T-lymphocyte-enriched murine peritoneal exudate cells. IV. Genetic control of cross-stimulation at the T-cell level

Failure to find holes in the T-cell repertoire

The ability of an animal to respond to a given antigenic peptide depends on its major histocompatibility complex (MHC) type. Some peptides are not immunogenic when combined with a particular form of the MHC-encoded molecule. This non-responsiveness is regulated by immune response (Ir) genes and is thought to arise by one of two distinct mechanisms. Either the MHC-encoded molecules physically fail to interact with the antigen, preventing the activation of T cells with appropriate receptors, or they limit the expressed repertoire of T cell clones so that no T cells are available to be activated by existing complexes of MHC-encoded molecules and antigen. Experimental evidence has been generated to support both mechanisms. However, the relative importance of each has not been clearly established. In this study we started with a peptide that was immunogenic in B10 mice; it was thus known to be able to interact with the MHC molecule, and T cells existed which could recognise the peptide-MHC complex. Based on previous experiments, we then changed only those parts of the peptide that we thought interacted with the T-cell receptor. All the new analogues created were still immunogenic, confirming that the amino-acid substitutions that we had made did not prevent productive interactions with the MHC-encoded molecule. No limitations ('holes') in the T-cell repertoire were found. The experiments demonstrate the vast potential of the T-cell population to recognize many different analogues, each in a unique way, and suggest that constraints on the diversity of the T-cell repertoire may not be a major explanation for Ir gene defects.

Antigen presentation by human antigen-presenting cells to antigen-specific xenogeneic murine T cells

Successful antigen presentation by xenogeneic human antigen-presenting cells (APC) to stimulate the proliferation of antigen-specific, keyhole limpet hemocyanin (KLH)-specific, ovalbumin (OVA)-specific, and purified protein derivative of Mycobacterium tuberculosis (PPD)-specific murine T cells was observed. Evidence indicating a direct cell interaction between antigen-specific murine T cells and xenogeneic human APC was given by experiments using antigen-specific murine T cell clones. The OVA-specific B10.S(9R) T cell line (9-0-A1) and PPD-specific B10.A(4R) T cell line (4-P-1) were stimulated by both xenogeneic human APC and murine APC from syngeneic or I-A compatible strains, while the PPD-specific human T cell line (Y-P-5) was stimulated by autologous human APC but not by murine APC. Anti-HLA-DR monoclonal antibodies (MoAb) blocked the xenogeneic human APC-antigen-specific murine T cell clone interaction. Thus, human xenogeneic APC can stimulate antigen-specific murine T cells through HLA-DR molecules in the same manner as syngeneic murine APC do through Ia molecules coded for by the I region of the H-2 complex, while murine APC failed to present antigen to stimulate human antigen-specific T cells.

HLA-linked immune responsiveness to (T,G)-A-L: a family study

The heredity of the immune response potential to the synthetic polypeptide poly(LTyr,LGlu)-poly(DLAla)-poly(LLys) [(T,G)-A-L] and its possible linkage to the major histocompatibility complex of man were studied in 24 families. Peripheral blood lymphocytes (PBL) obtained from 174 donors belonging to 24 unrelated families were educated to (T,G)-A-L on autologous antigen-pulsed adherent cells. The supernatants obtained from these activated PBL were tested for their antigen-specific helper activity in an in vitro antibody production system. All donors were typed for their HLA haplotypes. The results obtained indicated that the ability to respond to (T,G)-A-L by production of an antigen-specific T cell helper factor is inherited as an autosomal dominant trait linked to the responder HLA haplotype.

The immune response to (T,G)-A-L and GAT in man: an association of nonresponsiveness to (T,G)-A-L with HLA-DRw8

The response of human lymphocytes to synthetic polypeptides has been measured by sensitizing cells in vitro followed by restimulation with the sensitizing antigen or with cross-reacting antigens. It was found that there was considerable individual heterogeneity in the specific response and the cross-reaction obtained with the antigens (T,G)-A-L, GAT, GT, and GA. In spite of this heterogeneity, it is possible to define three different response patterns using nonresponsiveness to (T,G)-A-L and the failure of (T,G)-A-L to cross-restimulate GAT sensitized cells as discriminating criteria. The nonresponders to (T,G)-A-L show a significant association with HLA-DRw8 and it is suggested that this might represent a dominant HLA associated immune response gene involved in the regulation of the response to (T,G)-A-L. We further show that the individuals whose cells respond to (T,G)-A-L form a heterogeneous group which may explain the conflicting results previously published on the genetic control of the immune response to (T,G)-A-L in man.

