Significance of self-recognition and interleukin-2 for immunoregulation, autoimmunity and cancer

Dominant TNFα and impaired IL-2 cytokine profiles of CD4+ T cells from children with type-1 diabetes

Aberrantly activated CD4⁺ T memory cells play a central role in the development of type-1-diabetes. Interleukin-7 promotes generation of autoimmune memory T cells and increased Interleukin-7 availability is associated with type-1-diabetes susceptibility. T-cell-mediated immune pathology at onset of type-1-diabetes is well defined, but characteristics of long-term symptomatic disease stages remain largely elusive. In the present study, memory CD4⁺ T-cell activation and cytokine expression as well as sensitivity to Interleukin-7 in vitro were compared between patients with type-1-diabetes at clinical onset (n=25), long-term symptomatic disease (median duration 4.5 years, n=19) and matched healthy controls (n=21). T-cell responses of type-1-diabetes patients were characterized by higher frequencies of cytokine and activation marker expressing CD4⁺ memory T cells as compared to healthy controls. Notably, correction for individual cytokine expression levels revealed qualitative differences of cytokine profiles characterized by significantly increased TNFα and decreased IL-2-expressing T-cell proportions in long-term type-1-diabetes patients. IL-7-mediated T-cell co-stimulation induced quantitative and qualitative cytokine expression differences highly similar to type-1-diabetes-specific profiles. In addition, CD4⁺ memory T cells from children with long-term type-1-diabetes were more sensitive to in vitro IL-7 co-stimulation. Global transcriptome analysis revealed IL-7 induced expression differences of CD4⁺ T cells, including increased IL-2R expression and effects on subsequent T-cell receptor activation. We conclude that long-term symptomatic type-1-diabetes patients differed in memory T-cell cytokine profiles and Interleukin-7 co-stimulation. Regulation of IL-2 expression and sensitivity are affected with possible consequences for disease course and severity at long-term type-1-diabetes stages.

Interleukin-2 and systemic lupus erythematosus--fifteen years later

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder in which multiple immunologic abnormalities have been described. In this review, we thoroughly analyse the impaired T cell production of, and response to, interleukin-2 (IL-2) characteristic of patients with SLE. Since it was first reported, several articles have provided us with enlightening, but somewhat confusing, data that reveal the complexity of the subject. The IL-2 production by T cells is part of a complex network in which a discrete alteration is capable of disrupting the whole system. On the other hand, regulatory mechanisms exist that, in an attempt to compensate the primary alteration, provoke secondary defects. Evidence indicates that this defect is not intrinsic, but rather, results from multiple microenvironmental influences that act on the T cell and modify its activation state and its cytokine production. Abnormalities in co-stimulatory mechanisms and in cytokines that may be related to the IL-2 production deficiency, have been described in patients with SLE. We also consider the information derived from murine SLE models, IL-2 knockout models and reports concerning the immune dysregulation present in patients with SLE.

Promotion of macrophage-stimulated autoreactive T cell proliferation by interleukin-10: counteraction of macrophage suppressor activity during tumor growth

CD4+ autoreactive T cells are a major cell population in regulating immune responses to altered autologous neoplastic cells. Normal autoreactive T cells recognize major histocompatibility complex (MHC) class II molecules in association with self-peptides on antigen-presenting cells, such as macrophages (M phi). Tumor-bearing hosts (TBH) have decreased autoreactivity partly because tumors increase M phi secretion of suppressor molecules like prostaglandin E2 (PGE2) and decrease M phi MHC class II expression. Because interleukin (IL)-10, a cytokine produced by T cells, M phi, and tumor cells, inhibits production of most M phi suppressor molecules, we determined if IL-10 could reverse tumor-induced murine splenic M phi-mediated suppression of autoreactive T cell proliferation. Tumor growth enhanced activated M phi production of PGE2, nitric oxide, and tumor necrosis factor-alpha (TNF-alpha). IL-10 strongly reduced or inhibited M phi production of these molecules. When added to pure normal host (NH) CD4+ T cells, NH syngeneic splenic M phi stimulated autoreactive T cell proliferation more than did TBH splenic M phi. Exogenous IL-10 or M phi preincubation with IL-10 restored TBH M phi-stimulated autoreactivity to normal levels. IL-10 treatment had little or no effect on NH M phi-stimulated autoreactivity. IL-10 inhibited TBH M phi secretion of suppressor molecules in T cell proliferation assays because supernatants from IL-10-pretreated TBH M phi-syngeneic NH T cell cultures had decreased levels of suppressor molecules. When endogenous IL-10 activity was neutralized with anti-IL-10 monoclonal antibody, autoreactive T cell proliferation stimulated by NH or TBH M phi was slightly, but significantly decreased. Although IL-10 is known to inhibit M phi foreign antigen-presenting cell-dependent T cell proliferation, this study shows that IL-10 restores autoreactive T cell functions during tumor growth by counteracting M phi production of inhibitory molecules. These data suggest that IL-10 up-regulates anti-cancer autoreactive T cell responses by down-regulating suppressor M phi activity.

Tumour growth causes suppression of autoreactive T-cell proliferation by disrupting macrophage responsiveness to interferon-gamma

Normal immune homeostasis is regulated partly by a small population of CD4+ T cells that react to autologous major histocompatibility complex class-II molecules on self-cells. Decreased autoreactive T-cell responses are associated with cancer. Tumour growth causes syngeneic macrophages (M phi) to suppress autoreactive T-cell proliferation by decreasing M phi class-II expression and increasing M phi production of the suppressor molecule prostaglandin E2 (PGE2). Because interferon-gamma (IFN-gamma) is a potent M phi activation molecule which regulates both M phi PGE2 and class-II expression, the effects of IFN-gamma on tumour-induced suppression of autoreactive T-cell proliferation were investigated. Exogenous IFN-gamma increased normal host (NH) CD4+ autoreactive T-cell proliferation stimulated by syngeneic NH M phi but decreased proliferation stimulated by tumour-bearing host (TBH) M phi. Antibody (Ab) neutralization of endogenous IFN-gamma activity reduced TBH M phi-mediated suppression. Kinetic studies showed that endogenous IFN-gamma suppressor activity was not exclusive during T-cell activation. Indomethacin treatment blocked IFN-gamma-induced suppression in TBH M phi-T cell cultures. TBH M phi-T cell cultures contained significantly more PGE2 than those containing NH M phi. Exogenous IFN-gamma increased early PGE2 production in TBH M phi cultures but decreased production in NH M phi cultures. The Ab-mediated neutralization of endogenous transforming growth factor-beta or tumour necrosis factor-alpha reduced TBH M phi-mediated suppression and blocked IFN-gamma-induced suppression. Short-term treatment of M phi with IFN-gamma before their addition to T cells caused TBH M phi to stimulate T-cell proliferation, which suggests that early suppressor molecule production by TBH M phi inhibits synthesis or activity of IFN-gamma-induced stimulatory monokines. These results show that tumour growth causes M phi to suppress autoreactive T-cell responses by allowing IFN-gamma to induce M phi suppressor molecules, which block production or activity of stimulatory monokines.

