Lymphocyte transformation induced by autologous cells. IV. Human T-lymphocyte proliferation induced by autologous or allogeneic non-T lymphocytes

TNFR2 Expression on CD25(hi)FOXP3(+) T Cells Induced upon TCR Stimulation of CD4 T Cells Identifies Maximal Cytokine-Producing Effectors

In this study, we show that CD25^hiTNFR2⁺ cells can be rapidly generated in vitro from circulating CD4 lymphocytes by polyclonal stimuli anti-CD3 in the presence of anti-CD28. The in vitro induced CD25^hiTNFR2⁺ T cells express a conventional regulatory T cells phenotype FOXP3⁺CTLA4⁺CD127^lo/−, but produce effector and immunoregulatory cytokines including IL-2, IL-10, and IFN-g. These induced CD25^hiTNFR2⁺ T cells do not suppress target cell proliferation, but enhance it instead. Thus the CD25^hiTNFR2⁺ phenotype induced rapidly following CD3/28 cross linking of CD4 T cells identifies cells with maximal proliferative and effector cytokine-producing capability. The in vivo counterpart of this cell population may play an important role in immune response initiation.

Superantigen-mediated differentiation of bovine monocytes into dendritic cells

Although many effects of staphylococcal superantigens (SAg) on T cells are well established, less is known about their effects on APC. In this study, bovine PBMC were stimulated with a low dose of staphylococcal enterotoxin C1 (SEC1). The phenotype of adherent cells (Ac) derived from bovine PBMC cultured with SEC1 [SEC1-stimulated Ac (sAc)] for 192 h was CD14(-), CD68(-), CD163(-), dendritic cell (DC)-specific ICAM-3-grabbing nonintegrin(+), MHC class II (MHC II)(high), CD11a(low), CD11b(high), CD11c(high), and CD1b(high), suggesting these cells were dendritic cells (DC). SEC1 also induced transcription of the CXCL1, -2, and -3 family, CXCL6, CCL2, and CCL5 genes in sAc, which increased rapidly but returned to basal levels by 48 h. In contrast, increased transcription of CCL3, CCL8, and CXCL12, responsible for mononuclear cell migration and chronic inflammation, was sustained. In vitro cell migration assays showed vigorous migration of granulocytes, followed by migration of mononuclear cells. The autologous MLR showed that sAc induced a dose-dependent proliferation of CD4(+) T cells and an even stronger proliferation of CD8(+) T cells. This effect was inhibited or reduced by pretreatment with mAb to CD11b, MHC II, or MHC II plus CD18. These results indicate that stimulation of bovine PBMC by SAg induces differentiation of monocytes into DC.

Increased stimulatory capacity of spleen cells from adult thymectomized mice in mixed lymphocyte reactions

Conflicting results have been reported concerning the effect of adult thymectomy (A-Tx) on the mixed lymphocyte reaction (MLR) response. Our purpose was to test the reverse question, namely the effect of A-Tx on the stimulatory capacity of mouse lymphocytes carrying allelic disparities at the Mls and the H-2 loci. Spleen cells from A-Tx CBA donors were found to be significantly more stimulating than cells from normal donors. That A-Tx could eliminate suppressor T cells involved in MLR regulation or in preventing back stimulation is not likely according to our data. An increment in expression or in accessibility of Mls or H-2 antigenic determinants induced by A-Tx is no more likely, since a smilar increase in lymphocyte proliferation was observed in syngeneic cultures. The most probable explanation remains that A-Tx discloses a strongly stimulatory subpopulation, perhaps acting in part nonspecifically. The hypothesis of an enrichment in B cells versus a loss of T cells is not compatible with our findings, since B-cell-enriched fractions from various origins never attained the stimulating ability disclosed by A-Tx cells. Moreover, the cell involved is theta-positive, although slightly nylon-wool-adherent, and thus shares several properties with immature T cells involved in auto-rosette formation.

Multispecific responses by T cells expanded by endogenous self-peptide/MHC complexes

The paradox of autoreactivity to self-peptides in physiological as opposed to pathological immune responses is not well understood. Here, we directly examined the human T cell response to endogenous self-peptides in a series of healthy subjects. CFSE-labeled T cells were stimulated with unmanipulated antigen-presenting cells containing endogenous self-antigen, and the resulting CD4+ populations entering into cell cycle (CFSE(low)) or non-proliferating CD4+ cells (CFSE(high)) were single-cell sorted, cloned and screened against a panel of self-antigens and microbial recall antigens to interrogate their antigen reactivity. The percentage of CD4+ T cells entering cell cycle in response to self-peptide/MHC was calculated to be 0.04%, and entry into cell cycle was dependent upon CD28 costimulation. Clones derived from CFSE(low) T cells exhibited significantly greater cross-reactivity to multiple antigens than CFSE(high) clones or other CD4+ clones generated after microbial antigen stimulation. Sequencing the TCRbeta chains indicated that CFSE(low) clones were indeed clonal. These data demonstrate that T cell clones generated on stimulation by endogenous self-peptides exhibit a high degree of multispecificity, and we speculate that their multispecificity is based upon recognition of shared-backbone MHC determinants.

Tat-Functionalized Near-Infrared Emissive Polymersomes for Dendritic Cell Labeling

Dendritic cells (DCs) play a pivotal role in both immune tolerance and the initiation of immunological responses. The ability to track DCs in vivo is imperative for the development of DC-based cellular therapies and to advance our understanding of DC function and pathophysiology. Here, we conjugate a cell permeable peptide, Tat, to near-infrared (NIR) emissive polymersomes in order to enable efficient intracellular delivery for future DC tracking with these optical probes. NIR imaging allows quantitative, repetitive, in vivo detection of fluorophore-laden cells, at centimeter tissue depths without disturbing cellular function. Flow cytometry and confocal microscopy results indicate that Tat-mediated polymersome delivery to DCs is concentration and time dependent, resulting in punctate intracellular localization. Further, loading cells with Tat NIR emissive polymersomes does not interfere with cytokine-induced DC maturation and has modest effects on DC viability, but has a significant effect on mature DC-induced activation of naive T cells. We observe significant uptake of NIR emissive polymersomes when conjugated to the peptide, with a lower detection limit of 5000 labeled DCs. The extent of polymersome delivery is estimated as 70 000 +/- 10 000 vesicles/cell, equivalent to 0.7 +/- 0.1 fmol of NIR fluorophore. Our studies will enable future in vivo tracking of ex vivo labeled DCs by NIR fluorescence based imaging.

Studies of autologous T cell activation in the Kunkel laboratory

T helper cells and their antigen receptors were topics of keen interest in Henry Kunkel's laboratory during the early 1980s. The activation of human T cells by foreign antigen, allogeneic cells and autologous non-T cells had been established, but the most effective stimulator cells in those responses had not yet been identified. Dendritic cells, along with activated B cells, were demonstrated to be important stimulators of autologous T cells, and studies of peripheral blood from patients with SLE supported the conclusion that the non-T cells in those patients were deficient in their capacity to stimulate an autologous mixed lymphocyte reaction (AMLR). Subsequent studies have defined the role of apoptotic cells processed by dendritic cells in autologous T cell activation. In view of recent data demonstrating depletion of dendritic cell subsets in SLE peripheral blood and recruitment of those cells to sites of immune system activity, it is proposed that SLE T cells are indeed capable of self-reactivity and that the impaired in vitro proliferative response to autologous non-T cells as assessed in the AMLR may reflect the shift of dendritic cells, with their antigen presenting activity augmented by adjuvant-like factors, from peripheral blood to peripheral lymphoid organs and sites of disease.

