Helper factors derived from autologous mixed lymphocyte cultures

Reconstitution of impaired autologous mixed lymphocyte reactivity in rheumatoid arthritis

We examined the ability of recombinant IL-2 to reconstitute the autologous mixed lymphocyte reaction (AMLR) defect in peripheral blood mononuclear cells (PBM) from patients with rheumatoid arthritis (RA). Our results revealed an ability to fully reconstitute RA AMLRs with pharmacologic concentrations (100 units/ml), but not physiologic concentrations (10 units/ml) of IL-2. Full reconstitution of RA AMLRs was achieved whether IL-2 was added as the initiation of culture or at 48 or 72 hours prior to termination of the cultures. Impaired IL-2 production was noted throughout the time course of the RA AMLRs. Neither an inhibitor of IL-1 nor IL-2 was detected in AMLR culture supernatants. Moreover, IL-1 in pharmacologic concentrations up to 50 units/ml failed to reconstitute impaired AMLR reactivity. In 2 patients whose AMLRs failed to reconstitute fully with 100 units/ml IL-2, addition of 10 units/ml IL-1 in combination with IL-2 fully reconstituted the AMLR defect. The results may suggest that defective IL-2 generation alone cannot fully account for impaired AMLR reactivity in RA patients.

Mechanism of the immunoregulatory effect of cloned T cells on proliferation in mixed lymphocyte responses

The mechanism of the suppression of the mixed lymphocyte response (MLR) by T cell clones derived from the murine AMLR was studied in a system employing .45 microns membrane chambers to isolate the cellular reactants. The clones effectively suppressed MLR regardless of the MHC haplotype of the reactants in the absence of direct cellular contact, via a soluble factor able to pass through this membrane. Utilizing specific neutralizing antibodies, this factor was shown to be principally TNF alpha, with a contributing effect of gamma interferon. Production of TNF alpha by the cloned T cells was confirmed by direct assay of clone culture supernatants.

A novel autoregulatory cytokine is required for the regulation of autoaggressive responses

Limiting dilution studies indicate that cells with the potential to lyse autologous target cells exist in the peripheral blood of all normal individuals. In contrast to allocytotoxic cells, autocytolytic cells are down-regulated by a second less frequent cell population. When recombinant interleukin 2 is substituted for crude lymphocyte conditioned medium in these limiting dilution experiments, autocytotoxicity develops normally. Under these conditions, however, the autocytotoxic response is not down-regulated. Mixing crude lymphocyte-conditioned medium together with recombinant interleukin 2 restores the regulation of autocytotoxicity normally seen at high responder cell dose. These findings indicate that a second soluble factor present in the conditioned medium is necessary either for the activation, growth, or differentiation of the regulatory cell population or alternatively, to render the cytotoxic population responsive to the activity of regulatory cells. Gel filtration studies indicate that the molecular weight of this factor is between 60 and 80 kd. This factor appears to be distinct from known immunologically active cytokines. It is conceivable that deficiencies of this cytokine may be relevant to the pathogenesis of autoimmune diseases or graft-versus-host reactions.

The role of autoreactive T-cell lines in the restoration of the immune response to sheep red blood cells in C57Bl/6-lpr/lpr mice

Although autoimmune-prone mice bearing the lymphoproliferation (lpr) gene have polyclonally activated B cells and high serum titers of autoantibodies, they mount poor immune responses to exogenous antigens. In addition, they exhibit very low or nonexistent autologous mixed lymphocyte responses. Previous studies have shown that autoreactive T-cell clones have immunoregulatory properties: they can help suppress, or contrasuppress an immune response. Here we show that two autoreactive T-cell lines, GB4 and B1H1, can restore the defective response of C57Bl/6-lpr/lpr mice to the antigen sheep red blood cells. This restoration is antigen-dependent and requires the presence of other T cells.

Regulation of mucosal IgA production in vitro by autoreactive immunoregulatory T cells from murine Peyer's patches

In this study, we investigated whether Peyer's patch-derived T-cell subsets participate in vitro in self major histocompatibility (MHC) class II antigen (Ag)-mediated immunoregulatory circuits for gut-mucosal IgA isotype selection in the presence of Peyer's patch (PP)-derived syngeneic surface immunoglobulin M (sIgM)-bearing B cells. When fresh (in vitro unstimulated) sIgM-bearing B cells were cocultured with fresh, PP-derived L3T4+ Vicia villosa-nonadherent (VV-) T cells (T helper (Th) cells), the production of all class-specific immunoglobulins (Ig), but, in particular, IgA, was enhanced two- to sixfold. This augmented Ig production was, however, reduced by nearly 50% when fresh PP-derived Lyt2+ VV-T cells (suppressor T cells) were added. Furthermore, addition of PP-derived L3T4+ VV+ and Lyt 2+ VV+ T cells abrogated, by nearly 100%, the suppression induced by the Lyt 2+ VV-T cells (contrasuppression). When lipopolysaccharide (LPS)-stimulated, PP-derived sIgM-bearing B cells were cocultured with the Th cells, the production of each class-specific Ig was similarly enhanced, but Ig levels exceeded those obtained with cultures of the unstimulated B cells (P less than 0.001). Anti-I-A or anti-I-E monoclonal antibody (mAb) inhibited the induction of each immunoregulatory T-cell effector activity (P less than 0.001), and anti-I-A/E inhibited it synergistically. Thus, unstimulated fresh PP-derived T cells appear to be activated and then to exert T-cell effector functions in the sequential development of helper, suppressor, and contrasuppressor immunoregulatory networks in the presence of PP-derived sIgM B cells and, particularly, LPS-preactivated sIgM B cells. Based on the blocking effect of anti-I-A and/or anti-I-E mAb on the induction of each T-cell-mediated immunoregulatory function in class-specific Ig production, it appears that the autoreactive (self MHC class II Ag-reactive) activation of PP T cells evoked by Ia Ag on PP sIgM B cells largely controls mucosal IgA production by the latter cells. Furthermore, this immunoregulation by autoreactive effector T cells, especially the L3T4+ VV- helper T cell, may play a significant role in vivo in gut-mucosal IgA isotype production.