Tumor-induced macrophage tumor necrosis factor-alpha production suppresses autoreactive T cell proliferation

T cells can react to self-cells bearing the syngenic major histocompatibility complex class II molecule Ia. Decreased autoreactive T cell responses are associated with cancer. Tumor growth causes syngeneic macrophages (M phi) to suppress autoreactive T cell proliferation by decreasing M phi Ia expression and increasing M phi production of the suppressor molecule prostaglandin E2 (PGE2). Because M phi produce tumor necrosis factor-alpha (TNF-alpha) during cancer, and TNF-alpha stimulates M phi PGE2 synthesis, we determined if TNF-alpha mediates tumor-induced suppression of autoreactive T cell proliferation stimulated by syngeneic M phi. We showed that tumor growth increases TNF-alpha production because tumor-bearing host (TBH) M phi synthesized more TNF-alpha than normal host (NH) M phi when cultured with lipopolysaccharide. Exogenous TNF-alpha increased NH CD4+ autoreactive T cell proliferation stimulated by syngeneic NH M phi but not by TBH M phi. When endogenous TNF-alpha activity was neutralized by anti-TNF-alpha antibody addition, T cell proliferation decreased when stimulated by NH M phi but increased when stimulated by TBH M phi. Kinetic studies showed that TNF-alpha affected M phi-stimulated T cell proliferation during the first few hours (4h) of the 96 h culture time. Indomethacin-treatment allowed TNF-alpha to increase T cell proliferation stimulated by TBH M phi. A PGE2-specific enzyme-linked immunosorbent assay showed that TBH M phi T cell cultures contained significantly more PGE2 than those containing NH M phi, and that exogenous TNF-alpha increased PGE2 production in TBH M phi cultures more than in NH M phi cultures. Short-term (4h) pretreatment of M phi with TNF-alpha increased T cell proliferation stimulated by NH, but not TBH, M phi. However, long-term (16 h) TNF-alpha pretreatment reversed TBH M phi-mediated suppression, suggesting that early suppressor molecular production inhibits synthesis or activity of TNF-alpha-induced stimulatory monokines. Although TNF-alpha is known to increase T cell proliferation, these results show that the tumor-induced increase in M phi TNF-alpha synthesis suppress autoreactive T cell proliferation, which is mediated by PGE2 production.

HLA-B8,DR3 phenotype and the antibody response against Epstein-Barr virus

Antibodies against the viral capsid antigen (VCA) and nuclear antigens (EBNAs) of the Epstein-Barr virus (EBV) were determined in a sample of Sicilian population. A significant correlation was observed between HLA-B8,DR3 phenotype and reduced titres of antibodies to EBNAs, whereas HLA-B8,DR3 positive individuals displayed levels of antibodies to VCA comparable to those of HLA-B8,DR3 negative ones. These results further strengthen the suggestion that HLA-B8,DR3 positive subjects are low responders and that the depth of immune response depends on the fashion of antigenic challenge.

gamma-Interferon, interleukin-4 and interleukin-6 in vitro production in old subjects

It is well known that ageing is associated with various alterations of the lymphoid cell functions. Although both B and T cell are affected, the last appear to be more sensitive to ageing process. During the past years, to gain insight into thé mechanism(s) of this impairment, effort has been centered on the helper T cells specifically engaged in the production of interleukin-2 (IL-2) because of the pivotal role played by this cytokine in the activation of several immune functions. The results have demonstrated that the ability to produce IL-2 declines with age. In this paper we report the results of a study performed to determine the influence of age on the capacity to produce gamma-interferon (gamma-IFN), interleukin-4 (IL-4) and interleukin-6 (IL-6). Mononuclear cells from young and old subjects were assessed for cytokine producing capacity in response to phytohaemagglutinin stimulation. A significant decrease of gamma-IFN production by old subjects has been observed. No significant difference was instead observed between the old subjects and the young ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in elderly, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

The role of interleukin 2 in the development of autoimmune thyroiditis

Interleukin 2 (IL-2) is a lymphokine that may disrupt immunological self-tolerance. While being incapable of interfering with intrathymic or peripheral clonal deletion, IL-2 may overcome functional antigen unresponsiveness in anergic T lymphocytes. Anergy of T helper cells of the inflammatory phenotype implies selective silencing of the transcription of the IL-2 gene and thus precludes autocrine IL-2/IL-2 receptor (IL-2R) mediated growth, as well as delivery of help to other T cells or B lymphocytes. Thus, IL-2 serves as a servomodulator regulating post-deletional self-tolerance. IL-2-producing and IL-2-receptive cells are present in a variety of autoimmune lesions, including spontaneous autoimmune thyroiditis developing in the Obese strain (OS) of chickens, in Hashimoto's struma lymphomatosa, and in Graves' disease. Whereas the OS is characterized by a hyperinducibility of the IL-2/IL-2R system that predisposes to the development of severe thyroid infiltration, the state of the IL-2/IL-R system in circulating lymphocytes of patients developing thyroid autoimmunity, or at risk of doing so, remains to be defined. The most frequent autoimmune side-effect of IL-2 treatment concerns the thyroid gland. IL-2 induces a lymphoid thyroiditis leading to primary hypothyroidism, especially in those patients that have pre-treatment antithyroid autoantibodies. The hypothesis is extrapolated that IL-2 induces autoimmune disease in those patients that bear undeleted thyroid-specific T cells, and in which the lack of manifest thyroiditis relies upon peripheral, post-deletional tolerance.

