Selective participation of immunoglobulin V region and major histocompatibility complex products in antigen binding by T cells

Differentiation antigens in human T-cell activation: evidence that anti-VH antibodies react with a membrane structure on human T lymphocytes distinct from the antigens detected by monoclonal antibodies of the OKT and Leu series

The effect of a panel of monoclonal antibodies and heteroantibodies on T-cell proliferation in various assay systems has been examined. The antibodies tested were directed against T-cell differentiation antigens, HLA-DR antigens, and structures defined by an anti-human VH antiserum. As the test cell system highly purified subpopulations of T-cell growth factor (TCGF)-dependent T-cell lines activated either by mitogen or antigen were used. A survey of the data indicates the following: (1) Mitogenic and antigenic triggering of T lymphocytes are mediated through partly different membrane structures. (2) Antigenic stimulation by purified protein derivative (PPD) as well as polyclonal activation induced by OKT3/anti-Leu 4 monoclonal antibodies can be inhibited by heteroantibodies raised against human immunoglobulin VH fragments thus pointing to a possible connection between the antigens detected by these antisera. (3) There does not seem to be differences between the two major subpopulations of T lymphocytes (i.e., helper/inducer and suppressor/cytotoxic cells) as to how they respond to antigens or mitogens in the investigated assay systems. (4) A clear distinction was found between T blasts specific for PPD and allogeneic cells as compared to cytotoxic T cells (CTL), as the T4 and T8 antigens seem to be functionally important for antigen recognition among CTL but not for the blasts proliferating in response to PPD and allogeneic cells. (5) An inhibitory effect of OKT3/anti-Leu 4, OKIa1, and anti-HLA-DR on TCGF-dependent growth was detected, possibly indicating a steric relationship between these antigens and TCGF receptors on mitogen-induced T blasts. (6) Soluble factors obtained after incubating adherent cells with OKIa1 and anti-HLA-DR antibodies seemed to have an inhibitory effect on overall T-cell proliferation stressing the importance of studying the T-cell activation process at different levels in these kinds of experiments. (7) The results further suggest a complexity in the build up of antigen receptors on the various T-effector cells, perhaps also involving receptors for growth factors, HLA-DR antigens, and receptors for the latter.

Monoclonal anti-VH antibodies recognize a common VH determinant expressed on immunoglobulin heavy chains from various species

Our previous work using rabbit antibodies to the variable region of MOPC315 myeloma heavy chain (VH) has indicated the existence of framework determinant(s) common to many murine heavy chains. Here we report the characterization of anti-VH monoclonal antibodies (mAb) prepared in an attempt to elucidate the nature of the common VH determinant. We immunized AKR/J mice with a purified VH315 fragment and generated somatic cell hybrids by the fusion of the immune AKR/J splenocytes with the NS1 myeloma cells. Thirty-seven common anti-VH and 57 subgroup VHI-specific hybridomas have been established and characterized. Whereas the anti-subgroup mAb seemed to react with a determinant unique to the MOPC315 (mouse VHI) subgroup, all the anti-VH mAb reacted with myeloma heavy chains of different VH subgroups, class and allotypes. Antibody competition studies revealed that the VH subgroup determinants are distinct from the common VH determinants and that both were also recognized by the rabbit polyclonal antibodies. The common VH determinants were found to be "hidden" determinants on intact immunoglobulin molecules being exposed only on isolated heavy chains. Furthermore, they are sequential determinants since they are preserved on fully denatured heavy chains. The common VH determinants are shared by immunoglobulins of a wide range of vertebrates from amphibia to man and thus represent antigenic structures which were highly conserved throughout evolution.

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.

