Cellular receptors. effect of anti-alloantiserum on the recognition of transplantation antigens

Clonotypic antibodies which stimulate T cell clone proliferation

We have prepared a variety of antisera which recognize the T cell receptors on both alloreactive and antigen-specific functional clones. The antisera specifically stimulate the immunizing T cell clones to proliferate without cross-stimulating a variety of other clones and are thus clonotypic. The antisera specifically precipitate an 82k molecular weight complex unique to the immunizing clone and an independent common component present on all the helper T cell clones tested. The 82k molecular weight complex consists of a heterodimer, which can be resolved into an acidic (a) chain and a more basic (beta) chain. The beta subunit differs in its isoelectric focusing pattern when isolated from two A derived clones which recognize and respond to different alloantigens. Thus, the functional specificity of the antibodies is reflected in identifiable changes in molecules at the biochemical level.

F1-hybrid anti-parental-strain reactivity. I. Impaired proliferation of CBA lymphocytes in the spleens of irradiated C3H X CBA mice pretreated with CBA spleen cells

Previous investigations have indicated that C3H X CBA hybrid lymphocytes can neutralize lymphocytes which are reactive against the C3H-determined Mls antigen when injected into the H-2-compatible strain CBA. In this study we have inoculated C3H X CBA hybrids with CBA spleen cells and 2 weeks later lethally irradiated the mice and injected them with CBA lymphocytes to study their proliferation in the host spleen. Proliferation of lymphocytes from CBA mice, but not from C57Bl mice, was significantly impaired in such hosts, indicating that the hybrids had become immunized against the parental cells. In contrast, such an effect was not detected by treating CBA X C57Bl mice with CBA spleen cells. Humoral antibodies in the C3H X CBA hybrids capable of blocking the response of CBA lymphocytes against C3H X CBA cells could not be detected, indicating that inhibition of lymphocyte proliferation is cell mediated rather than by humoral factors.

The host component of the popliteal lymph node graft-versus-host (GVH) reaction. Identification of cells in the node and kinetics of cell proliferation

The cellular composition of rat popliteal lymph nodes undergoing a GVH reaction was examined. The great majority of cells isolated from the nodes were lymphocytes, while the contribution of phagocytic cells was negligible (less than 5%). Both T and B cells were present in GVH nodes. However, the proportion of B cells was higher than in normal lymph nodes (40-50% vs 30%). Cells synthesizing DNA were enumerated autoradiographically in sections of GVH nodes up to day 7 of the response. A significant increase in the proportion of 3H thymidine labelled cells had already been found on the third day of the GVH response, before lymph node enlargement was apparent. Of the differnt days tested a maximum of 6% labelled cells was found on day 7. Liquid scintillation counting of cell suspension from such nodes showed an even higher increase in 3H thymidine incorporation in GVH vs normal nodes. These findings indicate that cell proliferation is a central mechanism behind the lymph node enlargement.

Life cycle patterns and their genetic control: an attempt to reconcile evolutionary and mechanistic speculation

A model is proposed which implicates molecular recognition systems as the major controlling factors in life cycle expression. It is envisaged that such systems are important in immune functioning and catabolic, metabolic molecule recognition at both inter- and intra-cellular level. These recognition systems have the following characteristics: 1) Specific recognition molecules (recognisers), e.g. vertebrate antibodies, invertebrate agglutinins and plant agglutinins may recognise specific substances, e.g. antigens, catabolic and metabolic molecules. 2) The range of possible recognisable substances is very wide and variable. 3) The recognisers may themselves be recognised by other recognisers. 4) Recognisers are usually produced in large amounts only on presentation of the appropriate recognisable molecule. 5) The progressive introduction of new recognisable molecules increases the recogniser interaction, this interaction causing depression of some recogniser types (immune depression) and facilitation of other types among which may be recognisers specific for self components (e.g. auto-immunity). 6) Low juvenile viability is associated with a restricted range of available recognisers, high adult viability with increasing recogniser range and some auto-immunity/immune depression, senescence with a wide range of available recognisers and extensive auto-immunity/immune depression. Life cycle patterns and their control are discussed. It is suggested control mechanisms may include: 1) Dietary restriction and in some periods complete nutritional abstinence. 2) Specific recogniser depression, genes implicated here are the various antigens (species and polymorphic) found on cell surfaces, in the serum and in various body fluids of vertebrates, e.g. ABO, MNSs, P, Rh, Le and other blood groups, the ABO and Le secretor antigens and the HL-A antigens. In addition the immune response and mixed lymphocyte culture loci are implicated. Finally life cycle control is discussed with relation to sexual selection.