Determination of tumor necrosis factor alpha (TNF alpha) and interleukin 2 (IL 2) in women with idiopathic recurrent miscarriage

Some recurrent miscarriages may be due to a host versus graft reaction. Elevated Interleukin 2 (IL2) levels have been found during pregnancy and elevated TNF alpha levels during acute rejection crises of allotransplantats and so we determined IL2- and TNF alpha levels in women with recurrent miscarriages. Samples were taken for serum TNF alpha and IL2 radioimmunoassays (IRE Medgenix, Belgium) from 28 healthy non-pregnant women and in 49 women with at least 3 miscarriages between the 6th and 14th week of pregnancy, 38 women having their first or second miscarriage and 42 pregnant women with no complications. In women with recurrent miscarriage an increase in TNF alpha (P less than 0.05) and a decrease in IL2 serum levels (P less than 0.05) was found compared to women with normal pregnancies. These results support the concept that disturbances of immune tolerance of the fetus may account for some cases of recurrent miscarriage.

T cell interactions in active rheumatoid arthritis: insights from the human autologous mixed lymphocyte reaction as a model of T cell activation cascade

The autologous mixed lymphocyte reaction (AMLR) represents the activation, proliferation and differentiation of T cells in response to signals from autologous non-T cells. Using monoclonal anti-Leu8 antibody to isolate subpopulations of human CD4+ and CD8+ T cells, we have investigated the role of these subpopulations in the T cell activation cascade during the course of AMLR. In normal subjects, CD4+Leu8+ cells are necessary for the initiation of the AMLR response, and sequentially lead to activation and proliferation of both CD4+Leu8- cells and CD8+Leu8+ cells. The activated CD8+Leu8+ cells, in turn, induce CD8+Leu8- cells to generate proliferation of the latter cells. Soluble mediators could be involved in the T cell activation cascade induced by the AMLR. Patients with active rheumatoid arthritis have a profound defect in the AMLR. Further analysis indicates that rheumatoid arthritis CD8+ T cells are markedly defective as responding cells in the AMLR. The impaired AMLR response by CD8+ cells cannot be reconstituted with AMLR-derived supernatants from normal T cells. The data suggest that the defective CD8+ T cell function may contribute to the pathogenesis of the disease.

Markers of T lymphocyte activation in HLA-B8, DR3 positive individuals

Many autoimmune diseases are associated in Caucasians with HLA-B8 and/or HLA-DR3 antigens. There is evidence that bearers of these antigens may display significant changes in immune parameters when compared to individuals not having these antigens. Recently, increased numbers of blood activated T lymphocytes have been reported in the majority of these diseases. The increase in activated blood T lymphocytes is paradoxically characterized by an in vitro impairment of T cell activation. Particularly, an inadequate production of interleukins has been observed. We have studied blood levels of activated T cells in HLA-typed, healthy subjects. The results show that the percentage of activated T cells, as recognized by monoclonal antibodies anti-CD25, anti-Ia and anti-MLR3, was more frequent in HLA-B8, DR3 positive individuals. On the other hand, in the 24 h, PHA stimulated cultures IL-2, IFN-gamma and the percentage of T cells CD25 positive were decreased. Thus, there was an apparent discrepancy between the increase of blood activated T cells and the in vitro impaired T cell activation. Since there is evidence that HLA-B8, DR3 positive subjects are genetically low responders, a possible reason for the discrepancy might be their relative inability to remove antigenic stimuli from the body. In this case, the increased number of activated blood T cells may reflect a cellular activation caused by persistent antigenic stimulation.

Autoimmunity and malignancy

In patients with autoimmune diseases malignancy is observed more frequently than in an age-matched control group. In strains of mice susceptible to autoimmune diseases, the incidence of lymphoreticular malignancies is increased. Although viruses have not been directly implicated in their pathogenesis or etiology, there are suggestions that slow viruses may be involved. Viruses have been found to be important in the development of lymphomas. Hence in genetically susceptible animals, viruses can initiate the autoimmune process. Prolonged stimulation of the autoimmune process or a prolonged state of immunodeficiency could trigger or activate genes or their products, which could result in the development of malignancy.

Infiltrating mononuclear cells in salivary glands and kidneys in autoimmune MRL/Mp-lpr/lpr mice express IL-2 receptor and produce interferon-gamma

The salivary gland inflammatory lesions and renal vasculitic lesions of autoimmune MRL/lpr mice were analyzed for the presence of activated lymphocytes. Immunohistologic analysis revealed that the majority of lymphocyte-like cells in salivary glands and kidneys expressed CD4 antigen (greater than 50%). Lesser numbers of interleukin-2 receptor (IL-2R) expressing and interferon-gamma (IFN-gamma)-producing cells were present (1-5%). CD4+, IL-2R+, and IFN-gamma + mononuclear cells were found in small inflammatory foci. In larger inflammatory foci the IFN-gamma-producing cells were detected in the periphery in comparable numbers as the IL-2R expressing cells although with different location. Large numbers of cells in the inflammatory foci also expressed MHC Class II molecules (greater than 50%). The expression of IL-2R and production of IFN-gamma in the tissue lesions indicate presence of activated inflammatory T cells. Production of IFN-gamma by the infiltrating mononuclear cells may induce Class II antigens on epithelial cells and stimulate further T cell migration into the inflammatory site.

In vivo regulation of the murine syngeneic mixed lymphocyte reaction

Previous work from this laboratory has suggested that a CD8+ T suppressor (Ts) cell network regulated the murine syngeneic mixed lymphocyte reaction (SMLR). We have attempted to disrupt this network by the inoculation of anti-CD8 monoclonal antibodies (mAb) in vivo. Intraperitoneal inoculation of three mAbs resulted in a marked increase in the proliferation of CD4+, self-Ia-reactive splenic T cells in vitro to syngeneic, but not to allogeneic, spleen cells. Suppression was not limited to a specific mouse strain as the enhanced SMLR was reproducible following anti-CD8 treatment of three strains of mice. In vivo depletion of CD8+ T cells was not a prerequisite for enhancement of the SMLR as several mAb to CD8 augmented the SMLR independent of their capacity to cause CD8 T cell depletion. Moreover, enhancement of the SMLR could be mimicked in vitro by inclusion of anti-CD8 mAb in in vitro cultures of responder T cells and irradiated Ia+ syngeneic stimulators. Since the in vitro SMLR was enhanced following mAb treatment, it was expected that the in vivo SMLR would also be increased. However, no evidence of increased in vivo autoreactivity could be detected following in vivo treatment with anti-CD8 mAb, indicating that other mechanisms in addition to CD8+ regulatory T cells acted to regulate the in vivo activity of autoreactive T cells.