The preparation of mouse VH fragments and the characterization of heterologous anti-mouse VH antibodies

VH fragments were prepared from several mouse IgM molecules by cyanylation. In all cases VH fragments were purified to homogeneity by using Ig light chain affinity columns. Several different anti-VH antisera were prepared in rabbits and the specificities of these antibodies were studied. Two patterns of cross-reactivities were observed: (a) some anti-VH antibodies reacted only with closely related VH molecules, e.g., anti-VH HPC52 anti bodies reacted only with VH of phosphorylcholine-binding myeloma or hybridoma proteins, and concordantly, stained about 4% of mouse spleen B cells; (b) on the other hand, antisera-like anti-VH 104E and 8916 antibodies were very cross-reactive. Binding assays showed that both of these anti-VH antibodies reacted with 50-60% of mouse immunoglobulins. However, they recognized mainly nonoverlapping populations of mouse immunoglobulins, and thus the pool of these antibodies reacted with about 95% of mouse VH regions. Concordantly, anti-VH 104E antibodies stained in the fluorescence-activated cell sorter (FACS) analysis more than 50% of mouse spleen B cells. Cross-reactive anti-VH antibodies ("anti-framework") did not stain T cells nor did they immunoprecipitate VH-like molecules which were synthesized by T cells.

Defective induction of antigen-reactive proliferating T cells in B cell-deprived mice. II. Anti-mu treatment affects the initiation and recruitment of T cells

Mice injected from day of birth onwards with rabbit anti-mouse IgM (antim-mu) antibodies were found to be B cell-deficient and defective for the induction of antigen-reactive proliferating T cells (TPRLF). This defective induction was not due to the absence of circulating antigen-specific antibodies since the daily injections of such antibodies during exposure to antigen did not restore the ability of anti-IgM treated animals to generate TPRLF. Analyzing the cellular events implicated in the induction of virgin antigen-reactive T cells, anti-mu-treated mice manifested impairment of the three interacting cell types involved in the induction of TPRLF. Thus, peritoneal and splenic antigen-presenting cells from such animals were impaired in their capacity to signal a primary antigen-specific T cell reaction. Their splenic lymphocytes could not function as initiator cells in transferring immunogenic signals to recruit TPRLF in normal recipients. Potent antigen-specific splenic initiator cells failed to induce the recruitment of specific TPRLF in anti-mu-treated mice. The defective induction of TPRLF in anti-mu-treated mice may be due to a functional impairment of cells expressing membrane-bound IgM molecules which seemingly play a central role in the transfer of immunogenic signals for the recruitment of antigen-specific circulating T cells. We suggest that splenic B cells function as initiators in the transfer of antigen-induced signals from peritoneal antigen-presenting cells to T cells. These seems to be the primary targets of anti-mu treatment.

Effects of anti-Ig reagents on T cell functions I. Activation of rabbit T cells by anti-allotype antibodies

Rabbit lymphocytes were analyzed by flow microfluorometry, using anti-T cell and anti-Ig reagents. Rabbit T cells and cells expressing surface Ig (B cells) appeared to belong to distinct subpopulations which could be separated on the basis of their selective adherence to nylon wool columns or to anti-Ig-coated dishes. Using flow microfluorometry, no evidence was obtained for the expression of a allotypes (VH framework) on T cells. Separated lymphocyte populations were functionally characterized using an in vitro proliferation assay. B and T cells from rabbit spleen or peripheral blood responded in a differential fashion to B and T cell-specific mitogens and to anti-Ig antibodies. Although such T cells did not respond upon stimulation with anti-Ig antibodies alone, significant proliferation could be induced by simultaneous addition of anti-Ig and T cell growth factor. In addition, activated T cells, derived from lymph nodes of immunized rabbits, generated a proliferative response upon stimulation with anti-Ig reagents alone. The above-mentioned effects on T cells could be obtained using heterologous anti-Ig antibodies or isologous anti-allotype antibodies, directed either against a allotypes (VH framework) or against b allotypes (kappa light chain). Antibodies against the Fc portion of rabbit Ig or against irrelevant allotypic specificities were ineffective in triggering T cells. Fab fragments from anti-allotype antibodies were equally stimulatory for T cells as compared to intact IgG, indicating that cross-linking of Ig-like molecules is not a necessary requirement for anti-Ig-induced T cell activation.