Characterization of the fine specificity and antigen markers associated with the receptor of autoreactive T-cell hybridomas

In this study we attempted to define the determinants on Ia molecules recognized by autoreactive hybridomas obtained from (C57BL/6 X BALB/c)F1 mice. The epitopes recognized by the T cells were characterized (a) using stimulating cells from various congenic and H-2 recombinant inbred strains and (b) by inhibition of activation with anti-Ia antibodies. Our hybridomas were strictly autoreactive and did not exhibit any alloreactivity, as is often observed for such cells. Our results show that more epitopes than previously believed are recognized by autoreactive T cells. One T-cell hybridoma (QW27.1) is unique in that it recognizes a hybrid F1 Ia determinant. Antigenic markers associated with the receptor of the T-cell hybridomas were studied with monoclonal antibodies (mAbs) specific for L3T4 and a V beta "idiotype". The results indicate that all Lyt 1.2 autoreactive T cells express L3T4 antigen in association with their receptor. One clone (QW64.14) expresses the V beta idiotype recognized by F23.1 monoclonal antibody. Moreover, this clone is activated by F23.1, linked to Sepharose 4B beads, which was believed previously to activate only Lyt 2+, L3T4 T cells. The supernatant of one clone (QW17.5) helps B cells to differentiate into antibody-producing cells without requiring direct contact with the autoreactive clone.

On the immune reaction to autologous human lymphoblasts: evidence for the stimulation by activating factors rather than induction by autoantigens

This report questions the nature of stimulation in the lymphoblast-induced autologous mixed leukocyte reaction (AMLR). Using immobilized phytohemagglutinin (PHA) and pokeweed mitogen (PWM), we show that the AMLR generated with PHA lymphoblasts (PHA X AMLR) was not significantly different from the AMLR generated with untreated stimulators. The PWM lymphoblasts of 15 out of 33 apparently normal blood donors generated an AMLR (PWM X AMLR) greater than their respective normal AMLR. The positive PWM X AMLR was not related to the expression of HLA-DR or surface IgM, since expression of both was increased by both PHA and PWM, yet only PWM blasts stimulated in the AMLR. Fixation of PWM-stimulated cells prior to the AMLR completely abolished stimulatory capacity, indicating further against new or increased antigen expression. Inactivation by uv irradiation of surface HLA-D on the stimulators had no effect upon the PWM X AMLR, while intact protein synthesis was required in order to stimulate. The ability of cells to stimulate was associated with the release of soluble helper factors capable of stimulating autologous cells independently. These factors were neither contaminating PWM nor secreted IL-1 or IL-2, although IL-1-like activity was released by all cells regardless of their ability to stimulate. The individual variation in the PWM X AMLR response and secretion of helper factors is discussed in relation to B-cell hyperproliferation and altered immunoglobulin production in autoimmune manifestations.

Phenotypic identification of suppressor-effector, suppressor-amplifier and suppressor-inducer T cells of B cell differentiation in man

Using monoclonal anti-Leu8 antibody to isolate subpopulations of human helper/inducer (CD4+) and suppressor/cytotoxic (CD8+) T cells, we have investigated the role of these subpopulations in the regulation of B cell differentiation in the human autologous mixed leukocyte reaction (AMLR). Whereas AMLR-activated CD8+,Leu8- cells were capable of suppressing fresh AMLR cultures in the absence of fresh CD8+ cells, CD8+,Leu8+ cells suppressed only those cultures containing fresh CD8+ cells. On the other hand, CD8+,Leu8- cells became suppressor cells only when cultured in the presence of CD8+,Leu8+ cells. Finally, the development of CD8+ suppressor cells was dependent on the presence of CD4+,Leu8+ cells; CD4+,Leu8- cells were incapable of acting as suppressor-inducer cells, but have been shown previously to mediate T cell help for B cell differentiation. Thus, at least 3 phenotypically distinct subsets of T cells interact sequentially to generate suppression of B cell differentiation induced in the AMLR: CD4+,Leu8+ suppressor/inducer cells, CD8+,Leu8+ suppressor-amplifier cells and CD8+,Leu8- suppressor-effector cells.

Production of a cytokine with interleukin 3-like properties and cytokine-dependent proliferation in human autologous mixed lymphocyte reaction

The autologous mixed lymphocyte reaction (AMLR) was assayed in a medium containing fresh autologous serum, by using nylon-adherent stimulator cells and nonadherent responder T cells, which were prepared from human peripheral blood mononuclear cells in the absence of fetal calf serum (FCS) to avoid any sensitization to xenogeneic protein antigens. DNA replication without a background proliferative response was induced by stimulator cells in the responder cells. The addition of monoclonal anti-HLA-DR antibody to the culture or treatment of the responder cells with complement plus anti-T4 but not anti-T8 monoclonal antibody suppressed the AMLR, suggesting that this specific AMLR involves an interaction between HLA-DR antigens and helper/inducer T cells. Regardless of this specific DNA replication, the AMLR generated no production of interleukin 2 (IL-2) and interferon gamma (IFN-gamma), both of which could be found in the allogeneic (allo) MLR. In addition, DNA replication in the AMLR was not inhibited by the addition of specific antisera for IL-2 and IFN-gamma, both of which significantly inhibited the DNA replication in allo-MLR. The AMLR was accompanied by production of a soluble factor, which could stimulate the proliferation of murine interleukin 3 (IL-3)-dependent cell line 32Dcl but not the proliferation of IL-2-dependent cell lines. This factor was also found to be responsible for proliferation of responder nonadherent cells in the AMLR. It strongly stimulated bone marrow cells, as did the murine IL-3. The factor had an Mr range, as determined by gel filtration, of 15,000-28,000, but it did not bind to fast protein liquid chromatography (FPLC)-MonoQ column. Thus, the factor is distinguishable from IL-2 in physicochemical or biological properties, but similar to murine IL-3. These results suggest that the human AMLR may be primarily a phenomenon in which non-T cells mediated by the HLA-DR antigens on the cell stimulate helper/inducer T cells to produce a lymphokine with IL-3-like properties, but no IL-2, which in turn stimulates the factor-dependent cells to proliferate.

