MHC-restricted T cell activation: analysis with T cell hybridomas

Structure and function of the ubiquitin-proteasome system in platelets

Platelets are small anucleate blood cells with a life span of 7 to 10 days. They are main regulators of hemostasis. Balanced platelet activity is crucial to prevent bleeding or occlusive thrombus formation. Growing evidence supports that platelets also participate in immune reactions, and interaction between platelets and leukocytes contributes to both thrombosis and inflammation. The ubiquitin-proteasome system (UPS) plays a key role in maintaining cellular protein homeostasis by its ability to degrade non-functional self-, foreign, or short-lived regulatory proteins. Platelets express standard and immunoproteasomes. Inhibition of the proteasome impairs platelet production and platelet function. Platelets also express major histocompatibility complex (MHC) class I molecules. Peptide fragments released by proteasomes can bind to MHC class I, which makes it also likely that platelets can activate epitope specific cytotoxic T lymphocytes (CTLs). In this review, we focus on current knowledge on the significance of the proteasome for the functions of platelets as critical regulators of hemostasis as well as modulators of the immune response.

Versatility of using major histocompatibility complex class II dextramers for derivation and characterization of antigen-specific, autoreactive T cell hybridomas

Antigen-specific, T cell hybridomas are useful to study the cellular, molecular and functional events, but their generation is a lengthy process. Thus, there is a need to develop robust methods to generate the hybridoma clones rapidly in a short period of time. To this end, we have demonstrated a novel approach using major histocompatibility complex (MHC) class II dextramers to generate T cell hybridomas for an autoantigen, proteolipid protein (PLP) 139-151. Using MHC class II dextramers assembled with PLP 139-151 as screening and sorting tools, we successfully obtained mono antigen-specific clones within seven to eight weeks. In conjunction with other T cell markers, dextramers permitted phenotypic characterization of hybridoma clones for their antigen specificity in a single step by flow cytometry. Importantly, we achieved successful fusions using dextramer(+) cells sorted by flow cytometry as a starting population, resulting in direct identification of multiple antigen-specific clones. Characterization of selected clones led us to identify chemokine receptor, CCR4(+) to be expressed consistently, but their cytokine-producing ability was variable. Our work provides a proof-of principle that the antigen-specific, CD4 T cell hybridoma clones can be generated directly using MHC class II dextramers. The availability of hybridoma clones that bind dextramers may serve as useful tools for various in vitro and in vivo applications.

There is more than one interleukin 1

In 1972, Gery and co-workers(1) detected a factor that promotes murine thymocyte proliferation in culture supernatants of human peripheral blood adherent leukocytes. This factor is active across species lines, does not support the growth of interleukin 2 (IL-2)-dependent lymphocyte lines, is produced by monocytic rather than lymphocytic leukocytes, and has subsequently been termed interleukin 1 (IL- 1)(2). More recently, it has become evident that IL-1 activities can be produced by virtually every nucleated cell type and, in addition, IL-1 has been reported to have stimulatory effects on the growth and differentiation of numerous cell types. In this review, Joost Oppenheim and his colleagues discuss the biochemical characteristics, gene cloning, cell sources, biological properties and actions of IL-1, and give reasons why this pleitotropic, nonspecific hormone-like cytokine is of considerable concern to immunologists.

Trinitrophenol reactive T-cell hybridomas recognize antigens that require antigen processing

Protein antigens must be taken up, processed, and displayed on the surface of antigen-presenting cells in association with major histocompatibility complex molecules before they can be recognized by T cells. Whether recognition of the haptens used to study allergic contact hypersensitivity in murine models similarly requires processing has not been determined. We analyzed whether presentation of trinitrophenol to trinitrophenol reactive T-cell hybridomas requires antigen processing by studying the effects of inhibitors of antigen processing and presentation on the ability of a syngeneic B-cell tumor (A20) to present trinitrophenol to a series of interleukin-2 producing, trinitrophenol specific, major histocompatibility complex class II-restricted T-cell hybridomas. The ability of trinitrophenol modified A20 cells to stimulate the hybridomas was completely inhibited by monoclonal, anti-trinitrophenol, or anti-Ia antibodies and was significantly reduced by paraformaldehyde fixation immediately after trinitrophenol modification. Trinitrophenol-modified A20 cultured at 37 degrees C for 2 h prior to fixation was significantly more effective at stimulating the hybridomas than trinitrophenol-modified A20 fixed immediately. The ability of A20 to present trinitrophenol was inhibited by chloroquine. Paraformaldehyde fixation and chloroquine treatment had similar effects on the ability of trinitrophenol modified lymph node dendritic cells to stimulate the trinitrophenol specific hybridomas. Paraformaldehyde fixation and chloroquine treatment had similar effects on the ability of A20 cells to present ovalbumin to ovalbumin-specific hybridomas as they had on the ability of trinitrophenol modified A20 cells to present trinitrophenol to the trinitrophenol specific hybridomas. One of seven T-cell hybridomas responded to trinitrophenol modified ovalbumin but not other trinitrophenol modified proteins. These results suggest that, at least in part, T cells in the contact hypersensitivity response to trinitrophenol recognize antigens that require processing and that trinitrophenol modified proteins can be recognized.