Antigen-specific HLA-restricted human T-cell lines. II. A GAT-specific T-cell line restricted by a determinant carried by an HLA-DQ molecule

Human T-cell lines responsive to the polypeptide antigens GAT and (T,G)-A--L were developed. They were specific for the priming antigens and required the participation of accessory cells matched for HLA-linked determinants, as shown in family studies. In panel studies, the ability of accessory cells to present antigen was shown to be associated with HLA-D-region antigens. However, the specificity of these determinants did not fully correspond to any HLA antigens as currently defined. One GAT-specific subline, derived by limiting dilution, utilized a restriction determinant associated with, but distinct from, the DQw3 (MB3) allospecificity. Blocking studies with mouse monoclonal antibodies indicated that this restriction determinant was carried by HLA-DQ molecules. The epitopes recognized in these molecules appear to be distinct from the alloantigenic determinants currently defined by serology.

Development of specific and cross-reactive lymphocyte proliferative responses during chronic immunizing infections with Rickettsia tsutsugamushi

The development of antigen-responsive lymphocytes was followed in mice immunized with the Gilliam, Karp, or Kato strains of Rickettsia tsutsugamushi by utilizing an in vitro lymphocyte proliferation assay. Subcutaneous immunization with viable rickettsiae of all three strains resulted in the appearance of lymphocytes in the spleen responding to irradiated tissue culture-grown rickettsiae used as stimulating antigens. Although all animals demonstrated antigen-induced proliferation elicited by homologous antigen by 14 days after immunization, the time of peak responsiveness varied, depending on the strain of rickettsiae used for immunization. In all cases, peak proliferative responses occurred at a time after immunization that was after the previously reported time after immunization at which resistance to rechallenge was observed. Reactivity to heterologous strains of R tsutsugamushi developed roughly in parallel with homologous reactivity in Karp- and Gilliam-immunized mice, with a marked degree of heterologous reactivity evident. Kato-immunized mice demonstrated greater reactivity to heterologous antigens early in the development of antigen reactivity and demonstrated a somewhat greater degree of cross-reactivity, relative to homologous responses, than the other groups. It was found that nylon wool-nonadherent immune cells, if cultured with antigen and adherent cells obtained from normal spleens or peritoneal exudates, responded in culture. The thymus-derived lymphocyte nature of the responding cell was further suggested when treatment of immune spleen cells with anti-Thy 1.2 serum and complement eliminated antigen response.

Splenic B cells function as immunogenic antigen-presenting cells for the induction of effector T cells

Previous studies performed in our laboratory have revealed that an ordered, sequential, tricellular interaction is obligatory for the antigen-driven induction of a specific effector memory T cell. Thus, it was found that antigen-pulsed peritoneal macrophages signal, in spleen cells, the generation of antigen-specific initiator lymphocytes. These lymphocytes, following injection to syngeneic recipients, recruit, in the draining lymph nodes, "virgin" antigen-reactive T lymphocytes. Although the nature of the first and last cell in the interacting sequence was well characterized, the identity of the intermediary initiator splenic cell was obscure. Studies were carried out to characterize the nature of the splenic initiator cells. It was found that spleen cells from nu/nu, adult thymectomized and neonatal thymectomized, or spleen cells from normal donors which had been subjected to cytolysis using anti-Thy-1.2 antibodies in the presence of complement, did generate, following interaction with keyhole limpet hemocyanin (KLH)-fed macrophages, specific initiator cells. Carrageenan impairment of spleen macrophages did not affect the generation of initiator cells, nor did the depletion of dendritic cells from the spleen. On the other hand highly enriched B cell, but not highly enriched T cell populations, when seeded on KLH-pulsed macrophages, generated antigen-specific initiators, which, in vivo, recruited antigen-reactive T cells. It thus appeared that B lymphocytes can function as intermediary obligatory antigen-presenting cells and actively transfer immunogenic signals from peritoneal antigen-presenting cells to T lymphocytes. These findings may therefore suggest that antigen-specific B cells do not function solely as antibody-producing cells, but, once activated by macrophages, may control the induction and differentiation of some antigen-reactive T cell subsets. Thus, one can view the B cell as an important regulatory cell of both cellular and humoral immune functions. The significance of this observation with regard to Ir gene control at the level of B lymphocytes is discussed.

Ontogeny of delayed hypersensitivity in young turkeys

Hypersensitivity to phytohemagglutinin (PHA-P) and Freund's adjuvant containing Mycobacterium tuberculosis was investigated in turkey poults. The kinetics, as indicated by dosage and response time after sensitization, were similar to responses in other birds and laboratory mammals. Newly hatched poults demonstrated delayed hypersensitivity responses, and 2 week old poults exhibited responses of greater magnitude than 8 week old poults. The turkey is proposed as another acceptable species for study of cell-mediated immunity (CMI).