T cell idiotypes recognizing self-major histocompatibility complex molecules: H-2 specificity, allotype linkage, and expression on functional T cell populations

An anti-idiotypic serum (antiserum 5936, B. Rubin et al., J. Exp. Med. 1979. 150: 307) was used to demonstrate receptor sites for self-major histocompatibility complex (MHC) antigens on T lymphocytes. The antiserum was raised by injecting rabbits tolerant to mouse Ig with a B6 anti-CBA (anti-H2k) alloantibody. It recognized a large proportion of T cells from H-2k strains carrying the b, c, d or e allele at the Igh-1 locus, but only a few T cells from H-2k strains with Igh-1 alleles a, f and j. Allotype linkage of the 5936 idiotype was also demonstrated by segregation analysis. The antiserum did not recognize either H-2k B cells or T cells from other H-2 haplotypes despite the presence of a permissive Igh-1 allele. The 5936 idiotype was found to be associated with several different antigen specificities, indicating that it is not located on the binding site for foreign antigen. Furthermore, the 5936 antiserum inhibited the binding of soluble Ik antigens by H-2k, Igh-1b, T cells, and, in the presence of complement, eliminated T cells responding to different antigens in an I-Ak-restricted fashion. Collectively, the data indicate that the structure bearing the 5936 idiotype is a receptor for I-Ak antigens, expressed by strains carrying the I-Ak allele and a permissive allele at the Igh-1 locus. The relevance of this finding to the MHC-restricted recognition of antigens by T cells is discussed.

The still elusive T cell receptor: on the possibility of a common V-gene pool for B- and T-cell-antigen receptor molecules

The contention that VH constitutes a part of T-cell receptors for antigens was probed by purifying rabbit T cells and analysing these cells for non-immunoglobulin VH, i.e. VH not associated with L chain. A number of anti-VH antisera were employed for this purpose, the most important being goat antiserum, reacting with common a1 allotype determinants (allotype determinants expressed on free VH and H chain as well as on intact immunoglobulins), rat antibody against common non-allotype VH determinants (VH framework determinants expressed on VH and H chain as well as on intact immunoglobulins) and chicken antibody against unmasked non-allotype determinants (VH determinants accessible only in the absence of L chain). VH and L chain was quantified by radioimmunoassays on extracts and supernatants from unstimulated T cells as well as from T cells stimulated by concanavalin A and by allogeneic cells. Absolute depletion of Ig-containing and -producing cells was not achieved but in no case was an excess of VH over L chain observed. This indicated that all detected VH originated from cells of the B lineage. The cells were also cultured in the presence of labelled amino acids followed by analysis of detergent extracts and supernatants by immunoadsorption and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) fluorography. Again, no evidence for T-cell VH could be found. Affinity purified anit-VH antibody was used to label viable rabbit T cells through the use of secondary fluorescence-labelled anti-immunoglobulin antibody. No VH-specific labelling of T cells could be observed. Mixed lymphocyte cultures were carried out in the presence of affinity-purified anti-VH antibodies. No inhibition of the reaction could be discerned. The failure to detect T-cell VH is in agreement with the recent finding that the VH-genome in T cells is not rearranged in a functional manner similar to that in B cells.

Defective induction of antigen-reactive proliferating T cells in B cell-deprived mice

Mice were injected from day of birth onward with rabbit anti-mouse IgM antiserum or purified rabbit anti-mouse IgM antibodies. These mice completely lacked Ig-positive cells or serum Ig, as analyzed by specific fluoresceinated antibodies on the fluorescence-activated cell sorter (FACS-II), by polyclonal B cell mitogens and by specific precipitation in agar. These animals were then primed in vivo by antigen emulsified in complete Freund's adjuvant, and, subsequently, their draining lymph nodes were tested for their T cell proliferative responses in vitro, to the relevant antigen and were found to be severely impaired. However, the antigen-presenting capacity of both spleen cells and thioglycollate-induced peritoneal cells was found to be intact.