Tumor infiltrating leukocytes (tils) during progressive tumor growth and BCG-mediated tumor regression

Tumor regression was induced by intralesional injection with BCG, 7 days after inoculation of line 10 hepatocellular carcinoma cells into strain 2 guinea pigs. Tumor-infiltrating leukocytes (TILS) were characterized immunohistochemically with 11 monoclonal antibodies (MoAbs) during the induction phase of line 10-immunity, and during immune-mediated regression of the tumor, at days 12 and 28 after tumor cell inoculation, respectively. At day 5 after BCG-injection (day 12 after tumor cell inoculation), there were no major differences between the TIL subpopulations of the BCG-treated and untreated tumors. The TILS were mainly T-cells, as identified by MoAbs against Pan T-cells (CT5), T-cytotoxic/suppressor cells (CT6) and T-helper/inducer cells (H155). A limited number of macrophages was also present. However, at day 21 after BCG-treatment (28 days after tumor cell inoculation), the fibrous stroma was increased dramatically in most of the BCG-treated tumors, and as a result, the tumor cell islets were smaller than in control tumors. In the BCG treated tumors, the numbers of T-cells and macrophages were increased. In growing and regressing tumors, MHC class I and II antigens were strongly expressed in TILS and in the tumor stroma. Line 10 tumor cells prior to inoculation expressed no MHC class I or II antigens. In the centers of the tumor islets at days 12 and 28, expression of these antigens was not found. However, MHC class I and II antigens were expressed on tumor cells at sites where they lay close to the fibrous stroma or TILS. This observation was made in progressively growing tumors and was most apparent in BCG-treated tumors.

Investigation of the genetic regulation in allergic rhinitis

Human leukocyte antigen (HLA) population and family studies were performed to determine whether a specific HLA type is associated with allergic rhinitis. We analyzed hereditary characteristics of allergic rhinitis using 27 nuclear families. According to the results of HLA typing, we concluded that allergic rhinitis is certainly regulated by HLA haplotype linked autosomal recessive inheritance. In addition, the frequency of HLA DQw3 antigen, one of the HLA class II antigens, was higher in the patients allergic to Dermatophagoides farinae, Japanese cedar pollen and/or orchard grass pollen than in non-allergic controls. Secondly, the HLA DQw3 antigen was analyzed in detail by means of HLA DNA typing. Regardless of the type of cDNA probes or restriction enzyme, the serologically defined HLA DQw3 region was highly polymorphic at the DNA level. Furthermore, when we used DQ beta as a probe and BamHI as a restriction enzyme, the 8.1 and 6.3 kb restricted fragments were detected in lower frequency and 3.5 kb fragment in higher frequency in the patients of allergic rhinitis than in non-allergic controls. Further studies by the cloning of these fragments in the patients and the controls to clarify their function may be necessary to define molecular mechanism of the onset of allergic rhinitis.

Major-histocompatibility-complex-class-II-positive cells and interleukin-2-dependent proliferation of immune T cells are required to reject carcinoma cells in the guinea pig

Tumor immunity induced by bacillus Calmette-Guérin was studied in the line 10 hepatocellular carcinoma (line 10) in the strain-2 guinea pig. Line 10 immunity was investigated in vitro with a lymphocyte proliferation assay using line 10 tumor protein extracted with 3 M KCl and in vivo by adoptive transfer of line-10-immune spleen cells. Monoclonal antibodies against guinea pig leucocyte markers were used to block functional properties of the immune cells in order to determine which cell types or cell markers are involved in the immune response to the line 10 tumor. In vitro cells from the spleen, peripheral blood and regional lymph node of immune animals reacted with a proliferative response to line 10 protein. This antigen-specific response was caused by T cells and was regulated by major histocompatibility complex (MHC) class II molecules. In blocking experiments it was found that CT5 (anti-PanT), or MSgp4 [anti-(MHC class I antigen)] monoclonal antibodies did not block but sometimes stimulated the proliferative response. The effect of H159 (anti-PanT) was irregular, while H155 [anti-(T helper)], and 5C3 [anti-(IL-2 receptor)] monoclonal antibodies blocked the response almost completely. We studied the relevance of the results in vitro obtained and found that mAb 5C3 [anti-(IL-2 receptor)] inhibited the adoptive transfer of line 10 immunity, suggesting that the rejection of line 10 cells is caused by a mechanism that is interleukin-2 (IL-2)-dependent. Moreover, complement lysis of MHC-class-II-antigen-positive immune spleen cells inhibited completely the rejection of the line 10 tumor cell challenge in the adoptive-transfer experiments. In conclusion, our data show that MHC class II molecules or cells possessing these molecules are involved in immunity against line 10 tumor cells, as (a) monoclonal antibodies against MHC class II antigens inhibited the in vitro proliferative response of T cells to tumor antigens and (b) removal of MHC-class-II-positive immune spleen cells abrogated the antitumor effect in the adoptive-transfer experiments. Interleukin-2-dependent proliferation of immune T cells is required for the rejection of line 10 tumor cells.