Immunogenicity of four sequential polypeptides in inbred guinea-pigs and their recognition at the T lymphocyte and antibody levels

Four sequential polypeptides containing equimolar amounts of tyrosine, glutamic acid, alanine and glycine were shown to be T lymphocyte-dependent immunogens in inbred guinea-pigs. Poly (Glu-Ala-Tyr-Gly) was immunogenic only in strain 2 guinea-pigs; poly (Glu-Tyr-Ala-Gly) and poly (Ala-Tyr-Glu-Gly) were immunogenic only in strain 13 guinea-pigs; and poly (Ala-Glu-Tyr-Gly) was immunogenic in both inbred strains. The specificity of immune recognition was probed at the T lymphocyte and humoral levels with the heterologous polypeptides. Only a few cases of heterologous cross-stimulation or cross-reaction were observed, indicating the great selectivity of immune recognition. The results showed considerable variability in immune recognition from animal to animal. Nevertheless, at the T-cell level, cross-stimulation appears to necessitate that the antigen is itself immunogenic in that strain, whereas at the antibody level, cross-reaction is not similarly restricted. The structural basis for mutual recognition of immunogen and antigen at these levels is discussed.

Genetic regulation of delayed-type hypersensitivity responses to poly (Tyr,Glu)-poly(DLAla)--poly(Lys): expression of the genetic defect in the induction and manifestation phases in H-2s and H-2f mice

The genetic defect of H-2s and H-2s non-responder mouse strains in both the induction and manifestation phases of delayed-type hypersensitivity (DTH) responses to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L] was analysed. Utilizing an in vitro system to activate DTH effector T cells, we observed that non-adherent T cells of (H-2f X H-2b) F1 or (H-2s X H-2b)F1 responder mice, could not be activated on antigen bearing adherent cells of H-2f or H-2s haplotypes. On the other hand, these T cells were effectively sensitized on adherent cells derived from either F1 or parental (H-2b) responder mice. These results indicate that in these mouse strains the genetic defect, in the induction phase of DTH, is expressed at the level of the antigen presenting cell. In subsequent experiments, we were able to "correct' the non-responsiveness of H-2s recipients by transfer of educated and irradiated (H-2s X H-2b)F1 T cells together with normal F1 adherent cells. Normal non-adherent and nylon wool enriched T cells failed to restore these responses. Similarly, antigen-pulsed F1 irradiated peritoneal exudate cells could stimulate DTH responses in SJL recipients of (SJL X C57BL/6)F1 (T,G)-A--L educated cells. The genetic defect of H-2s mice in the manifestation phase of the DTH reaction is thus also expressed on the antigen presenting cell.

Immune response potential to poly(Tyr,Glu)-poly(DLAla)--poly(Lys) of human T cells of different donors

Human peripheral blood T cells of normal donors were activated in vitro with autologous adherent cells pulsed with poly(LTyr,LGlu)-poly(DLAla)--poly(LLys) [abbreviated (T,G)-A--L]. The "educated" T cells were tested: (i) for their ability to produce a (T,G)-A--L-specific T cell-replacing factor in the cooperation with B cells for antibody responses in vivo or in vitro and (ii) for their ability to proliferate in the presence of a second stimulus of (T,G)-A--L. Results of screening of 66 donors demonstrated that educated T cells of about 50% of the donors produced an active (T,G)-A--L-specific factor, whereas activated cells of only half of the factor producers were capable of proliferating in the presence of the antigen. Thus, as reported for all other species studied, human individuals differ in their response potential to (T,G)-A--L.

Specificity of antigen binding by T cells; competition between soluble and Ia-associated antigen

Competitive antigen binding experiments were performed with purified T and B cells of C3H.SW (H-2b) mice. As antigen, (T,G)-A--L [poly-L(Tyr,Glu)-poly-DL-ALa-poly-L Lys] was used, both in an Ia-containing form, released by adherent cells (IAC-Puri and Lonai, Eur. J. Immunol. 1980. 10:273), and in regular solution. It was found that regular (T,G)-A-L did not compete with the binding of 125I-labeled-IAC-(T,G)-A--L even at a 10(4)-fold excess, whereas IAC-(T,G)-A--L inhibited binding at 10-fold excess. The specificity of (T,G)-A--L binding to high-responder T and B cells was compared by using related branched synthetic copolymers as competitors. B cells cross-reacted with (T,G)-A--L, (H,G)-A--L, (G)-A--L and (T,G)-Pro--L. In contrast, antigen binding C3H.SW T cells cross-reacted only with (T,G)-A--L and (Phe, G)-A--L to both of which they are Ir gene-controlled high responders. Evidence for the Ir gene control of IAC-binding T cells was obtained by showing that high X low responder F1 hybrid T cells preferentally bind IAC-(T,G)-A--L processed by processor cells deriving from the high-responder parental strain. These data are interpreted to suggest that T cells have high affinity for antigen plus self Ia complexes, whereas they have a much lower, if any, affinity for free antigen. It also follows from the results that the structure of the complex ligand may have a role in defining the specificity, H-2 restriction and Ir gene control of T cells.

