice injected with picryl-sulphonic (trinitrobenzenesulphonic) acid and then painted with picryl chloride. Supernatant activity was found around 50-60 and 90 kDa on Sephadex gel filtration. The activity at 50-60 kDa was due to two separate (or readily separable) molecules, one antigen binding and the other bearing I-J determinants as shown by affinity chromatography on insolubilized antigen and anti-I-J. These two separate molecules were inactive alone but complemented each other and may be designated as the variable chain of TsF (TsFv) and the I-J+ chain. The use of gel filtration and sequential absorption of individual pools on anti-I-J antibody followed by antigen, together with a complementation assay, also showed a TSFv chain at 30-40 kDa and an I-J+ chain at 20-30 kDa. The higher-molecular-weight activity around 90 kDa was due to a single molecule which was both antigen binding and I-J+. This molecule dissociated on treatment with the reducing agent dithioerythritol followed by alkylation into two separate chains, one antigen binding and the other I-J+, both of which were required for activity. There was a requirement for genetic matching between the antigen-binding chain (TsFv) and the I-J+ chain for biological activity. These data support a two-chain model of TsF in which TsFv and the I-J+ chain occur as a single disulphide-bonded molecule around 90 kDa, or as two separate (or readily separable) chains of lower molecular weight which were inactive alone but complemented each other.

Functional roles of two polypeptide chains that compose an antigen-specific suppressor T cell factor

The functional roles of the two polypeptide chains that compose the T cell suppressor factor (TsF) that mediates the antigen-specific and genetically restricted suppressor function were studied by using the heavy or light chains isolated from the conventional TsF or the 11S and 13S mRNA translation products of TsF. Either the heavy or the light chain of mRNA translation products reconstitutes the active TsF that suppresses the antibody response in an antigen-specific and genetically restricted manner when it is combined with the isolated heavy or light chain from the conventional TsF. As a consequence, the antigen-binding heavy chain mediates the antigen specificity of TsF. On the other hand, the I-J-positive light chain works as an element to determine the genetic restriction specificity. Thus, the identity of the histocompatibility between the I-J haplotypes on the light chain and the responding cell is essential for the functional expression of TsF. No genetic preference, however, was observed, in the association of the heavy and light chains of TsF.

Cell-type-specific cDNA probes and the murine I region: the localization and orientation of Ad alpha

Labeled cDNA probes highly enriched for B-cell-specific (B-T) and T-suppressor-cell-specific (Ts-B) sequences were used to screen a set of genomic cosmid clones spanning 230 kilobases of the murine immune response (I) region. With the B-cell derived probe, four I-region genes were detectable (A beta, E beta, E beta 2, and E alpha), as well as an additional (fifth) region of hybridization. The T-cell probe, prepared from a putative I-J positive suppressor cell hybridoma, was negative in a parallel experiment. A genomic fragment corresponding to the new region of hybridization seen with the B-cell cDNA probe identified a discrete mRNA species in RNA blotting analysis that had a pattern of expression strikingly similar to E alpha mRNA in a variety of lymphoid tumor lines. This fragment was also used to isolate cDNA clones from a library highly enriched (20-40 times) for B-cell-specific sequences (selected cDNA cloning). DNA sequence analysis of one of these cDNA clones indicates that this gene encodes the A alpha molecule of the d haplotype (Ad alpha). These findings establish that the order of the class II genes in the Ia complex is as follows: centromere-A beta-A alpha-E beta-E beta 2-E alpha.