Major histocompatibility complex class II antigen expression during potentiation of line-10 tumor immunity after intralesional administration of bacillus Calmette-Guérin

Intralesional injection of BCG into an established line-10 hepatocellular carcinoma in the strain-2 guinea pig causes regression of the tumor and induction of line-10 immunity. We found that the animals were already protected for a second challenge with line-10 tumor cells 7 days after BCG treatment. We studied whether this early induction of immunity was correlated with the expression of MHC class II antigens on line-10 tumor cells and was correlated with an increased expression of MHC class II antigens on leukocytes in the primary tumor and in the regional lymph node (Ln. axillaris accessorius). The MHC class II antigens and the leukocyte subpopulations were measured with monoclonal antibodies and flow cytofluorometry. In the draining lymph node the number of nucleated cells increased about 10-fold during the first 5 days after intralesional injection of BCG. At this time the MHC class II antigen expression of these cells was increased from 21%-32% in the naive controls to 39%-53% in animals with BCG-treated tumors. This implies that the number of MHC-class-II-positive cells increased about 20-fold in the draining lymph node. Surprisingly, the increase in percentage of MHC-class-II-antigen-positive cells was mainly due to an increase of IgM-positive B cells from 8%-11% to 22%-41% and an increase of IgG-positive B cells from 7%-27% to 25%-44%. In the tumor, BCG treatment induced a small increase of MHC-class-II-antigen-positive cells from 11%-12% to 15%-20%. Probably this increase came not from tumor cells but mainly from a BCG-induced infiltration of mononuclear cells, as an increase of T cells from 14% to 20%, an increase of macrophages from 8% to 18%, and an increase of B cells from 0 to 6% was observed. We conclude that the potentiation of anti-(line-10 tumor cell) immunity correlated with a 20-fold increase of MHC-class-II-antigen-positive cells in the lymph nodes and a small increase in the number of MHC-class-II-antigen-positive tumor-infiltrating cells.

Murine hybrid cell lines expressing the NLDC-145 dendritic cell determinant

Dendritic cells play an important role as accessory cells in the immunological defense system. Investigations into the biological functions of this population have been limited by the difficulties encountered in isolating sufficient numbers of cells, and therefore different approaches have been described to immortalize accessory cell populations. In this report, four murine hybrid cell lines (H1-H4) are described that were produced by fusion of in vitro isolated dendritic cells and a tumor cell. The hybrid lines are characterized by the expression of the dendritic cell specific marker NLDC-145, Ia expression and the absence of macrophage or T cell markers. The cell lines have no phagocytic activity and are functionally active as accessory cells. The expression of the NLDC-145 antigen in vitro was found to be inducible. These NLDC-145-positive cell lines will be useful for the further characterization of the NLDC-145 antigen and in the study of dendritic cell and lymphocyte interactions.

Development of autoreactive L3T4+ T cells from double-negative (L3T4-/Ly-2-) Thy-1+ spleen cells of normal mice

Thy-1+/L3T4-/Ly-2- spleen cells were purified from normal C57BL/6 (B6) and C,B-17 mice. Cells within this subset expressed the T cell receptor (TcR) for antigen: the majority of cells in this subset were CD3+; a fraction of the cells was stained with the monoclonal antibody (mAb) F23.1; and the TcR molecule was immunoprecipitable with mAb F23.1 from cells within this subset. In limiting dilution analyses, about 1/30 cells within this subset were growth inducible in vitro by stimulation with phorbol myristate acetate (PMA) plus ionomycin; conditioned media containing interleukin (IL) 1, IL2, IL3 or IL4 activity neither triggered nor promoted in vitro growth of these cells. The in vitro generated T cells displayed the Thy-1+/L3T4+/Ly-2- surface phenotype and were self-reactive, i.e., proliferated preferentially in response to syngeneic stimulator cells, and secreted IL2 and IL3 only in response to syngeneic but not allogeneic stimulator cells. The proliferative response of these cells to syngeneic stimulator cells was blocked by anti-self Ia mAb. This autoreactive helper T cell subset was not inducible in purified Thy-1+ spleen cell subsets from athymic nude mice or scid mice. Autoreactive helper T cells did not express detectable levels of the IL2 receptor (IL2R), and their proliferative response was not blocked by anti-IL2R mAb. From PMA plus ionomycin-stimulated double-negative Thy-1+ spleen cells, 14 T cell clones were established in long-term culture which displayed the CD3+CD4+CD8- surface phenotype and were self-reactive.

