The Effect of Safranal on Th1/Th2 Cytokine Balance

Background: Several biological and medical benefits of Saffron, Crocus sativus (Iridaceae), have been demonstrated. However, mechanisms of actions for purified constituents are greatly unknown. Objective: To examine the effects of Safranal, a main constituent of Saffron stigma, on cell viability and cytokine profile of peripheral blood mononuclear cells (PBMC) were examined. Methods: Effects of Safranal at 0.1, 0.5 and 1 mM concentrations were evaluated on cell viability and production of interleukin 4 (IL-4), IL-10 and interferon-γ (IFN-γ) from non-stimulated and phytohemagglutinin (PHA) stimulated PBMCs, compared to 0.1 mM dexamethasone and saline. Results: In stimulated cells, different concentrations of Safranal caused significant decrease of lymphocytes viability (p<0.001 for all concentrations). All concentrations of Safranal inhibited IFN-γ and IL-10 secretion in stimulated cells (p<0.01). In addition, high concentration of Safranal significantly decreased cell viability of non-stimulated PBMCs (p<0.001). The effect of 1 mM Safranal on IL-4 secretion was less than dexamethasone (p<0.05). Safranal showed a stimulatory effect on IFN-γ secretion in non-stimulated cells. The IFN-γ/IL-4 ratio at the presence of two higher Safranal concentrations both in non-stimulated and stimulated cells were significantly higher than those of control and PHA stimulated groups, respectively (p<0.05). Conclusion: The IFN-γ/IL-4 ratio increases in the presence of Safranal which indicates an effect on Th1/Th2 balance. Therefore, Safranal may have therapeutic effects in inflammatory diseases associated with Th1/Th2 imbalance.     

Further characterization of interleukin-2 production by lymphocytes of patients with systemic lupus erythematosus

To further characterize the mechanisms responsible for defective interleukin-2 (IL-2) production in patients with systemic lupus erythematosus (SLE), we studied the effect of irradiation on the capacity of lymphocytes to produce this lymphokine when stimulated with phytohemagglutinin (PHA), or with a combination of PHA and a phorbol myristic acid ester (PMA). Irradiation increased PHA induced IL-2 production in patients with SLE and normal controls, and reached normal levels in 10 of 16 patients with SLE. This effect was due to inactivation of CD8+ suppressor cells. When PMA was used as a costimulant, maximal enhancement of IL-2 production was observed in both groups, but values in SLE remained significantly lower than in normals. These differences were not overcome by irradiation, raising the possibility that SLE suppressor cells act upon a site proximal to protein kinase C. Our studies have confirmed that active endogenous suppression may be responsible for most of the defective PHA induced IL-2 production in SLE and that this suppression is radiosensitive.     

Influence of immune complexes containing HBsAg and HBeAg on IL-2 dependent human lymphocyte proliferation

Studies were undertaken to evaluate the effect of hepatitis B virus (HBV) immune complexes (HBV-IC) on IL-2 dependent human lymphocyte proliferation. The following parameters were studied: 1) Effect of HBV-IC (HBsAg-IgG or HBeAg-IgG) on PHA-mediated lymphocyte proliferation; 2) Influence of HBV-IC on the ability of PHA-stimulated peripheral blood lymphocytes (PBL) for IL-2 production and IL-2 receptor expression. HBV-IC induced a dose dependent and antigenic dependent suppression of PHA stimulated lymphocytes. The suppressor effect exerted by HBsAg-IgG was irreversible. In contrast, the suppression mediated by HBeAg-IgG was reversible: lymphocytes preincubated with this preparation washed and activated with PHA responded well to mitogen. The presence of HBV-IC in the cultures of PHA-activated PBL decreased their ability to produce IL-2: HBeAg-IgG exerted a stronger suppressor effect. This effect was partially reversible: removal of HBV-IC from the culture by washing and subsequent stimulation of PBL with PHA increased the capacity of lymphocytes to produce IL-2. This was particularly evident with HBeAg-IgG. Decreased activity of IL-2 observed in the cultures, was also partially dependent on the ability of HBV-IC to bind IL-2 present in the culture medium. Experiments performed using ultracentrifugation indicated that HBV-IC, especially HBsAg-IgG, may bind to IL-2 and inactivate it. HBV-IC had also an effect on IL-2 receptor expression: 1) their presence in the cultures of PHA-stimulated PBL decreased the number of Tac positive cells; 2) the response of HTCL to exogenous IL-2 was decreased by HBV-IC present in the culture medium. This was especially observed in the case of HBsAg-IgG. We suggest that the observed inhibition of PHA-induced lymphocyte proliferation exerted by immune complexes containing HBsAg-IgG or HBeAg-IgG may be caused mainly by their influence on IL-2 dependent mechanism of lymphoproliferation.     