T cell proliferation induced by autologous non-T cells is a response to apoptotic cells processed by dendritic cells

Self-reactive T cells are present in the mature immune repertoire as demonstrated by T cell proliferation induced by autologous non-T cells in the autologous mixed lymphocyte reaction. This reaction generates regulatory T cells in vitro and may reflect immune regulatory pathways in vivo, but the antigenic peptides recognized remain uncharacterized. We revisited this issue in light of the importance of apoptosis in immune regulation. We found that apoptosis among peripheral blood non-T stimulator cells is associated with augmented induction of autologous T cell proliferation. Our data show that caspase activity in the non-T stimulator population is essential for induction of autologous T cell proliferation, suggesting that cellular components in the non-T cell fraction are enzymatically modified, most likely by effector caspases, and have a direct or indirect effect on autoreactive T cell activation. Furthermore, exposure of macrophage-derived dendritic cells to apoptotic non-T cells augments autologous T cell proliferation, and blockade of alpha(v)beta(5) integrin, but not alpha(v)beta(3), inhibits the capacity of irradiated non-T cells or dendritic cells to stimulate autologous T cell proliferation. These experiments, using an entirely autologous system, suggest the interpretation that autoreactive T cells may recognize self-Ags modified through the actions of caspases and presented to T cells by dendritic cells. Induction of an in vivo autologous mixed lymphocyte reaction by caspase-modified self-Ags present in apoptotic cells may represent a mechanism to maintain peripheral immune tolerance.

Initiation of the Autologous Mixed Lymphocyte Reaction Requires the Expression of Costimulatory Molecules B7-1 and B7-2 on Human Peripheral Blood Dendritic Cells

The human autologous mixed lymphocyte reaction (AMLR) consists of a proliferative response of primarily CD4+ T lymphocytes stimulated by autologous non-T cells expressing class II MHC-encoded gene products and is thought to represent a self-recognitive mechanism that might be important in regulating the cellular interactions involved in the generation of normal immune responses. To further define appropriate stimulator cell populations, as well as the molecular mechanism responsible for the initiation of AMLR, we compared the T cell-stimulatory capacity of highly purified populations of peripheral blood dendritic cells (DCs) and monocytes (Mos) under serum-free conditions, thus carefully avoiding the presence of xenogeneic Ags. Whereas both freshly isolated Mos and DCs were found to be poor stimulators of autologous T cell proliferation, preactivation of DCs, but not of Mos, for 48 h with granulocyte-macrophage CSF led to a 113-fold increase in DC stimulatory capacity. AMLR was inhibited by mAbs against HLA-DR and CD4 molecules, and, in addition, showed a higher dependence on the granulocyte-macrophage CSF-induced up-regulation and/or de novo expression of the costimulatory molecules B7-2 and, in particular, B7-1 as compared with an Ag-specific or allogeneic MLR. Thus, our data suggest that the high density of costimulatory molecules together with MHC class II molecules on competent APCs appear to be the major triggers for the initiation of AMLR.

The proliferative responses of lymphocytes from foetal calves and adult cattle

This paper describes the proliferative responses of prescapular lymph lymphocytes and peripheral blood lymphocytes of foetal calves compared with cells of similar origin from adult cattle. Lymph lymphocytes were collected continuously by means of cannulation of efferent lymphatic ducts of the prescapular lymph node of foetal calves and adult cattle. Peripheral blood lymphocytes were collected from the foetus by means of cannulation of superficial veins of the foetus or of the umbilical vessels and from the jugular vein of adults. Foetal lymphocytes in one-way mixed lymphocyte culture stimulated and responded as well as adult lymphocytes. Foetal cells stimulated and responded more to cells from unrelated animals than to cells from their dam. Lymph lymphocytes from foetal calves between 188 and 253 days of gestation proliferated as well as adult lymphocytes and at a high level after stimulation with concanavalin A, phytohaemagglutinin and pokeweed mitogen. Response to stimulation with lipopolysaccharide, soybean agglutinin and wheat-germ agglutinin was variable but generally low and within the same range recorded by adult cells. Proliferation by foetal and adult whole-blood cultures was on occasions as high as that recorded by separated lymphocytes, even though fewer lymphocytes were initially present in the whole-blood cultures. Foetal lymph lymphocytes exhibited lower proliferative responses in autologous lymph plasma than in foetal calf serum or pooled foetal lymph plasma. There was no consistent depression of proliferation by culture medium supplements from pregnant animals. Rabbit serum consistently abrogated responses. Fetuin at final concentrations of greater than 2.5 mg/ml significantly depressed proliferation in foetal and adult lymphocytes from efferent lymph and peripheral blood.

Induction of autologous mixed lymphocyte culture responses by myelin basic protein-reactive T cell clones

Myelin basic protein is an autoantigen present in the central nervous system suspected to be the target of destruction in multiple sclerosis. In the present study, we have demonstrated that T cell clones specific for myelin basic protein have the ability to induce proliferative responses in resting T lymphocytes in the autologous mixed lymphocyte culture (AMLC). T cell recognition of the AMLC stimulatory determinants on the clones required the presence of autologous monocytes. T lymphocytes primed against an autologous myelin basic protein-specific T cell clone displayed specific memory responses against the original stimulating clone and failed to exhibit secondary reactivity to 'sister' myelin basic protein-reactive clones and to autologous T cell clones specific for another antigen. Monoclonal antibodies specific for class II HLA-DR antigens inhibited secondary AMLC responses. Modulation of the T cell receptor from the surface of the clones decreased their AMLC stimulatory ability. These results indicate that idiotype-like determinants on the T cell receptor of autoantigen-specific T cell clones are capable of triggering anti-idiotypic T cell responses.

Enhanced proliferative response of myasthenic thymus cells in mixed lymphocyte reaction

To determine the functional diversity of thymic lymphoid cells in patients with myasthenia gravis (MG), we evaluated mixed lymphocyte reactions (MLR) using thymus cells in 7 MG patients and 8 controls. In the MLR, we used thymus cells as responder cells and mitomycin C-treated peripheral non-T cells as stimulator cells. In an autologous MLR test, a low proliferative response was observed in both the MG patients and controls. In an allogeneic MLR test, in which thymus cells were co-cultured with allogeneic non-T cells, the thymus cells from MG patients showed an increased proliferative response to stimulator cells, whether they were from MG patients or the controls. However, thymus cells from the controls showed a low proliferative response to any allogeneic stimulator cells. The enhanced allo-reactivity of thymus cells from MG patients thus suggests that there is an increase in the number of functionally mature T lineage cells in the MG thymus.