Function and behavior of surface immunoglobulin receptors in antigen-specific T cell-B cell interaction

The expression and function of surface immunoglobulin (sIg) receptors was analyzed using antigen-specific monoclonal B cells and T cells. When B cells were incubated with antigen (hapten carrier), hapten-specific sIg receptor expression was greatly reduced. The specific antigen-presentation activity of the B cells was also markedly reduced. Following the removal of antigen, expression of the sIg receptors was restored to original levels within 3-4 hr. Specific antigen-presentation activity of these B cells was concomitantly restored. Reduction of sIg receptor expression and specific antigen presentation were inhibited by the addition of competing free hapten, suggesting that crosslinking of sIg receptors is required for the observed changes in sIg receptor expression and that specific antigen presentation is hapten specific. Using oligopeptide-specific Th cells, we could show the requirement for processing of antigen in the interaction between hapten-specific B cells and carrier-specific T cells. These results indicated that the expression of sIg receptors for a specific antigen and the ability to present the antigen are interrelated.

Cytotoxic function of a cloned helper T cell line

The cytotoxic function of a well-characterized helper T hybridoma was investigated utilizing 2,4,6-trinitrophenyl (Tnp) specific B cells. The T hybridoma which is ovalbumin (Ova) specific recognizes the Ova synthetic peptide 323-339 Tyr. A number of experiments using several different antigens, Ova, Tnp-Ova and 323-339 Tyr clearly demonstrated that the cytotoxic function of the T hybridoma is strictly correlated with antigen presentation.

Assessment of antigen-specific receptor function of surface immunoglobulin M and D with identical hapten specificity

Monoclonal B-cell lines expressing antigen-specific surface IgM or IgD were established by transferring the genes encoding immunoglobulin heavy (mu or delta) and light (kappa) chains specific for the hapten 2,4,6-trinitrophenyl (TNP) into a B-cell lymphoma line. Two IgMTNP and two IgDTNP transformants were selected on the basis of similar levels of anti-TNP idiotype expression by flow microfluorimetric analysis. The IgMTNP and IgDTNP transformants were compared in quantitative assays for their ability to bind TNP-carrier and present TNP-carrier to carrier-specific T cells. Our results indicate that IgMTNP and IgDTNP transformants have an equal capacity to bind and present specific antigen. Thus surface IgM and IgD, when present in equivalent amounts, function similarly as antigen receptors.

An antiviral T-cell clone defines a functional supertypic specificity shared by different HLA-DR molecules from DR2-short, DRw11, and DRw13 haplotypes

An influenza virus-specific HLA class II-restricted human T4+ clone (Ij) allows us to define a new functional supertypic HLA class II specificity shared by three different haplotypes. Influenza A virus-infected antigen-presenting cells of these three haplotypes, HLA-DR2 short, DRw11, and DRw13, are able to stimulate Ij cells. The same precise viral specificity is seen in all three cases. Proliferation inhibition experiments using HLA-specific monoclonal antibodies demonstrate that HLA-DR products are involved in all cases. However, according to the DR specificity of the antigen-presenting cell, differential blockings by a series of DR-specific monoclonal antibodies suggest that the functional epitope is shared by different HLA-DR molecules. This is confirmed by two-dimensional gel analysis of the HLA-DR beta chains expressed in the three haplotypes.

Antigen presentation by hapten-specific B lymphocytes. III. Analysis of the immunoglobulin-dependent pathway of antigen presentation to interleukin 1-dependent T lymphocytes

The ability of antigen-specific murine B lymphocytes to present antigen to a normal (nontransformed) antigen-specific, interleukin (IL)1-dependent T cell clone and to heterogeneous T lymphocytes was investigated. Hapten-specific lymphocytes present protein antigens to both the D10G.4.1 T cell clone and heterogeneous immune T cells. When the antigen bears an epitope recognized by the specific B cell, the subsequent presentation of this antigen is 10(2)-10(4)-fold more efficient, as compared to the same, but nonhaptenated protein. The requisite B lymphocyte binds hapten, is radiosensitive and is nonadherent to plastic. The hapten-specific antigen presentation is blocked by antibodies to the surface Ig receptor, while the presentation of unmodified protein is unaffected. These observations are identical to our findings in studies of B cell antigen presentation to T-T hybridomas and therefore demonstrate the generality of the immunoglobulin-dependent pathway of presentation. However, in contrast to the results with T-T hybridomas, the specific B lymphocytes are necessary, but not sufficient, to activate IL 1-dependent T cells. A third cell is required for both B lymphocyte immunoglobulin-dependent and nonspecific antigen-presentation. This cell is radioresistant, plastic adherent and of low density. The requirement for this third cell can be circumvented by supplementing cultures with highly purified IL 1. These results demonstrate that the remarkably efficient ability of B lymphocytes to present antigen is operative with factor-dependent T lymphocytes. Furthermore, conventional accessory cells also appear to play a role in this process, which is consistant with their known requirement in antigen-specific T-B interactions in the generation of antibody responses.