Liposomes as immunological adjuvants in eliciting antibodies specific to the synthetic polypeptide poly(LTyr, LGlu)-poly(DLAla)--(LLys) with high frequency of site-associated idiotypic determinants

The antibody response to the synthetic polypeptide, poly(LTyr, LGlu)-poly(DLAla)--poly(LLys), [(T,G)-A--L], injected entrapped in liposomes which served as adjuvant has been analyzed. The liposomes used were composed of phosphatidylcholine, cholesterol, dicetylphosphate and DL alpha-tocopherol (molar ratios as 4:3:0.1:0.5) and therefore, were negatively charged. Since the (T,G)-A--L is also negatively charged, no free complexes were formed. The (T,G)-A--L was found to be entrapped inside the enclosed volume of the liposomes, and no (T,G)-A--L antigenic determinants could be detected on the liposomal membranes. Injection of high-responder C3H.SW (H-2b) mice with (T,G)-A--L-bearing liposomes demonstrated that the i.p. and the i.v. routes of immunization were efficient in eliciting (T, G)-A--L specific antibodies, whereas the i.d. injection led to poor antibody responses. The latter route of immunization is the most effective when (T,G)-A--L is injected in complete Freund's adjuvant (CFA). When low doses (0.1 and 1 microgram) of (T, G)-A--L were used for immunization, the liposomes were better adjuvants than CFA. The effectiveness of the liposomes as immunological adjuvants was also shown in their ability to induce high-potential, primed memory cells. The pattern of low (H-2k,a) and high (H-2b) responsiveness to (T,G)-A--L was retained following immunization with (T,G)-A--L entrapped in liposomes, as tested in two pairs of congenic strains. (T,G)-A--L-specific antibodies induced by injection with 1 microgram antigen entrapped in liposomes bear the (T,G)-A--L site-related idiotypic markers of C3H.SW (Igh-1a) mice in a significantly higher frequency than the homologous idiotypes, namely the antibodies elicited in this strain against (T,G)-A--L in CFA. Thus, liposomes may serve as adjuvants for the production of relatively restricted (T,G)-A--L-specific antibodies of high quality.

T lymphocyte-dependent B lymphocyte proliferative response to antigen. I Genetic restriction of the stimulation of B lymphocyte proliferation

For the purpose of examining more closely the interaction between T and B lymphocytes, we have developed an in vitro T lymphocyte-dependent B lymphocyte proliferation assay. Proliferation of B lymphocytes in response to antigen was found to depend on the presence of primed T lymphocytes; the B lymphocytes could be derived from nonprimed animals. It appears that these B cells were nonspecifically recruited to proliferate. This nonspecific recruitment, however, was found to be Ir-gene restricted in that B lymphocytes from B10.S mice, which are genetic nonresponders to the polymer Glu60-Ala30-Tyr10 (GAT), could not be stimulated by GAT-primed (responder X nonresponder) F1 T cells. The apparent lack of antigen specificity in the face of Ir gene-restricted T-B interaction may have important implications in our understanding of the recognition unit(s) on T lymphocytes.

Enhancing effect of murine anti-idiotypic serum on the proliferative response specific for poly(LTyr, LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L]

Murine anti-idiotypic serum against C3 H.SW anti-poly(LTyr, LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L] antibodies was elicited in C57BL/6 mice. The effect of the anti-idiotypes on the proliferation of primed lymph node cells was investigated. The anti-idiotypic serum stimulated the proliferative response of the (T,G)-A--L-specific lymph node cells as well as of nylon wool-enriched T cells. In the presence of suboptimal doses of (T,G)-A--L, the addition of the anti-idiotypes enhanced the proliferation to the levels obtained with the optimal dose of (T,G)-A--L itself. These results suggest the existence of shared idiotypic determinants between antibodies and the (T,G)-A--L-specific proliferative T cells.

