Tetranactin, a macrotetrolide antibiotic, suppresses in vitro proliferation of human lymphocytes and generation of cytotoxicity

Tetranactin, a hydrophobic cyclic antibiotic produced by Streptomyces aureus, has previously been shown to suppress in vitro activation of rat lymphocytes by concanavalin A as well as the onset of experimental autoimmune uveoretinitis in Lewis rats. Here we report the effects of tetranactin on human T and NK lymphocytes in vitro. Tetranactin, at concentrations up to 100 ng/ml, was not toxic to human lymphocytes but completely abrogated the proliferation of human T lymphocytes in response to allogeneic cells in mixed lymphocyte cultures. Tetranactin also blocked the initiation of proliferation in response to interleukin-2, but did not block proliferation of interleukin-2-activated cells. Tetranactin also blocked generation of cytotoxic T lymphocytes and activated killer cells in the mixed lymphocyte culture. However, up to 100 ng/ml tetranactin did not alter the lytic activity of cytotoxic T or NK lymphocytes generated in its absence. The ability of low doses of tetranactin to block the induction of lymphoproliferation is similar to the action of cyclosporin A. Since cyclosporin A is also a cyclic hydrophobic molecule, the immunosuppressive actions of these two agents may involve a similar mechanism.     

Influence of beta-endorphin on phytohemagglutinin-induced lymphocyte proliferation and on the expression of mononuclear cell surface antigens in vitro

Recent evidence suggests that opiates can modulate the immune responses. In particular it has been shown that beta-endorphin and morphine are able to depress some T lymphocyte functions in humans. In the present study, experiments were designed to evaluate the effect of beta-endorphin phytohemagglutinin-induced lymphocyte proliferation and determine the mechanism of this action. The ability of naloxone to block the effect of beta-endorphin was also investigated, and the influence of beta-endorphin on the expression of mononuclear cell surface antigens using the OKT3, OKT4, OKT8, anti-HLA-DR and anti-beta 2-microglobulin monoclonal antibodies was evaluated. Phytohemagglutinin-induced lymphocyte proliferation was significantly inhibited by beta-endorphin. This effect occurred when beta-endorphin was added to cells at the beginning of the culture period (30 min before, simultaneously or 30 min after phytohemagglutinin), but not when added after 48 h of incubation. The preincubation of cells with BEP for 1 h, 4 h or 24 h did not affect lymphocyte activation by phytohemagglutinin. A ten-fold excess of naloxone, added to cultures 30 min prior to beta-endorphin, did not block the inhibitory effect. Incubation with beta-endorphin had different effects on each surface antigen tested. The OKT8+ and beta 2-microglobulin+ cells did not show significant variations. The OKT4+ cells significantly decreased, after 4 h of incubation with beta-endorphin, both in mononuclear cell and in purified T lymphocyte cultures and, after 24 h, in mononuclear cell cultures only. The OKT3+ cells decreased, in mononuclear cell cultures only, after 24 h beta-endorphin incubation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of a single intravenous dose of verapamil on some immune parameters in duodenal ulcer patients

The effect of a single intravenous dose of calcium channel blocking agent verapamil (VER) on immune parameters in humans remains uncertain. In this study the effects of VER on lymphocyte subpopulations, interleukin 1 (IL-1) and 2 (IL-2) production in vitro, autologous mixed lymphocyte reaction (AMLR), IL-2 receptor expression (Tac positive cells) and natural killer (NK) cell activity were assessed. The investigations were undertaken on 12 hospitalized men, aged 19-23 years, with small abdominal complaints. None of them had active duodenal ulcer disease, while in the remaining no signs of organic disease were found. VER was given intravenously in a dose of 0.15 mg/kg and examinations were performed on peripheral blood mononuclear cells (PBL) drawn before and 30 and 150 min following VER injection. The single VER dose induced a significant, but transient increase in T, T helper, T suppressor lymphocytes and monocytes, and decrease in IL-1 and IL-2 generation as well as diminished Tac antigen expression. These data provide evidence that calcium channel blockers may transiently disturb immunoregulation.     

Lymphocyte-suppressing effect of simvastatin in mixed dyslipidemic patients but not impaired glucose tolerance patients

This study compared the effect of simvastatin on lymphocyte secretory function between patients with impaired glucose tolerance (IGT) (n=30) and mixed dyslipidemia (n=29). Lipid profile, glucose metabolism markers (fasting and 2-h post-glucose challenge glucose levels, HOMA-IR and glycated hemoglobin), plasma CRP levels and the release of interleukin-2 and interferon-γ by phytohemagglutinin-stimulated T lymphocytes were determined before and after 30 and 90 days of simvastatin administration (20 mg daily). Phytohemagglutinin-stimulated T cells from both IGT and mixed dyslipidemic subjects released significantly higher amounts of both cytokines than lymphocytes of 30 dyslipidemia-free individuals with normal glucose tolerance. Despite improving the lipid profile, simvastatin produced no effects on glucose metabolism markers in either treatment groups. The drug normalized the lymphocyte cytokine release and plasma hsCRP in mixed dyslipidemic patients but not in IGT patients. Our study indicates that the presence of mixed dyslipidemia and IGT is associated with the enhanced secretory function of human lymphocytes. Simvastatin is an effective lymphocyte-suppressing agent in mixed dyslipidemic patients but not in IGT patients.     