Antigen presentation by a B-cell line transfected with cloned immunoglobulin heavy- and light-chain genes specific for a defined hapten

The rearranged genes encoding immunoglobulin heavy (mu) and light (kappa) chains specific for the hapten 2,4,6-trinitrophenyl (Tnp) were introduced into a B-lymphoma line that bears surface IgG with an unknown specificity and expresses surface Ia molecules. A transformant expressing surface IgM specific for Tnp was obtained. The transformant was found to present Tnp-proteins to antigen (protein)-specific T cells far more efficiently than the parenteral B-lymphoma line. This artificial system, utilizing recombinant DNA technology and gene transfer, provides several approaches for the study of T-cell-B-cell interactions.

Effect of purified human interferon-alpha on the expression of differentiation antigens and mitogen reactivity of cultured human thymic cells

Human thymic cells were cultured in vitro either alone or with the addition of a highly purified preparation of human interferon-alpha. Immunofluorescence techniques using a series of monoclonal antibodies showed that 2-day cultured thymocytes express a more mature phenotype (low HTA 1, high T3 and HLA-A,B,C) than normal, uncultured thymocytes. Interferon addition to the cultures results in a strong increment in the number of HLA+ cells and in the total amount of HLA expressed by the cultured cells. Experiments with purified cell populations showed that the cortical, immature, thymocyte was the target cell for interferon action. Phytohemagglutinin responses--but not interleukin 2 responses--were diminished after pretreatment of thymic cells with interferon. We suggest that interferon may favor a pathway of intrathymic differentiation phenotypically characterized by a high content of Class I HLA antigens.

TAP, a novel T cell-activating protein involved in the stimulation of MHC-restricted T lymphocytes

Five mAbs have been generated and used to characterize TAP (T cell activating protein) a novel, functional murine T cell membrane antigen. The TAP molecule is a 12-kD protein that is synthesized by T cells. By antibody crossblocking, it appears to be closely associated with a 16-kD protein on the T cell membrane also identified with a novel mAb. These molecules are clearly distinct from the major well-characterized murine T cell antigens previously described. Antibody binding to TAP can result in the activation of MHC-restricted, antigen-specific inducer T cell hybridomas that is equivalent in magnitude to maximal antigen or lectin stimulation. This is a direct effect of soluble antibody and does not require accessory cells or other factors. The activating anti-TAP mAbs are also mitogenic for normal heterogeneous T lymphocytes in the presence of accessory cells or IL-1. In addition, these antibodies are observed to modulate specific immune stimulation. Thus, the activating anti-TAP mAbs synergise with antigen-specific stimulation of T cells, while a nonactivating anti-TAP mAb inhibits antigen driven activation. These observations suggest that the TAP molecule may participate in physiologic T cell activation. The possible relationship of TAP to known physiologic triggering structures, the T3-T cell receptor complex, is considered. TAP is expressed on 70% of peripheral T cells and therefore defines a major T cell subset, making it perhaps the first example of a murine subset-specific activating protein.

Strategies for the modulation of neuroimmunological disease at the level of autoreactive T-lymphocytes

Cell lines of autoimmune T-lymphocytes have been established in several neuroimmunological model diseases and also in a human neurological autoimmune disease, myasthenia gravis. These cell lines generally have the T helper/inducer phenotype and recognize autoantigen in the context of class II histocompatibility antigens. Autoreactive helper T cell lines may become useful tools for the evaluation of new immunotherapeutic strategies. (1) Treatment with anti-Ia monoclonal antibodies presumably interferes with the interaction between Ia on the surface of antigen-presenting cells and the autoreactive T cell receptor; (2) Therapy with unmodified or modified autoantigen may be used to tolerize or delete the autoimmune T cells; (3) Monoclonal antibodies against the 'T cell domains' of autoantigen may prevent its recognition by the autoreactive T cells; (4) Treatment with monoclonal antibodies against T cell clonotypic or differentiation antigens may effectively delete or inactivate the autoreactive T cells. Furthermore, autoreactive helper T cells may be used to induce and establish anti-idiotypic suppressor T cell lines, or the autoimmune helper T cells may themselves display suppressive effects in an allogeneic system.