Cell mediated immunity to liver fluke antigens during experimental Fasciola hepatica infection of cattle

Summary Cell mediated immunity (CMI) to Fasciola hepatica antigens was detected by lymphocyte proliferation and interleukin-2 (IL-2) production tests in cattle during the first 4 weeks following liver fluke infection. From the fifth week of infection onwards peripheral blood lymphocytes were unresponsive to fluke antigens by these in vitro tests. Investigations into the cause of this unresponsiveness found no evidence to suggest a selective loss of the IL-2 producing lymphocyte sub-population or that macrophages were responsible for the suppression or that antigen responsive cells were being sequestered in the spleen and mesenteric lymph nodes. Tests carried out on culture supernatants demonstrated the production during this unresponsive period of factors capable of suppressing in vitro responses to PHA. Although further tests failed to show antigen specific suppressor factors the presence of MHC restricted suppressor factors could not be ruled out. The early and transient appearance of CMI during F. hepatica infection of cattle indicates that delayed type hypersensitivity is unlikely to be important in protective immunity in cattle.     

Prolonged defects of interleukin-2 production, responsiveness, and receptor expression in patients with acute lymphoblastic leukemia

The proliferative responsiveness to, production of, and the expression of cell-surface receptors for interleukin-2 (IL-2) were examined in 14 children with acute lymphoblastic leukemia (ALL) in remission and receiving maintenance chemotherapy for 6 to 35 months; in 19 children with ALL in remission and off all therapy for 2 to 138 months; and 15 control subjects. Short-term concanavalin A (Con A)-activated, purified T lymphocytes from patients on, as well as patients off, therapy had a significantly decreased proliferative responsiveness to a saturating amount of exogenous, recombinant IL-2 as compared to control subjects (P less than 0.005 and less than 0.05, respectively). Phytohemagglutinin (PHA)-stimulated IL-2 production by peripheral blood mononuclear cells (PBMC) was also substantially decreased in both patient groups with the median values of IL-2 produced being 2.2, 2.1, and 8.1 U/mL in the on therapy, off therapy, and control groups, respectively. In addition, PHA-induced expression of cell-surface receptors for IL-2 on PBMC was significantly decreased in both patient groups as compared to control subjects (P less than 0.01). Lymphocyte proliferation to mitogens (PHA, Con A, and pokeweed mitogen) was similar in all three groups studied. These results demonstrate that substantial quantitative and qualitative abnormalities of the IL-2-T lymphocyte system are present in the majority of treated patients with ALL, not only during maintenance therapy, but also for a prolonged period after the cessation of all chemotherapy. These long-lasting defects of the IL-2 system are most likely a late effect of chemotherapy and may result in increased complications in some long- term survivors of ALL.     