Stimulation of murine lymphocyte responses by cations

The capacity of the heavy cations Pb, Ni, and Zn to modulate murine in vitro lymphocyte responses was examined. Pb and Ni (100 microM) were shown to enhance the in vitro plaque-forming cell (PFC) response to sheep red blood cells while 100 microM Zn had inhibitory effects. Each metal was able to stimulate the proliferation of murine splenocytes as determined by [3H]thymidine incorporation and autoradiography. The enhancing effect of the metals on the PFC response was observed whether the results were expressed on a per culture or a per cell basis, indicating an actual increase in B-cell differentiation. Both the PFC response and the proliferative response were shown to be sensitive to the type of medium employed (M-199 gave optimum results) and to the presence or absence of 2-mercaptoethanol. As in autologous mixed-lymphocyte responses peak proliferation occurred after Day 5 in culture, was cell density dependent, and required the presence of both T cells and Ia+ cells. Treatment of splenocytes with anti-Thy-1.2, anti-Lyt-1, or anti-L3T4 plus complement completely abrogated the proliferative response, indicating that a Lyt-1+, Lyt-2-, L3T4+ T-cell was required for the induction of proliferation. The data are consistent with the hypothesis that the metals are capable of modifying the immune response directed at self either by directly altering self constituents (class II) or by modulating the autologous T-cell response.

Regulation of the cytotoxic activity of alloreactive cytotoxic T lymphocytes by helper cells and lymphokines

The cytotoxic activity of alloreactive cytotoxic T lymphocytes (CTL) was maintained and augmented by transferring cells from a 5-day mixed lymphocyte culture MLC into a host culture (HC) containing indomethacin, freshly explanted normal spleen cells, and peritoneal cells which were syngeneic to the MLC cells. The MLC cells used in the transfer experiments were generated by culturing untreated H-2b splenic responders with irradiated H-2d stimulators, or were generated by culturing Lyt-2-depleted H-2b splenic responders with irradiated H-2d stimulators. The allo-CTL were found to be derived from the donor MLC (first culture) when unfractionated MLC cells were transferred into a host (second) culture and incubated for 5 days. In contrast, the allo-CTL were derived from host culture cells when Lyt-2-depleted MLC cells were transferred and the combined cultures incubated for 5 days. In the former case, the augmentation of MLC-derived cytotoxicity did not result from nonspecific expansion of all donor T cells; instead it was mediated by lymphokine(s), distinct from IL-2, produced by helper T cells generated in host culture, which appeared to selectively expand the antigen-specific CTL or to increase the cytotoxic activity of these CTL. The helper T cells were Thy-1+, L3T4+, and Lyt-2-. These findings indicate that antigen-nonspecific help was provided by helper cells or helper factors (lymphokines) generated in the host culture, which maintained and augmented the cytotoxic activity of the fully generated allo-CTL. This helper effect was also seen in the induction of primary allo-CTL responses which could be generated with fewer stimulating cells and with a stronger cytotoxic response at different R/S ratios tested. The generation of allo-CTL in second culture following transfer of Lyt-2-depleted MLC cells to host cultures appears to have involved antigen carryover from the MLC; however, antigen carryover alone was not sufficient. It appears that in the absence of Lyt-2+ suppressor T cells, antigen-specific help might be generated in donor cultures (Lyt-2-depleted MLC) which promoted or recruited the generation of antigen-specific CTL in host culture.

In the murine syngeneic mixed lymphocyte reaction, one T cell subset replicates in the presence of B cells or macrophages and replication is inhibited by simultaneous presence of both stimulator cells

The murine T-non-T cell syngeneic mixed lymphocyte reaction has been examined to determine whether B cells and macrophages stimulate the same or different subpopulations of T cells. By using experiments in which replicating T cells were suicided, we found that the two different stimulators caused replication of what appears to be the same subset(s) of T cells. Since B cells and macrophages carry the same stimulating antigens (class II plus mls or others), one would expect them to stimulate the same T cell subpopulations were it not that they have been reported to stimulate two different subpopulations in humans. When B cells and macrophages were simultaneously used as stimulators, diminished T cell replication occurred. We have found the reduced response is not attributable to exhaustion of culture nutrients or to displacement of the response peak. Other possibilities to account for this marked reduction have been discussed from the viewpoint of suppression emanating from macrophages and/or T cells.

Factors in AMLR culture supernatant which mediate the cytotoxic T-cell response to hapten-altered self: interaction with macrophages

Supernatants from autologous mixed lymphocyte reaction (AMLR) cultures mediated the cytotoxic T-cell response in a system containing T cells and mitomycin C-treated, TNP-modified syngeneic thymocytes. No cytotoxic activity developed in the absence of the AMLR supernatants. The removal of thymic adherent cells abrogated the effect of the AMLR supernatants in the generation of cytotoxic cells. AMLR helper activity was restored following the addition of small numbers of splenic adherent cells. These results led to speculation that the AMLR supernatant interacted with accessory cells. Examination of the supernatant revealed significant levels of colony stimulating factor (CSF), and interferon-gamma (IFN-gamma). Functionally, incubation of the AMLR supernatant with P388D1, a macrophage tumor line, resulted in the production of interleukin 1 (IL-1). CSF is a major inducer of IL-1 synthesis. In addition, the AMLR supernatant induced the expression of Ia antigens on the P388D1 cells. IFN-gamma has been reported to mediate this activity. Although both lymphokines were present and appeared to have an effect on macrophages, it was unknown if both were required for cytotoxic T-cell development in this system. Samples of AMLR supernatant were incubated for 10 min at various temperatures. The ability of the AMLR supernatants to mediate cytotoxic T-cell activation was sensitive to incubation at 80 or 90 degrees C. Interestingly, at these temperatures CSF activity in the bone marrow colony-forming cell assay was enhanced. In separate experiments, AMLR culture supernatant was dialyzed against a pH 2 buffer. The induction of IA antigens by these supernatants was sensitive to dialysis at this pH. The similarity with IFN-gamma provides further evidence that this activity was mediated by IFN-gamma in the AMLR supernatants. The ability of the AMLR supernatants to mediate the cytotoxic T-cell response to altered self was also pH 2 sensitive. In contrast, IL-1 inducing capability and bone marrow colony growth, both CSF activities, were not reduced by pH 2 dialysis. Taken together, these data demonstrate a primary role for an IFN-like molecule, present in the AMLR supernatant, on cytotoxic T-cell activation. CSF involvement in this response is suggested by its IL-1 inducing activity, but cannot be definitively proven in the present study.