Distinct recognition phenotypes exist for T cell clones specific for small peptide regions of proteins. Implications for the mechanisms underlying major histocompatibility complex-restricted antigen recognition and clonal deletion models of immune response gene defects

Using synthetic peptides as antigens, it was found that T cell clones of a given haplotype specific for 13-16 amino acid peptides could be clearly distinguished by the varied influence of amino acid substitutions on recognition. This was true for different antigenic determinants within peptides 81-96 and 74-86 of hen egg-white lysozyme, recognized in the context of the I-Ab and I-Ak molecules, respectively. Considerable complexity was demonstrated in the induced T cell repertoire specific for apparently single determinants, which implies that diversity of T cell recognition approaches that for B cells. The implications of the degeneracy of T cell recognition are discussed in the context of mechanisms through which Ia molecules restrict recognition and theories of Ir gene defects.

Analysis of responder cell-cell interactions in the syngeneic mixed leukocyte response

In a previous study we identified the target antigens on stimulator cells in the murine syngeneic mixed leukocyte response (MLR) as self Ia molecules. The experiments reported here utilized analysis of log-log cell number-response titration slopes to study the responder T-cell population in the syngeneic MLR. The data indicated that in the peripheral lymphoid population at least two cell populations interact to produce a murine syngeneic MLR. One of these cell types appeared to be a member of an Lyt 2- subset, another a member of an Lyt 2+ subset. A potential third cell type, which was detected in the presence of (PMA)-induced EL4 supernatants, was found in the thymus, an organ that did not appear to contain either of the other two subsets. Experiments with adult thymectomized and neonatal mice suggested that the cell populations involved in the syngeneic MLR were mature T cells and were not an early differentiation state of T lymphocytes whose ability to be stimulated by Ia antigens alone was a transient event.

Incorporation of antigen 125I IgG into particular cell compartments: binding by chromatin

Incorporation of [125I]IgG into spleen cells was studied in vivo and in vitro. In vivo, the antigen after uptake into the cytoplasm migrated into cell nuclei, where it was bound to chromatin up to the saturation level. One day after immunization the constant level of [125I]IgG was 1.3 X 10(12) molecules per spleen (10(8) cells). The same number of [125I]IgG molecules were bound to chromatin in cell cultures. The uptake of [125I]IgG was competitively inhibited by non-labelled IgG. Binding of [125I]IgG molecules reextracted from cytoplasm and chromatin with specific anti-human IgG serum argues against the uptake of degraded [125I]IgG molecules. [125I]IgG was tightly bound to DNA. Approximately 50 per cent of [125I]IgG was present in the residual chromatin fraction (after removal of 0.35 M and 2 M NaCl-soluble fractions) and 40 per cent was complexed with DNA (after removal of histones and non-histones AP1, AP2, AP3 and AP4). Binding of [125I]IgG by isolated chromatin was inhibited by the cytoplasmic fraction but not by BSA. Binding of [125I]IgG by fractionated chromatin, (chromatins remaining after removal of 0.35M, and 2M NaCl-soluble fractions or histones + non-histones AP1 + AP2 + AP3 + AP4) occurred at a level similar to that observed with native chromatin. The results suggest that interaction of antigen with immunocompetent cells is not restricted to the cell surface but that antigen seems to be taken up into cytoplasm, migrates to the nuclei and is bound to chromatin, probably directly to DNA. The results are discussed in relation to the induction of the immune reaction.

Role of macrophage D-region antigens and T-lymphocyte differentiation antigens in induction of gamma interferon

Macrophage-T-lymphocyte cultures from patients with recent recurrent herpes labialis were stimulated to produce gamma interferon by either herpes simplex antigen or mitogens (PHA and Con A). The ability of monoclonal antibodies to HLA-DR and DC/DS, HSV glycoprotein antigens and T-lymphocyte surface antigens to inhibit interferon production and lymphocyte proliferation were studied. Anti-D region antibodies inhibited HSV antigen-induced but not mitogen-induced interferon and proliferation. The extent of inhibition varied mainly according to the determinants recognized by the antibodies and, to a lesser degree, between patients. Inhibition probably resulted from inhibition of antigen presentation, through antibody binding to macrophage D-region antigens. Interferon production was a more sensitive index of inhibition than lymphocyte proliferation. With one antibody (L227) a marked difference in inhibition in the two assays was noted, suggesting that lymphocytes producing gamma interferon may differ from the majority of the proliferating cells in their recognition of D-region determinants. Antibodies to the HSV glycoprotein antigens (gA/B, gC, gD, gE) did not produce consistent significant inhibition of interferon production and had no effect on proliferation. Anti-Leu 4 and -Leu 5 inhibited HSV antigen and mitogen induction of gamma interferon (and proliferation). Anti-Leu 2 and anti-Leu 3, mildly inhibitory alone, produced synergistic inhibition together. Hence, in human systems, the interaction between macrophages and T lymphocytes in producing gamma interferon appears to differ according to mode of induction. Macrophage D-region antigens are required for antigen induction probably via presentation whereas other factor(s), probably monokine secretion, are necessary for mitogen induction. Antibodies acting on the T-lymphocyte surface appear to affect a final common pathway of interferon induction, similar to their effects on proliferation and secretion of other lymphokines.