Antigen-specific suppressor T cell interactions. II. Characterization of two different types of suppressor T cell factors specific for L-glutamic acid50-L-tyrosine50 (GT) and L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT)

We have previously reported that two types of suppressor T cell factors (TsF) specific for L-glutamic acid50-L-tyrosine50 (GT) or L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT) can be distinguished based upon differences in their ability to suppress responses by allogeneic mice. Injection of GAT or GT induces a suppressor T cell subset that produces an antigen-binding, I-J+, genetically unrestricted, specific suppressor factor (TsF1). Injection of this factor plus small amounts of antigen induces a second-order suppressor T cell that produces an antigen-binding, I-J+, genetically restricted, specific suppressor factor (TsF2). In this report, we demonstrate that these two factors are also biochemically distinct. Monoclonal TsF1 molecules are composed of a single polypeptide chain that bears both the antigen-binding site and I-J determinant, whereas TsF2 molecules are composed of two disulfide-linked polypeptide chains, one of which is antigen-binding and I-J-, and the other, nonantigen-binding, I-J+. The antigen-binding chain must be added at culture initiation to achieve suppression, but the I-J+ chain can be added as late as day 3 with complete suppression observed. However, isolated chains from TsF2-producing hybridomas derived from three different haplotypes were unable to suppress immune responses when chains from heterologous TsF2 were mixed. Indirect evidence is presented that suggests that this restriction is because the chains fail to interact rather than the inability of the target cells to recognize both chains.

The role of I-J and Igh determinants on F1-derived suppressor factor in controlling restriction specificity

In the 4-hydroxy-3-nitrophenyl acetyl (NP) contact sensitivity system, the activity of third-order suppressor cells and their factors is restricted by H-2(I-J) and Igh linked genes. The present report analyzes the specificity of NP-specific Ts3 cells and factors derived from H-2 and Igh heterozygous (B6 X C3H)F1 mice. Two approaches were used. First, heterogeneous populations of F1 Ts3 cells were activated in vitro and then assayed in Ts3-depleted recipients which carried different combinations of H-2 and Igh alleles. The second approach was to hybridize the Ts3 cells and analyze the specificity of the F1-derived TsF3. The combined data demonstrated four functionally distinct populations of Ts3 cells. The activity of each population was restricted by a particular combination of H-2 and Igh haplotypes. Thus, Ts3 cells derived from F1 donors can demonstrate an apparent scrambling of H-2 and Igh restriction specificities. There was functional allelic exclusion of the H-2(I-J) and Igh determinants expressed on (B6 X C3H)F1 hybridoma-derived TsF3. Thus, TsF3 from each cloned hybridoma line expressed only one set of I-J and Igh determinants. Furthermore, there was a complete correlation between the I-J and Igh linked determinants expressed on TsF3 and the restriction specificity. In view of the recent findings on the molecular biology of the I-J region, an alternative interpretation of the role of I-J determinants on suppressor cells and factors is offered.

The mouse T cell receptor: structural heterogeneity of molecules of normal T cells defined by xenoantiserum

We have previously demonstrated that T lymphomas may express clonally specific epitopes that are carried by a T-cell-restricted, disulfide-bonded heterodimeric glycoprotein. We have used a monoclonal antibody, 124-40, to isolate the lymphoma-specific antigen and raise a xenoantiserum to the molecule. This antiserum immunoprecipitates a family of disulfide-bonded dimers from normal thymocytes and T cells, but is unreactive with B cells. Peptide maps prepared after limited proteolytic digestion indicate that the molecules from the different cell populations have homologous primary structures. Comparison of two-dimensional tryptic peptide maps indicate that, in addition to several common peptides, the molecules exhibit considerable structural heterogeneity. Taken together, these data indicate that the T-cell-specific heteroduplex has regions of constant and variable structure consistent with the properties expected for the T cell antigen receptor.