Suppression of a polyclonal B-cell response by supernatants from the murine autologous mixed lymphocyte reaction

Previously, we have demonstrated that supernatants from autologous mixed lymphocyte (AMLR) cultures contain helper factors which can mediate the development of a cytotoxic T-cell response to hapten modified self. In the current study, the effect of AMLR supernatants on the humoral response was explored. BALB/C splenic non-T cells produced a large polyclonal antibody response to lipopolysaccharide (LPS), as measured in a Protein A SRBC plaque assay. Surprisingly, syngeneic AMLR supernatants suppressed the LPS-induced generation of plaque-forming cells. The presence of T cells in the stimulated cultures did not affect suppressor activity. The decreased response was not the result of a shift in kinetics, as maximal activity was observed on Day 4, whether or not AMLR supernatants were added. The AMLR culture supernatants were most effective in suppressing the plaque-forming cell response when added at the initiation of culture. AMLR supernatants added after 24 hr of culture resulted in only about 50% of maximum suppression. Supernatants added at 48 or 72 hr had no effect. Interferon-gamma (IFN-gamma) has been detected in AMLR culture supernatant and has been reported to suppress the development of plaque-forming cells in response to LPS. However, it is unlikely the suppressive activity observed in these studies is due to IFN-gamma. Dialysis of the AMLR culture supernatant against a pH 2 buffer for 24 hr or incubation at 70, 80, or 90 degrees C for 10 min, treatments that inactivate IFN-gamma, enhanced suppression. These results suggest that in addition to cytotoxic-T-cell helper factors, the cellular interactions in the AMLR induces the production of a stable mediator(s) which is able to directly suppress B cells at an early stage of their development into plasma cells.

Characterization and function of autoreactive T-lymphocyte clones isolated from normal, unprimed mice

Self-Ia-reactive cloned T-cell lines, designated PK, were established by long-term culture of T cells from normal DBA/2 mice with irradiated syngeneic splenic adherent cells (SAC), rich in macrophages and dendritic cells. The cell lines were Thy 1+, Lyt 1+, Lyt 2-, produced IL-2 following stimulation with syngeneic spleen cells, and did not exhibit alloreactivity when screened against six different H-2 haplotypes. Of the five cloned PK cell lines tested, four were I-Ed restricted while one was I-Ad restricted as determined by genetic mapping and blocking studies carried out with monoclonal anti-Ia sera. Extensive specificity studies suggested that the PK cells reacted to syngeneic Ia molecules alone and not to foreign antigens such as fetal calf serum (FCS) used in the culture medium, in association with self-Ia. SAC pulsed with FCS or other protein antigens such as turkey gamma-globulin (TGG) were tested for their ability to induce proliferation of autoreactive T cells and other antigen-specific T cells using culture conditions consisting of serumless medium and interleukin 2 (IL-2). The data showed that the autoreactive T cells proliferated better in response to antigen-unpulsed SAC, while FCS-specific and TGG-specific cell lines, developed independently, proliferated only in response to FCS- or TGG-pulsed SAC, respectively, but not to antigen-unpulsed SAC. These results clearly distinguished the autoreactive T-cell clones from the antigen-specific T-cell clones. Preliminary studies carried out to investigate the functions of autoreactive T cells suggested that these cells helped in the in vitro differentiation of alloantigen-specific cytotoxic T lymphocytes (CTL) from CTL precursors obtained from the thymus and augmented syngeneic, allogeneic, and antigen-specific immune responses in vitro. The autoreactive T cells were also capable of inducing both proliferation and differentiation of antigen-specific populations of B cells in the absence of antigen. The present investigation suggests that autoreactive, non-antigen-reactive T cells can be cloned from normal, unimmunized mice and that such cell lines may provide a powerful tool for analyzing the role of the syngeneic mixed lymphocyte reaction in induction and maintenance of both T-and B-cell immune responses.

The autologous mixed lymphocyte reaction is decreased in Freund's adjuvant-injected rats of arthritis-susceptible and -insusceptible strains

We examined the T-non-T cell autologous mixed lymphocyte reaction (AMLR) of spleen cells from rats with arthritis induced by Freund's complete adjuvant in an effort to establish an animal model for the study of the relationship between the AMLR and autoimmune disease. We found that the splenic T-non-T AMLR was markedly decreased in rats with adjuvant-induced arthritis and that this decrease was mediated by suppressor cells within the nylon-wool-adherent stimulator cell population. However, we also found a similar decrease in the AMLR of arthritis-resistant Fisher 344 rats that received Freund's complete adjuvant but did not develop arthritis. Control animals with local inflammation induced by turpentine, a non-arthritogenic inflammatory substance, had normal AMLR, whereas other controls given Freund's incomplete adjuvant, also a non-arthritogenic substance, had a modest responder cell-mediated decrease in AMLR. These studies help to clarify the relationship between the decreased AMLR and the pathogenesis of adjuvant-induced arthritis by demonstrating that: 1) the acute-phase inflammatory response does not reduce the AMLR; and 2) the decreased AMLR can occur in the absence of overt autoimmune disease. This latter observation calls into question the proposed pathogenetic relationship between the AMLR and autoimmune disease states.

Autologous mixed lymphocyte reaction in man. XIII. Characterization of the T-T autologous mixed lymphocyte reaction

In this study we have demonstrated that in the T-TA autologous mixed lymphocyte reaction (AMLR), OKT4+ T cells are the major responders; however, in the presence of additional interleukin-2 (IL-2), OKT8+ T cells also respond by proliferation. Both OKT4+ and OKT8+ T cells, activated in the T-non-T AMLR, act as stimulators in the T-TA AMLR. OKT4+ T cells activated in the T-TA AMLR suppress the proliferative response of the fresh T-non-T AMLR; control OKT4+ cells show no immunoregulatory activity in this system. In contrast, control OKT8+ T cells spontaneously suppress the proliferation of the T-non-T AMLR, but activation of OKT8+ T cells in the T-TA AMLR does not result in a further increase in the suppressor activity of OKT8+ T cells. In summary, in the T-non-T and T-TA AMLR phenotypically similar T-cell subpopulations proliferate but express distinct immunoregulatory functions and perhaps regulate the tempo of the AMLR.