T-lymphocyte receptors for alloantigens

Recent developments in research on T-cell receptors for alloantigens have been reviewed. Recognition of these antigens is T-cell dependent and, when measured in the PAR test, can be shown to take place with receptors present on T cells, with those shed spontaneously from T cells and also with "recognition structures" of as yet unknown origin and structure present in post-transplantation alloantiserum but absent from B-cell induce alloantiserum. All recognizing structures of parent T-cell origin mentioned above also induce formation of anti-T cell receptor antisera when injected into appropriate F1 hybrid animals. The highly specific inhibitory activity of the sera can be demonstrated both in vitro and in vivo, and the most fascinating aspect constitutes cytotoxic elimination of T cells bearing receptors for a given alloantigenic specificity without harming T cells with other alloreceptors. The biochemical nature of T-cell receptors is not known and, depending on the physical form in which it is investigated, high molecular weight as well as considerably lower molecular weight structures have been found. It has, on the other hand, become quite clear that the antigen-binding region of B- and T-cell receptors shows idiotypic similarity and it is, therefore, likely that this part of the receptor molecule of both lymphocyte classes is similar if not identical

Shared idiotypic determinants on B and T lymphocytes reactive against the same antigenic determinants. II. Determination of frequency and characteristics of idiotypic T and B lymphocytes in normal rats using direct visualization

Anti-idiotypic antibodies made against the antigen-binding receptors of T lymphocytes for a given antigen (Ag-B locus antigens in rats) can be shown to react with IgG antibodies of the same antigen-binding reactivity. Using such anti-idiotypic antibodies, normal Lewis T lymphocytes of B and T type can be visualized by the use of anti-(Lewis-anti-DA) antibodies. Visualization was made possible by the use of direct fluorescent antibody tests or by autoradiography. Using the first technique and naked eye observations 6.2% of normal Lewis T lymphocytes expressed idiotypic markers signifying anti-DA reactivity, whereas anti-DA-reactive B lymphocytes as measured by this approach was in the order of 1.1%. Autoradiography was purified normal Lewis T lymphocytes gave similar figures. When comparing the intensity of fluorescence at the single cell level using quantitative cytofluorometry anti-idiotypic antibodies reactive with T lymphocytes gave a similar degree of intensity as was obtained using anti-Ig antibodies against B lymphocytes.

Spontaneous release of T cell receptors for alloantigens. III. The effects of anti-T cell receptor antiserum, of alloantiserum and of trypsin on T cell receptor release

Spleen and lymph node T lymphocytes cultivated in vitro spontaneously released receptors for alloantigens. Among the various specificities, those receptors fitting certain alloantigens could be absorbed by formolized cells or proper genotype without influencing receptors for other alloantigens. Shedding of T cell receptors could be inhibited for 8 h by treating cells with antisera directed against T cell receptors (anti-RS antisera). Inhibition experiments indicated that resynthesis of T cell receptors appears to be complete by 8 h. Experiments on prevention of receptor shedding revealed highly specific and presumably cytotoxic elimination of T cells with receptors for given alloantigens. Treatment of cells with alloantiserum obtained by skin graft rejection failed to inhibit spontaneous release of T cell receptors, whereas treatment of lymphocytes with trypsin resulted in an 8-h delay of receptor shedding similar to that after treatment of cells with anti-RS antisera. This inhibition was, however, nonspecific.