Defective autologous mixed lymphocyte reaction (AMLR) and killer activity generated in the AMLR in cancer patients

The autologous mixed lymphocyte reaction (AMLR) and the killer activity generated in the AMLR (AMLR-killer) in the spleen and the peripheral blood of patients with gastric cancer were investigated. The AMLR in cancer patients was suppressed, especially in the spleen, compared to that seen in controls. There was no correlation between AMLR activity and the stage status of the cancer. The cytotoxic activity of AMLR-killer cells against various tumor-cell lines was also suppressed in the spleen, and had a tendency to be suppressed in the peripheral blood of cancer patients. The autologous tumor-killing activity of AMLR-killer cells was developed in cancer patients with high AMLR activity, but was not induced in patients with low AMLR activity. Autotumor killing activity was decreased by the elimination of CD4+ cells, whereas the elimination of CD16+ cells resulted in a marked reduction in cytotoxicity against K562, indicating that the non-specific killer cells which lysed K562 were different from the specific killer cells that lysed autotumor cells. This suggests that AMLR activity is related to the differentiation and proliferation of lymphocytes with specific or non-specific cytotoxic activity and that this activity plays an important role in immune surveillance against tumors.

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.

Identification of a cord blood T cell subset of CD3+4-8-45R+ suppressing interleukin 2 production in the autologous mixed lymphocyte reaction and the mode of action of exogenous IL2 in the induction of IL2 production

As previously reported, the inability of cord blood T cells to produce IL2 in the autologous mixed lymphocyte reaction (AMLR) could be recovered by the treatment of stimulator non-T cells with interferon-gamma (IFN-gamma) and of the AMLR with exogenous IL2. In the present study, we showed that addition of untreated autologous cord blood T cells to the above-mentioned AMLR abrogated the IL2 production in a dose-dependent manner, suggesting active suppression by the untreated T cells because untreated cord blood T cells did not consume IL2. Suppressor activity was abrogated by the treatment of cord blood T cells with monoclonal anti-CD3 antibody plus complement or with monoclonal anti-CD45R (Leu 18) antibody, but not by the treatment with monoclonal anti-CD4 antibody and/or anti-CD8 antibody plus complement. These data showed that the cord blood suppressor T cells were CD3+4-8-45R+. This suppressor activity also disappeared by culturing with rIL2 for 8 hr. As the frequency of CD45R+ cord blood T cells was comparable to that of CD45R+ adult T cells and was minimally affected by the IL2 treatment, functional modulation of CD45R+ suppressor T cells by IL2 is suggested. Moreover, in spite of the inhibitory effect of anti-CD45R antibody on the suppressor activity, IL2 production was not induced merely by addition of anti-CD45R antibody directly to the responder cells in AMLR. Taken together, these data suggest the requirement of exogenous IL2 for IL2 production in that IL2-producing-precursor T cells themselves should be stimulated by IL2 in addition to the modulation of CD45R+ suppressor T cells by IL2.

Induction of mouse syngeneic MLR by in vivo xenogeneic immunization with HLA-DR antigens

To study in mice the effects of in vivo xenogenic immunization with human major histocompatibility complex (MHC) class II antigens, the animals were injected with HLA-DR antigens and their proliferative responses tested in vitro. The results showed that small amounts of HLA-DR proteins, acting as nominal antigens, were not only able to prime mice for a secondary in vitro xenogenic mixed lymphocyte reaction but also induced a syngeneic mixed lymphocyte reaction. In contrast, allogeneic or syngeneic immunization of mice with soluble MHC class II molecules failed to stimulate an autoreactive response. The syngeneic mixed lymphocyte reaction was primarily directed against syngeneic MHC class II molecules since the murine T lymphocytes reacted against MHC class II-positive dendritic spleen cells and MHC class II-transfected mouse fibroblasts. A self-reactive T-cell line induced under these experimental conditions did not react in xenogeneic and allogeneic mixed lymphocyte reactions. However, these T lymphocytes proliferated when human peripheral blood lymphocytes of various haplotypes were presented in the context of syngeneic mouse antigen presenting cells.

Function of autoreactive T cells in immune responses

We have constructed a model (Fig. 2) to explain the activation and regulation of autoreactive T cells by antigen. Antigen priming appears to be important for both antigen-specific and autoreactive T cells. Once activated, these T cells have the capacity to stimulate B cells to produce antibody in a very similar manner. It is possible that these two types of T cells work in concert to maintain an active immune response. Under circumstances where antigen-specific T-cell help may be limiting, autoreactive T cells may function to enhance B-cell responses. In addition, antigen appears to activate the regulatory mechanisms that are important for down-regulating the B-cell antibody response. Carrier-specific T-suppressor cells are antigen-specific in their activation but can be antigen-nonspecific in their effector function. In this way the regulatory mechanism driven by antigen can function to inactivate the antigen-specific and the autoreactive T-cell activation of B cells.

Impairment of autologous mixed lymphocyte reaction in the spleen and peripheral blood lymphocytes of patients with idiopathic portal hypertension

The etiology of idiopathic portal hypertension (IPH) is unknown, although many studies have suggested that it might be an autoimmune disease. The autologous mixed lymphocyte reaction (AMLR) involves the proliferation of T lymphocytes when co-cultured with autologous non-T cells and may reflect immune control mechanisms in vivo. The AMLRs in the spleen and peripheral blood of three patients with IPH were measured and it was shown that the AMLRs both in the spleen and peripheral blood were significantly suppressed compared to those of normal healthy subjects. By allogeneic MLR, there was a tendency that the disturbance of non-T cells was more intensive than that of T cells. The AMLR of peripheral blood did not improve by splenectomy. Thus, the depressed cause of AMLR in patients with IPH was suggested mainly to disturbance of the antigen-presenting ability of non-T cells, and it was suggested that not only the spleen cells, but systemic immune disturbance caused the impairment of AMLR in IPH.

Activated CD4-positive T-lymphocytes and impaired cell-mediated immunity in patients with carcinoma of the urinary bladder with schistosomiasis

Patients with schistosomiasis of the urinary bladder (SB) associated with carcinoma of the bladder (SCB) or carcinoma of the prostate (SCP) have a variety of immunologic abnormalities, including the presence of HLA-DR+ and interleukin-2 receptor-positive (IL-2R+) T-lymphocytes in circulating blood. This study demonstrated that, the HLA-DR+ and IL-2R+ antigens are selectively expressed on majority of the CD4+ T-lymphocytes of patients with SCB, whereas, these antigens are expressed almost equally on both CD4+ and CD8+ T-lymphocytes of patients with SB and SCP. Expressions of HLA-DR+ and IL-2R+ antigens in CD4+ T-lymphocytes, and a depressed response of this T-cell subset to phytohemagglutinin and Concanavalin A stimulations seems to be the characteristic feature of these patients with SCB. In addition, the autologous mixed lymphocyte reaction (AMLR) and allogenic mixed lymphocyte reaction (MLR) was depressed in patients with SCB. However, patients with SCP demonstrated a normal MLR, even though the AMLR was highly depressed. The immunoregulatory role of the HLA-DR+, IL-2R+, CD4+ helper/inducer T-lymphocytes, and the AMLR and MLR abnormalities we have identified in patients with SCB may be important and could play a role in the pathobiology of these diseases in humans.