Responsiveness of human T-lymphocyte subpopulations in autologous mixed-lymphocyte reaction using xenoprotein-free separated cells: autologous reactivity lies chiefly in a low density T-cell fraction

The responsiveness in the autologous mixed-lymphocyte reaction (AMLR) by human T cells separated using two different methods not involving xenoantigen contract was examined. Although T cells from nylon-wool columns were active in AMLR, T cells separated by a Percoll gradient method responded poorly. Further separation of T cells from nylon-wool columns into low density (TL) and high density (TH) fractions by Percoll revealed that TL was enriched, while TH was depleted, in AMLR responsiveness. This difference could not be accounted for by differences in the helper or suppressor cells in the fractions. Moreover, TH responded well in secondary AMLR. Therefore the T cells reactive in AMLR reside chiefly, although not exclusively, in the low density fraction.

Reactivity of inducer cell subsets and T8-cell activation during the human autologous mixed lymphocyte reaction

To characterize the responding T cells in the autologous mixed lymphocyte reaction (AMLR), T cells were fractionated into purified subpopulations employing monoclonal antibodies and a variety of separation techniques including fluorescence-activated cell sorting. It was found that isolated T4 cells, but not T8 cells, proliferated in response to autologous non-T cells. More importantly, within the T4 subset, the autoreactive population was greatly enriched in a fraction reactive with an autoantibody from patients with juvenile chronic arthritis (JRA) or the monoclonal antibody anti-TQ1. Although T8 cells themselves were unable to proliferate in the AMLR, they could be induced to respond in the presence of either T4 cells or exogenous IL-2 containing medium. This was demonstrated by direct measurement of tritiated thymidine uptake by T8 cells during the course of the AMLR as well as by analysis of their relative DNA content. Taken together, these data indicate that the AMLR represents a complex pattern of immune responsiveness distinct from that observed in response to soluble antigen or alloantigen. The precise function of this T-cell circuit remains to be determined.

Dendritic cells induce T lymphocytes to release B cell-stimulating factors by an interleukin 2-dependent mechanism

Dendritic cells (DC) are essential accessory cells for T-dependent antibody responses in culture (1). We have outlined a three-stage mechanism to explain the capacity of DC to stimulate primary antibody responses to heterologous erythrocytes. First, DC induced T cells to produce and to become responsive to interleukin 2 (IL-2). This stage corresponded to the syngeneic mixed leukocyte reaction (2) and involved the clustering of DC and T cells into discrete aggregates. Isolated clusters, representing 5-10% of the culture, were critical for IL-2 release and the production of IL-2-responsive T blasts. In the second stage, IL-2 directly triggered the responsive T cells to release B cell helper factors. This role for IL-2 was documented with a rabbit anti-IL-2 reagent, purified IL-2, and T cells that had been rendered IL-2 responsive by an initial co-culture with DC. T cell growth was not required for IL-2-mediated helper factor release, since irradiated and untreated responders produced similar levels of factor and did so within 3 h of the addition of IL-2. In the final stage, helper factors stimulated the development of antibody-secreting cells from purified B lymphocytes. The helper factors were not H-2 restricted, but for both sheep and horse erythrocytes, the response to factors was antigen dependent and specific. The IL-2 that was present in the DC/T cell-conditioned medium did not act on B cells, since helper activity was neither neutralized nor absorbed by our anti-IL-2 reagent. We conclude that the ability of the DC to induce IL-2 release and responsiveness underlies its capacity to trigger both T and B lymphocyte reactions.

Human autologous mixed lymphocyte reactions (a review)

The literature concerning the autologous mixed lymphocyte reactions has been reviewed. This analysis supports the following conclusions: human subjects have self-responsive cells which are capable of proliferating when co-cultured with irradiated autologous non-T or Ia+ T cells. Since monoclonal antibodies recognizing distinct determinants of Ia antigen have different effects on AMLR with non-T cells and on Ia+ type AMLR, there is the possibility that different Ia molecule determinants have different functional role in the process of cell-to-cell interaction. The presence of AMLR abnormalities in disease strongly suggests that reactivity among different cell subsets plays a role in immunological homeostasis.

Differences in the kinetics of the autologous mixed lymphocyte reaction between the various connective tissue diseases

Kinetic studies of autologous mixed lymphocyte reaction (AMLR) over 7 days were made in 86 patients with various connective tissue diseases. None was receiving any treatment and each disease group was controlled with age-sex matched healthy controls. There were exceptions, but, as a rule, SLE patients (n = 22) had decreased responses on days 6-7. This was more apparent in patients with active disease than in those with inactive disease. Patients with scleroderma (n = 21) had early (day 4) proliferative responses. Half of the patients with RA (n = 14) had early (day 3) proliferation, but as a group they had normal increase in 3HtdR uptake on day 7. Patients with primary Sjögren's syndrome showed flat curves throughout and no significant proliferation on days 6-7 of culture. The pattern found in patients with mixed connective tissue disease (n = 11) was also peculiar in that they had peak proliferative responses on day 3 and normal 3HtdR uptake on days 6 and 7 of the AMLR. The number of patients with dermatomyositis or polymyositis was small (n = 6), but they showed a significant mean decrease in uptake on days 6-7. Studies using subpopulations of stimulatory cells further indicate that these patterns reflect immunoregulatory disturbances peculiar to each disease.

Production of interferon-gamma in the syngeneic mixed lymphocyte reaction

Cocultures of nylon wool-separated, non-adherent (T enriched) mouse spleen cells with mitomycin C-treated adherent cells resulted in the production of antiviral activity in the culture supernatants. This antiviral activity was defined as interferon gamma (IFN-gamma) because of its lability at pH 2 and the susceptibility to inactivation by anti mouse IFN-gamma antibodies. Treatment of non-adherent cells with anti-Thy 1.2 or anti-Lyt 1.2 antibody plus complement abolished IFN production. In contrast, anti-Lyt 2.2 plus complement treatment had no effect on IFN production. Abrogation of IFN production was also seen when anti-Ia antibodies were added. IFN could be observed in the SMLR, regardless of the H-2 haplotype of the mouse strains with the exception of NZB mice. Addition of hydrophilic polymers such as polyethyleneglycol or DEAE-dextran enhanced IFN production.