Inhibition of antigen-specific T lymphocyte activation by structurally related Ir gene-controlled polymers. II. Competitive inhibition of I-E-restricted, antigen-specific T cell responses

Our previous studies have defined a highly specific competitive inhibition between a pair of structurally related antigens (GT and GAT) for antigen presentation by accessory cells. The present report investigates this phenomenon in a second antigenic system, which is controlled by a distinct Ir gene product. Two GL phi-specific, I-Ed-restricted, interleukin 2-producing T cell hybridomas were constructed. The antigenic fine specificity of these two hybrid clones was distinct. One hybrid reacted solely with GL phi while the second cross-reacted with GLleu and GLT. These latter two copolymers, as well as the antigen GL, were found to inhibit the GL phi response of the non-cross-reactive hybrid. The structurally related antigen G phi was not inhibitory for this clone's response. The cross-reactive GL phi hybrid could also be inhibited, but, in this case, G phi and not GL caused the inhibition. Reciprocal inhibitions could be demonstrated between these and other hybrids (e.g., GAT responsive), indicating a very high degree of specificity to the inhibition. The inhibition caused by the various copolymers was reversible by increasing the concentration of GL phi, This effect was localized to the antigen-presenting cell and not the T cell hybridoma. Functionally, this competition did not appear to be for antigen uptake or general antigen processing. These findings generalize the phenomenon of antigen competition to a second antigen system in the context of a second Ia molecule. The possible mechanisms accounting for the complex pattern of specificities in this system are discussed.

Functional properties of T cell clones with a double specificity for alloantigens and foreign antigens

Four keyhole limpet hemocyanin (KLH)-specific clones prepared from the lymph node of CB6F1 mice immunized with KLH had a proliferative response restricted to parental major histocompatibility complex (MHC)-encoded antigens. These clones provided help for CB6F1 trinitrophenyl-ovalbumin (TNP-OVA)-primed B cells to mount IgM and IgG plaque-forming cell (PFC) responses in the presence of KLH-TNP conjugate. In addition, two of these clones (A12.11 and F6) proliferated in response to allogeneic cells from mice strains bearing H-2k or H-2q haplotypes, respectively. However, they did not provide help for C3H/He or B10.Q primed B cells. The clonal nature of A12.11 and F6 was demonstrated by subcloning and in BUdR-suicide experiments. The proliferative response to KLH was ablated by anti-Iad antibodies, whereas the proliferation induced by C3H/HeJ stimulating cells was ablated by anti-Iak antibodies. Furthermore, both responses were inhibited by a monoclonal anti-clonotype (idiotype) antibody. Taken together, these results strongly support the hypothesis that the same receptor recognizes alloantigens and KLH associated with self-antigens.

Antigen presentation by hapten-specific B lymphocytes. I. Role of surface immunoglobulin receptors

The present study examines the ability of hapten-specific murine splenic B lymphocytes to present hapten-proteins to carrier-specific T cell hybridomas. BALB/cB cells specific for 2,4,6-trinitrophenyl (TNP) were isolated from spleens of immune mice by elution from TNP-gelatin-coated dishes. Such cells presented the TNP-modified terpolymer, GL phi, at concentrations as low as 0.1 microgram/ml, to a GL phi-specific, I-Ed-restricted, interleukin 2-producing T cell hybridoma. In contrast, the same B lymphocytes required 1,000-fold higher concentrations of unmodified GL phi to stimulate the same T cell hybridoma. The presentation of low concentrations of TNP-GL phi by TNP-specific B lymphocytes was significantly or completely blocked by anti-Ig antibody or TNP-proteins, indicating that surface Ig receptors were critically involved in this phenomenon. Finally, binding of TNP-proteins did not alter the ability of the B cells to present unrelated, unhaptenated proteins or to stimulate alloreactive T cells. These results suggest that surface Ig receptors serve to focus antigens onto specific B lymphocytes and that such cells are highly efficient at presenting linked antigenic determinants to T cells. The implications of these findings for the mechanisms of physiologic, histocompatibility-restricted T-B collaboration are discussed.