CCA [N-(2-carboxyphenyl)-4-chloroanthranilic acid disodium salt], a newly developed immunomodulating drug, suppresses T-cell activation by acting on macrophages

The cellular mechanism of action of a newly developed drug, CCA, N-(2-carboxyphenyl)-4-chloroanthranilic acid disodium salt, on PHA-, autologous mixed lymphocyte reaction (AMLR)-, and phorbol myristate acetate (PMA)-stimulated T-cell proliferation was investigated. Addition of 50 micrograms of CCA per milliliter suppressed PHA- and AMLR-stimulated T-cell proliferation. In contrast, CCA failed to suppress PMA-stimulated macrophage-depleted T-cell proliferation. After treatment of T cells or macrophages with CCA for 12 h, recombined T cells and macrophages were stimulated with phytohemagglutinin. [3H]Thymidine incorporation by T cells was suppressed when macrophages but not T cells were treated with CCA. These results indicate that CCA suppresses T-cell proliferation by acting on macrophages. The mechanism involved in this suppression of CCA was due to the loss of Ia antigen on macrophages and the loss of interleukin-1 (IL-1) secretion from macrophages.

Autologous mixed lymphocyte reaction in human neonatal lymphocytes

Human neonatal mononuclear cells were examined to determine their ability to participate in an autologous mixed lymphocyte reaction (AMLR). Stimulator cells were isolated by plastic adherence and nylon wool adherence. The nylon wool-nonadherent cells were used as responder cells. In 10 of 10 neonatal samples and 6 of 7 adult samples, a significant AMLR was present when plastic-adherent cells were used as stimulators. Neonatal blood showed a mean increase in proliferation of 7.6 (3.6-14.9), while adult cultures showed a mean stimulation index of 11.8 (1.0-39.0). When nylon wool-adherent cells were used as stimulator cells, only 2 of 7 neonatal blood samples and 1 of 5 adult blood samples showed a significant AMLR. When recombinant interleukin 2 (IL-2) was added to AMLR cultures of plastic-adherent cells and nylon wool-nonadherent cells, a mean augmentation of 12.0 was seen in the neonatal AMLR, while the adult cultures were augmented by a mean response of 4.1. Addition of IL-2 to nylon wool-nonadherent cells alone produced a 5.9-fold increase in adult cells, while neonatal cells showed an 85.8-fold mean increase in proliferation. The results suggest that autoreactive T cells are present in neonatal blood and that these cells can be activated by plastic-adherent autologous cells. However, neonatal and adult nylon wool-adherent cells do not consistently activate autoreactive T cells.

Lymphocyte transformation induced by autologous cells. XVI: Distinctive role of discrete regions of class I MHC antigens in the autologous mixed leucocyte reaction

The role of Class I major histocompatibility complex (MHC) molecules in the autologous (AMLR) and allogeneic mixed lymphocyte reactions was investigated by using monoclonal antibodies (MoAb) directed to polymorphic MHC determinants. The AMLR from subjects with the HLA-A2 phenotype was consistently inhibited by the anti-HLA-A2 MoAb, CR11-351, and the inhibition was dose-dependent and complete even at low antibody concentrations. The allogeneic MLR was inhibited by CR11-351 less than 30% when HLA-A2-bearing cells were used either as stimulator or responder cells. Addition of interleukins 1 and/or 2 to the AMLR in the presence of the inhibiting MoAbs did not restore the proliferative response. These studies suggest that Class I MHC polymorphic determinants, or closely related structures, participate in the induction of the AMLR.

T-cells of multiple myeloma patients triggered by the autologous mixed lymphocyte reaction suppress polyclonal immunoglobulin synthesis

To elucidate the possible role of T-cells of patients with multiple myeloma (MM) in the suppression of polyclonal immunoglobulin synthesis. T-cells with and without prior activation by the autologous mixed lymphocyte reaction (AMLR) were added to normal immunoglobulin (Ig)-secreting cultures. The suppression induced by AMLR-activated T-cells from patients with MM was compared to that induced by AMLR-activated T-cells from apparently normal controls. The addition of 10% unstimulated autologous T-cells from patients with MM resulted in minimal suppression of IgG synthesis (87 +/- 19% of baseline values for patients and 115 +/- 21% for controls, no significant difference). The suppression sharply increased when T-cells were preactivated by AMLR and then added in the same concentration to the IgG-secreting cultures (38 + 12% of baseline values for patients compared to 106 + 14% for controls, P less than 0.05). AMLR cultures were performed in the presence of adherent monocytes and after their depletion. The T-cell suppressor effect on normal IgG synthesis was unchanged after monocyte depletion. T-cells preactivated in the AMLR from patients with MM sharply suppress in vitro polyclonal IgG synthesis, and the activation of these suppressor T-cells is not dependent on the presence of monocytes.

Possible regulation of autologous mixed lymphocyte reaction by OKM1+ NK cells

T cells are stimulated by autologous non-T cells and interleukin 2 (IL-2) is produced in the conventional autologous mixed lymphocyte reaction (AMLR) in young healthy controls. The role of cells with natural killer (NK) cell markers (OKM1+ cells or Leu 7+ cells) in the AMLR was studied. There were significant inverse correlations between the percentage of input OKM1+ cells minus monocyte (OKM1+ NK cells) and either AMLR proliferation (gamma = -0.9, P less than 0.001) or IL-2 production (gamma = -0.75, P less than 0.01) in the AMLR cultures after 7 days measured at 7 days. A statistically significant correlation was observed between the percentage of input Leu 7+ cells and AMLR proliferation (gamma = -0.64, P less than 0.05), but not IL-2 production. These results suggest that the AMLR is controlled by OKM1+ NK, perhaps acting through IL-2 regulation.

Interferon gamma modulates the ability of autologous non-T cells to stimulate T cells to produce and respond to interleukin 2

The interactions of T-cell receptor with self-Ia antigen on non-T cells induced IL-2 production and IL-2 receptors on the cell surface and thus responsiveness to IL-2 of T cells in autologous mixed-lymphocyte reaction (AMLR). Four-day-cultured autologous non-T cells lost their ability to stimulate T cells to produce and respond to IL-2 with concurrent decrease of HLA-DR and HLA-DQ antigen expressed on the cell surface. Culturing of non-T cells with 500 U/ml of recombinant interferon gamma (IFN-gamma) maintained their stimulating ability which was otherwise lost. Treatment of non-T cells with monoclonal anti-HLA-DR or anti-HLA-DQ antibody before mixture with T cells abrogated their ability to induce IL-2 production and IL-2 responsiveness of T cells. The combined data suggested that Ia antigen expressed on non-T cells is modulated by IFN-gamma, which increases the ability of non-T cells to stimulate autologous T cells to produce and respond to IL-2.