The autologous mixed lymphocyte reaction is not primarily due to xenoantigenic stimulation

Autologous mixed lymphocyte reaction (AMLR) is an interesting in vitro system in which T lymphocytes proliferate when cultured with non-T cells from the same individual. Because this system has both memory and specificity and elicits help, suppression, cytotoxicity, and soluble mediators, it has been proposed that it reflects in vitro the complex interactions of the immunologic network as it operates in vivo. A recent study, however, has cast doubt on the significance of this reaction by implicating xenoantigens, present during separation and/or culture procedures (e.g., sheep red blood cells or fetal calf serum), in the proliferative response of T cells. This question is analyzed by performing AMLR studies with cells (from eight normal subjects) that were separated with and without the use of sheep erythrocytes, and incubated with either fetal calf serum on normal human AB serum. Results were similar in all circumstances and negate a primary role of xenoantigens in AMLR.

Ia-restricted interaction between normal lymphoid cells and SJL lymphoma (RCS) leading to lymphokine production. I. Enhancement and suppression of antibody formation to TI antigens by supernatants and cells from cocultures of RCS and lymphoid cells

Addition of gamma-irradiated reticulum cell sarcoma (RCS) cells causes suppression of the antibody response to trinitrophenyl (TNP)-keyhole limpet hemocyanin (KLH)-primed syngeneic SJL spleen cells to TNP-polyacrylamide (PAA) in vitro. The response of anti-brain antigen (BAT) + C-treated spleen cells is not suppressed by gamma-RCS, but is suppressed by cells from 48-hr SJL lymph node or thymus + gamma-RCS cultures. Addition of as few as 2.5 x 10(5) cultured (anti-I-A + C treated to remove gamma-RCS) cells causes significant inhibition of the responses of both syngeneic and allogeneic spleen cells. Treatment of gamma-RCS-induced suppressor cells with anti-BAT + C reduces their suppressive activity. In contrast to the cells, supernatants (SN) from (lymph node (LN) + gamma-RCS) cultures greatly enhance, in an antigen-dependent fashion, the responses of untreated or anti-BAT + C-treated Sephadex G10-passed spleen cells to TNP-PAA. TNP-SIII polysaccharide, or TNP-Ficoll, but not as much to TNP-KLH. Addition of SN as late as Day 3 of culture still causes about half as much enhancement as leaving SN in throughout the culture period, but it has no effect if left with the spleen cells for only the first day of culture. SN contains high levels of IL-2 and IFN-gamma; absorption with cells from an IL-2-dependent cytotoxic T-cell line removes the enhancing activity, while treatment with pH 2 to remove the IFN-gamma has no effect. SN from an IL-2-producing T-cell line (LBRM-33) has a similar effect on antibody production to TI antigens as does SN of (LN + gamma-RCS). The results suggest a marked dependency of PFC responses to TI antigen on IL-2 in all strains examined, including SJL, LAF1, DBA/2Ha, and CBA/N, probably through a direct activation of B cells. The findings also suggest that suppressor T cells, induced by gamma-RCS in syngeneic lymphoid cells, absorb the IL-2 needed for responses to TI antigens in vitro.

Autologous mixed lymphocyte reaction in health and disease states in man

In this review are discussed the nature of T cell subsets, defined with monoclonal antibodies, responding in T-non-T and T-T autologous mixed-lymphocyte reactions (AMLR) and antigens stimulating in AMLR, soluble products of AMLR and generation of suppressor, helper and cytotoxic functions. On the basis of these data a model of immunoregulation in vivo can be proposed. We believe that AMLR is a real-phenomenon and not an artefact and perhaps represents a mechanism by which various immune functions are regulated, including feedback regulation of AMLR. The significance of AMLR is further supported by studies in various human and animal diseases.

Studies of rheumatoid synovial fluid lymphocytes. II. A comparison of their behavior with blood mononuclear cells in the autologous mixed lymphocyte reaction and response to TCGF

Synovial fluid lymphocytes (SFL) and peripheral blood lymphocytes (PBL) from patients with rheumatoid arthritis were compared for their response to lectin stimulation and for their behavior in the autologous mixed lymphocyte reaction (AMLR). The SFL proliferative response to phytohemagglutinin (PHA), as measured by tritiated thymidine incorporation at 72 hr, was lower than that of PBL (P less than 0.001). When T-cell growth factor (TCGF) was added to the medium, there was an increase in the SFL proliferative response to PHA (P less than 0.05). In contrast, TCGF did not alter significantly the PBL proliferative response to PHA. Mixing experiments were performed to determine whether the poor SFL proliferative response was due to passive absorption and removal of in situ-generated TCGF by "suppressor" cells. When cultured together, SFL did not suppress the PBL proliferative response to PHA, suggesting that decreased production of TCGF rather than competitive binding of TCGF results in the poor SFL proliferative response to lectin stimulation. In the AMLR, synovial fluid non-T cells were found to be more stimulatory to peripheral blood T cells than were peripheral blood non-T cells (P less than 0.001). In comparison to peripheral blood T cells, synovial fluid T cells were poor responders in the AMLR. Repetitive in vitro autologous stimulation of peripheral blood T cells resulted in proliferative responsiveness analogous to that of SFL, i.e., a relatively poor proliferative response in the AMLR and a poor response to PHA. The latter could be augmented by TCGF. The SFL requirement for exogenous TCGF is consistent with a state of immune activation. In vivo stimulation by non-T cells may play an important role in the immune activation which characterizes rheumatoid SFL.

Studies of autologous mixed lymphocyte reactions in patients with systemic lupus erythematosus

The autologous mixed lymphocyte reaction (AMLR) measures the proliferative response of peripheral blood T cells to surface antigens of non T cells. The AMLR of SLE patients with active or inactive disease either with (13) or without (6) immunosuppressive treatment was low compared with age and sex-matched controls, confirming previous reports. Only one patient with inactive, untreated SLE and one with drug induced lupus (procainamide) showed normal AMLR. Autologous reactivity was also reduced in 2 patients without treatment who presented with clinically complex disease syndromes, including primary biliary cirrhosis, or polyarteritis nodosa, together with Sjögren's syndrome and serological evidence of lupus. The AMLR could not be increased by changing the ratio of responder to stimulator cells. Patients with decreased AMLR also showed a decreased response to phytohemagglutinin which suggested a general depression of T cells. There was no correlation between the decreased AMLR and age, clinical features or anti-DNA antibody levels of the patients. In allogeneic mixed lymphocyte reactions (MLR) it was shown that non-T cells from SLE patients were poorer stimulators of allogeneic T cells than normal cells, and T lymphocytes from SLE patients were poorer responders to allogeneic non-T cells than were normal T cells. Both effects were much more marked in patients with active disease than in those with inactive SLE. This suggests a defect in both responder and stimulating cell populations in SLE.