Inhibition of mixed leukocyte culture by anti-idiotypic antibodies

(CBA x C57BL/6)F1 antisera prepared by injecting F1 mice with CBA T lymphocytes or CBA anti-C57BL/6 alloantibodies were tested for their ability to inhibit the mixed leukocyte culture (MLC) response. Presence of antiserum throughout the culture period in the absence of complement did not have any effect on the MLC response. Treatment of CBA responder cells with F1 antiserum and complement prior to the culture specifically inhibited the MLC response. Specificity of the suppression was ascertained; absorption of the F1 sera with F1 or C57BL/6 spleen cells did not remove the suppressive factor, whereas absorption with CBA spleen cells did so. F1 antiserum treatment left intact the response to third party alloantigens (DBA/2). Immunabsorbent columns with alloantibody of corresponding specificity removed the suppressive factor from anti-T cell sera as well as from antisera to alloantibody. The data suggest that the circulating alloantibody population contains molecules which share idiotypic determinants with surface receptors on T cells recognizing the same alloantigens.

Idiotype positive T cells visualized by autoradiography and electron microscopy

Anti-idiotypic antibodies were prepared in (CBA X C57BL/6)F1 hybrid mice by immunization either with CBA anti-C57BL/6 alloantiserum or with purified CBA thymus-processed lymphoid cells (T cells) Iodinated anti-mouse Ig or triple sandwich ferritin-labeling techniques served to visualize the reaction between idiotype and anti-idiotype. From 5 to 10% of purified CBA T cells appeared to carry receptors for C57BL/6 antigens. Heavily labeled cells had the morphology of small lymphocytes.

Shared idiotypic determinants on B and T lymphocytes reactive against the same antigenic determinants. I. Demonstration of similar or identical idiotypes on IgG molecules and T-cell receptors with specificity for the same alloantigens

Antigen-binding receptors on T lymphocytes and IgG antibodies with the same antigen-binding specificity as the T-cell receptors display shared or identical idiotypes. This was shown using a system where adult F1 hybrid rats between two inbred strains were inoculated with T lymphocytes from one parental strain. Such F1 hybrid rats produce antibodies directed against idiotypic determinants present on IgG alloantibodies, produced in the T donor genotype strain and with specificity for the alloantigens of the other parental strain. The idiotypic nature of the F1 antialloantibody serum against the parental alloantibodies was demonstrated both by indirect hemagglutination tests or by gel diffusion using alloantisera with different specificity as targets. Furthermore, the F1 anti-T-lymphocyte sera could be shown to contain antibodies against idiotypic parental T lymphocytes as well. This was shown by the capacity of the antisera, in the presence of complement, to wipe out the relevant parental T-cell reactivity against the other parental strain (as measured in MLC or GVH) whilst leaving the T-lymphocyte reactivity against a third, unrelated allogeneic strain intact. These findings demonstrate that F1 hybrid rats inoculated with parental T lymphocytes make anti-idiotypic antibodies directed against both the T cell receptors and IgG alloantibodies of that parental strain with specificity for alloantigens of the other parental strain. In order to prove identity between the anti-idiotypic antibodies against the B and T-cell antigen-binding molecules the following experiments were carried out; highly purified IgG from relevant alloantibody-containing serum in immunosorbent from could be shown to selectively remove both anti-idiotypic activities from the F1 antiserum. Further more, parental normal T lymphocytes could be shown capable of removing from the anti-idiotypic antisera all those antibodies that would cause agglutination of the relevant alloantibody-coated erythrocytes in the indirect agglutination assay. We would thus conclude that T and B lymphocytes reactive against a given antigenic determinant use receptors with antigen-binding areas coded for by the same variable gene subset(s).

