Defect of autologous mixed lymphocyte reaction and interleukin-2 in aged individuals

The proliferative responsiveness of T cells of aged individuals is known to be depressed in both autologous mixed lymphocyte reaction (AMLR) and in PHA-stimulated cultures. In the present study we confirm previous results and also report decreased IL-2 and normal IFN-gamma production (PHA-induced) in aged subjects as compared to young normals. In addition, similar percentages of T lymphocytes expressing surface IL-2 receptors both in the peripheral blood and after different stimulations, i.e. AMLR and PHA, were detected in young and aged individuals. The addition of exogenous IL-2 induces a sharp increase of spontaneous and AMLR proliferation in young individuals, whereas the increase is only slight in aged subjects. The experiments reported herein suggest that in general the T cell proliferation in AMLR is not completely dependent on the presence of IL-2 in the cultures and that aged subjects are probably defective in the production of other factor(s) presumably involved in AMLR proliferation, since the addition of exogenous IL-2 does not produce T-cell proliferation comparable to normal young subjects. The possible meanings of these experimental evidences in AMLR and in the defective immune responses of aged subjects are discussed.

Proliferation of T8-positive cytolytic T lymphocytes in response to thyroglobulin in human autoimmune thyroiditis: analysis of cell interactions and culture requirements

These experiments were designed to analyze the involvement of T-lymphocyte subpopulations in autoimmune thyroid disorders such as Graves' Disease (GD) and Hashimoto's Disease (HD). In a first set of experiments, lymphocytes isolated from thyroid infiltrates or from peripheral blood of GD and HD patients were analyzed for the expression of various surface antigens. While HLA-DR + T cells were numerous among thyroid infiltrating T lymphocytes in both groups of patients, the proportions of T8 + cells (as defined by their reactivity with the B 9.4 monoclonal antibody specific for T8 surface molecule) were strikingly different in HD and GD. In the latter group of patients only 19% of infiltrating T cells were T8 +, whereas these cells represented approximately 50% in four HD patients. Given the previous demonstration that all T cells expressing T8 antigen are cytolytic T lymphocytes (CTL) or their precursors (CTL-P) in conjunction with the fact that lymphocytes from HD or GD patients are known to proliferate in vitro in response to human tg (Htg), we further analyzed the T-cell subset(s) responsible for in vitro proliferation to Htg. In these experiments, peripheral blood T lymphocytes purified from patients with GD or HD were cultured with 1 microgram/ml Htg and irradiated autologous T-depleted mononuclear cells as the source of antigen presenting cells (APC). The proportions of T8 + cells declined considerably during culture in GD patients, but at Days 6 to 9, T8 + cells represented as much as 51% of cultured T lymphocytes from patients with HD. Moreover, the majority of T8 + cells were medium-large size lymphoblasts. Removal of Htg at Day 6 resulted in both abrogation of proliferative responsiveness and in decreases of T8 + percentages. Further analysis of the cell interactions leading to T8 + cell proliferation in response to Htg showed that helper/inducer T cells, as defined by 5/9 antigen expression, were strictly required. Collectively, these features are reminiscent of the T-cell involvement in experimental autoimmune thyroiditis of mice and stress for the first time the potential role of CTL in tissue damage occurring in Hashimoto's thyroiditis.

Autoimmune thyroid disease: purification and phenotypic analysis of intrathyroid T cells

A phenotypic analysis of T cells infiltrating the thyroid of patients with autoimmune thyroid disease (both Graves' disease and Hashimoto's thyroiditis) was performed. T lymphocytes were purified from mononuclear cells extracted from surgically removed tissue. The following markers were evaluated: la antigens, MLR4 antigen (expressed on activated T cells) 5/9 antigen (expressed on a subset of lymphocytes containing the whole "helper-inducer" activity in vitro), Fc gamma-receptors, B9 antigen (expressed by cytotoxic, or precursor of cytotoxic, T cells). We observed increased percentages of 5/9-, MLR4- and la-positive T cells with respect to peripheral blood in both HT and GD: on the contrary, in specimens from nonautoimmune thyroid diseases mononuclear infiltrate was minimal, and even T cell evaluation was not possible. In addition, B9- and Fc gamma-positive T cells were increased in Hashimoto's, but not in Graves' thyroid tissue, thus suggesting a different role of cytotoxic effector mechanisms in the two diseases.