Autologous mixed lymphocyte reaction in man. IV. Decreased autologous mixed lymphocyte culture response in patients with common variable immunodeficiency

The autologous mixed lymphocyte reaction (AMLR) was studied in 18 patients with common variable immunodeficiency. The AMLR was decreased in 10 of 18 (55%) patients with common variable immunodeficiency compared to healthy controls. In allogeneic MLR, T cells from patients were found to be poor responders, and non-T cells poor stimulators, compared to allogeneic MLR between healthy normal controls. In allogeneic MLR, B cells (B cells + null cells) from patients were poor stimulators, whereas macrophages stimulated normally compared to controls. The deficient AMLR could be one of the mechanisms responsible for the increased risk of autoimmune phenomena in a subset of patients with primary immunodeficiency.

Helper cells in the autologous mixed lymphocyte reaction. III. Production of helper factor(s) distinct from interleukin 2

In normal mice, the autologous mixed lymphocyte reaction (AMLR) can activate helper T cells that, in the presence of hapten-modified syngeneic cells, can induce a hapten-specific cytotoxic response. Supernatants from AMLR cultures contain a factor(s) that will mediate a cytotoxic T cell response to hapten-altered self. The AMLR factor is effective in facilitating the generation of cytotoxicity only in those cultures containing both T cells and hapten-altered, syngeneic, nonstimulatory cells. Factor production requires an interaction between Lyt-1+23- cells and non-T cells (the T cells synthesize it). The AMLR factor does not appear to be interleukin 2 (IL-2) because it does not activate thymocytes in the presence of antigen, nor does it maintain an IL-2-dependent cell line or function in co-stimulator assays. For the AMLR factor to facilitate the generation of cytotoxicity, thymic adherent cells are a necessary intermediate. These data suggest that the factor recoverable from AMLR cultures acts early in the cytotoxic pathway, before IL-1 production.

Potentiation of the PFC response to thymus-independent antigens by heterologous erythrocytes

Immunization with horse erythrocytes (HRBC) and a thymus-independent (TI) antigen of the TI-2 category, such as a native dextran, dinitrophenyl-dextran (DNP-dextran), or DNP-Ficoll, resulted in a three- to four-fold enhancement of the plaque-forming cell response to the TI antigen. The effect was found to be T-cell associated, since cyclosporin A abrogated enhancement. The T cells of T-cell factor involved were elicited early in the response to HRBC and acted on the initial stages of the TI response. The HRBC-induced potentiation affected only B cells activated by the TI antigen; it could not induce a TI response when TI-2 antigen was given under nonresponsive conditions; and it had only a slight effect on the response to a thymus-dependent (TD) antigen. A soluble TD antigen, bovine serum albumin-coupled dextran (BSA-dextran), did not have potentiating ability equivalent to that of the particulate HRBC. It was concluded that non-specific T-cell help can influence TI-2 responses when they are present simultaneously.

Autologous mixed lymphocyte reactions in patients with rheumatoid arthritis and juvenile rheumatoid arthritis: both non-T cells and in-vivo-activated T cells can act as stimulator cells

The lymphocyte responses in autologous mixed lymphocyte reactions (AMLR) between irradiated non-T and T lymphocytes from the peripheral blood (PB) of rheumatoid arthritis (RA) and juvenile RA (JRA) patients were decreased compared with the AMLR responses of normal PB lymphocytes. Normal AMLR responses were seen in synovial tissue and the synovial fluid lymphocytes from RA and JRA patients. The lymphocyte responses were also decreased in AMLR between irradiated non-T cells from peripheral blood and T cells from synovial tissue (ST) in RA patients and between irradiated non-T from PB and synovial fluid (SF) T cells in JRA patients. However, when irradiated non-T cells from ST of RA patients or from SF of JRA patients were mixed with autologous PB T lymphocytes, increased lymphocyte responses were observed. SF T lymphocytes and ST T cells were also shown to stimulate autologous PB T lymphocytes.

Immunoglobulin secretion in the human autologous mixed leukocyte reaction. Definition of a suppressor-amplifier circuit using monoclonal antibodies

The induction of immunoglobulin (Ig) synthesis in the autologous MLR has an absolute requirement for helper/inducer (Leu-3) T cells, whereas an excess of suppressor/cytotoxic (leu-2) cells suppresses the response. The current study was an effort to assess the immunoregulatory potential to T cells activated in the autologous mixed-leukocyte response (MLR). T cells were cultured with autologous non-T cells for 8-9 d, after which the activated T cells were fractionated into subsets with monoclonal antibodies to T cell markers and HLA-DR antigen. Each population was co-cultured in fresh autologous MLR, and on the 8th day of culture, Ig-secreting cells were measured in a reverse hemolytic plaque assay. The results show that activated Leu-2, DR+ T cells, but neither Leu-2, DR- nor Leu-3 T cells, were at least 50 times more potent as suppressors of IgM and IgG synthesis than fresh Leu-2 cells alone. The activation of this Leu-2, DR+ subpopulation required Leu-3 cells in the primary culture. Furthermore, in the absence of Leu-2 cells in the second culture, little or no suppression was observed, suggesting that the Leu-2, DR+ cells act to amplify or induce suppressor effects of fresh Leu-2 cells. This indicates that at least two distinct subpopulations of Leu-2 cells are required for maximal suppression of an immune response, and that immunoregulatory circuits analogous to those described in the mouse exist in man.

The autologous mixed lymphocyte reaction in systemic lupus erythematosus

The autologous mixed lymphocyte reaction (AMLR) represents the proliferation of T cells in response to signals from autologous non-T cells. Fractionation of the non-T population into B enriched and macrophage enriched cells demonstrated that both could serve as effective stimulator cells in the AMLR. Cytolytic treatment of both populations with a macrophage specific, monoclonal antibody abrogated stimulation of the macrophage but not the B cell population. Utilizing a series of negative selection procedures - cytolysis with T cell specific monoclonal antibody, metabolic suicide with 5-bromo-2-deoxyuridine (brdU) and light - it could be demonstrated that T cells responding to autologous macrophage were distinct from those responsive to autologous B cells. Studies of the AMLR reactivity to B cells and macrophage in a small number of patients with active systemic lupus erythematosus (SLE) demonstrated that although reactivity to both populations was diminished, the response to autologous B cells was reduced more than the response to autologous macrophage. These studies suggest that the AMLR represents the sum reactivities of two responder T cells. Moreover, they suggest that a relatively selective deficiency in only one of these cells may occur in SLE.