Nicotinamide inhibits enhanced in vitro production of interleukin-12 and tumour necrosis factor-alpha in peripheral whole blood of people at high risk of developing type 1 diabetes and people with newly diagnosed type 1 diabetes

Macrophages and T lymphocytes are the first cells to appear in pancreatic islets in the development of autoimmune diabetes. It has been suggested that cytokines released by monocytes/macrophages, including interleukin-1beta (IL-1beta), interleukin-12 (IL-12) and tumour necrosis factor-alpha (TNF-alpha) could have an initial role in islet B-cell damage. The aim of the present study was to estimate the effect of human insulin and nicotinamide on the levels of monocyte/ macrophage derived cytokines in the peripheral blood of humans at risk of Type 1 diabetes, and in patients with newly diagnosed Type 1 diabetes compared to healthy control subjects. The study was carried out on three groups of subjects: 20 first degree relatives of people with Type 1 diabetes (with two or more antibodies against pancreatic B-cell antigens); 22 patients with recent onset of Type 1 diabetes (duration of the disease 3-6 months); and 25 age- and sex-matched healthy subjects. Cytokine levels (IL-1beta, IL-12, and TNF-alpha) in the supernatants of whole blood cultures incubated with PHA alone (10 microg/ml), or PHA + human insulin (50 microg/ml), or PHA + nicotinamide (100 micromol/l) were quantified by ELISA. In the cultures with nicotinamide the concentration of IL-12 and TNF-alpha was significantly lower in the prediabetic group, diabetic patients, and the healthy controls than in the cultures with PHA only or with PHA + insulin. There were no significant differences in IL-1beta production in the cultures after incubation with the different stimuli in the studied groups and healthy controls. No significant influence of human insulin on macrophage/monocyte cytokines secretion in in vitro cultures of the peripheral blood was found. This suggests that nicotinamide could influence monocyte/macrophage function in peripheral blood by inhibiting production of IL-12 and TNF-alpha.     

Growth, interleukin-2 production, and responsiveness to IL-2 in T4- positive T Lymphocyte populations from malignant cutaneous T cell lymphoma (Sezary's syndrome): the effect of cyclosporin A

Functional analysis and surface phenotyping using monoclonal antibodies have revealed that malignant T lymphocyte populations in the peripheral blood of patients with Sezary's syndrome resemble the T helper cell populations from normal individuals. In this article we have studied the effects of the immunosuppressive drug cyclosporine A (CsA) on growth, interleukin-2 (IL-2) production, and the induction of IL-2 responsiveness of peripheral blood monocytes (PBMs) from five patients with Sezary's syndrome in vitro, using the lectin phytohemagglutinin (PHA) and the phorbol ester phorbol myristate acetate (PMA) as stimuli. The following results were obtained: PHA-induced cell proliferation was significantly more sensitive to inhibition by CsA than that induced by PMA or a combination of PMA and PHA (P less than .005). Sezary PBMs produced only small amounts of IL-2 in response to PHA. Stimulation with PMA, however, resulted in significant IL-2 production. PMA and PHA, when given in combination, acted synergistically. The low levels of IL-2 production induced by PHA or PMA were more sensitive to CsA- mediated suppression than those induced by a combination of PHA and PMA (75% and 55% suppression, respectively). CsA-mediated growth suppression could be overcome if the cultures were supplemented with appropriate amounts of exogenous IL-2. We conclude from our data, that CsA in Sezary PBMs inhibits T cell growth indirectly as a consequence of suppression of IL-2 growth indirectly as a consequence of suppression of IL-2 production. Moreover, like normal T lymphocytes, Sezary PBMs do not express the IL-2 receptor spontaneously, but can be induced to do so. CsA does not interfere with intracellular events leading to the expression and the biologic function of the IL-2 receptor.     

Reduced dopamine D4 receptor mRNA expression in lymphocytes of long-term abstinent alcohol and heroin addicts