Macrophages but not B cells from aged mice are defective in stimulating autoreactive T cells in vitro

In the present study the effect of aging on the capacity of Ia+ cells to stimulate autoreactive T cells in the syngeneic mixed lymphocyte reaction (SMLR) was investigated. Using young CD4+ T cells as responders, it was observed that unseparated whole spleen cells from aged mice had normal stimulatory activity comparable to that of young spleen cells. Interestingly, however, when purified splenic adherent cells (SAC) enriched for macrophages or splenic B cells were used as stimulators, aged SAC but not aged B cells were found to be defective in stimulating autoreactive T cells. This defect in aged SAC was not due to decreased expression of Ia antigens since the percentage of Ia+ SAC and density of Ia antigen expression was similar in both young and old mice. Also, the B cells from aged mice expressed normal levels of Ia antigens. Aged SAC, when mixed with young SAC could also actively suppress the normal SMLR. However, this suppression was not due to increased prostaglandin production but was found to be associated with interleukin-1 (IL-1) regulation, inasmuch as addition of exogenous IL-1 could completely reconstitute the defective stimulatory activity of aged SAC and also abolished the suppressor activity of the SAC. Aged mice also demonstrated an intrinsic defect in the CD4+ T cells responding in the SMLR. Together, our studies on the SMLR demonstrate an age-related defect in responder autoreactive T cells and in stimulator splenic macrophages but not in the stimulatory activity of B cells.

Aldicarb treatment inhibits the stimulatory activity of macrophages without affecting the T-cell responses in the syngeneic mixed lymphocyte reaction

Aldicarb, a carbamate pesticide used extensively throughout the United States, has been shown in several areas to contaminate drinking water at levels exceeding 100 p.p.b. Recent studies have suggested that aldicarb at levels well below these found in drinking water may lead to alterations in mammalian health. In the present study, we investigated the possible toxic effects of aldicarb on the mammalian immune system. Specifically examined in these studies were the effects of aldicarb on syngeneic mixed lymphocyte reaction (SMLR) in which CD4+ T-helper cells (autoreactive T-cells) respond to self or syngeneic Ia molecules expressed on macrophages. The effect of aldicarb was delineated at both the responder and stimulator cell-level. When C3H mice were injected intraperitoneally with a single dose of 0.1-1000 p.p.b. of aldicarb, it was observed that there was a decrease in the stimulatory functions of macrophages, as studied by decreased capacity to stimulate normal autoreactive T-cells. Further analysis revealed that the decreased stimulatory capacity of macrophages from aldicarb-treated mice was not due to decrease in the expression of Ia antigens, since flow cytometric analysis of macrophages from aldicarb-treated mice demonstrated normal levels of Ia expression. Also, cell-mixing experiments failed to demonstrate any suppressor macrophages in aldicarb treated mice. Addition of exogenous interleukin-1, however, completely reconstituted the defective stimulatory activity of macrophages from aldicarb-treated mice. In contrast to these effects on macrophages, it was observed that in C3H mice treated intraperitoneally with single dose of 1-1000 p.p.b. of aldicarb, there was no evidence of alteration in the ability of autoreactive T-cells to respond to syngeneic Ia molecules expressed on normal macrophages. In addition, responsiveness of T-lymphocytes obtained from aldicarb-treated mice to allogeneic Ia antigens was also unaltered. These data suggested that aldicarb may selectively suppress the stimulatory activity of macrophages by inhibiting IL-1 mediated signal to the T-cells without directly affecting the T-cell functions.

Relation between soluble interleukin 2 receptor and clinical findings in patients with systemic lupus erythematosus

The concentration of soluble interleukin 2 receptor (IL-2R) was determined in the serum of 54 patients with systemic lupus erythematosus (SLE) by an enzyme linked immunosorbent assay (ELISA) using two monoclonal antibodies with the IL-2R. Concentrations of soluble IL-2R in the serum of the patients with SLE (study group) were significantly higher than in 20 normal subjects (control group). The relation between concentrations of soluble IL-2R and clinical findings was investigated. The concentration of soluble IL-2R showed no particular relation with the clinical manifestations and did not correlate with the level of anti-DNA antibody or CH50. Significant correlation between the concentration of soluble IL-2R and disease activity did exist, however. Furthermore, the concentration of soluble IL-2R in some cases changed simultaneously with the disease activity. Thus the concentration of soluble IL-2R may serve as a new clinical indicator of disease activity in patients with SLE.

B cell hyperresponsiveness to interleukin 2 and the age-associated decline in murine lupus

In young NZB x NZW (B/W) F1 mice there was a population of B cells that were hyperresponsive to interleukin 2 (IL-2) and that proliferated but did not differentiate, even in the absence of a prior activation signal, and hence were already stimulated in vivo and were prepared to respond to IL-2. These B cells belonged to the population that was nonadherent to the Sephadex G-10 (G-10) column. We found that such hyperresponsiveness was progressively reduced with the aging of these mice. This event did not appear to be related to the age-associated changes of IL-2 receptors on B cells, since the IL-2-binding ability and the density of IL-2 receptor alpha expressed on B cells in culture did not differ between the young and the old mice. Studies suggested that two major mechanisms are responsible for the age-associated decline in the IL-2 responsiveness of B cells. First, the capacity of IL-2 hyperresponsiveness of such B cells decreases in B/W F1 mice with aging, probably through further activation and differentiation of the B cells. Second, the G-10 adherent, but not nonadherent, B cells from the aged mice inhibit the IL-2 response of G-10 nonadherent B cells. The G-10 adherent B cells from the old mice also inhibited the IL-2 production of T cells from the young B/W F1 mice. Taken together, it appears that young B/W F1 mice bear a population of B cells already stimulated so that they can respond to IL-2 without prior stimuli. With aging, activation of the B cells progresses and they appear to down-regulate the IL-2 hyperresponse of B cells and the IL-2 synthesis by T cells.

A specific defect in the proliferative capacity of B cells from old mice stimulated with autoreactive T cells

B lymphocytes from aged mice were found to be defective in their ability to proliferate in response to stimulation with an autoreactive T cell clone D1.4. The differentiative response leading to antibody secretion was also impaired in the auto D1.4 T cell-stimulated B cells from old mice in comparison to similarly stimulated B cells from young mice. The B cells from old mice were competent in activating the autoreactive T cells such that the T cells were induced to proliferate. The B cell defect appears to be restricted to a certain phase of B cell activation, since old mouse B cells responded to the auto D1.4 T cells by increasing cell surface Ia as well as size, but failed to incorporate tritiated thymidine. The responsiveness to interleukin-4 was found to be similar between B cells from young and old mice. It appeared that the B cells from old mice are specifically defective in progressing from the G0 phase of cell cycle into the S phase when stimulated with the auto D1.4 T cells.