Suppression of the normal autologous mixed leukocyte reaction by sera from patients with systemic lupus erythematosus

Sera from 15 patients with active systemic lupus erythematosus and 7 patients with inactive lupus were added to normal autologous mixed leukocyte reaction (MLR) cultures. Twelve of the 22 sera reduced autologous T cell proliferative responsiveness to B plus null (B + N) cells or macrophages by 50% or more. This inhibition correlated with defective autologous MLR in fresh mononuclear cells from those patients. When normal responding and stimulating cell populations were preincubated with suppressive lupus sera, then added to autologous MLR cultures that contained normal serum, proliferative responses were also reduced; inhibitors are directed against participating mononuclear cell subpopulations. The suppressive serum factors were directed variously against monocyte/macrophage (M phi), B + N, or T cell populations; M phi/T interactions were suppressed most frequently. The inhibitors were not removed by high-speed centrifugation or by depletion of antibodies to DNA, and they did not correlate with the presence of lymphocytotoxic antibodies. The presence of serum inhibitors of normal M phi/T and B + N/T autologous MLR may be an immunologic abnormality important in the initiation, perpetuation, or exacerbation of systemic lupus erythematosus.

The effect of protease inhibitors on the polyclonal B cell activator from the serum of patients with rheumatoid arthritis

It has been reported that polyclonal B cell stimulation results in formation of autoantibodies and immune complexes. We have previously reported that a polyclonal B cell activator (PBA) associated with alpha 2-macroglobulin (alpha 2M) is present in the serum of patients with rheumatoid arthritis and related diseases. Here we studied the possibility that patient alpha 2M (Pt-alpha 2M) carries a trypsin-like protease responsible for the PBA activity. This activity was determined by the Ig-turnover assay developed in our laboratories. The small molecular weight protease inhibitors, aprotinin (Trasylol, Bayer) and phenylmethylsulfonylfluoride (PMSF), and the large molecular weight soybean trypsin inhibitor (SBTI) were used. These inhibitors did not affect the PBA activity of dextran sulfate of LPS. However, as expected, trypsin had a PBA-activity which was blocked by all of the above mentioned inhibitors. A trypsin-normal alpha 2M complex (Tr-N alpha 2M) and PBA activity which was inhibited by PMSF or aprotinin but not by SBTI. The PBA associated with Pt-alpha 2M was also inhibited by PMSF or aprotinin but not by SBTI. Moreover, the Tr-N alpha 2M complex and the Pt-alpha 2M, but not that from normal donors, had esterase activity for p-toluenesulfonyl-L-argininemethyl ester. These data suggest a similarity between the Pt-alpha 2M and Tr-N alpha 2M complex. Thus, we concluded that the esterolytic activity is sufficient for PBA activity, that Pt-alpha 2M has esterolytic activity and that this PBA activity can be blocked by small molecular weight protease inhibitors.

Monoclonal antibody analysis of human T lymphocyte subpopulations exhibiting autologous mixed lymphocyte reaction

In autologous mixed lymphocyte reaction (MLR), T cells proliferate in response to the stimulation by autologous non-T cells. In the present study, human T cell subpopulations, defined by murine monoclonal antibodies OKT4, OKT8, or 9.3, were examined for their capacity to proliferate in autologous and allogeneic MLR. It was observed that the treatment of responder T cells with OKT4 or 9.3 antibody (both defining helper/inducer T cells) and complement (C') ablated their proliferative response in autologous MLR and markedly reduced their allogeneic MLR proliferative response. In contrast, treatment of T cells with OKT8 antibody (defining suppressor/cytotoxic T cells) and C' had no or minimal effect on their proliferative response in autologous MLR. Furthermore, OKT4, 9.3, 9.6 (PAN), or 7.2 anti-human Ia (framework specific) but OKT8 antibody, when present during the entire culture period, in the absence of C' inhibited in a dose-dependent manner the proliferative response in both autologous and allogeneic MLR. Inhibition of proliferation was also observed when the responder T cells were pretreated with OKT4 or 9.3 antibody, washed, and then stimulated with irradiated autologous or allogeneic non-T cells. Pretreatment of T cells with OKT8 or 7.2 anti-Ia antibody in the absence of C' did not influence their proliferative response in autologous MLR. Thus, T cells containing cells with helper/inducer activity defined by OKT4 or 9.3 antibody appear to be the major responder T-cell subpopulation in autologous MLR.

Autologous mixed lymphocyte reaction in man. III. Regulation of autologous MLR by theophylline-resistant and -sensitive human T-lymphocyte subpopulations

Human peripheral blood T lymphocytes were separated into theophylline-resistant (TR) and -sensitive (TS) subpopulations. Proliferative responses TR, TS and unfractionated T cells were studied, using irradiated autologous or allogeneic non-T cells as stimulators. TR cells proliferated vigorously in both autologous and allogeneic mixed lymphocyte cultures (MLC). TS cells. which constitute about 20% of unfractionated T cells, exhibited poor proliferative responses to autologous and allogeneic stimulation. The magnitude of proliferation in autologous and in allogeneic MLC was found to be directly dependent on the number of TR cells in the culture. Mitomycin-C (MMC)-treated TR cells augmented and MMC-treated TS cells suppressed (P less than 0.05) the autologous and allogeneic MLC responses of unfractionated T cells. However, the response of TS cells did not increase in autologous or allogeneic MLC when co-cultured with MMC-treated TR cells. MMC-treated TS cells, when co-cultured with TR cells, suppressed the responses of TR cells (P less than 0.05). The enhancing effect of TR cells was radiation-resistant. Suppressor influence of TS cells, in contrast, was abolished by irradiation (P less than 0.05). These findings demonstrate that TR cells are the responding cell in autologous MLR and augment the MLC responses of unfractionated T cells. TS cells, on the other hand, respond poorly in autologous or allogeneic MLC and suppress the response of TR cells.