Antigen-specific T lymphocytes efficiently cluster with dendritic cells in the human primary mixed-leukocyte reaction

Experimental conditions have been developed to detect the efficient interaction of antigen-presenting cells and antigen-specific CD4+ T lymphocytes early in the human primary mixed-leukocyte reaction (MLR). When monocytes are depleted from the stimulator population, it is evident that small numbers of allogeneic dendritic cells form multicellular aggregates with responsive T cells. B cells and monocytes in allogeneic stimulator populations do not appear to form aggregates in the first 2 days of the MLR. Upon return to culture, most of the lymphocytes that have clustered with dendritic cells become IL-2 responsive, proliferating lymphoblasts. The nonclustered cells exhibit little growth, while mixtures of clusters and nonclusters proliferate comparably to clusters alone. Cluster-derived lymphocytes respond rapidly to rechallenge with foreign leukocytes from the original donor but are greater than 90% depleted of reactivity to other "third party" donors. Nonclustered lymphocytes, in contrast, are greater than 90% depleted in specific reactivity but respond normally to third party. Therefore antigen-specific (alloreactive) resting CD4+ lymphocytes efficiently and selectively aggregate with dendritic cells. Dendritic-T-cell aggregates represent a stable microenvironment in which the MLR begins and might be useful in the experimental analysis of early events in the sensitization phase of cell-mediated immunity in man.

Improvement of decreased interleukin 2 (IL-2) responsiveness and IL-2 production in autologous mixed-lymphocyte reaction of cord blood lymphocytes by interferon-gamma and IL-2 and the role of HLA-DQ antigen

Cord blood T cells did not produce interleukin 2 (IL-2) nor acquire responsiveness to it in autologous mixed-lymphocyte reaction (AMLR) as they do when activated by phytohemagglutinin (PHA). The ability of the cells to respond to IL-2 was restored either by the addition of recombinant IL-2 to the AMLR culture or by the preculture of non-T stimulator cells with recombinant interferon-gamma (IFN-gamma). IL-2 production was also induced when the T cells were added with recombinant IL-2 at the initiation of the AMLR culture, preceded by the treatment of non-T cells with recombinant IFN-gamma. IL-2-producing cells of cord blood induced in the above-mentioned condition were defined to be OKT4+ T cells, because the deletion of OKT4+ T cells from T-cell population abrogated the reaction, while that of OKT8+ T cells did not. Acquisition of IL-2 responsiveness and IL-2 production of T cells seemed to be mediated by HLA-DR and HLA-DQ molecules of non-T cells because these reactions were blocked by the treatment of non-T cells either with monoclonal anti-HLA-DR or with anti-HLA-DQ antibody. The HLA-DR and HLA-DQ densities of cord blood non-T cells were low as compared with those of adult, but the expression of HLA-DQ was remarkably improved by IFN-gamma treatment. In regard to IL-2, both IFN-gamma and IL-2 were needed to enable the lymphocytes to produce. This may suggest that some functional maturation by IL-2 of responder T cells is further required. These combined data suggested that cord blood non-T cells are defective as a stimulator in AMLR and this could be corrected by enhancing the expression of HLA-DQ antigen.

Defects of autologous mixed lymphocyte reaction-activated immunoregulatory T cells in patients with systemic lupus erythematosus

The present study was undertaken to determine the nature of the immunoregulatory T-cell defect after autologous mixed lymphocyte reaction (AMLR) activation in patients with systemic lupus erythematosus (SLE). Although AMLR was decreased in patients with SLE compared with normals, there was no difference in major proliferative cells (T4 cells and T4+JRA+ subset) in response to AMLR. Functional activity of AMLR-stimulated T4 subsets in patients with SLE and normals was examined in helper and suppressor/inducer assay, using pokeweed mitogen (PWM)-driven IgG synthesis. The T4+JRA- (helper) subset from SLE patients showed no greater activity than normals. However the T4+JRA+ (suppressor/inducer) subset from SLE patients showed decreased suppression induction compared with normals. This defect in the suppressor/inducer function was demonstrated even in patients with inactive SLR or in remission.

A syngeneic MLR induced in vivo results in T-cell mediated immune suppression

The proliferation of murine T lymphocytes in response to syngeneic Ia bearing non-T cells (syngeneic mixed lymphocyte reaction, SMLR) has been shown to generate regulatory T cells in vitro. An in vivo regulatory role has therefore been proposed for the SMLR. To study this role more directly, we examined the effects of repeated iv injection of mice with activated syngeneic B cells. Three such weekly injections induced a suppression of the plaque forming cell response to a subsequent injection of trinitrophenylated keyhole limpet hemocyanin (TNP-KLH). The suppression was transient and could not be maintained by additional injections of activated syngeneic B cells. The suppression was transferable to syngeneic recipients with splenic lymphocytes. Continued weekly iv injections of LPS induced blasts, as well as weekly intraperitoneal injections, caused enhancement rather than inhibition of the response to iv injected TNP-KLH. The enhancement was prevented by injection of anti-L3T4. Spleen cells from mice which had received three iv injections of activated syngeneic cells suppressed an in vitro secondary response to TNP-KLH by normal immune spleen cells. The cells responsible for the immune suppression were Thy 1.2+. The results indicate that repeated exposure to activated B cells causes activation of suppressor pathways but does not bring about a chronic state of immune suppression.

Induction of suppression following autologous mixed lymphocyte reaction; role of a novel 2H4 antigen

In this study, we have investigated the cellular and molecular basis for immunoregulatory function of T4+ cells after autologous mixed lymphocyte reaction (AMLR) activation. We demonstrated that the T4+ 2H4+ subset but not the T4+2H4- subset can proliferate maximally in response to autologous non-T cells. T4+ cells activated by AMLR exerted suppressor activity on pokeweed mitogen-driven IgG synthesis of autologous peripheral blood lymphocytes. The suppressor activity by AMLR-activated T4+ cells required the presence of fresh T8+ cells in the secondary culture, indicating that AMLR-activated T4+ cells functioned as a suppressor inducer rather than as a suppressor effector population. Following activation of T4+ cells in AMLR, it is the T4+2H4+ subset which induces suppression through the T8 population. Moreover, the treatment of AMLR-activated T4+2H4+ cells with anti-2H4 antibody, but not other antibodies, resulted in the abolishment of suppressor inducer function of such cells, suggesting that the 2H4 molecule itself may be involved in the suppressor inducer function. The 2H4 antigen on such cells was shown to be comprised of 220-kDa and 200-kDa glycoproteins. These results support the notion that the AMLR may play an important role in generating suppressor inducer signals and in down-regulating the immune response following self major histocompatibility complex recognition. More importantly, the present studies indicate that the 2H4 antigen on T4 cells serves not only as a phenotypic marker of suppressor inducer cells, but may have a functionally important role itself inducing suppression.

Activation of lymphocyte anti-tumour responses in man: effector heterogeneity and the search for immunomodulators

Data continues to accumulate on the immunological reaction against solid human cancers. The evidence at the present time supports the view that rather than being immunologically invisible, tumour cell antigens are recognised by at least three lymphocyte subsets. Helper T cells can be induced to proliferate upon exposure to cells of the autologous tumour and to secrete detectable levels of interleukin 2 (IL-2). Cultured T cell lines and clones can be shown to respond in primed lymphocyte tests not only to autologous tumour cells but also to allogeneic tumour cells of the same histology and anatomic location. Cytotoxic T cells manifest specific reactivity against cells of the autologous tumour which is distinguishable from natural killing (NK) on the basis of specificity and organ distribution. Natural killer cells can lyse freshly isolated autologous tumour cells after purification on Percoll gradients or when activated by IL-2. There is thus a demonstrable heterogeneity of response to human cancer in unseparated lymphocyte populations and at the clonal level. In limiting dilution assays lymphocytes at the tumour site respond more frequently to autologous tumour relative to NK targets. For at least some tumours there is evidence that the expression of auto-tumour reactivity but not NK correlates with the clinical course of the disease and is a favourable prognostic indicator. The finding of these auto-tumour reactivities has important implications for the search for immunomodulating drugs for cancer treatment. However, it must be recognised that the response is heterogeneous and that the immune system comprises multiple interactive elements that exhibit both positive and negative control. Any treatment modality must take this into account and seek to focus on specific activation of the tumour lytic populations or the inhibition of negative regulatory elements as opposed to seeking a more general augmentation of immune reactivity which may, by stimulating suppressor cells, have a counterproductive effect.