Fractionation of T cell subsets on Ig anti-Ig columns: isolation of helper T cells from nonresponder mice, demonstration of antigen-specific T suppressor cells, and selection of CD-3 negative variants of Jurkat T cells

In the present experiments we have explored the possibilities of a modified immunoadsorbent technique to select for (1) mutagenized T cell receptor (Tcr) negative variants of Jurkat T lymphoma cells and (2) purified CD-4+ or CD-8+ T lymphocytes. The basic principle was to make large numbers of immunoglobulin (Ig) negative T cells Ig+ by T cell subset-specific monoclonal antibodies (mAb), and to select such cells on Ig anti-Ig columns. Our results demonstrated that Thy-1+, Fc receptor positive, antigen-specific T cells regulate the immune response in mice nonresponders to pork insulin, and the "autologous" mixed lymphocyte reaction. In addition, the immunoadsorbent method very efficiently selects Tcr/CD-3- variants from mutagenized Jurkat cell populations incubated with anti-CD3 mAb. The described method is easy and quick and can fractionate large numbers of cells; it is the "poor-man's cell sorter." The most important finding is the demonstration of antigen-specific Thy-1+, CD-8+, and Fc receptor+ T suppressor cell that apparently react with antigen in a non-major histocompatibility complex-restricted manner.

Familial occurrence of impaired interleukin-2 activity and increased peripheral blood B cells actively secreting immunoglobulins in systemic lupus erythematosus

PURPOSE

We tested the hypothesis that some abnormalities of immune functions are genetically controlled in patients with systemic lupus erythematosus (SLE).

SUBJECTS AND METHODS

We used a phytohemagglutinin-induced interleukin-2 (IL-2) activity assay and a spontaneous plaque-forming cell assay to evaluate T-cell and B-cell function, respectively, in 34 clinically healthy family members of six SLE probands.

RESULTS

Impaired IL-2 activity was found in 15 of the 29 consanguineous relatives. There was no relation between the household relatives and the nonhousehold relatives; none of the five nonconsanguineous household persons had abnormal results. Results for the B-cell assay were abnormal in 22 of the 29 consanguineous relatives. The B-cell abnormalities were more commonly observed in the consanguineous household relatives; four of the five nonconsanguineous household relatives also had abnormal assay results.

CONCLUSION

The findings indicate that the impaired IL-2 activity in relatives appears to strongly correlate with a genetic relationship. Although the evidence favors a genetic basis for the B-cell abnormalities, environmental effects may also contribute to the familial occurrence of these abnormalities.

Effect of interferon-gamma on the abnormality of T cell activation in NZB mice

It is known that New Zealand black (NZB) mice have a defect in the autoantigen recognition mechanism by T cells. The present study was carried out to examine whether the defect could be improved by normalizing the self Ia molecule expression on thymic reticuloepithelial cells (TRC) by using interferon-gamma (IFN-gamma). Syngeneic mixed lymphocyte reaction (SMLR) was used as an indicator of the mechanism of autoantigen recognition. In the reaction, T cells separated from the thymus were used as responders, and machrophages separated from the spleen were used as stimulators. When the responders were cultured with TRC, in which self Ia molecule expressions had been enhanced by IFN-gamma, for activation, the low level of SMLR in NZB mice was elevated close to the normal level. It was suggested, therefore, that IFN-gamma could normalize the defective autoantigen expression on TRC in NZB mice and improve the abnormal T cell activation against autoantigens.

Impaired autoreactive T cell-induced T cell-T cell interaction in aged mice

Self-Ia-reactive (autoreactive) L3T4+ T cell clones have been shown earlier to stimulate the proliferation of syngeneic naive L3T4+ T cells and initiate a T cell-T cell (T-T) interaction leading to the generation of immunoregulatory circuits. Since aging has been shown to be associated with a decline of the immune responsiveness, age-related alterations in the T-T interaction was investigated in the present study. Using several I-Ed-specific autoreactive T cell clones isolated from 2- to 3-month-old (young) DBA/2 mice as stimulators, it was observed that L3T4+ T cells from 22- to 24-month-old (aged) DBA/2 mice, failed to demonstrate a significant response to the autoreactive T cells. In contrast, L3T4+ T cells from young mice responded strongly to the autoreactive T cell clones. The deficient T-T cell interaction in aged mice correlated with an impaired syngeneic mixed lymphocyte reaction in these mice, thereby suggesting that aging induces a defect both in the autoreactive T cells and in T cells which react with the autoreactive T cells. When exogenous recombinant interleukin 2 (rIL-2), recombinant interleukin 4 (rIL-4), or a combination of these was added to the interaction, it was observed that rIL-4 but not rIL-2 enhanced the T-T interaction in young mice. However, rIL-4 or a combination of rIL-2 and rIL-4 failed to correct the defective T-T interaction in aged mice. Since the T cell network is believed to play an important role in the maintenance of normal immune system homeostasis, the present study suggests that age-related alterations in T and B cell functions and increased susceptibility to autoimmune diseases with age may result from a defect in the T cell network regulation.

Deficient phytohemagglutinin-induced interleukin-2 activity in patients with inactive systemic lupus erythematosus is correctable by the addition of phorbol myristate acetate

In systemic lupus erythematosus (SLE) patients, the production of interleukin-2 (IL-2) by blood T lymphocytes in response to stimulation with phytohemagglutinin (PHA) either alone or with phorbol myristate acetate (PMA) or ionomycin, a Ca2+ ionophore, was examined. Deficiency in PHA-stimulated IL-2 production by cells from SLE patients was repaired by the addition of PMA, but not ionomycin. PMA alone did not stimulate IL-2 production but, in concert with PHA, induced IL-2 synthesis. Moreover, PMA was effective in the repair of the deficiency of PHA-induced IL-2 production by both T4+ and T8+ subsets. Thus, for effective IL-2 production, SLE T cells required signals either distinct from or in addition to those supplied by PHA.