Specificity of genes controlling immune responsiveness to (T,G)-A--L and (Phe,G)-A--L

Mice possessing the H-2b haplotype are high responders to the cross-reactive antigens (T,G)-A--L and (Phe,G)-A--L whereas mice with the H-2k haplotype respond only to (Phe,G)-A--L. On the level of cross-immunization we have demonstrated that either (Phe,G)-A--L or (T,G)-A--L primed high responder C3H.SW (H-2b) mice could be boosted with both antigens. On the other hand, low responder C3H/DiSn (H-2k) mice which were primed to (Phe,G)-A--L and thus possess (T,G)-A--L specific antibodies, could not be boosted with (T,G)-A--L to mount a secondary response. Only (Phe,G)-A--L primed and boosted H-2k mice produced high levels of (T,G)-A--L reactive antibodies. Furthermore, the binding of the anti-(Phe,G)-A--L antibodies of either C3H/DiSn or C3H.SW mice to 125I-(T,G)-A--L was better inhibited by guinea-pig anti-idiotypes than the binding of C3H.SW anti-(T,G)-A--L antibodies which are the homologous idiotypes (T,G)-A--L was found to be an equally efficient tolerogen in both high and low responder mice. Thus, when C3H.SW and C3H/DiSn mice were injected with a tolerogenic dose of (T,G)-A--L and then immunized with (Phe,G)-A--L, they were found to be tolerant to (T,G)-A--L antigenic determinants, since they produced only the unique antibodies to (Phe,G)-A--L. These results suggest that the H-2 linked Ir genes controlling antibody response to (T,G)-A--L are not involved in the induction of tolerance to (T,G)-A--L.

Ir-gene control of T cell proliferative responses: two distinct expressions of the genetically nonresponsive state

Two distinct modes of unresponsiveness to hen egg-white lysozyme (HEL) have been demonstrated in the "nonresponder" C57BL/10 Sn (B 10) mouse strain at the level of T cell proliferation. The first is an apparent inability to respond to a peptide of HEL comprising 70% of the molecule, LII (amino acids 13--105, when HEL is used as immunogen. On its own, LII is capable of eliciting a strong response from B 10 draining lymph node cells, but this capacity is concealed when the whole molecule is used for immunization (by suppressor cell activity raised against another part of HEL, as described by Adorini et al., J.Exp. Med. 1979. 150: 293). In the B 10.A mouse, LII and HEL are equally immunogenic. The second is an actual failure, presumably unrelated to suppression, to contrive a response to particular determinants on HEL, demonstrated for certain epitopes on LII and LIII (amino acids 106--129). Such a failure to respond was maintained despite an increase in the immunizing dose of peptide to a molarity at which HEL itself could overcome Ir gene control. B 10 cells responding to a high dose of HEL, or to the immunogenic lysozyme from ring-neck pheasant, were also unable to respond to these epitopes. These deficits in responsiveness appear to be characteristic manifestations of the relevant haplotype of the major histocompatibility complex. They may not only reflect the balance between competing T cell subpopulations, but also the constraints of associative recognition that may underlie the presentation of particular antigenic specificities.

Genetic regulation of delayed-type hypersensitivity responses to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys). II. Evidence for a T-T-cell collaboration in delayed-type hypersensitivity responses and for a T-cell defect at the efferent phase in nonresponder H-2k mice

The intercellular interactions and the site of the genetic defect in delayed-type hypersensitivity (DTH) response to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys) [(T,G)-A--L] has been studied in a system where the T-cell education phase was separated from the efferent phase. In the cellular response, T-T-cell collaboration is required, because T cell-depleted mice were unable to manifest DTH responses after they were transferred with educated and irradiated T cells. Reconstitution of adult thymectomized mice that were irradiated and supplemented with bone marrow cells after treatment with anti-Thy-1.2 serum and complement, with T cells but not with accessory cells gave rise to significant responses. Educated, radioresistant cells required the presence of normal radiosensitive T cells for successful DTH responses to (T,G)-A--L. The genetic defect of nonresponder H-2k and H-2a mice has been located in the above-mentioned, second T-cell population that participates in the efferent phase of this immune reaction. Further characterization revealed that the educated cells are of the Lyt1+ phenotype and that the second normal T cells are expressing the Lyt 1+,2+,3+ phenotype. Thus, the genetic defect of H-2k and H-2a mice in the DTH response to (T,G)-A--L is expressed on the non-antigen-stimulated Lyt 1+,2+,3+ T cells.

Genetic regulation of delayed-type hypersensitivity responses to poly(LTyr,LGu)-poly(DLAla)--poly(LLys). I. Expression of the genetic defect at two phases of the immune process