Activation of T lymphocytes and autologous mixed lymphocyte reaction in allergic patients

In allergic patients the authors previously observed high proportions of circulating T lymphocytes bearing Ia antigens, assumed to be "activated" T cells. In the present investigation they employed other T cell activation markers (4F2, insulin receptor, MLR4) which differ in the kinetics of appearance upon the surface of stimulated T cells. They report high proportions of Ia and 4F2-positive T cells, normal levels of MLR4-positive T lymphocytes and no insulin binding on T cells. However, T cells of allergic subjects are able to express insulin receptors in PHA-induced culture, such as normal subjects do. The authors conclude that these data, supported by similar observations in autoimmune diseases, indicates differences between in vivo and in vitro features of expression of T cell activation markers. In addition the autologous mixed lymphocyte reaction (AMLR) in atopic patients was studied. The results indicate that AMLR responsiveness is defective in allergic patients.

Thyroglobulin-induced T-cell in vitro proliferation in Hashimoto's thyroiditis: identification of the responsive subset and effect of monoclonal antibodies directed to Ia antigens

Recently it was reported that the peripheral blood and thyroid gland of patients with Hashimoto's thyroiditis contain activated (Ia+ and/or MLR4+) T cells and high levels of 5/9+ ("helper") T lymphocytes. In normal individuals the 5/9 monoclonal antibody recognizes a T-cell fraction that includes all T lymphocytes with inducer activities. Here, circulating 5/9+ and 5/9- T lymphocytes were isolated from patients with Hashimoto's disease, and the proliferative response induced by human thyroglobulin was investigated. The results show that the total thyroglobulin-induced lymphocyte DNA synthesis is confined to the 5/9+ T-cell fraction. Further subfractionation of 5/9+ into MLR4+ and MLR4- cells clearly indicates that no substantial differences exist in their proliferative capacities. Whether 5/9, MLR4, and Ia antigens, all expressed on the thyroglobulin-responsive T-cell subset, are involved in thyroglobulin-induced cell proliferation, was also analyzed. Although both 5/9 and MLR4 monoclonal antibodies had no effect, complete inhibition of antigen-induced blastogenesis was observed upon addition of monoclonal antibodies (D1/12 and BT2/9) directed to common determinants of Ia antigens. This inhibitory effect was also observed when T or non-T fractions were separately incubated with the monoclonal antibodies before culture. These results indicate that in humans, as in animals, the major histocompatibility complex may play a role in autoimmune thyroiditis. The data show that (a) the thyroglobulin-induced proliferative response is confined to a subset (5/9+) of T lymphocytes and (b) Ia antigens are involved in thyroglobulin-induced lymphocyte DNA synthesis in Hashimoto's disease.

Incidence of T cell subset imbalance in relatives of Graves' disease patients

In previous reports we demonstrated imbalances of T cell subsets in patients with autoimmune thyroid disease. In the present investigation, we studied several T cell markers with different functional meaning (Fc gamma-receptors, HLA-Ia antigens, MLR4 and 5/9 antigens) in first degree relatives of Graves' disease patients. Our data suggest that imbalances of circulating T cell subpopulations are apparent only when abnormal hormone levels and/or thyroid autoantibodies are present.

Deficiency of the autologous mixed lymphocyte reaction in patients with autoimmune thyroid disease

The proliferative response of T lymphocytes when cocultured with autologous non-T cells in the absence of any other stimulating substance has been termed the autologous mixed lymphocyte reaction (AMLR). The AMLR has been shown to be impaired in several autoimmune disorders, such as systemic lupus erythematosus, Sjögren's syndrome, and primary biliary cirrhosis. In this study we report marked deficiency in the AMLR in two autoimmune disorders: Hashimoto's and Graves' diseases. This impaired AMLR, probably related to previously described T cell subset imbalances, provides further evidence of altered interactions between the immunocompetent cellular subsets in patients with these pathological conditions. Additional preliminary observations suggest defective allogeneic mixed lymphocyte reactions as well.