Characterization of an endogenous Lyt2+ T-suppressor-cell population regulating autoreactive T cells in vitro and in vivo

Autoreactive T cells have been defined by their capacity to respond to self-Ia antigens expressed on non-T cells. Several recent studies have suggested that these cells may play important immunoregulatory functions. However, it is not clear what regulates the responsiveness of autoreactive T cells and why such cells are not demonstrably stimulated in vivo, where they are in the constant presence of self-Ia antigens. In the present study we examined the role of T suppressor (Ts) cells in regulating autoreactive T cells. We observed that enhanced autoreactivity occurred in vitro when Lyt2+ T cells were depleted from the responding and/or stimulating spleen cells in a syngeneic mixed-lymphocyte reaction. Similarly, addition of irradiated Lyt2+ T cells but not L3T4+ T cells inhibited the response of L3T4+ T cells to self-Ia antigens. The activity of the suppressor cells was specific to the autoreactive T cells since antigen-specific and alloreactive T-cell proliferation were not inhibited. Furthermore, depletion of Lyt2+ T cells by in vivo treatment of mice with anti-Lyt2 monoclonal antibodies caused enhanced endogenous proliferation of lymph node and splenic T cells and increased the T-cell response to self-Ia antigens in vitro. These studies, therefore, suggest that T-cell tolerance to self-Ia antigens in vivo may be maintained by naturally occurring Lyt2+ Ts. Mice having enhanced autoreactivity may provide a useful tool to address the role of autoreactive T cells in the immune response to foreign antigens and in the pathogenesis of autoimmune diseases.

Neuroimmunomodulation: potentiation of delayed hypersensitivity and antibody production by chronic electrical stimulation of the rat brain

This study deals with the structural and functional correlates of the immunoneuroendocrine interconnections, and explores the effects of localized brain stimulation on immune response. Bilateral symmetrical electrodes were placed in the dorsomedial nucleus, ventromedial nucleus and posterior area of the hypothalamus, and in the sensorimotor cerebral cortex of the rat brain. Electrical stimulations were applied for 39 consecutive days, 10 days before and 29 days after single immunization. In sham-stimulated rats, electrodes were lowered into the hypothalamic areas and sensorimotor cortex without passing any current. Animals with electrodes were divided post mortem into groups according to the histological location of the electrode tips. Intact rats served as additional controls. All animals were immunized with bovine serum albumin in complete Freund's adjuvant and tested for immune reactions 7, 14, 21, and 28 days after immunization. The most significant finding was the potentiated delayed skin hypersensitivity and, to a lesser extent, antibody production to bovine serum albumin in rats with stimulated dorsomedial hypothalamus and sensorimotor cortex. On days 21 and 28, skin reactions increased in rats with stimulated posterior hypothalamus. These immune effects could not be obtained when the stimulation was applied to the hypothalamic ventromedial nucleus. Several pathways of the immunoneuroendocrine interplay are suggested.

Autologous immune response of tonsillar lymphocytes

Tonsillar (TL) and peripheral blood lymphocytes (PBL) from patients with pustulosis palmaris et plantaris (PPP) or recurrent tonsillitis (RT) were analysed for their proliferative response of T-cells upon stimulation with non-T-cells in the autologous mixed lymphocyte reaction (AMLR). TL and PBL from the same donor were cultured in the AMLR for up to 7 days. Maximum proliferation was observed after a 6-day culture in PBL, whereas that of TL was observed on the 3rd day of the culture. It was also observed that the AMLR of TL in patients with PPP was significantly (p less than 0.01) lower than in patients with RT. On the other hand, it has previously been proved by an immunofluorescence study that there is an identical antigenicity between tonsillar epithelium and skin. From this result, a blastoid transformation study of TL and PBL from patients with PPP was performed by using homologous or autologous skin extracts. Both homologous and autologous skin extract induced blastoid transformation of TL but PBL scarcely responded. These results may support the opinion that an auto-immunological mechanism may take part in the onset of PPP.

Inhibitor of interleukin-2 synthesis and response in rheumatoid synovial fluid

We studied the effects of a factor present in rheumatoid arthritis (RA) synovial fluid (SF) on interleukin-2 (IL-2)-dependent cell proliferation and on the production of IL-2 by mitogen-stimulated peripheral blood mononuclear cells. RA SF suppressed the responsiveness of a mouse T cell line (HT-2) to IL-2, indicating that it contained an inhibitor of the IL-2 response. When RA SF was fractionated by Sephadex G-200 gel filtration, the inhibitory activity was detected mainly in fractions with a molecular weight of approximately 150,000, but was also found in a 15-19-kd fraction. Removal of IgG from the 150-kd fraction, by means of an anti-IgG affinity column, did not reduce the activity of the fraction, nor was activity found in the eluted IgG. The inhibitory fractions reduced mouse thymocyte proliferative responses to IL-1 in the presence of phytohemagglutinin, and reduced the production of IL-2 by human peripheral blood mononuclear cells, but did not inhibit IL-1-induced human foreskin fibroblast proliferation; this suggests that the factor was not an IL-1 inhibitor. The inhibitory activity of the RA SF factor was blocked by an antibody against an inhibitor of IL-2 that was purified from a culture of the human monocytic leukemia cell line, THP-1. This finding also supports the conclusion that RA SF contains an IL-2 inhibitory factor. The observed inhibition of both IL-2 synthesis and IL-2 response suggests that the target of the inhibition was the T lymphocyte.

The role of L3T4+ cells in the pathogenesis of lupus in lpr-bearing mice. I. Defects in the production of interleukins 2 and 3

Mice which bear the lpr gene spontaneously develop autoimmune syndromes characterized by massive expansion of an unusual T cell subset which is phenotypically Thy-1+, L3T4-, Lyt-2-, B220+. The mutant T cells are refractory to stimulation with mitogenic lectins and, by implication, are thought to be solely responsible for the defects in lymphokine production manifested by lpr mice. The contribution of the remaining L3T4+ T cell subset to the latter derangements has not been previously examined and is the focus of this study. We found that abnormalities in concanavalin A-induced interleukin 2 and 3 production in the spleens of MRL-lpr/lpr and C57BL/6.lpr mice occurred in the presence of limited infiltration with B220+, L3T4- T cells. Mixing experiments indicated that B220+ T cells were not suppressive. Furthermore, lpr spleen cells enriched for L3T4+ cells and depleted of sIg+, B220+ and Lyt-2+ cells demonstrated reductions in lymphokine production which were comparable to those seen in unfractionated preparations. Spleen cells from C57BL/6.lpr mice, enriched for L3T4+ cells, were also markedly impaired in a mixed leukocyte reaction in response to stimulator cells from the class II major histocompatibility complex mutant bm12. The results indicate that the aberrations in lymphokine production and proliferation in the spleen cells of lpr mice involve not only B220+ T cells but also L3T4+ cells and suggest a potential role for the L3T4+ subset in the pathogenesis of lupus in lpr-bearing mice.