Delayed-type hypersensitivity (DTH) responses served in this study as an experimental model for the analysis of genetic regulations of T-cell responses. Educated irradiated cells from H-2b mice mediated responses in syngeneic recipients, whereas mice of the a, d, f, k, and s haplotypes were nonresponders to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L]. These results suggest that cell-mediated immune responsiveness to (T,G)-A--L is linked to the H-2 complex, as was shown for humoral responses. Educated irradiated T cells of F1 hybrids between high and low responders mediated DTH responses, which indicates that the gene(s) controlling the DTH responses is dominant. To analyze the genetic defect in DTH responses to (T,G)-A--L, we separated the T-cell activation phase from the effector phase that was determined in recipient mice. Two types of nonresponders were observed: (a) When lymphocytes of the a or k haplotypes were educated in a syngeneic environment and then transferred into hybrids between the parental (nonresponder x responder) F1 recipients, DTH responses could have been manifested. (b) On the other hand, no DTH responses could be mediated by transferring educated cells of the H-2s or H-2f origin into the appropriate F1 recipients. In addition, irradiated F1 cells that had been activated to (T,G)-A--L could not mediate DTH responses in both types of nonresponder recipients. These results suggest that T cells of H-2k or H-2a mice can be activated to generate DTH responses to (T,G)-A--L and that the defect in these mouse strains is expressed in another cell population needed for the manifestation of the DTH reaction in the recipient mice. In contrast, T cells of H-2s and H-2f origin cannot be activated to (T,G)-A--L and, thus, fail to manifest DTH responses.

Idiotypic analysis of antibodies against the terpolymer L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT). IV. Induction of CGAT idiotype following immunization with various synthetic polymers containing glutamic acid and tyrosine

The immune responses of all inbred strains of mice specific to the synthetic terpolymer poly(LGlu60LAla30LTyr10), referred to as GAT10, are characterized by the presence of anti-GAT antibodies which share a common (CGAT) idiotype. In this report, we describe the ability of the synthetic polymers, LGlu33LAla33LTyr33, LGlu51-LAla34LTyr15 and poly-L(Tyr, Glu)-DLAla--LLys [(T,G)-A--L] to induce antibodies with CGAT idiotypic specificities. All of these polymers contain "GT"-related determinants. Following immunization with these polymers, antisera from responder mice bind the corresponding 125I-labeled antigen and 125I-labeled poly(LGlu50LTyr50) or GAT10. These antisera shared the CGAT idiotype which is associated with the antibody fraction with binding specificity for GAT10. Collectively, the present results indicate that GT-related determinants are required for the induction of the CGAT idiotype. Moreover, since the immune responses to these synthetic polymers are under distinct H-2-linked immune response (Ir) gene control, a mouse strain can be nonresponder to one polymer and responder to another; in this case, only the latter polymer induces CGAT idiotype. Thus, although the immune responses of inbred strains of mice to different polymers are under distinct Ir gene control, the antibody responses can be idiotypically related.

Gene complementation in the T-lymphocyte proliferative response to poly (Glu55Lys36Phe9)n. A demonstration that both immune response gene products must be expressed in the same antigen-presenting cell

The immune response (Ir) to the random copolymer GLphi depends upon the function of two Ir genes, Ir-GLphi-beta[beta] and Ir-GLphi-alpha[alpha], mapped to the I-A and I-E/C subregions of the major histocompatibility complex, respectively. In this paper, the site(s) of expression of the products of these two Ir genes was examined by evaluating T-lymphocyte proliferative responses of bone marrow radiation chimeras. Chimeras were created in [alpha+beta- X alpha-beta+]F1 responder mice by lethal irradiation and reconstitution with a mixture of bone marrow cells from both parental strains. These chimeras failed to respond to GLphi, although they were capable or responding to the much weaker antigens, (T,G)-A--L, TEPC-15, pigeon cytochrome c, and (H,G)-A--L. This failure to respond to GLphi was shown not to be the result of a cryptic mixed lymphocyte reaction, as similar chimeras created in (alpha+beta+ X alpha-beta+)F1 mice responded well to GLphi, although they possessed almost the same potential histoincompatibility. Furthermore, the lack of response to GLphi could not be attributed to a general failure of the two parental cell types in the chimeras to collaboratc with each other, as each chimeric parental cell type could respond to dinitrophenyl conjugated ovalbumin presented on nonimmune spleen cells from the other parent. Thus, the failure of low responder parental into F1 high responder chimeras to generate an immune response to GLphi suggests that immune competence for this antigen requires at least one cell type in the immune system to express gene products of both the Ir-glphi-alpha and -beta genes, i.e. one cell must be of high responder genotype. The the antigen-presenting cell is one such cell type was shown by experiments in which GLphi-primed T lymphocytes from responder F1 mice were stimulated with antigen bound to nonimmune spleen cells. Only spleen cells from responder F1 and recombinant mice could present GLphi. Neither of the two complementing nonresponder parental spleen cell populations, either alone or mixed together, could present GLphi, although both could present purified protein derivative of tuberculin. This was shown to be the case for T cells positively selected in vitro as well as freshly explanted T cells. Thus, both Ir-GLphi-alpha and Ir-GLphi-beta gene products must be expressed in the same antigen-presenting cell to generate a T-lymphocyte proliferative response to GLphi. The implications of these findings for models of two gene complementation are discussed.