Local graft-versus-host-reaction in mice specifically inhibited by anti-receptor antibodies

The local graft-versus-host (GVH) reaction provoked by parental spleen cells in F1 mice was shown to be T-cell-dependent. GVH reactions were suppressed in F1 hybrid mice immunized with parental T lymphocytes of the same genotype, but not in F1 mice immunized with parental B cells. In some cases this immunity could be passively transferred by serum into normal F1 mice. The specific activity of such sera could be removed by absorption with either parental T or B cells. Some of the F1 antisera were specificlly cytotoxic for parental GVH-reactive lymphocytes.

Spontaneous release of T cell receptors for alloantigens. II. Induction of antibodies to T cell receptors

Spleen cells from normal mice, when cultivated in vitro, released receptors or recognition structures (RS) for alloantigens into the surrounding medium. The spontaneous shedding of receptors was revealed by their ability to induce the formation of anti-recognition structure(anti-RS) antibodies upon injection into appropriate F1 hybrid recipients. Cell suspensions containing T and B lymphocytes and those containing T lymphocytes were capable of inducing anti-RS antibody formation, whereas suspensions devoid of T cells were incapable of doing so. Receptors shed from such cell suspensions during a 24-hour cultivation period gave exactly the same results. Cell-free culture supernatants, however, incited higher anti-RS antibody titers, presumably because of an accumulation of RS. The capacity of released T cell receptors to recognize alloantigens as determined in the PAR assay and their ability to induce anti-RS antibodies went roughly parallel.

Neonatal tolerance induced by antibody against antigen-specific receptor

Specific immunologic unresponsiveness is induced by injecting adult or neonatal mice with antibody against antigen-specific receptor (antireceptor antibody). Suppression in mice treated as adults lasts several weeks, and cells from these suppressed mice respond normally in culture. In contrast, unresponsiveness induced in neonatal mice is long-lasting; cells from these mice do not respond in culture and do not affect the response of normal cells. Evidently, antireceptor antibody reversibly blocks antigen receptors in adult animals, but induces unresponsiveness in neonatal mice by depleting the clone of receptor-bearing cells.

Cell-bound receptors for alloantigens on normal lymphocytes. II. Antialloantibody serum contains specific factors reacting with relevant immunocompetent T lymphocytes

The rat popliteal node graft-vs.-host assay was shown to depend on the presence of parental T cells in the inoculum. Antialloantisera raised in F(1) hybrid rats against alloantibodies of one parent directed at transplantation antigens of the other parent displayed some or all of the following specific effects on parental T cells: They inhibited local GvH by purified T-cell suspensions; they blocked the capacity of GvH-reactive cells to adsorb onto fibroblast monolayers of the relevant genotype; together with complement, they killed GvH-reactive cells.

Inhibition of specific cell-mediated cytotoxicity by anti-T-cell receptor antibody

The present study describes a method for the production of a specific anti-T-cell receptor antiserum, and characteristics of its ability to block specific cell-mediated cytotoxicity in vitro. Immunization and antiserum adsorption procedures were designed to select for idiotypic differences in the recognition units of C3H lymphocytes immune to two different strains of mouse cells, such that the reactivity of only one population of effector cells is inhibited by this antiserum. Both in vivo and in vitro sensitized effector T cells are subject to this inhibition. That the site of the antiserum blockade is clearly on the effector cell and not on the target cell is demonstrated.

Cell-bound receptors for alloantigens on normal lymphocytes. I. Characterization of receptor-carrying cells by the use of antibodies to alloantibodies

Antialloantibodies were prepared in F(1) hybrid rats by immunization with alloantibodies from one parent raised against antigens of the other parent. The Ig fraction of such antialloantibodies was iodinated and used to investigate the nature of idiotype-carrying normal lymphoid cells. Lymphoid cell populations of the proper genotype fixed radioactive antialloantibody in proportion to their B-cell content. Activated T-cell populations, when depleted of B cells, did not fix significant amounts of radioactivity. Idiotype-carrying cells were sensitive to rabbit antirat Ig serum lysis and to antialloantiserum lysis, but not to rabbit anti-T-serum lysis. Also, the normal idiotype-containing B cell could be shown to have the expected antigen-binding specificity of its receptor. This was shown by the use of fibroblast cell monolayers that adsorbed specifically those cells capable of fixing the proper antialloantibody.