Structural analysis of antigen-specific Ia-bearing regulatory T-cell factors: gel electrophoretic analysis of the antigen-specific augmenting T -cell factor

An antigen-specific T-cell factor (TaF) that specifically augments the antibody response was purified and biochemically analyzed by NaDodSO4/polyacrylamide gel electrophoresis and isoelectric focusing. Biosynthetically labeled TaF was separated from the Nonidet P-40 extract of T-cell hybridoma FL10, which produces a keyhole limpet hemocyanin-specific TaF, by affinity chromatography either with antigen or with monoclonal anti-I-A antibodies. The material thus obtained was composed of two different types of molecules of molecular weights of 67,000 and 33,000 under nonreducing conditions. After reduction with dithiothreitol, all the molecules migrated to the position of molecular weight 33,000. The absorption studies with immunoadsorbents of antigen and antibodies revealed that the intact TaF is a heterodimer of two discrete polypeptide chains, one carrying a determinant detectable by a monoclonal anti-Tindd directed to an Igh-I -linked allotypic structure of T cells and being associated with the antigen-binding site and the other expressing a unique determinant controlled by the I-A subregion of murine H-2 major histocompatibility complex but being different from known class II polypeptide chains. The antigen-binding polypeptide has an isoelectric point of pH 5.6, and the I-A polypeptide has an isoelectric point of pH 6.3.

RNA transcripts for I-J polypeptides are apparently not encoded between the I-A and I-E subregions of the murine major histocompatibility complex

The I-J subregion of the mouse major histocompatibility complex has been reported to encode antigenic determinants expressed by suppressor T cells. Previously, cosmid clones were obtained from mouse sperm DNA that contain all of the sequences between the I-A and I-E subregions, where I-J has been mapped genetically. However, hybridization of these sequences to RNA prepared from several I-J-positive suppressor T-cell hybridomas did not reveal the presence of a transcript. In addition, no rearrangements in this DNA were detected in the suppressor T cells that we have analyzed. Our results indicate that the I-J polypeptides are not encoded between the I-A and I-E subregions of the major histocompatibility complex. We discuss several hypotheses concerning the possible location and expression of I-J genes.

Idiotypic and fine specificity analysis of a (4-hydroxy-3-nitrophenyl)acetyl (NP)-specific suppressor T cell hybridoma at the level of cell surface structures, isolated receptor material and functional suppressor factor

The (4-hydroxy-3-nitrophenyl)acetyl (NP)-specific T suppressor cell hybridoma 7C3-13 was established by fusing splenic B10.BR T cells enriched on NP-coated petri dishes with the AKR thymoma BW5147. 7C3-13 was selected by anti-NPb idiotypic and anti-I-Jk antibodies in microcytotoxicity tests. The hybridoma expressed H-2k, I-Jk, Qa-1, Thy-1.1 as well as idiotypic (binding site-related) and framework Ig VH determinants, while it was negative for I-A, I-E/C, Thy-1.2, Lyt-1, Lyt-2 and Ig constant region determinants. Hapten-binding receptor material could be isolated from 7C3-13 cells on NP-coupled nylon nets and functionally active T suppressor factor (TsF) could be extracted from the hybridoma. Both types of soluble molecules express NPb idiotype, but the TsF carries I-J determinants in addition while the isolated receptors do not. The molecular weight of the isolated receptor material is 80 000, that of the TsF activity is 27 000 and 57 000-64 000, respectively. We thus were able to show that NP-binding molecules can be obtained in the form of cellular surface receptors, isolated receptor material and extracted TsF from one and the same, monoclonal, cell source.

T cell hybrids that express a VH idiotope-related determinant on a glycoprotein distinct from H-2, Thy-1, and Lyt-1 molecules