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

Antigen-binding inhibition studies using microscopic autoradiography were performed on T or B cell-enriched lymphocyte populations. Antibodies specific for the "framework" of immunoglobulin heavy or light chain variable domains (VH or VL), or anti-H-2 and anti-Ia antisera were used. T cell subclasses were separated with anti-Lyt antisera and complement. It was found that antigen-binding T cells of different subclasses can be inhibited selectively with only one of the two anti-V region antibodies. Antigen binding to Lyt-1+ cells was inhibited by anti-VH, while Lyt-2+,3+ cells were inhibited by anti-VL specifically. Anti-Ia antisera inhibited unprimed Lyt-1+ antigen-binding cells, whereas anti-H-2K or anti-H-2D anti-sera inhibited unprimed Lyt-2+,3+ antigen-binding cells, and both classes of immune T antigen-binding cells.

Specificity and crossreactivity of idiotypes of murine antibodies induced by poly(Tyr,Glu)-poly(DLAla)-poly(Lys) and poly(Phe,Glu)-poly(DLAla)-poly(Lys)

Antibodies elicited against the two synthetic polypeptides, poly(Tyr,Glu)-poly(DLAla)-poly(Lys) [(T,G)-A-L] and poly(Phe,Glu)-poly(DLAla)-poly(Lys) [(Phe,G)-A-L], are crossreactive although the humoral responses to these immunogens are under different genetic controls. The fine specificity of the antibodies elicited by the two polypeptides was studied in the present work. Antisera against (Phe,G)-A-L bind both (125)I-labeled (T,G)-A-L and iodinated modified (Phe,G)-A-L. However, while the binding to (T,G)-A-L could be inhibited completely with the two antigens, the binding to (Phe,G)-A-L was inhibited completely with (Phe,G)-A-L and only partially with (T,G)-A-L. The binding of (125)I-labeled (T,G)-A-L to antisera against (T,G)-A-L was inhibted more efficiently by the homologous antigen than by (Phe,G)-A-L although both antigens completely inhibited the binding. (T,G)-A-L specific antibodies were purified on (T,G)-A-L immunoadsorbents from antisera of high and low responder mice to (T,G)-A-L immunized with (Phe,G)-A-L. (Phe,G)-A-L specific antibodies that did not bind (T,G)-A-L were isolated from the effluent of these columns. By use of anti-idiotypic antibodies of guinea pig against C3H.SW antibodies to (T,G)-A-L it was shown that (T,G)-A-L specific antibodies isolated from antisera against (Phe,G)-A-L of C3H.SW and C3H/DiSn mice possess part of the idiotypic determinants existing on antibodies of C3H.SW obtained by immunization with (T,G)-A-L. In contrast, antibodies to (Phe,G)-A-L that did not bind (T,G)-A-L did not share idiotypic determinants with C3H.SW antibody molecules against (T,G)-A-L. These results suggest that the B cell repertoire expressed by high and low responders to (T,G)-A-L after immunization with (Phe,G)-A-L is similar and represents only part of that of high responders immunized with (T,G)-A-L.

Antigen presentation in the murine T lymphocyte proliferative response. II. Ir-GAT-controlled T lymphocyte responses require antigen-presenting cells from a high responder donor

The activation of T lymphocytes from poly (Glu60Ala30Tyr10)n (GAT)-primed donors by GAT-pulsed nonimmune spleen cells was shown to require identity at the I-1 subregion of the major histocompatibility complex. However, GAT-primed T lymphocytes from (responder x nonresponder) F1 hybrids could only be stimulated to proliferate by GAT bound to high responder or F1 spleen cells but not by GAT bound to spleen cells from the low responder parent. The failure of spleen cells from low responder parental strains to present GAT was shown not to be due to the presence of suppressor cells in either the antigen-presenting or the responding cell populations. These results indicate that control of antigen-presenting cell-T lymphocyte interactions is one site of Ir gene expression.

Inhibition of dual Ir gene-controlled T-lymphocyte proliferative response to poly (Glu56Lys35Phe9)n with anti-Ia antisera directed against products of either I-A or I-C subregion

Previous studies have demonstrated that both the antibody and T-lymphocyte proliferative immune responses to poly(Glu53Lys36Phe11)n (GLphi) are under the control of two major histocompatibility-linked immune response (Ir) genes. One gene, termed Ir-GL phi-alpha, has been mapped to the I-C or I-E subregion of the major histocompatibility complex, while the other, termed Ir-GL phi-beta, has been mapped to the I-A subregion. In this paper we examine the effect of anti-I-region-associated (Ia) antisera on the T-lyphocyte proliferative response to GL phi. Antibodies directed against Ia antigens coded for by genes in either the I-A or I-C subregion were found to inhibit the proliferative response to GLphi. These results suggest that a function mediated by two Ir gene products can be blocked by anit-Ia antisera directed against either one, and thus, that both products are expressed on the cell surface.