Aim It has been repeatedly suggested that dopamine receptor expression in peripheral blood lymphocytes reflects, to some extent, brain status. The aim of the present study was to investigate dopamine receptor expression in peripheral blood lymphocytes of long‐term abstinent alcohol and heroin addicts against the background of the hypothesis, that a persisting dysfunction of the dopaminergic system contributes a biological cause to the chronic character of addiction. Design Dopamine D3 and D4 receptor mRNA expression in peripheral blood lymphocytes was measured by real‐time polymerase chain reaction (PCR) in 19 alcohol addicts, abstinent for 6.2 ± 4.7 months (mean ± SD), and 20 heroin addicts, abstinent for 6.7 ± 3.7 months (mean ± SD), and compared to a control group of 29 age‐ and sex‐matched individuals with no life‐time history of substance abuse. Findings One‐way anova showed significant differences in D4 mRNA expression between the groups (P = 0.005): both groups of addicts showed an approximately 50% reduction in D4 receptor mRNA expression in peripheral blood lymphocytes (PBL) compared to controls. No differences were found for D3 mRNA expression between the groups. Conclusion The results of the present study indicate a withdrawal‐persisting dopaminergic imbalance in abstinent addicts as measured by a suggested peripheral marker.     

Enhanced proliferative response to beta-endorphin of phytohemagglutinin-activated lymphocytes from patients with ulcerative colitis

We investigated the effect of a known T cell mitogen, phytohemagglutinin (PHA) and the neuropeptide beta-endorphin on the in vitro lymphocyte proliferative response in patients with ulcerative colitis and in health persons. We found that patients with ulcerative colitis show enhanced reactivity to PHA, when incubated in the presence of beta-endorphin. The activity of the disease during the period of the investigation seemed to play no role, since lymphocytes from both patients in exacerbation or remission reacted in a similar manner.     

Interleukin-11 promotes accessory cell-dependent B-cell differentiation in humans.

Interleukin-11 (IL-11) is a recently described stromal-derived cytokine that supports the growth of an IL-6-dependent murine plasmacytoma line in the presence of antibody to IL-6 and appears to act in a manner similar to IL-6 on hematopoietic stem cells. Because IL-6 is known to promote differentiation of normal human B cells, the role of IL-11 on B-cell differentiation in vitro was characterized. IL-11 does not result in significantly increased DNA synthesis or Ig secretion by purified B cells alone or B cells cultured with Staphylococcus Cowan I, a T-cell-independent B-cell mitogen. In contrast, purified B cells cultured in the presence of pokeweed mitogen (PWM), irradiated T cells, and monocytes show increased DNA synthesis at day 3 and increased IgG and IgM secretion at day 7 of culture; addition of IL-11 further augments Ig secretion without change in DNA synthesis, an effect that can only be partially blocked by monoclonal antibody to IL-6. Similar experiments confirmed that increased IgG secretion was demonstrable when either IL-11 or IL-6 was added to B cells + CD4+/45RA- T cells + monocytes + PWM; in contrast, Ig secretion was low and equivalent when CD4+/45RA+ T cells were cultured with B cells+monocytes+PWM with or without IL-6 or IL-11. Neither IL-6 nor IL-11 could significantly increase phytohemagglutinin (PHA)-induced DNA synthesis by CD4+/45RA- or CD4+/45RA+ T cells. Although PWM or IL-11 induced IL-6 mRNA expression in both CD4+/45RA- T cells and monocytes, in neither cell did IL-11 increase IL-6 mRNA expression over that noted to PWM alone. These observations support the view that IL-11 promotes differentiation of human B lymphocytes only in the presence of accessory T cells and monocytes and that a minor component of this effect may be through stimulation of IL-6 production by CD4+/45RA- T cells and monocytes.     

Impaired insulin response to glucose but not to arginine in heroin addicts

Plasma glucose, insulin, glucagon and growth hormone responses to both oral glucose and iv arginine were evaluated in 15 heroin addicts and 15 control subjects matched for age, sex and weight. The heroin users had an exaggerated rise in plasma glucose concentrations following oral sugar, which persisted until the end of the study (102 +/- 5 mg/dl in addicts vs 72 +/- 3 mg/dl in controls at 240 min, p less than 0.01) and significantly lower insulin responses (insulin peak 28 +/- 4 microU/ml in addicts vs 67 +/- 8 microU/ml in controls, p less than 0.01). The inhibitory effect of glucose on glucagon concentrations was less evident in addicts than in controls. The responses of plasma glucose, insulin and glucagon to arginine were not significantly different between addicts and controls, while the growth hormone rise was significantly greater in addicts. These results demonstrate that heroin users have impaired insulin secretion to oral glucose but not to arginine and suggest that: the impaired insulin secretion in heroin addicts is not dependent on beta-cell exhaustion, and a selective inhibition of glucose-induced insulin secretion is operative in these subjects, as it happens in patients with noninsulin-dependent diabetes mellitus.     