Two mouse monoclonal antibodies to chicken immunoglobulin VH-associated idiotypes (Id), CId-1 and CId-2, were used as probes for Id determinants on mouse T cells. CId-1, which recognized chicken antibodies to N-acetyl glucosamine (NAGA), and approximately 0.4% of chicken T lymphocytes also reacted with approximately 0.2% of BALB/c splenic Thy-1.2+ cells. When enriched CId-1+ splenic T cells from NAGA-immune BALB/c mice were fused with the AKR thymoma BW 5147 cell line, 2 of 72 resulting hybrids, termed CId-1A and CId-1B, were reactive by indirect immunofluorescence with the CId-1 antibody. CId-1 determinants were expressed both in the cytoplasm and on the cell surface. Immunofluorescence studies revealed that both CId-1+ T cell hybrids were phenotypically identical: CId-2-/Ig-/Lyt-1+2-/Thy-1.2+/II-2d+/I-Ad-/I-Ak-/I-Jd+/I-Jk+. Incubation of CId-1B hybrid cells with concanavalin A or lentil lectin resulted in capping of the CId-1 determinant, whereas incubation with pokeweed mitogen, lipopolysaccharide, phytohemagglutinin, and wheat germ agglutinin had no effect on the cell surface distribution of the CId-1 molecule. Trypsin or pronase treatment resulted in the loss of detectable CId-1 determinant on the cell surface. Treatment of CId-1B cells with tunicamycin also reduced the immunofluorescence intensity of the surface CId-1 determinant, but had no effect on its cytoplasmic expression. CId-1 antibody-induced capping of the CId-1 marker did not affect the surface distribution of Lyt-1, Thy-1.2, H-2d, I-Jd, or I-Jk molecules. Conversely, capping of I-Jd and I-Jk determinants did not alter the surface distribution of CId-1. These results suggest that the CId-1 determinant is on a glycoprotein that is not physically linked to the Lyt-1, Thy-1.2, H-2d, I-Jd, and I-Jk molecules. The clonal restriction of CId-1 expression by T cells suggests that the CId-1+ molecule could be a T cell antigen receptor.

Presence of IgT-C and I-A subregion-encoded determinants on distinct chains of monoclonal antigen-specific augmenting factor derived from a T cell hybridoma

Monoclonal antibodies specific for mouse T cell alloantigens, Tindd and Tsud, linked to the Igh-1 locus on chromosome 12, were used to directly define the antigen-binding molecule produced by a cloned hybridoma. The T cell hybridoma, FL10, was established from antigen-binding T cells of A/J mice. FL10 produces an antigen-specific augmenting T cell factor (TaF) that bears a unique I region-controlled determinant (I-A) and has antigen-binding capacity. The Tindd, but not the Tsud, determinant was detected on the surface of FL10. The presence of both Tindd and I-A subregion-controlled determinants on FL10-derived TaF was directly demonstrated by the adsorption of TaF with immunoadsorbents prepared with monoclonal antibodies. The Igh-1-linked T cell alloantigen, Tsud, was not found on TaF. Further experiments indicated that Tindd is present on the antigen-binding polypeptide chain and not on the second chain bearing the I-A determinant. Despite the presence of the Tindd determinant on hybridoma-derived TaF, augmentation induced by TaF was restricted by the H-2 type of the responding mice and not by the Igh-1 allotype.

Clonotypic structures involved in antigen-specific human T cell function. Relationship to the T3 molecular complex

Monoclonal antibodies were produced against a human cytotoxic T cell clone, CT8III (specificity: HLA-A3), with the view of defining clonally restricted (clonotypic) surface molecules involved in its antigen recognition function. Two individual antibodies, termed anti-Ti1A and anti-Ti1B, reacted exclusively with the CT8III clone when tested on a panel of 80 additional clones from the same donor, resting or activated T cells, B cells, macrophages, thymocytes, or other hematopoietic cells. More importantly, the two antibodies inhibited cell-mediated killing and antigen-specific proliferation of the CT8III clone but did not affect the functions of any other clone tested. This inhibition was not secondary to generalized abrogation of the CT8III clone's function, because interleukin 2 responsiveness was enhanced. To examine the relationship of the structures defined by anti-clonotypic antibodies with known T cell surface molecules, antibody-induced modulation studies and competitive binding assays were performed. The results indicated that the clonotypic structures were associated with, but distinct from, the 20,000-mol wt T3 molecule expressed on all mature T lymphocytes. Moreover, in contrast to anti-T3, anti-Ti1A and anti-Ti1B each immunoprecipitated two molecules of 49,000 and 43,000-mol wt from 131I-labeled CT8III cells under reducing conditions. The development of monoclonal antibodies to such polymorphic T cell surface structures should provide important probes to further define the surface receptor for antigen.