Circulating T-cell subsets in Graves' disease: differences between patients with active disease and in remission after 131I-therapy

In the present investigation some surface markers in peripheral blood T lymphocytes of patients with active Graves' disease and subjects in remission after 131I-therapy have been studied. We confirmed low TG levels in untreated patients and normal values in treated subjects. Increased percentages of DR+, MLR4+ (activated T cells), and 5/9+ (inducer-helper) T cells were detected in patients with active disease, thus indicating the presence of activated T cells and suggesting increased levels of helper T cells. High percentages of MLR4+ and 5/9+, but normal levels of DR+ were found in 131I-treated subjects. The different distribution of DR and MLR4 positivities on 5/9+ and 5+9-T cells confirm the different meaning of these two markers of the activation state. The imbalance of T-cell subsets found in 131I-treated subjects and the normal values observed in patients with hyperthyroidism due to toxic adenoma indicate that hyperthyroidism per se is not sufficient to explain the T-cell alterations. The possible meaning of these findings is discussed with respect to previous hypotheses on the pathogenesis of Graves' disease.

Circulating T cell subsets in euthyroid Graves' disease

T cell subpopulations recognized by surfaces markers of different functional meaning have been evaluated in 12 female patients with euthyroid Graves' disease and in 2 patients with ophthalmopathy and Hashimoto's thyroiditis. We have used the following markers: i) receptors for Fc fragments of IgG; ii) antigens recognized by the monoclonal antibodies MLR4, 5/9, BT 2/9 (anti-DR). In the 12 patients with euthyroid Graves' disease a marked decrease of TG cells (which proved to exert suppressor function in several in vitro systems) was observed, as previously reported in hyperthyroid Graves' disease. The 2 Hashimoto's patients with eye changes had normal or high TG. 5/9+ T cells (which contain cells with helper activity in vitro), as well as MLR4+ and BT 2/9+ cells (activated T cells) were normal in the majority of patients, but elevated in the 2 Hashimoto's thyroiditis. The observed abnormality of TG cells in euthyroid Graves' disease might be consistent with the hypothesized autoimmune pathogenesis of endocrine ophthalmopathy.

T lymphocyte subpopulations in Graves' disease: relationship with clinical conditions

T lymphocytes were fractionated according to their receptors for IgG (TG) or IgM (TM) and scored in 37 patients with Graves' disease (17 hyperthyroid and untreated. 10 euthyroid on antithyroid drugs, 10 in long-term remission after radioiodine therapy). TG percentages were very low both in untreated and in drug-treated patients. By contrast, normal TG levels were observed in patients in long-term remission. These data are consistent with the hypothesis of a defective suppressor cell activity in Graves' disease.

Abnormalities of circulating T cell subsets in atopy: influence of specific immunotherapy

Blood samples of patients with severe respiratory allergic diseases contain increased numbers of T cells bearing surface HLA-DR antigens, indicating the presence of activated T cells. In the same group of patients, MLR3 and MLR4, two monoclonal antibodies (Mab) directed to subsets of activated peripheral T cells, recognize T cell percentages within the normal range. Thus, it seems possible that specialized subsets of activated T cells (HLA-DR+/MLR3-MLR-) are represented in the peripheral blood of atopic patients. Such cells are lacking in patients after specific immunotherapy. Similar results--an increased percentage of 5/9+ T cells in untreated patients and normal counts of 5/9+ T cells in treated ones--were obtained in the two groups of patients by using another Mab, 5/9, which serves as a reliable marker of helper T cells in resting peripheral T lymphocytes. These data further support the concept of a T cell imbalance in allergic patients and suggest a possible role of specific immunotherapy in correcting the modification of peripheral T cell abnormalities.