C-reactive protein reduces the promotion of human B-cell colony formation by autoreactive T4 cells and T-cell proliferation during the autologous mixed-lymphocyte reaction

Utilizing a dual liquid/semisolid culture system with human B cells suspended in a semisolid matrix, T4 helper cells activated in the autologous mixed-lymphocyte reaction (AMLR) were much more effective than T8 suppressor cells in promoting B-cell colony formation in the presence of Staph protein A. C-reactive protein (CRP) inhibited the promotion of B-cell colony formation by autoactivated T cells and inhibition was observed only when CRP was present during the early AMLR. Coculture experiments revealed that CRP directly reduced T4 promotion of colony formation rather than inducing T8-mediated suppression of T4 cells. B cells preincubated with CRP responded normally to facilitative signals from autoactivated T cells; however, monocytes or T cells preincubated with CRP were reduced in AMLR promotion of colony formation. Other results indicated that CRP inhibition of colony formation during the AMLR was associated with considerable reductions in the proliferation of autoreactive T cells. These data demonstrate that CRP can directly reduce the ability of autoreactive T4 cells to expand the B-cell compartment and that CRP blocks T-cell activation events proximal to proliferation.

A macrophage defect in women with recurrent Candida vaginitis and its reversal in vitro by prostaglandin inhibitors

The possible involvement of a defect in cellular immunity in the etiology of recurrent vaginal candidiasis was explored. The mean and range of in vitro lymphocyte proliferative responses induced by mitogens were comparable in 65 patients and 36 control subjects. In contrast, Candida-directed proliferation was reduced at least 70% below the mean control value in 73% of the patients. Further analyses on selected patients demonstrated that lymphocytes of the patients responded in the normal range to Candida if incubated in the presence of control macrophages. Conversely, macrophages of patients inhibited the responses of control lymphocytes to Candida. These effects were independent of mixed leukocyte reactions between allogeneic cells. Addition of the prostaglandin inhibitors ibuprofen and indomethacin prevented macrophages of patients from inhibiting patient or control lymphocyte proliferation. In response to Candida, macrophages from some women with recurrent vaginitis produce prostaglandin, which blocks the lymphocyte proliferation response to this organism.

In vitro allostimulation of peripheral blood mononuclear cells generates autologous reactive T lymphocytes: analysis at the clonal level

Cells from two siblings within family PER with a maternal crossing-over were used as responder and stimulator cells; they differed in class II MHC gene products. The responder cells were cloned and studied for their specificity. All the clones were T4+, most of them, were allospecific cytotoxic T-cell clones, some were only proliferative. Among the 62 clones that have been screened for their phenotype and function, we could expand, in our cloning system, two autoreactive T-cell clones specific for the self-class II MHC products. The results indicated that this autoreactivity was also observed in serum-free medium, which excludes any serum components susceptible to alter the self-class II MHC products. For the autorecognition, the two clones used the T3-Ti complex, and only one of them, the T4 structure.

Autologous induction of the human T-cell-dependent monocyte procoagulant activity: a possible link between immunoregulatory phenomena and blood coagulation

Activated monocytes acquire the ability to induce clot formation in platelet-poor citrated human plasma. The generation of this procoagulant activity (PCA) is dependent upon an interactive pathway between monocytes and T lymphocytes. Here we show that an ongoing autologous mixed lymphocyte reaction (AMLR) can elicit a T-cell-instructed PCA. PCA was measured by the ability of the cells to accelerate the clotting time of pooled citrated platelet-poor human plasma. AMLR was measured by tritiated thymidine incorporation. PCA and AMLR had very similar kinetics. Correlation coefficients between both reactions ranged from 0.59 to 0.99. Addition of an anti-DR monoclonal antibody blocked both reactions. T-Lymphocyte-depleted cell populations did not increase their level of PCA after 6 days in culture. Addition of autologous T cells to the T-depleted population restored its ability to produce PCA. Cyclosporin A blocked the peripheral blood mononuclear cell ability to generate PCA. A lymphokine generated during the AMLR was able to induce PCA in normal mononuclear cells. The results indicate that self recognition activates monocytes to produce PCA and suggests that this mechanism may represent a link between immunoregulatory phenomena and blood coagulation.

T cell proliferation induced by anti-self-I-A-specific T cell hybridomas. Evidence of a T cell network

Allo-I-A-reactive T cell hybridomas were generated from MLR-activated lymphoblasts. Cloned hybridomas T1.203, T1.321, and T1.426 were stimulated by I-Ab determinants, as shown by their ability to secrete IL-2 in response to a panel of MHC-recombinant mice. T2.146, T2.205, and T3.116 were found to be specific for I-Ak determinants using a similar panel of MHC-recombinant mice. Inhibition of IL-2 secretion by anti-I-A mAb confirmed these data. Some I-Ab-specific hybrids stimulated the proliferation of T cells from C57BL/6 (H-2b) mice. Similarly, some I-Ak-specific hybrids stimulated the proliferation of T cells from C3H/HeJ (H-2k) mice. These hybrids expressed no detectable surface I-A, and stimulation of T cells was not inhibited by anti-I-A mAb. These results are consistent with the hypothesis that normal mice possess a population of T cells responsive to idiotypic determinants on anti-MHC class II T cell receptors.

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.

Selective activation of functional suppressor cells by human seminal fluid

The ability of seminal fluid (SF) to induce suppressor cell activity from peripheral blood mononuclear cells (PBMN) was examined. PBMN were incubated with SF for 48 h, washed to remove SF components, treated with mitomycin C (mit C) and co-cultured with Raji cells, a lymphoblastoid cell line. Raji cell proliferation was inhibited by SF-treated PBMN proportionally to SF concentration. SF (50-200 micrograms), mit C-treated Raji cells or mit C-treated PBMN pre-incubated with phytohaemagglutinin were without effect on Raji cell growth. Suppressor T lymphocytes generated by incubation of PBMN with concanavalin A inhibited Raji cells to the same extent as did SF-treated PBMN. All activity was lost following heating at 56 degrees C for 30 min; freezing and thawing reduced the ability of SF to induce suppression by 50%. Dialysis of SF or treatment with antibody to prostaglandin E2 led to a 50% reduction in suppression.