Monoclonal vs. heterogeneous anti-H-8 antibodies in the analysis of the anti-phosphorylcholine response in BALB/c mice

Biological activities of monoclonal A/J antibodies to the T15 idiotype in BALB/c mice were compared to heterogeneous antibodies raised by conventional immunization procedures. Two monoclonal antibodies, AB1-2 and GB4-10, which are of the gamma 1, chi class, appeared to have identical specificities by binding criteria and reacted similarly to conventional antibodies in their abilities to induce neonatal suppression, inhibit plaque-forming cell induction by phosphorylcholine (PC) antigens and to inhibit specifically, anti-PC plaque-forming cells. However, in functional analyses of anti-PC responses in various strains of mice, discrepancies were noted in the T15 responses as defined by monoclonal antibodies and conventional antisera. This heterogeneity was also observed in adult mice suppressed with the GB4-10 monoclonal antibody. These animals eventually produced an anti-PC responses of AB1-2 idiotype but lacking the GB4-10 marker. These results show that the T15 IgM anti-PC response in BALB/c and other strains of mice is heterogeneous and probably consists of a family of clones. Particular clones can be precisely eliminated by the use of appropriate monoclonal antibodies, and the anti-PC response that eventually recovers is still T15+ but lacking the suppressed clones.

H-2-restricted helper factor secreted by clone hybridoma cells

Biological and serological characteristics of a helper factor secreted by cloned hybridoma cells was described. The factor is carrier specific and contains determinants shared with immunoglobulin VH bu does not react with V kappa- or V lambda-specific antibodies. Presence of four H-2I-controlled antigenic specificities, Ia.ml, Ia.m2, Ia.17, and Ia.m7, was detected. Hence, it is possible that both A beta and E alpha loci may be involved in its control. Helper effect could be obtained only toward B cell sources that shared the H-2K and I-A antigens with the hybridoma cells. Similarly, the factor was absorbed only by spleen cells syngeneic in I-A. Previous studies have demonstrated that this clone binds antigen in an H-2-restricted manner. It follows that H-2-restricted helper cells produce H-2-restricted helper factors. Hence, they support the view that specific T cell factors may represent secreted T cell receptors.

Rabbit antisera with specificity for isolated mouse T-lymphocyte receptors

Rabbit antibodies obtained after immunization of mouse immunoglobulin (MIg)-tolerant rabbits with B6 anti-CBA IgG and having specificity for B6 anti-CBA IgG and T-cell receptors (antiserum 5936) were used to isolate 5936-reactive molecules from B6 anti-CBA mixed lymphocyte culture supernatants. Such 5936-reactive molecules were produced by the B6 T cells, and they did not react with rabbit anti-MIg antisera. They had a mol. wt of 50,000-75,000, and were single-chain polypeptides that did not react with concanavalin A (Con A)--Sepharose. These molecules were in turn injected into rabbits, and the antisera thus obtained had the following characteristics: (1) they reacted against B6 anti-CBA T-cell receptor material but not against B6 anti-CBA IgG; (2) they reacted with about 35% of B6 (H-2b, Ig-1b) anti-CBA T cells, 25% of B6 Con A blasts and 0-10% of normal B6 T cells but not with B6 lipopolysaccharide (LPS) blasts, C3H.B10 (H-2b, Ig-1j) anti-CBA or CBA anti-B6 T cells, CBA Con A blasts or normal CBA T cells; and (3) they reacted with the same 50,000-75,000 mol. wt, T-cell-derived molecules as did antiserum 5936. The implications of these findings are discussed in relation to the nature of T-cell receptors.

Expression of an antigen receptor on T cells does not require recombination at the immunoglobulin JH-C mu locus

Considerable evidence has accumulated suggesting that the antigen receptor(s) on T cells is coded for by genes for the variable (V) region of the immunoglobulin heavy (H) chains. In B cells, a complete gene for the immunoglobulin VH region is formed by somatic recombination of VH and joining region heavy chain (JH) gene segments [through an intermediate diversity(D) region gene segment]. In an attempt to determine whether a complete immunoglobulin VH region is expressed on T cells that bear an antigen receptor, we analyzed the restriction map of the JH-C mu locus in genomic DNA from two cloned murine cytotoxic T-lymphocyte (CTL) lines specific for the x-ray-induced leukemia RL male 1. We found no rearrangement of the JH C mu locus in the CTL lines, indicating that the T-cell antigen receptor(s) in these CTLs is not coded for by a complete immunoglobulin VH gene formed by joining of VH, (DH), and JH genes. In addition, we determined that C mu genes on both chromosomes were present and that there was no rearrangement of the C alpha, C kappa, or lambda chain genes in these CTL cells.