Analysis of thymocyte MHC specificity with thymocyte hybridomas

Medullary, peanut agglutinin-negative (PNA-), thymocytes were activated in vitro with either exogenous interleukin 1 (IL-1) or accessory cells. T cell blasts from these cultures were subsequently fused to BW5147 to generate thymocyte hybridomas. Fusion frequencies similar to those obtained with peripheral T lymphocytes were observed. A high frequency of these hybrids are triggered to produce IL-2 in the presence of syngeneic accessory cells. Exogenous, nominal antigens do not appear to be required for this activation. Using accessory cells from a series of recombinant inbred mice, the specificity of this hybrid-accessory cell interaction could be mapped to either I-Ak or I-Ek or both. This was confirmed by blocking with alpha Ia monoclonal antibodies (mAbs). A high frequency of these self-reactive cells are also alloreactive. Interestingly, several clones were identified that appear to recognize public Ia determinants broadly shared by different alleles and genetic subregions. Such specificities appear to contrast with those of peripheral T lymphocytes whose specificity is dominated by the genetically polymorphic portion of the Ia molecule. These results document the clonal specificity occurring in the cultures of in vitro activated thymocytes and allow an analysis of at least a portion of the intrathymic repertoire for major histocompatibility complex (MHC) determinants. The implications of these findings are discussed.

Selective modification of a private I-A allo-stimulating determinant(s) upon association of antigen with an antigen-presenting cell

A large panel of alloreactive, interleukin 2 (IL-2)-producing T cell hybridomas was constructed from B10 alpha BALB/c primary mixed lymphocyte cultures (MLC). Functional hybrids had specificity for either I-Ad or I-Ed. These cells were used to probe determinants on Ia molecules in an attempt to detect molecular association between a nominal antigen and an Ia molecule on an antigen-presenting cell (APC). The response of a small number of these clones was significantly blocked by the addition of the Ir gene-controlled copolymer L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT) to culture. A comparison of the inhibited and uninhibited hybrids revealed an identical dose response curve. Further, both types of hybrids were activated by the same stimulator cell and frequently recognized the identical Ia molecule on that cell. Nevertheless, the inhibitory effect of GAT was localized to the stimulator cell and not to the T cell hybrids. All of the hybrids whose stimulation was blocked had specificity for the I-A molecule, which is the gene product known to control and restrict responsiveness to GAT. Further, only GT, but not a number of other related antigens, was also specifically inhibitory, which correlates with the known associational specificity of these antigens on an APC. Finally, the same stimulator cell could be shown to coordinately lose an allostimulatory determinant(s), while it was gaining an I-Ad plus GAT determinant(s). The implications of these findings on the nature of antigen-Ia association and on the role of polymorphic Ia determinants are discussed.

Thymic T cells are driven to expand upon interaction with self-class II major histocompatibility complex gene products on accessory cells

Murine thymocytes induce the monokine interleukin 1 upon in vitro coculture with a radioresistant Ia-bearing accessory cell [murine Ia molecule is a class II major histocompatibility complex (MHC) antigen]. The generation of interleukin 1 is critically dependent on the function of I-region gene products on accessory cells. The induced interleukin 1 appears to allow the activation and proliferation of self-MHC-specific thymocytes. Thus, in the absence of added exogenous factors, there is an Ia-dependent thymocyte proliferation. This selective activation of thymocytes is observed with both mature and immature thymic T cells. This in vitro response results in the selective amplification of developing T cells with self-MHC specificity and could be of importance to the in vivo commitment of T cells to MHC determinants that occurs in the thymus.

Analysis of T-cell cultures and clones from a patient with classic rheumatoid arthritis--evidence for the existence of autoreactive T-cell clones in blood and synovial fluid

Using lectin-free IL-2 as the only initial stimulus, bulk cultures and T-cell clones were established from synovial fluid (SFL) and peripheral blood lymphocytes (PBL) of a patient with rheumatoid arthritis (RA). The cloning efficiency of growing bulk cultures was 3%-4% as evaluated by Poisson statistics and was not enhanced by the addition of autologous synovial fluid or serum. The majority of the cloned T cells expressed the OKT8+ phenotype; several clones were OKT4+ and one clone expressed OKT8+ and OKT4+ antigens. None of the cloned T cells exhibited high NK or lectin-dependent cytotoxicity, although bulk cultures had high NK activity. In primed lymphocyte typing responses, bulk cultures and two T-cell clones established from rheumatoid SFL and PBL showed consistent autoreactivity, which we have never before observed with MLC-derived bulk cultures and T cell clones. One of the autoreactive rheumatoid T-cell clones (B25) was found to provide strong helper activity to autologous B cells in the absence of mitogen. Attempts to reveal reactivity of RA-derived T-cell clones to microbial antigens have so far only been successful with Mycoplasma pneumoniae preparations. Careful analysis of this reactivity revealed, however, that Mycoplasma pneumoniae induces a stimulator cell-dependent mitogenic effect rather than an antigen-specific MHC-restricted T-cell proliferation.