Differential recognition of tumor-derived and in vitro Epstein-Barr virus-transformed B-cell lines by fetal calf serum-specific T4-positive cytotoxic T-lymphocyte clones

Two interleukin-2 (IL-2)-dependent cytotoxic T-cell clones were obtained by limiting dilution from a lymphocyte culture stimulated in vitro with the autologous Epstein-Barr virus-transformed lymphoblastoid cell line (LCL) in the presence of fetal calf serum (FCS). Both clones uniformly had a T3+, T4+, Dr+ phenotype and lysed autologous B blasts, the autologous LCL, and allogeneic B cell lines sharing major histocompatibility complex (MHC) class II antigens. The cytotoxic function was triggered by FCS-derived components. There was no killing if the sensitive targets were cultured in serum-free medium or in medium supplemented with human serum. Sensitivity to lysis could be restored by exposing the targets to FCS for at least 6 hr at 37 degrees C. Monoclonal antibodies directed to T-cell-specific surface antigens and MHC class II antigens inhibited lysis with different efficiencies depending on the target cell origin. Killing of Burkitt's lymphoma (BL)-derived cell lines was blocked more easily than killing of LCLs. LCLs but not BL lines induced proliferation of the T-cell clones in the absence of exogenous IL-2. The differences were not related to quantitative variations in the expression of MHC class II antigens, indicating that BL lines differ from LCLs in other cell membrane properties that may influence antigen presentation. The results suggest that the affinity of effector/target binding, which is probably influenced by the concentration of antigenic determinants expressed on the target cell membrane, determines whether proliferative responses or cytotoxicity are induced in the antigen-recognizing T cells.

Staphylococcal protein A primed leukocytes enhance the autologous mixed lymphocyte reaction

Human peripheral blood mononuclear cells (PBMC) were preincubated for 3 days in medium alone or with various mitogens then washed and irradiated. The preincubated cells then were cultured with autologous T-cells in an autologous mixed lymphocyte reaction (AMLR). Staphylococcal protein A (SPA) pretreatment of PBMC enhanced autologous T-lymphocyte proliferation from 1375 +/- 321 cpm (mean +/- SEM untreated PBMC) to 42,467 +/- 7,985 cpm (SPA primed PBMC) (p less than 0.01). The ability of SPA treated PBMC to enhance the AMLR was not simply a reflection of their proliferation in preculture, as PBMC precultured with phytohemagglutinin and concanavalin A showed greater proliferation than SPA-treated PBMC yet only minimally enhanced the AMLR. Kinetic studies and pre-exposure of PBMC to graded doses of gamma radiation showed that SPA augmentation of the AMLR was mediated by 2 components which differed in kinetics and radiosensitivity. Although incubation of PBMC with SPA did not increase the percentage of cells with detectable surface Ia antigen, SPA did increase the density of Ia in the preincubated cells. Cell separation studies revealed that SPA enhancement of the AMLR was not mediated by T-cells, but was mediated by a non-adherent non-E-rosetting fraction of cells. SPA enhancement of the AMLR was associated with an increased Ia density in the stimulator population but not with an increase in Ia positive cells and was mediated by proliferation-dependent and proliferation-independent mechanisms.

Defective autologous mixed lymphocyte reactivity in multiple sclerosis

T cells from patients with multiple sclerosis (MS) and normal controls were assessed for their ability to respond in the autologous mixed lymphocyte reaction (AMLR). Cells from stable MS patients demonstrated a significant defect in their proliferative response to non-T cells in comparison to normal controls. Despite the defective AMLR response, T cells from MS patients reacted as well as T cells from normal controls to allogeneic stimuli. Furthermore, MS non-T-cells were fully capable of stimulating allogeneic MLR responses by normal and MS T cells. Since the T4+ cell is the major subpopulation which proliferates in the AMLR, these studies suggest a functional defect in a subpopulation of T4+ cells in MS patients. Since the AMLR may represent an important mechanism by which immune responses are regulated, a defect in the ability of MS T cells to respond to autologous cells could account for several of the autoimmune features of the disease.

Self-tolerance to host and donor following HLA-mismatched bone marrow transplantation

The transplantation of T cell-depleted HLA-haploidentical bone marrow can correct the severe combined immunodeficiency disease (SCID) caused by the inherited absence of T lymphocytes. Despite a different environment, no severe graft-vs.-host reaction occurred and engrafted T lymphocytes became functional. We have studied tolerance of engrafted T lymphocytes to donor and host HLA antigens in four SCID patients who have been transplanted with bone marrow from one of their HLA-haploidentical parents. Graft-vs.-host reaction was prevented by T cell depletion of infused bone marrow using E rosetting and by in vivo administration of cyclosporine A. Subsequent to bone marrow transplantation (BMT), the engrafted T lymphocytes were shown to be unresponsive in vitro towards host cells collected prior to BMT. Generally, this tolerance could not be explained by a suppressive mechanism. Nevertheless, in one patient suppressive cells were found transiently. In contrast to the early appearance of a tolerance towards host, a reactivity of engrafted donor cells towards donor was always observed within the first 300 days post-grafting. This autoreactivity was mediated by T cells of donor origin and its targets were HLA class II molecules (at least HLA-DR and DQ). The progressive disappearance of this autoreactivity was correlated with the engraftment of Ia-positive cells (monocytes plus B lymphocytes) of donor origin and the achievement of complete immunological reconstitution. In the patient showing the strongest autoreactivity, a donor-specific T cell line has been grown which was shown to specifically inhibit the proliferative response of donor lymphocytes. Concomittantly, the immunological reconstitution remains poor in this patient. These data suggest that tolerance to HLA class II molecules is dependent on the presence of the relevant HLA class II molecule-expressing cells allowing the elimination or the suppression of T lymphocytes specifically directed at these molecules.

Functional heterogeneity of human antigen-presenting cells: presentation of soluble antigen but not self-Ia by monocytes

These studies were undertaken to examine the phenotype of the antigen-presenting cells (APC) circulating in human peripheral blood. Cells adherent to glass were found to be efficient APC, restoring antigen-induced 3H-thymidine incorporation to T4-positive T cells that had been rigorously depleted of contaminating APC. In order to identify the APC within the glass-adherent cells (AC), these cells were stained with a number of monocyte-specific monoclonal antibodies (Mo-Mab) including 3C10, 63D3, and 61D3, and the Mo-Mab-positive and -negative cells were separated with the fluorescence-activated cell sorter. This method of preparation yielded Mo-Mab(+) AC populations that were more than 98% positive for the relevant Mab when reanalyzed with the fluorescence-activated cell sorter. Less than 1% of the Mo-Mab(-) AC populations were positive when reanalyzed with the Mab used for the separation. However, each Mo-Mab(-) AC population was contaminated with variable numbers (4-60%) of Mo as detected by morphologic criteria, histochemical analysis for esterase activity, or staining with a different Mo-Mab. Both Mo-Mab(+) and (-) AC populations were found to be similarly effective APC, with as few as 500 cells/well supporting responses to streptokinase-streptodornase, tetanus toxoid, and Candida albicans antigen. In the absence of antigen, only 3C10(-), 63D3(-), or 61D3(-) AC consistently stimulated 3H-thymidine incorporation of autologous T4 cells; large numbers (greater than 5 X 10(3)/well) of APC were necessary to induce this response. These results support the conclusion that cells identified by Mo-specific Mab are capable of functioning as APC, inducing 3H-thymidine incorporation in response to exogenous antigens. However, Mo-Mab(+) AC are not unique in this activity since Mo-Mab(-) AC also appeared to be able to present antigen. These Mo-Mab(-) AC appear to contain the majority of cells inducing autologous T4-cell reactivity.