Lyt-2 and lyt-3 antigens are on two different polypeptide subunits linked by disulfide bonds. Relationship of subunits to T cell cytolytic activity

Lyt-2 and Lyt-3 antigens are carried on separate disulfide-bonded subunits of the same cell surface macromolecules. These are present on thymocytes in a variety of multimeric forms consisting of disulfide-bonded dimers, tetramers, and hexamers of pairwise combinations of three subunits (30,000, 34,000, and 38,000 Mr). From reduced and alkylated Nonidet-P40 thymus extracts, a monoclonal anti-Lyt-3 precipitates only the 30,000 Mr subunit, but not the 30,000 Mr subunit. Almost all of the Lyt-2 and Lyt-3 subunits on the cell are covalently linked by disulfide bonds. However, small amounts of free Lyt-3 subunit was seen in some experiments. Similarly, small amounts of Lyt-2-3- material, consisting of dimers of the 38,000 and 34,000 Mr subunits were identified. Each of the three subunits migrated with a basic charge (pI greater than 8) on two-dimensional gels. Cytotoxic effector cells that are blocked by anti-Lyt-2 and anti-3 can be treated with trypsin and other arginine-specific proteases to remove these antigens. At low concentrations of these proteases, Lyt-3 antigens are selectively removed. After selective removal of Lyt-3 antigens, cytotoxic effector cells are still active and blocking of activity by anti-Lyt-3 is significantly reduced, whereas blocking of activity by anti-Lyt-2 is significantly increased. Neither Lyt-2 nor Lyt-3 is allelically excluded on thymocytes or T cells. These results suggested that the Lyt-2, Lyt-3 macromolecules are associated with but do not serve as the T cell antigen receptor.

The T suppressor cell alloantigen Tsud maps near immunoglobulin allotype genes and may be an heavy chain constant-region marker on a T cell receptor

The mouse T cell alloantigen, Tsud, is expressed on a minority of mature, Lyt-2+ cells, and its expression is controlled by a gene linked to the immunoglobulin heavy chain gene cluster, Igh. Tsud can be assayed by immunofluorescence staining with an antiserum made in BALB/c mice against C.AL-20 concanavalin A blasts. This antiserum can also be used to induced T suppressor cells in mice expressing Tsu(d). Both of these assays were used to type several panels of recombinant inbred strains and Igh recombinant strains to accurately map the Tsu(d) locus. The Tsu(d) gene is located very near the heavy chain constant-region genes, Igh-C, on the side toward the prealbumin gene, Pre-1. Tsu(d) is not among the heavy chain variable-region genes, Igh-V, and thus is not a variable-region framework allotype, subgroup determinant, or idiotype. The map position suggest that the Tsu(d) antigen is a constant region allotypic determinant on the as yet uncharacterized T cell receptor.

H-2-restricted antigen binding by a hybridoma clone that produces antigen-specific helper factor

Somatic cell hybrids were prepared by fusing the AKR mouse lymphoma BW-5147 with splenic T cells from mice immunized with 4-hydroxy-3-nitrophenylacetic acid (NP) conjugated to chicken serum globulin (CG). From 500 fusion lines 11 were selected on the basis of binding radioiodinated NP-CG. The autoradiographic binding assay was based on previous findings which showed that Lyt-1+ T cells need a lymphokine, lymphocyte-activating factor (LAF), for optimal antigen binding and that they bind preferentially a self-Ia-associated antigen complex, IAC, which is released by adherent cells upon incubation with antigen. Six of the 11 antigen-binding positive lines were tested for helper activity and specific helper factor production in vitro. All of them were found to be positive. One clone was characterized in more detail. It secretes a CG-specific helper factor that contains immunoglobulin heavy chain variable region and I-A determinants. The hybridoma cells bind Ia-containing CG complexes specifically. For binding they need to be treated with LAF, and the binding is restricted to syngenicity in H-2 between the adherent cells used to produce IAC and the antigen-binding hybridoma cells. Regular CG does not bind significantly and does not compete even at high excess with the binding of CG-IAC. These data are interpreted to suggest that the antigen is bound by cells of a clone functional helper T-cell hybridoma line in conjunction with products controlled by H-2I and that the receptor of these cells may have considerably higher affinity for Ia-associated than for regular antigen.