Monoclonal alloantibodies specific for the constant region of T cell antigen receptors

We established three distinct monoclonal antibodies (7C5, 7D1; IgM and 6A4; IgG1) by the fusion of P3U1 and BALB/c (Igh-1a) spleen cells hyperimmunized with T cell blasts from the immunoglobulin heavy chain (Igh) allotype congenic CB-20 (Igh-1b) mice. The 7C5 or 6A4 antibody reacts with the constant region determinants on the antigen-binding molecule (Ct) of the antigen-specific suppressor T cell factor (TsF) or augmenting T cell factor (TaF), respectively. The 7D1 antibody, however, recognizes the shared determinants on the Ct molecules of TsF and TaF. Genetic studies of determinants recognized by these monoclonal antibodies have also suggested that the distinct Ct molecules of TsF and TaF are encoded by two discrete genes linked to the Igh-1b genes, which are located on the right side of the variable genes of Igh on the 12th chromosome. By using the immunoadsorbent columns of 6A4 antibody and anti-I-Ab, TaF, in a manner similar to TsF, was demonstrated to be composed of two chains, i.e., the Ct molecules and the I-A-encoded products. Furthermore, the Ct-bearing molecules were shown to possess the antigen-binding moiety.

Fine antigenic specificity and genetic restriction of lysozyme-specific suppressor T cell factor produced by radiation leukemia virus-transformed suppressor T cells

Culture supernatants obtained from a radiation leukemia virus-transformed, hen egg-white lysozyme (HEL)-specific, suppressor T cell line are able, when injected into mice, to specifically suppress the anti-HEL antibody response. Suppression is observed on both primary and secondary anti-HEL antibody responses evaluated by direct and developed hemolytic plaque assays. Culture supernatants from this HEL-specific suppressor T cell line do not suppress the antibody response induced by a structurally related lysozyme, demonstrating the presence in the culture supernatant of a suppressor factor endowed with fine antigenic specificity. The suppressor factor is able to selectively suppress the anti-HEL antibody response induced by the N-terminal C-terminal peptide of the HEL molecule indicating that the fine specificity of this factor is restricted to an antigenic epitope present in this region of the HEL molecule. The suppressive activity is restricted by genes located within the H-2 complex and analysis of the suppression induced in recombinant mice demonstrates that the interaction between HEL-specific suppressor T cell factor and its cellular target requires identity in the I-J region of the H-2 complex.

Products of the IgT-C region of chromosome 12 are maturational markers for T cells. Sequence of appearance in immunocompetent T cells parallels ontogenetic appearance of Tthyd, Tindd, and Tsud

Monoclonal antibodies specific for three T cell alloantigens linked to the immunoglobulin complex on chromosome 12 were used to establish the order of expression of these antigens on immunocompetent cells and in ontogeny. Modification of monoclonal antibodies with fluorescein isothiocyanate (FITC) and use with anti-FITC and complement has amplified lytic capacity of the monoclonals and allowed us to complete a distribution study of Tsud, Tindd, And Tthyd alloantigens on immunocompetent cells. Tthyd is expressed on both cortisone-sensitive and cortisone-resistant thymocytes; Tsud and Tindd are on "mature" cortisone-resistant cells. Tthyd is also expressed on a Thy-1.2-bearing recirculating marrow cell but is undetectable in the peripheral T cell pool. In contrast, resting spleen and lymph node T cells express Tsud and Tindd; antigen-activated populations express these two cells in high frequencies. These antigens must be markers for relatively differentiated cells because "nude" animals, which have pre-T cells, fail to express these determinants. All three antigens segregate independently in our T cell hybrids, arising from adult peripheral node cells, supporting the hypothesis that these are three separate structural products of a gene complex. In contrast, fetal T cell hybrids fail to express these antigens. The appearance of all three antigens on the cell surface in ontogeny is postnatal; Tthyd is expressed at days 1-2, Tindd at days 2-3, and Tsud at days 5-6. If the T cell isotype genes are organized similar to the immunoglobulin loci, then the parallels in maturational expression on immunocompetent cells and in ontogeny would lead one to speculate a gene order of Tthyd leads to Tindd leads to Tsud. Orientation with respect to the centromere is unknown.