AMLR and MLR stimulating activity of human T lymphocytes activated in vitro by soluble HLA-DR antigens

We have examined the allogeneic mixed lymphocyte reaction (MLR) and autologous mixed lymphocyte reaction (AMLR) stimulating activities of T cells precultured in vitro with soluble allogeneic or autologous HLA-DR antigens. These cells (Ts) are known to suppress the human MLR: this suppression is specific in that it occurs only when stimulator cells have the same HLA-DR antigen as that used to induce differentiation of suppressor cells. Ts cells express new membrane specificities; they can be separated by immunoabsorption into two populations: Ts enriched (Tx+; with suppressive activity) and Ts depleted (Ts-; with helper function). In the present study, we have demonstrated that both Ts cell subsets activated by soluble HLA-DR alloantigens are able to stimulate both MLR and AMLR. Ts cells activated by soluble autologous HLA-DR antigens are able to stimulate MLR, but not AMLR.

Autologous responses to human leukaemic cells in mixed leucocyte culture

Cryopreserved leukaemic blasts and remission non-T cells from 22 patients with acute leukaemia (15 lymphocytic, 7 non-lymphocytic) were tested as stimulators of autologous remission T cells and normal allogeneic T cells in primary and secondary MLC. In most cases the autologous response elicited by leukaemic cells was less than or equal to that elicited by remission non-T cells. However, T cells from 2 patients in long-standing first remission from ANLL displayed greater proliferation in response to leukaemic blasts than to remission non-T cells in both primary and secondary MLC. The results are suggestive of sensitization of these 2 patients to leukaemia-specific antigens, but other possible explanations are discussed.

Lymphocyte proliferation induced by autologous cells. XV. Relationships between the human autologous mixed lymphocyte reaction stimulated by non-T and activated T cells

The human (T:T act) AMLR was characterized in its relationship to the (T:Non-T) AMLR and its validity as a nonxenogeneic antigen induced response was extended. Human T cell lines, established from responding T cells in an autologous mixed lymphocyte reaction (MLR), were maintained in medium containing human serum and interleukin-2 (IL-2). These cells stimulated 3H-thymidine incorporation by autologous T cells and by autologous unfractionated blood mononuclear cells. Freshly activated T cells isolated from an autologous MLR stimulated autologous T cells to a lesser extent could be enhanced by adding IL-2. Twenty-five to 50% of T cells stimulated by activated T cells express the T8 determinant. In contrast, we have previously shown that less than 10% of T cells activated after 6 days in culture with non-T cells express the T8 determinant. The number of T8 bearing cells were increased significantly after 10 days in culture with non-T cells. This suggested that two types of reactions, the (T:Non-T) and (T:T act) AMLR, might occur in sequence when T cells and autologous non-T cells are cocultured: first, the activation of T4 cells by non-T cells, then by the activation of T8 cells by activated T4 cells. Finally, activated T cells can stimulate unfractionated autologous mononuclear cells without prior exposure to sheep erythrocytes or fetal calf serum.

A role for self-recognizing T cells in the regulation of antibody-forming and cell-mediated cytotoxic responses in the mouse

Mitogen- or antigen-activated murine spleen and thymus cell blasts have been used as inducer cells to stimulate production of suppressor T cells (Ts) in autologous mixed leucocyte culture. Ts cells were induced in an MHC-restricted fashion and produced suppression of cell-mediated lympholysis and antibody synthesis from fresh spleen cells sharing MHC haplotypes with the Ts pool. Ts were Thy 1+, Lyt 1+ cells. Induction of Ts depended upon expression of class II MHC antigens on stimulating cells, but the level of Ts induced by different populations of suppressor inducer cells was not correlated with the level of Ia antigen expression. Activity of suppressor inducer cells was correlated with the functional activity of the inducer pool. The data are interpreted to favour a model in which Ts are induced by associative recognition on stimulator cells of class II MHC antigens and lymphocyte recognition receptors as nominal antigen (i.e. Ts are auto anti-idiotypic in nature). Using as stimulator/responder cells in AMLR lymphocytes taken from normal (8-week) or aged (greater than 24-month) mice, data were obtained consistent with this model and with earlier evidence for an altered expression of both lymphocyte recognition receptors and/or class II antigens in senescence.

A subpopulation of suppressor cells in Richter's syndrome with both monocytic and T-lymphocytic characteristics

We evaluated T-lymphocyte functions in the peripheral blood of a patient with B-cell chronic lymphocytic leukemia after transformation to large cell lymphoma (Richter's syndrome). A subpopulation of E-rosette adherent cells were found with T-lymphocytic surface markers (OKT3+/8+/4+), monocytic characteristics (latex ingestion, nonspecific esterase staining), and suppressor activity. In contrast to the patient's nonadherent T-cells, this subpopulation suppressed PHA proliferation of autologous lymphocytes, pokeweed mitogen (PWM)-induced proliferation of normal non-T cells, and a mixed lymphocyte reaction. Further studies are warranted in patients with Richter's syndrome, in order to determine the frequency and significance of our findings.

Activated human T cells can present alloantigens but cannot present soluble antigens

Human T cells, when activated by antigen or mitogen, express Ia antigens. We have examined the capacity of activated T cells to stimulate autologous and allogeneic T cells and their ability to present soluble antigen. Interleukin 2-dependent T-cell lines (TCL), free of accessory cells, were used for antigen-presenting cells. These activated T cells were potent stimulators in an autologous mixed lymphocyte reaction (AMLR), more so than autologous irradiated non-T mononuclear cells. Activated T cells were also able to stimulate proliferation of allogeneic T cells in the absence of any other accessory cells, and this stimulation was blocked by anti-Ia antibodies. Resting unstimulated T cells were unable to stimulate autologous or allogeneic responses. Thus, activated T cells were able to present self antigens and alloantigens. However, activated T cells could not present soluble antigens to autologous T cells or to antigen-specific TCL even if exogenous interleukin 1 was added to cultures. The ability of activated T cells to stimulate an AMLR in vitro may reflect an important immunologic amplification mechanism in vivo. The ability of activated T cells to present alloantigens but not soluble antigens suggests an inability to process antigen, and this may provide further insights into the complexities of antigen presentation.

T-suppressor clones derived from murine AMLR

Panels of cloned T-cell lines were derived from the autologous mixed lymphocyte reactions of NZB and C58 mice. These clones were all Thy 1+. In addition, various clones expressed appropriate Ia, Lyt 1 and/or Lyt 2 antigenic specificities. None of these clones produced the lymphokines IL-2, CSF or AMLR-helper factor. The clones suppressed fresh syngeneic AMLR and MLR responses when added at low cell numbers at the initiation of culture. This suppression was not abrogated by treatment with mitomycin c or reversed by the addition of a source of T-cell growth factor. The mechanism of suppression was not cytotoxicity, as the clones were non-cytotoxic for either syngeneic or allogeneic cells. Many of the clones appeared to require the presence of Lyt 2+ cells in the MLR responding population to suppress, and therefore can be classified as T-suppressor inducers. Two clones did not require the Lyt 2+ subset to suppress the MLR, and are therefore T-suppressor effectors.