Antigen-binding receptors on T cells from long-term MLR. evidence of binding sites for allogeneic and self-MHC products

Antibody inhibition of radiolabelled stimulator membrane vesicle binding by T blasts activated in the mixed lymphocyte reaction (MLR) was used to identify responder-cell determinants involved in the binding phenomenon. Antisera or monoclonal antibodies against Thy-1, Lyt-1, Lyt-2 and Ly-6 antigens were not inhibitory. However, antibodies against heavy-chain V region (VH) determinants strongly inhibited vesicle binding by both primary and long-term MLR blasts. Anti-Ia (both alloantisera and monoclonal reagents) caused inhibition of antigen binding by primary MLR blasts only. T blasts from long-term MLR lines were neither Ia-positive, nor susceptible to blocking of antigen binding with anti-Ia. However, these cells were capable of specifically absorbing soluble syngeneic Ia material, with the concomitant appearance of vesicle-binding inhibition with anti-Ia sera. Acquisition of syngeneic Ia by T blasts was effectivelly blocked with the anti-VH reagent. Passively bound self-Ia did not interfere with vesicle binding in the absence of anti-Ia. These results strongly suggest the existance of specific self-Ia acceptor sites closely linked to the receptors for stimulator alloantigens on T cells proliferating in MLR. A receptor model based on these findings is briefly discussed.

Major histocompatibility complex-restricted and unrestricted T helper cells recognizing minor histocompatibility antigens of B cell surfaces

The present experiments analyze the functional properties of helper T cells specific for "minor" histocompatibility antigens. T cells from C3H/HeJ mice, primed in vivo and highly enriched in vitro for reactivity to membrane antigens of C3H/Tif B cells, specifically proliferate, and provide polyclonal help to splenic B cells from strains carving a variety of different H-2 haplotypes on C3H or BALB backgrounds, while failing to respond to cells carrying the same H-2 haplotypes on C57BL or A backgrounds. Since it has been previously demonstrated (A.A. Augustin and A. Coutinho, J. Exp. Med. 1980. 151: 587) and B cell activation in this system strictly requires direct, specific recognition of B cell surface antigens by helper cells and does not result from the production of soluble "mitogenic" or "nonspecific helper factors", it is concluded that this phenomenon represents specific, major histocompatibility complex (MHC)-unrestricted T cell help. In addition, it has now been found that expression of helper activity requires viability of the helper cells and is partially radiation-sensitive. Lack of MHC restriction is not a general property of specific helper cells which directly recognize B cell "minor" antigens, since BALB.C3H anti-C3H/Tif T cells appear to be restricted by H-2 in their polyclonal helper activity. The helper activity mediated by specific anti-"minor", H-2 restricted helper cells could not be inhibited by anti-VH antibodies, and the inhibition obtained with anti-Ia antibodies appeared to operate at the level of B cell induction, rather than at the level of helper cell activation.

Surface component of primate thymus-derived lymphocytes related to a heavy chain variable region

In a study designed to determine whether T cells of man and higher primates express a surface component related to the variable region of immunoglobulin heavy chain (VH), chickens were immunized with the purified VH fragment of a monoclonal Waldenström macroglobulin. The antibody preparation reacted with a mu chain determinant contained in the Fd fragment and with individual determinants characteristic of the orginal Waldenström protein. As estimated by immunofluorescence analysis, a subpopulation of normal human peripheral T cells (approximately 30%) bound the anti-VH antibody. B-Cell lymphoma lines grown in vitro, as well as some T-cell leukemia lines of the cotton-topped marmoset (Sagiunus oedipus), also bound the anti-VH antibody. The VH-bearing component of the T-cell line 70-N-2 was labeled biosynthetically by incorporation of [3H]leucine and was precipitated specifically by anti-VH antibody. This component was characterized by an apparent mass of 70,000 daltons as assessed by polyacrylamide gel electrophoresis under reducing conditions in buffers containing sodium dodecyl sulfate. These data provide direct support for the hypothesis that some T cells express and synthesize a component related to immunoglobulin heavy chains.