Abnormalities of immunocompetent cells in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic progressive liver disease frequently associated with various immunological abnormalities. We have studied the influence of normal and PBC adherent cells (AC) on peripheral blood lymphocytes (PBL) colony growth both in liquid and soft agar culture. Co-culture experiments with different combinations of AC and PBL of PBC patients and normal donors provided evidence that PBC adherent cells function abnormally. However, this impaired function is not the sole factor involved, since the number of colonies formed by PBC lymphocytes in the presence of normal AC was twice the normal value. The possibility that this increase is correlated with the state of activation of T cells is discussed in the light of the high number of DR-positive T cells found in the PBC patients studied. Finally, none of these immunological abnormalities was related to the stage of the disease.

Density distribution profiles of T cells: TM, TG and TA cells and response patterns in autologous versus allogeneic MLRs

Discontinuous Percoll gradients have been used to obtain selected human peripheral blood T lymphocytes without having to resort to interactions with immune complexes in the fractionation of Tm, Tg and Ta cells. Here, we could show that Ta cells represent a heterogeneous population with no distinct density profile, in contrast to light (Tg) and heavy (Tm) cells. Enriched, heavy Tm cells could be shown to be excellent responders in allogeneic MLR while failing to react in autologous MLR. In contrast, T cells of light density preferentially respond in autologous compared with allogeneic MLR.

Inhibition of autologous mixed lymphocyte reaction by aggregated IgG molecules

Human autologous and allogeneic mixed lymphocyte reactions (MLR) were studied using various T cell subsets as responding cells. T cells expressing Fc gamma receptor for IgG (TG) were weak responder while T cells with Fc mu receptor and T cells lacking Fc receptor responded vigorously in both types of MLR. Percoll-separated T cells of low density (TL) enriched for TG cells were, however, excellent responders in autologous MLR, whereas T cells of high density (TH) were the major responders in allogeneic MLR. Continuous presence of or short-term pulse with aggregated IgG significantly reduced the autologous MLR of unfractionated T and TL cells while largely sparing proliferation in allogenic MLR. These findings are discussed with respect to diminished autologous MLR reactivity in certain autoimmune diseases.

Human T-lymphocyte subpopulations in Hashimoto's disease

An inherited defect os suppressor T-lymphocytes has been hypothesized in Hashimoto's thyroiditis. To assess this hypothesis, human T-lymphocyte subsets (TG, T lymphocytes with surface receptors for the Fc fragment of immunoglobulin G; TM, T lymphocytes with Fc receptor for immunoglobulin M) have been studied in nine patients affected by the disease. To cells have been previously shown to be suppressors in the pokeweed mitogen-stimulated B-cell differentiation and have proved abnormal in several autoimmune or immunodeficiency disorders. The number of TG lymphocytes in the patients did not differ from that in normal controls. It is possible that 1) suppressor T-lymphocytes are not involved in the pathogenesis of Hashimoto's disease or 2) antigen-specific suppressor T-cells are involved, but too are low in number with respect to total TG.

Suppressor activity of T cells bearing Fc receptors for IgG on lymphoid colony formation

Human T lymphocytes, upon phytohaemagglutinin stimulation, are able to form colonies in semisolid media. Peripheral T cell bearing Fc receptors (TG) were studied for their possible regulatory activity on lymphoid colony development. Although no substantial differences were observed between the cloning efficiency of unfractionated T cells (thus including TG cells) and T cells depleted of TG, a sharp suppression of colony formation occurred when positively selected TG cells were readded to TG-depleted suspensions. Therefore, TG suppressor activity seems to be strictly dependent upon cell interaction with ox IgG immune complexes used for TG cell isolation. Different experimental approaches failed to demonstrate, although did not exclude, that suppression in this system is mediated by soluble factors. gamma-irradiation of TG cells abrogated their suppressor capacity.

Imbalances of T cell subpopulations in patients with atopic diseases and effect of specific immunotherapy

Reduced numbers of T cells with Fc receptors for IgG (TG cells) are present in blood samples of patients with respiratory allergic disease, mainly those with severe symptoms. TG cells have been previously shown to be suppressor in the pokeweed mitogen- (PWM) dependent B cell differentiation. T cells with Fc receptor for IgM (TM cells), which help immunoglobulin production, are in a normal range. After specific hyposensitization, resulting in a sharp improvement of clinical symptoms, TG cell subset reached normal values.