Genetic control of the T-lymphocyte proliferative response to cytochrome c

Cytochromes c have been used as antigens in a murine T-lymphocyte proliferation assay in order to characterize the nature of determinants whose recognition is under immune response (Ir) gene control. The cytochromes are advantagous as antigens because 1) they have well-characterized primary and tertiary structures, 2) they are antigenically simple, differing from mouse cytochrome c at only a small number of amino acid residues, and 3) there exist a large number of evolutionary variants which can be used to locate antigenic sites by cross-stimulation. In the present studies, the T-lymphocyte proliferative response to pigeon cytochrome c was shown to be under the control of two complementing major histocompatibility (MHC)-linked Ir genes in mice of the H-2a and H-2k haplotypes. Mice of the H-2b, H-2d, H-2p, H-2q, H-2s, and H-2u haplotypes were low or nonresponders. Complementation was demonstrated by showing that an F1 hybrid between two nonresponder recombinant strains, B10.A(4R) and B10.A(5R), could respond to pigeon cytochrome c. The determinant on the cytochrome recognized in this immune response was located to the C-terminal portion of the molecule around residues 89 and/or 100. This was shown by the failure of closely related cytochromes from the Pekin duck and chicken to cross-stimulate T lymphocytes immune to pigeon cytochrome; position 89 and 100 carry the only residues different from those in mouse cytochrome c that are unique to pigeon cytochrome among the three bird cytochromes tested. This localization was further substantiated by demonstrating that the cyanogen bromide cleavage-fragment (residues 81-104) from pigeon cytochrome, but not the same fragment from Pekin duck cytochrome, was as good a stimulant of T cells immune to the whole molecule as the intact cytochrome. These results identify the immunogenic site on the molecule as one which differs from mouse cytochrome c by only one or two amino-acid residues. Thus, T-cell immune responses, which are under MHC-linked Ir gene control, are as capable as antibody responses of recognizing subtle differences in protein structure. However, the ability of T cells to respond equally well to stimulation with polypeptide fragments or with the whole molecule suggests either that T-cell recognition involves certain differences from B cell recognition or that in some cases the fragments possess a similar spatial structure to that of the corresponding segment in the native protein.

Physiological regulation of antigen binding to T cells: role of a soluble macrophage factor and of interferon

A soluble product of macrophages (MF) and mouse viral interferon (IF) increase both major histocompatibility antigenic determinants and the number of antigen-binding cells in nonstimulated T cell-enriched mouse lymphocyte cultures. MF increases Ia and not H-2 antigens; IF increases H-2 but not Ia antigens. The increased antigen binding due to MF can be inhibited by anti-Ia but not by anti-H-2 sera, whereas IF-induced binding is sensitive to anti-H-2 but not to anti-Ia sera. The specificity of IF- or MF-induced binding of branched synthetic polypeptides by T cells is different from that of B cells and similar to the specificity of the Ir gene regulation. MF increases antigen binding only in Ir high-responder animals. The IF-induced antigen binding is not dependent on the Ir genotype. MF-reactive cells express the Ly-1 marker, and the IF-reactive antigen binders express the Ly-2 phenotype. It is suggested that MF and IF are physiological mediators of antigen binding by T cells.

Antigen presentation in the murine T-lymphocyte proliferative response. I. Requirement for genetic identity at the major histocompatibility complex

A method is described for stimulating proliferation in primed populations of murine T lymphocytes using antigen bound to mitomycin-C-treated spleen cells. This form of antigen presentation appears to be an active process because heat-killed spleen cells are ineffective, and because genetic similarity at the major histocompatibility complex (MHC) between the responder T cells and the presenting spleen cells is required for effective interactions. At all times examined, from day 3 to day 6 of the proliferative response, syngeneic spleen cells presented antigen better to peritoneal exudate T-lymphocyte-enriched cells (PETLES) than semisyngeneic F(1) spleen cells, which in turn could present antigen better than totally allogeneic spleen cells. Spleen cell mixing experiments demonstrated that these genetic restrictions were not the result of suppression by the ongoing mixed lymphocyte reactions (MLR) in the allogeneic and F(1) cases. Furthermore, incompatibility at the Mls locus generated a strong MLR but failed to prevent antigen presentation if the spleen cells and PETLES were compatible. Genetic mapping studies demonstrated that compatibility at only the I-A subregion of the MHC was sufficient for effective presentation of the antigen, dinitrophenylated ovalbumin. Compatibility at only the K region, or the K and D regions was not sufficient. These results support the concept that functional activation of primed, proliferating T lymphocytes requires the participation of gene products coded for by the I region of the MHC. This conclusion is consistent with a growing body of evidence which suggests that most T cells recognize antigen in association with MHC gene products.