Antibodies to immunoglobulin heavy chain variable regions protect helper cells from specific suicide by radiolabeled antigen

The antigen-binding receptor of helper T cells was studied by radioactive antigen-caused suicide in vitro. Purified antibodies to immunoglobulin variable regions, obtained from sera of rabbits immunized with isolated VH and VL fragments of mouse myeloma proteins (MOPC 315, XRPC 25), were used to inhibit the binding of radiotoxic antigen. Anti-VH, but not anti-V lambda or anti-V chi inhibited suicide of carrier-primed cells.

Antigen- and receptor-driven regulatory mechanisms. III. Induction of delayed type hypersensitivity to azobenzenearsonate with anti-cross-reactive idiotypic antibodies

Delayed-type hypersensitivity (DTH) to p-azobenzenearsonate (ABA) can be induced in A/J mice with intravenous injection of minute amounts of anti-cross-reactive idiotypic (CRI) antibodies, providing that the animals have been pretreated 2 d earlier with low doses of cyclophosphamide (50 mg/kg). However intravenous injection of the F(ab')2 fragments of the anti-CRI antibodies or subcutaneous administration with anti-CRI antibodies induces comparable immunity in both cyclophosphamide-pretreated and normal nontreated animals. Furthermore adoptive transfer experiments indicate that lymph node cells taken from animals sensitized with anti-CRI 4 d earlier can adoptively transfer immunity to naive recipients. Transfer of immunity is mediated by a population of thymus-dependent (T) cells, which express idiotypic structures on their surface. Treatment of effector cells with either anti-theta serum or anti-idiotypic antibodies plus complement completely abrogated their ability to transfer immunity. In addition idiotype-bearing suppressor T cells induced with ABA-coupled spleen cells inhibit the development of ABA-specific DTH induced with anti-CRI antibodies. Genetic analysis revealed that the ability of anti-CRI antibodies to induce ABA-specific DTH was linked to Igh-1 heavy-chain allotype. Anti-idiotypic antibodies to the major CRI associated with anti-ABA antibodies in A/J mice failed to induce significant immunity in BALB/c mice (H-2d, Igh-1a). Nevertheless, they were able to induce significant immunity in C.AL20 mice (H-2d, Igh-1d) which possess a heavy-chain allotype similar to that of A/J mice.

Correlated expression of VH framework and VH idiotypic determinants on T helper cells and on functionally undefined T cells binding group A streptococcal carbohydrate

Antibodies to framework determinants of the VH and V lambda fragments of MOPC 315 and antisera to the VH idiotype determinants of the A 5 A antibody were used to analyze the antigen receptors of mouse T (and B) cells. This was done by using the antibodies as inhibitors in (a) an assay in which the binding of radiolabeled streptococcal carbohydrate (A-CHO) antigen by primed and unprimed T and B cells is determined and (b) an assay in which the helper activity of group A streptococcal vaccine-primed T cells is determined. The results suggest that the major proportion of primed and unprimed T cells binding A-CHO (70-90%) exhibit VH framework and VH idiotypic determinants. This population appears to include the helper T cells. A minor proportion of T cells (10-30%) express V lambda-related framework determinants and lack VH framework and VH idiotypic determinants. This population does not include T helper cells. Taken together, the data suggest that a subpopulation of T cells, including the helper cells, uses entire Ig VH regions as part of their antigen receptor system.