Genetic chasing of T helper cell idiotype and allotype genes

The present experiments were performed to study whether the genes responsible for the expression of T-idiotypes and allotypes could be mapped in relation to immunoglobulin (Ig) heavy chain V- and C-genes. Use was made of our antiserum 5936, which detects idiotypes in B6 and anti-B10.BR sera and on Lyt-1+, 2.3-B6 anti-B10.BR T-cell populations, and antiserum 6036, which detects allotypes on Lyt-1+, 2.3-B6 T cells, but which does not react against Ig. The reactivity of these antisera with T cells from (B6 X C3H.OH) X C3H.OH backcross mice and CBA-allotype congenic B6 mice was investigated because 5936 idiotypes and 6036 allotypes appeared to be associated with Igh-1b genes (B6) and not with Igh-1j genes (C3H.OH,CBA). Our results will show, first, that 5936 idiotypes on Lyt-1+, s.3-B6 anti-B10.BR T cells are synthesized by genes linked to Igh-1b allotype genes and they are situated either within Ig heavy chain V-genes or centromeric to them. Second, our results will show that 6036 allotypes on Lyt-1+, 2.3-B6 T cells are produced by genes also linked to Igh-1b-allotype genes, and the 6036 allotype genes are situated between Ig-VH and prealbumin genes.

A critical analysis of the T cell hybrid technique

The T cell hybridization technique can be used to prepare continuous cell lines which express the antigen specificity and function of T cells within the milieu of a proliferating lymphoma. Technical details for the preparation and maintenance, selection and analysis of T cell hybrids are defined. Techniques for cloning of hybrid cells and production of hybrid-derived tumors are also presented. Parameters influencing the hybridization frequency and the production of functional hybrids are discussed. A variety of T cell subsets, including suppressor cells and delayed-type hypersensitivity effector cells as well as T cells maintained on TCGF, are excellent sources of primary parents for hybridization. When BW 5147 is used as the T lymphomas parent in these experiments, the resulting hybridization frequencies range between 10 and 434 X 10(-7). We have had moderate success using YAC-1; however, additional lines such as L5178Y, BALENTL 5, EL4 BU and S491TB.2 have proved ineffective as sources of T lymphoma parents. The technique of T cell hybridization is evaluation in terms of retention of differentiated functions and the stability and growth characteristics of the resultant hybrids.

Cell-free translation of a biologically active, antigen-specific suppressor T cell factor

In vitro synthesis of an antigen-specific T cell suppressor factor (TsF) has been accomplished by using partially purified poly(A)-containing RNA in a rabbit reticulocyte lysate cell-free translation system. The poly(A)-containing mRNA was isolated from a cloned T cell hybridoma that constitutively produces a TsF specific for the synthetic polypeptide antigen poly-(LGlu60LAla30LTyr10) (GAT). The RNA was fractionated by size and translated in vitro. The 16S RNA fraction stimulated synthesis of a biologically active protein that specifically suppressed both the GAT-specific antibody response by spleen cells in vitro and the proliferation response to GAT by lymph node T cells from GAT-primed mice. Further, the suppressor factor had a binding site for GAT, a determinant encoded by the I subregion of the major histocompatibility complex (MHC), and an apparent Mr 19,000 estimated by functional assays on protein separated by NadodSO4/polyacrylamide gel electrophoresis. These results indicate that virtually no posttranslational modifications (other than proteolytic cleavage) are necessary to obtain biologically active TsF. Hence, the presence of carbohydrate or other chemical groups does not contribute to either the serological properties of GAT-TsF or its biological properties.