Immunomodulatory effects of treatment with naproxen in patients with rheumatic disease

We evaluated the effects of a nonsteroidal antiinflammatory drug, naproxen, on phytohemagglutinin (PHA)-induced lymphocyte proliferation. When added in vitro to cultures of peripheral blood mononuclear cells, naproxen enhanced the proliferative response toward PHA of lymphocytes from rheumatoid arthritis (RA) patients but not from healthy volunteers, and it reduced prostaglandin E2 (PGE2) synthesis in the cultures. Oral treatment for 7 days with naproxen also resulted in a significant enhancement of the in vitro PHA-induced proliferation of lymphocytes from RA patients and from age-matched control patients with noninflammatory rheumatic diseases, but not from young healthy controls. This enhancement of PHA-induced lymphocyte proliferation after oral intake of naproxen was not accompanied by diminished in vitro PGE2 production in the cultures. It did occur when PGE2-producing monocytes were removed and when in vitro PGE2 synthesis was blocked with indomethacin. We conclude that oral treatment with naproxen has an immunomodulatory effect and improves in vitro PHA-induced proliferation of lymphocytes from rheumatic disease patients. This effect is not due to reduced PGE2 synthesis in the in vitro cultures, but reflects a more fundamental in vivo change in immunoregulation.     

Clinico-immunological study of the patients infected with Mycobacterium avium complex (MAC)]

Lymphocyte functions of the peripheral blood in the patients infected with MAC (MAC-pts) were evaluated comparatively with age-matched normal controls by using flow cytometry. The results obtained were as follows: 1) In normal controls, the number of total lymphocytes and the proportion and number of T lymphocyte subsets significantly decreased with age. The proportion of natural killer lymphocytes significantly increased in elder controls. 2) In MAC-pts, the number of total lymphocytes and T lymphocyte subsets were significantly lower and the proportion of natural killer lymphocytes were higher respectively than normal controls. 3) The lymphocyte proliferation induced by PPD-S stimulation in vitro in MAC-pts was significantly lower than the normal controls in both age groups of 50-69 and 70-89 years old. 4) The lymphocyte proliferation induced by PPD-S stimulation in MAC-pts was increased slightly by adding recombinant IL-2 and significantly higher by depletion of monocytes. By combination of both treatments, it recovered to the level of normal controls. From these results, we suggested that the decline of lymphocyte proliferation induced by PPD-S stimulation in MAC-pts was due to the decrease of IL-2 production by antigen committed lymphocytes and suppression by monocytes. 5) Lymphocyte proliferation induced by PHA stimulation in vitro was also significantly depressed in MAC-pts as compared with normal controls.     

The role of interleukin 2 in hemorrhage-induced abnormalities of lymphocyte proliferation

Depression of lymphocyte proliferative response occurs after trauma and hemorrhage. Because abnormalities in production or utilization of interleukin 2 (IL-2) can result in depression of mitogen-induced lymphocyte proliferation, we investigated the effects of unanesthetized hemorrhage on the generation of IL-2 by rat peripheral blood lymphocytes and the response of these cells to exogenous IL-2. Two hours after loss of 30% of total blood volume, IL-2 production was reduced by greater than 90%. Return to normal levels of IL-2 generation occurred by 48 hr after hemorrhage. Addition of purified rat IL-2 to cultures of phytohemagglutin-stimulated peripheral blood lymphocytes obtained from normal animals resulted in suppression of the proliferative response. Exogenous IL-2 produced a similar degree of suppression in the proliferation of cells obtained from hemorrhaged animals. These results show a profound hemorrhage-induced suppression of IL-2 generation, but no benefits of exogenous IL-2 in improving the depressed lymphocyte proliferative response that exists after hemorrhage.     