Immunocytochemical analysis of HLA class II (DR) antigens in liver disease in man

The in situ distribution of the major histocompatibility (HLA) class II (DR) antigens was studied in 113 liver biopsy specimens and five livers obtained at necropsy, using monoclonal antibody CR3/43. In 20 normal livers HLA-DR antigens were not detected in bile duct epithelium, hepatocytes, or portal vein endothelium. Normal arteriolar, sinusoidal and central venous endothelium often expressed HLA-DR. Kupffer cells always expressed these antigens. HLA-DR positive spindle cells were identified in the connective tissue of portal tracts, large hepatic veins, and liver capsule: most shared antigens common to all leucocytes and reacted with the histiocytic maker EBM11. Bile duct epithelium expresses HLA-DR in primary biliary cirrhosis, large duct obstruction, and drug induced cholestasis, indicating that HLA-DR positive spindle cells are phenotypically similar to histiocytes.

Interleukin 2 is a proliferative signal for B cells from autoimmune mice

T cells from murine lupus strains manifest complex defects in interleukin 2 (IL 2) production and receptor expression. The capacity of B cells from such mice to utilize IL 2 as a growth factor has not been previously reported and is examined herein. Anti-Thy-1.2 plus complement-treated spleen cells from 6-8-week-old autoimmune MRL-lpr/lpr mice and from age and sex-matched immunologically normal CBA/J mice were cultured with lipopolysaccharide (LPS) for 36 h and analyzed for the expression of IL 2 receptors using the monoclonal antibody 7D4. The percentage of B cells expressing IL 2 receptors was comparable in MRL-lpr/lpr and CBA/J mice. In contrast to those from CBA/J, BALB/c and (BALB/c X NZW)F1 mice, LPS-stimulated B cells from MRL-lpr/lpr and from (NZB X NZW)F1 mice were capable of proliferating in response to IL 2. Fractionation of MRL-lpr/lpr B cells using Percoll gradient density separation demonstrated that the IL 2-responsive population consisted predominantly of large cells. In addition, unfractionated B cells from MRL-lpr/lpr mice were found to be substantially more responsive to IL 2 than those from CBA/J and BALB/c mice following activation with anti-immunoglobulin plus LPS. The hyper-responsiveness to IL 2 may be a consequence of the state of activation of autoimmune B cells and is of potential importance in the pathogenesis of systemic lupus erythematosus.

The autologous mixed lymphocyte reaction (AMLR) as a possible indicator of immunoregulation in chronic inflammatory periodontal disease

Immunoregulatory control at both a local and systemic level is likely to be an important factor in the control of chronic inflammatory periodontal disease, explaining, at least in part, the individual variations between patients as well as the cyclical nature of the disease process. The autologous mixed lymphocyte reaction (AMLR), which is due to the stimulation of T cells by autologous HLA-DR positive non-T cells in the absence of specific antigen, is thought to be an in vitro correlate of immunoregulation. It is possible therefore, that the AMLR may detect systemic immunoregulatory phenomena in chronic inflammatory periodontal disease and that aberrations in the AMLR may be a manifestation of the disease and in turn reflect disease activity. Recent evidence does in fact suggest that the peripheral blood AMLR may identify particular disease groups, provided age and time of peak responsiveness are taken into account and hence may have an epidemiological application. It remains to be determined, however, that when used in a longitudinal fashion, the AMLR does reflect individual disease activity. These results are reviewed and areas of future research discussed.

Analysis of interleukin-2 activity in patients with Behçet's disease. Ability of T cells to produce and respond to interleukin-2

We examined interleukin-2 (IL-2) activity in patients with Behçet's disease. T cells from all patients with Behçet's disease were able to produce normal levels of IL-2 in response to phytohemagglutinin; however, responsiveness to IL-2 was impaired in their concanavalin A-activated lymphoblasts. This defect was due to decreased numbers of cells bearing IL-2 receptors in patients with early active disease; in patients with chronic active or with inactive disease, there was a decrease in density of IL-2 receptors on T cells bearing these receptors. Unresponsiveness of T cells to IL-2 may thus contribute to immunologic aberrations in Behçet's disease.

Long-term low-dose glucocorticoid therapy associated with remission of overt renal tubular acidosis in Sjögren's syndrome

Renal tubular acidosis and focal interstitial inflammatory cell infiltrate secondary to Sjögren's syndrome remitted with low-dose glucocorticoid therapy over five and one half years in a patient with associated mild systemic lupus erythematosus. Such response has not been previously documented. This observation may have therapeutic applications for renal tubular acidosis associated with Sjögren's syndrome that deserve further investigation.

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.

Human T-cell clones from autoimmune thyroid glands: specific recognition of autologous thyroid cells

The thyroid glands of patients with autoimmune diseases such as Graves' disease and certain forms of goiter contain infiltrating activated T lymphocytes and, unlike cells of normal glands, the epithelial follicular cells strongly express histocompatibility antigens of the HLA-DR type. In a study of such autoimmune disorders, the infiltrating T cells from the thyroid glands of two patients with Graves' disease were cloned in mitogen-free interleukin-2 (T-cell growth factor). The clones were expanded and their specificity was tested. Three types of clones were found. One group, of T4 phenotype, specifically recognized autologous thyroid cells. Another, also of T4 phenotype, recognized autologous thyroid or blood cells and thus responded positively in the autologous mixed lymphocyte reaction. Other clones derived from cells that were activated in vivo were of no known specificity. These clones provide a model of a human autoimmune disease and their analysis should clarify mechanisms of pathogenesis and provide clues to abrogating these undesirable immune responses.