Antireceptor antiserum causes specific inhibition of reactivity to rat histocompatibility antigens

The antigen receptor of lymphocytes destined to form antibody appears to have the characteristics of the immunoglobulin produced. Antibody directed against the combining region of this immunoglobulin should interact with the combining region of the cell receptor for the antigen. Purified Lewis rat alloantibody prepared against Brown Norway (BN) rat histocompatibility antigens was used to immunize L x BN F(1) hybrids. The resultant antiserum has anti-receptor activity because (i) it yields precipitin lines in gel diffusion when reacted against the immunizing alloantibody; (ii) it inhibits the hemagglutinin antibody response of Lewis rats to BN histocompatibility antigens; and (iii) it inhibits the local graft-versus-host response of Lewis lymphoid cells against BN antigens. This suggests that antireceptor antibody may inhibit cell-mediated responses as well as antibody responses to histocompatibility antigens and may play a role in the regulation of immune responses to such antigens.

Mechanism of graft-versus-host-induced lymphadenopathy in mice. Trapping vs. proliferation

Graft-vs.-host (GVH)-induced lymphadenopathy of the popliteal lymph node has been produced in C57BL/6 x A/J F(1) (BAF(1)) mice by injecting A/J spleen cells into the rear footpads. By giving (51)Cr-labeled BAF(1) lymphoid cells intravenously to the hosts, 24 h before sacrifice, we have demonstrated that a large portion of the GVH-induced lymphadenopathy is due to the trapping of circuating lymphocytes in the challenged lymph nodes. Most of the remaining enlargement can be attributed to proliferation of host cells within the reacting lymph nodes. Conditions have been defined under which the weights and [(14)C]thymidine incorporation of the popliteal nodes can be plotted against the dose of injected A/J spleen cells on a double-log scale to give a linear dose-response. The popliteal lymph node GVH assay is a simple and effective means of quantitating immune reactivity to histocompatibility antigens in mice.

Cellular receptors: binding of radioactively labeled anti-alloantiserum

RAT ALLOANTISERA OF THE FOLLOWING SPECIFICITIES WERE OBTAINED AFTER SINGLE SKIN GRAFT REJECTION: DA anti-BN, BN anti-DA, DA anti-Lewis, and Lewis anti-DA. Anti-alloantibodies were raised by injecting the first two alloantisera into (DA x BN)F(1) hosts and the last two alloantisera into (DA x Lewis)F(1) hosts. In this manner, four anti-alloantisera were raised: anti-(DA anti-BN), anti-(BN anti-DA), anti-(DA anti-Lewis), and anti-(Lewis anti-DA). From each anti-alloantiserum a gamma globulin fraction was prepared and trace labeled with (125)I. The labeled anti-alloantibodies could be shown to be fixed preferentially by red cells coated with the alloantibody used to induce them. They were also preferentially fixed by normal rat lymphoid cells presumed to carry recognition structures similar to alloantibody. For instance, anti-(DA anti-BN) was fixed by BN red cells coated with DA anti-BN and by normal DA lymphoid cells presumed to carry RS(BN). Conversely, anti-(BN anti-DA) was fixed by DA red cells coated with BN anti-DA and by normal BN lymphoid cells, carrying RS(DA). Absorption and inhibition experiments showed that alloantibodies and normal lymphoid cells compete for the same labeled anti-alloantibodies. We conclude that cellular receptors and circulating alloantibody are antigenically similar: They have the same aliotype.