Active suppression of interleukin 2 secretion in mice infected with Trypanosoma brucei AnTat 1.1. E

Impairment of T cell proliferation in mice infected with the pleomorphic Trypanosoma brucei AnTat 1.1 E clone was found not to be related to a depletion of T cells or to an absence of functional accessory cells, but rather to an active suppression of interleukin 2 (IL-2) production. Lymph node cells derived from infected mice failed to produce IL-2 following Con A stimulation, whereas an exogenous supply of recombinant IL-2 could restore the impairment of the mitogen (Con A)-induced proliferative responses. Furthermore, lymph node cells derived from infected mice suppressed both secondary T-cell proliferative responses and IL-2 secretion, indicating that the trypanosome-induced suppression is mediated by a suppressive cell which interferes at the level of IL-2 secretion.     

Influence of exogenous interleukin-2 on the proliferation of lymphocytes from normal donors and from patients after autologous bone marrow transplantation

The influence of two interleukin-2 (IL-2) preparations on the proliferative response of normal lymphocytes to phytohemagglutinin (PHA) was examined. A recombinant IL-2 (rIL-2) and an IL-2 containing conditioned medium (LyIL-2) markedly enhanced 3H-thymidine incorporations at low PHA concentrations, whereas at optimal mitogen concentrations, this effect was marginal. In lymphocyte cultures of 3 patients after autologous bone marrow transplantation (ABMT), exogenous IL-2 augmented PHA-induced stimulations. Moreover, a dose-dependent increase of the 3H-thymidine uptake was observed in unstimulated cultures of all normal donors and patients. Combined autoradiography and surface marker analysis allowed to identify cells spontaneously proliferating in the presence of exogenous IL-2. Comparison of phenotypes of these cells revealed pronounced differences between a normal donor and a patient after ABMT.     

Phosphocholine-containing antigens of Brugia malayi nonspecifically suppress lymphocyte function

The immunosuppressive effect of Brugia malayi antigen (BmA) on phytohemagglutinin (PHA) driven T cell proliferation was evaluated in patients with filariasis (n = 14) and compared to control individuals (n = 12). When peripheral blood lymphocytes were co-cultured with BmA and PHA, BmA markedly suppressed the T cell proliferative response to PHA in both filarial patients and control individuals in a dose-dependent manner. The suppression resulted neither from any direct toxicity of BmA nor from nonspecific absorption of the PHA mitogenic activity by BmA. The major suppressive component appears to be phosphocholine (PC), an immunodominant molecule present in abundance on filarial parasites and on circulating filarial antigen. Both purified PC as well as PC-containing antigens affinity purified from BmA were capable of suppressing the proliferative responses of co-cultured autologous lymphocytes to PHA. The suppressive activity was not abolished by mitomycin-C treatment and was greater in patients with filariasis than in normal controls, suggesting that levels of PC-containing antigens determines the magnitude of the suppressive effect of PC-antigen. Further, as induction of the suppressive activity was completely abrogated when antigen pre-treated cells were T cell-depleted, the suppressive effect appears to be mediated primarily by T cells.     

In vitro production of granulocyte-macrophage colony-stimulating factor in aplastic anemia: possible mechanisms of action of antithymocyte globulin