Abnormalities in autologous mixed lymphocyte reaction-activated immunologic processes in systemic lupus erythematosus and their possible correction by interleukin 2

The autologous mixed lymphocyte reaction (AMLR) represents the activation, proliferation and differentiation of T cells in response to signals from autologous non-T cells. Upon stimulation by autologous non-T cells, OKT4+ cells produce interleukin 2 (IL2); cells contained within both OKT4+ and OKT8+ cell populations can also be activated by autologous non-T cells to become sensitive to IL2. Once these activated OKT4+ and OKT8+ cells are exposed to IL2 produced by OKT4+ cells, they will proliferate and go on to differentiate into effector cells. Patients with systemic lupus erythematosus (SLE) have a defect in the AMLR. The ability of OKT4+ cells to produce IL2 in the AMLR is impaired. Upon triggering with autologous non-T cells, their OKT8+ cells become sensitive to proliferative signals of IL2; however, their OKT4+ cells fail to express IL2 receptors. These defects are a consistent feature in patients with SLE. AMLR-induced immunologic processes which require cell interactions between OKT4+ cell subpopulations are not correctable even by the addition of normal IL2. However, the immunologic processes mediated through OKT4+-OKT8+ cell interactions can be corrected with normal IL2. The latter finding suggests that the partial correction of the AMLR-induced immunologic processes with IL2 might lead to suppressed B cell hyperactivity of patients with SLE.

Anti-Ia reactivity in sera of untreated patients with active Hodgkin's disease

The effect of sera from eight patients with Hodgkin's disease on the autologous and allogeneic mixed lymphocyte response of normal individuals was examined. Sera from three patients with active disease caused marked inhibition of both autologous and allogeneic mixed lymphocyte reaction without inducing significant reduction of the phytohemagglutinin-induced proliferative response. The inhibitory activity of Hodgkin's disease sera on the autologous mixed lymphocyte reaction was removed by adsorption with non-T, but not T, lymphocytes and it was correlated with the ability of such sera to block the binding of monoclonal anti-Ia antibody to Ia-positive target cells. Anti-Ia antibodies were detected in the same sera by double antibody radioimmunoassay and analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, using 125I-labeled, partially purified, Ia antigens from two different human B-cell lines. This anti-Ia reactivity was strongly reduced or absent in sera taken from the same patients at the completion of multidrug chemotherapy.

Characterization of the defective autologous mixed lymphocyte response in rheumatoid arthritis

In order to characterize the autologous mixed lymphocyte response (AMLR) in patients with rheumatoid arthritis (RA) and to define the relationship with disease activity, peripheral blood T lymphocytes were stimulated with either a B lymphocyte-enriched (B cells) or a macrophage-enriched (macrophages) population. A significant reduction (P less than 0.01 to P less than 0.001) of T cell proliferation stimulated both by B cells and macrophages was observed in patients with active disease. The B lymphocytes were significantly less stimulatory (P less than 0.02 to P less than 0.001) than macrophages in the patients compared with the controls. In the normal controls, macrophages in higher concentrations were capable of suppressing the B lymphocyte-stimulated AMLR, but macrophages from patients with RA were not excessively suppressive. A significant association (P less than 0.02) was observed between disease activity and the AMLR. Using the B-enriched population, the AMLR proliferative response was significantly associated (P less than 0.001) with the production of interleukin-2. Defects in proliferation could only be partially restored by the addition of interleukin-2. These data indicate that the defective AMLR observed in patients with RA is related to disease activity and is associated with altered cellular interactions among T lymphocytes, macrophages, and the B lymphocyte-enriched population.

Alterations of both responder T cells and stimulator non-T cells are responsible for abnormal mixed lymphocyte reaction in aged humans

The autologous and allogeneic mixed lymphocyte reactions of 15 young and 15 aged human adults were compared. Both autologous and allogeneic mixed lymphocyte reactions were significantly reduced in the aged group. T cells from aged adults displayed a reduced proliferative response to non-T cells of either aged or young adults. T cells from young adults also showed a reduced proliferative response to non-T cells from aged adults. Sera from aged adults, showing depression of autologous and allogeneic mixed lymphocyte reaction, did not exert any inhibitory effect on the autologous and allogeneic mixed reaction of lymphocytes from young donors. These data suggest that depression of mixed lymphocyte reaction in aged humans probably reflects intrinsic abnormalities of both responder T cells and stimulatory non-T cells.

Association of HLA-DR antigens with the autologous mixed lymphocyte reaction

A study was performed to evaluate the association of HLA-DR antigens with the proliferative response of T cells in autologous mixed lymphocyte cultures. Peripheral blood mononuclear cells from 100 normal healthy individuals were typed for HLA-DR antigens and autologous mixed lymphocyte cultures were established. A low proliferative response from autologous cultures was found with individuals bearing HLA-DR3 antigens and in individuals with only one identifiable HLA-DR antigen. In contrast, a strong proliferative response was associated with HLA-DR6 and two identifiable HLA-DR antigens. These data are consistent with the hypothesis that HLA-DR3 antigens are associated with a weak immune response gene and HLA-DR6 antigens are associated with a strong immune response gene.

Role of aberrant HLA-DR expression and antigen presentation in induction of endocrine autoimmunity

Immune responses are initiated by HLA-DR+ cells, which present antigen to T cells. Observations that HLA-DR may be experimentally induced on thyroid epithelium and that HLA-DR occurs on thyrocytes in autoimmune thyroid diseases suggest a mechanism of autoimmunity with special relevance to organ-specific diseases. This involves the local aberrant expression of HLA-DR antigens by epithelial cells and their subsequent capacity to present autoantigens occurring on their surfaces to T lymphocytes. For autoantigens which T cells recognise infrequently because of their restricted tissue location and low concentration in the circulation, T-cell tolerance is unlikely, and so induction of autoreactive T cells would occur. Because interferon is the best known inducer of DR antigen expression and viral infections may predate endocrine autoimmunity, the following sequence seems likely: local viral infection which causes interferon production, or other local environmental factors which would induce DR expression, presentation of autoantigens, and subsequent autoimmune T-cell induction. These T cells would activate effector B and T cells. Whether the initial induction of autoimmune T cells leads to autoimmune disease would depend on factors such as abnormalities of the suppressor T-cell pathway, reported to coexist with autoimmunity and necessary to induce autoimmune disease in mice. This mechanism of autoimmune disease induction explains vague associations with viral infections and long latency periods before disease becomes manifest and gives a simple explanation for the well-documented association between HLA-DR and autoimmune diseases in man.

Mechanisms of autoimmunity: a role for cross-reactive idiotypes

Ehrlich was rarely given to trivial pronouncements and his recognition of the central importance of the distinction between self and non-self by the immune system, embodied in his concept of 'horror autotoxicus'(1), is no exception. This is despite the apparent paradox of the idiotype network in which antibodies recognize self-epitopes on other antibody molecules or antigen receptors as part of the normal process of immune regulation. In this review Anne Cooke and her colleagues examine the possible factors which may contribute to the breakdown of self-tolerance and the establishment of autoimmune states.