Polyclonal activation of Ts cells with antiserum directed against an IGH-1 linked candidate for a T-cell receptor constant region marker

An anti-T cell serum raised in allotype congenic mice recognizes the product of a new locus coding for a heavy chain-linked polypeptide found on a subpopulation of T cells. Anti-Tsd raised in BALB/cAnN mice against selected C.AL-20 T cells reacts with a cell surface antigen in virgin animals that is found on 25% of mature thymocytes and Lyt-bearing T cells, but not on prothymocytes, Lyt1 T cells or B cells. The antigen is restricted to strains bearing the Ig-1d and Ig-1e heavy chain allotype haplotypes, and is expressed in the F1 animal. The antigen is unlinked in expression to the Lyt2, H-2, or kappa light chain loci. The antigen is not detected in the hematopoietic cells in the bone marrow and appears to mark only the mature peripheral pool of T cells. As previously reported, the antiserum blocks the binding of suppressor T cells to the cross-reactive idiotype for arsonate, while reagents specific for Fab, Fc and Ig were ineffective. It seems probable that the marker may represent a T cell constant region marker analogous to the Igh products on immunoglobulin. Antiserum against this marker induces in vivo triggering of Ts cells for a wide variety of T-dependent antigens. All subclasses of anti-hapten antibodies are suppressed; no affinity restrictions or clonotype specificity is observed in suppressed adult mice. Results suggest that precursor T cells regulating major serum idiotypes regulate individual idiotypes.

A mature T lymphocyte subpopulation marker closely linked to the Ig-1 allotype Ch locus

An antiserum raised in BALB/c AnN mice against selected CAL.20 T cells reacts with a cell surface antigen in virgin animals that is found on 25% of mature thymocytes and Lyt-2-bearing T cells, but not on prothymocytes, Lyt-1 T cells or B cells. The antigen is restricted to strains carrying the Ig-1d or Ig-1e heavy chain allotype haplotypes. It is expressed in F1 mice. The antiserum blocks the binding of suppressor T cells to the cross-reacting idiotype for arsonate while reagents specific for Fab, Fc or Ig were ineffective. We suggest that the antigen described represents a determinant on the product of a new locus coding for a heavy chain-linked polypeptide found on a subpopulation of T cells.

T helper lymphocytes recognize the VL domain of the isologous mouse myeloma protein 315

The localization of a major determinant on an isologous myeloma protein (M315) which stimulates BALB/c helper T cells was investigated. Augmentation of the adoptive secondary antibody response to NIP-M315 and the idiotype of M315 (Id315) was used as an indicator of helper effects. Spleen cells primed with the light chain of M315 (L315) and its V-domain (VL315) were highly efficient helpers; priming with the fragment containing the two V-domains of M315 (FV315) induced a somewhat weaker helper effect than L315 or VL315. The helper effect was abolished or markedly reduced by treating the primed cells with rabbit anti-brain theta + C. Cells primed with the heavy chain of M315 (H315) effected weak but significant help. The V-domain of H315 (VH315) was incapable of eliciting cells with detectable helper effect. The data indicate that the VL315 embodies a major determinant for T helper lymphocytes. This determinant is expressed on the free VL315 as well as on the complete M315. In contrast, previous studies have shown that BALB/c antibodies produced against Id315 recognize antigenic sites that are only displayed on associated (VL315 + VH315) domains.

Anti-V region framework antibodies affect the ligand binding of VL dimer

The effect of antibodies to the light chain variable region (VL) of protein MOPC-315 (alpha, lambda 2), on the binding of hapten by VL315 dimer or Fv315 (VL + VH) was studied by equilibrium dialysis. Anti-VL did not change the binding properties of Fv but affected the binding properties of VL dimer. At pH 5, the binding properties of VL in the presence or absence of anti-VL were the same, whereas at pH 8, anti-VL reduced the number of ligands bound to VL from two to one. It has previously been shown that VL dimer binds one ligand at pH 5 and two ligands at pH 8, and that VL conformation at pH 5 is tighter. Hence, our results suggest that anti-VL tightens the conformation of VL dimer at pH 8.0 such that it can bind only one ligend. Since Fv is not affected by anti-VL, the results indicate that a combining site made of two identical chains (VL dimer) can undergo a conformational change upon interaction with its antibody. Such conformational change can indirectly affect the binding properties.