Various abnormalities of lymphokine production have been described in patients with aplastic anemia. To determine if abnormal production of hematopoietic growth factors could contribute to the process of aplastic anemia we studied the in vitro production of human granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) by phytohemagglutinin (PHA)- and antithymocyte globulin (ATG)-stimulated peripheral blood lymphocytes from 29 patients with aplastic anemia and 15 normal controls. GM-CSF production in response to 1% PHA was seen in nearly all samples (43 of 44) and similar amounts of GM-CSF were produced by patients with aplastic anemia and normal controls. Production of GM-CSF by ATG-stimulated lymphocytes was seen in 7 of 23 patients with aplastic anemia (30%); two of these patients also demonstrated low-level spontaneous production of GM-CSF. Production of GM-CSF in response to ATG was also seen in 2 of 11 normal controls (18%) and barely detectable spontaneous production of GM-CSF was seen in both. Biologically active IL-3 could also be detected in PHA- or ATG-stimulated peripheral blood mononuclear cells in several patients and normal controls. Our results indicate that lymphocytes from patients with aplastic anemia can be stimulated in vitro to produce normal quantities of GM-CSF, suggesting that impaired potential for production of T-cell derived hematopoietic growth factors is unlikely to account for the marrow hypoplasia seen. In several patients overproduction of GM-CSF was observed, consistent with the notion that some patients with aplastic anemia may have circulating activated T cells. We also demonstrate that ATG can stimulate the production of growth factors such as IL-3 and GM-CSF, supporting the role for ATG in stimulating hematopoiesis.     

Defective T-cell Proliferation and IL-2 Production in a Subgroup of Patients with Coronary Artery Disease

Atherosclerosis is a chronic inflammatory disease of the arterial wall characterized by innate and adaptive immune responses to a variety of microbial and self-antigens. Given the crucial role of adaptive immunity in the pathogenesis of atherosclerosis, this study was performed to investigate the proliferative response of peripheral blood mononuclear cells (PBMC) and interleukin (IL)-2 production in patients with coronary artery disease (CAD). In this study, 25 patients with chronic stable CAD and 25 healthy individuals were investigated. The PBMCs were separated and stimulated with phytohaemagglutinin (PHA). MTT assay was performed to measure cell viability and proliferation. IL-2 concentrations in cell culture supernatants were determined by Enzyme-Linked Immunosorbent Assay. PHA-stimulated cells revealed a significantly increased optical density (OD) in both groups of patients (p=0.004) and controls (p<0.001). However, the patient group showed a significantly lower Stimulation index (SI) (p=0.001). Upon in vitro stimulation with PHA, IL-2 levels were significantly increased in both groups of patients and controls (p<0.001). However, IL-2 concentrations were significantly lower in the patient group (p=0.018). Six patients showed defective IL-2 production, whereas similar finding was not observed in the normal control subjects (p=0.022). PBMCs from patients with coronary artery disease showed defective PHA-induced mitogenesis and IL-2 production. Considering the autoimmune nature of atherosclerosis, decreased IL-2 production may potentially enhance the atherogenic process, leading to spontaneous activation of autoreactive T lymphocytes.     

Modulation of interleukin 2 receptor expression on normal human lymphocytes by thymic hormones.

The expression of interleukin 2 receptors (IL-2R) is a critical step leading to normal lymphocyte proliferation. Since thymosin fraction 5 (TF5), a thymic hormone preparation, enhances lymphoproliferative responses of human cells, we examined the effects of TF5 on the expression of IL-2R on mitogen-stimulated human lymphocytes. TF5 significantly increased the percentage and antigen density of cells expressing IL-2R after stimulation with an optimal concentration of phytohemagglutinin (PHA) when the cells from the same donor exhibited suboptimal responses to PHA alone. The same effect was observed with a suboptimal PHA concentration and with OKT3 monoclonal antibody stimulation. Thymosin alpha 1, a synthetic polypeptide originally isolated in its native form from TF5, was also able to increase IL-2R expression in response to PHA, suggesting that it is the active species in TF5. The enhancement of IL-2R expression was paralleled by increased proliferative responses. Increased IL-2R expression appears to be the direct effect of thymic hormones, since abrogation of interleukin 2 production by cyclosporin A did not affect TF5-mediated enhancement of PHA-induced IL-2R expression. These results point to a physiological role of thymic hormones in the maintenance of normal levels of IL-2R expression. This immunoregulatory activity of thymic hormones might be relevant in the treatment of conditions where there is decreased IL-2R expression, such as the acquired immune-deficiency syndrome, or in the restoration of normal IL-2R expression to lymphocytes from aged individuals.