Induction of antitumor resistance to mouse leukemia L1210 by spergualins

Spergualin and its analog, 15-deoxyspergualin showed a marked antitumor effect against L1210 by intraperitoneal and oral administrations. After treatment with these substances 40- or 60-day survivors (cured mice of L1210) were resistant to reinoculation of L1210 cells. They were resistant only to L1210. The antitumor effector cells in these mice were determined to be T cells. NK activity of spleen cells was also enhanced by spergualins. The antitumor activity of 15-deoxyspergualin was markedly reduced in immuno-deficient mice. IL (interleukin)-2 production, but not IL-1, was enhanced in supernatant of mixed lymphocyte cultures by treatment with 15-deoxyspergualin. The mechanism of action of 15-deoxyspergualin on the immune system was discussed.     

组胺对细胞免疫反应调节作用的实验研究

目的　了解组胺对 CD4和 CD8T细胞白细胞介素 - 2 (IL- 2 )产生和细胞增生活性的影响。方法　密度梯度离心及吸附法分离外周血单个核细胞 (PBMC)和外周血淋巴细胞计数 (PBL C) ,采用抗 CD4和抗 CD8抗体分别制备 CD8和 CD4T细胞进行培养 ,然后采用酶联免疫吸附法 (EL ISA法 )和四氮唑蓝快速比色法(MTT)测上清液 IL - 2含量及增生活性。结果　 1组胺 +CD4(CD8)培养上清液中 IL - 2水平及 MTT增生指数与T细胞自然培养孔比较明显降低 (P<0 .0 5 )。 2组胺 +CD4(CD8) +西咪替丁培养孔上清液中 IL - 2水平及 MTT增生指数明显高于未加西咪替丁孔 (P<0 .0 5 )。 3 CD4T细胞自然培养孔上清液中 IL- 2水平显著高于 CD8T细胞自然培养孔。结论　 1组胺可抑制 T细胞 IL- 2产生及增生 ;2西咪替丁可阻断组胺对 T细胞的抑制作用 ;3CD8T细胞也可产生 IL- 2 ,但其功能较 CD4T细胞为低     

枸杞多糖对小鼠T、杀伤T和NK细胞的免疫药理作用及对抗环磷酰胺的免疫抑制作用(英文)

枸杞多糖(LBP)5～10 mg/kg,ip,可以提高小鼠脾脏T淋巴细胞的增殖功能,增强CTL的杀伤功能,特异杀伤率由33％提高到67％.LBP 5mg/kg.ip,可以增强NK细胞的杀伤功能,杀伤率由12.4％提高到18％. LBP 5～10 mg/kg可以对抗环磷酰胺(Cy)对小鼠T、CTL和NK细胞的免疫抑制作用;其中T淋巴细胞的相对增殖指数(RPI)由33％提高到105％,Cy对CTL的抑制率由单用的51％降低到与LBP合用的19％和36％,NK细胞的杀伤率亦由Cy单用的9.5％提到15％和16％.以上结果说明LBP增强了正常小鼠和Cy处理鼠的T细胞介导的免疫反应与NK细胞的活性.     

BF02, a recombinant TNFR2 fusion protein,alleviates adjuvant arthritis by regulating T lymphocytes in rats

Aim:

To investigate the therapeutic effects of BF02 on adjuvant arthritis (AA) in rats and the regulatory effects of BF02 on T lymphocyte function.

Methods:

SD rats received a single intradermal injection of Freund''s complete adjuvant emulsion into the right hind metatarsal footpad. After the onset of AA, the rats were injected BF02 (1, 3, or 9 mg/kg, sc) every 3 d for a total of 15 d. Intragastric administration of methotrexate (MTX, 0.5 mg/kg, every 3 d for a total of 15 d) was taken as the positive control drug. Arthritis index, swollen joint count, ankle joint histopathology, spleen histopathology and the paw radiography were used for evaluating the drug effects on AA rats. T lymphocyte function was assessed by measuring T lymphocyte cytokine levels, IL17 and TNF-α mRNA expression levels, and percentage of T lymphocyte subsets.

Results:

In the AA rats, remarkable secondary inflammatory responses exhibited, accompanied by significantly higher levels of IL-1, IL-6, TNF-α, IL-17, LTα, RANKL, and MMP-13. The expression of IL17 and TNF-α mRNAs was also substantially higher than in normal rats. The percentages of CD3⁺CD4⁺ and CD4⁺CD25⁺ T lymphocytes were increased, whereas the percentages of CD4⁺CD62L⁺ and CD4⁺CD25⁺FoxP3⁺ T lymphocytes were decreased. Treatment of the AA rats with BF02 (9 mg/kg) or MTX significantly decreased the arthritis index, swollen joint count and arthritis global assessment. Moreover, both BF02 (9 mg/kg) and MTX significantly inhibited T lymphocyte proliferation, and blocked the above mentioned aberrance in T lymphocyte cytokine levels, IL17 and TNF-α mRNA expression, and percentages of T lymphocyte subsets.

Conclusion:

BF02 exerts therapeutic effects on AA rats via the regulation of T lymphocytes.     

Interpretation of lymphocytotoxicity assays and the demonstration of auto-tumor reactive lymphocytes in patients: central issues of present day tumor immunology

The outcome of a short term cell-mediated cytotoxic assay depends on the susceptibility of the target and the activation profile of the lymphocyte population. Certain cultured cell lines are highly sensitive to the lytic effect of lymphocytes of unimmunized donors, provided they have been derived from the same species--NK effect. This cytotoxicity seems to be independent of lymphocyte receptor-target antigen interaction but is likely due to some membrane property of the target. Specificity is only on the species level. With fresh, non-cultured targets, in certain systems which operationally conform with the natural killing henomenon, antigen specific recognition defines the effect. We propose that on fresh targets, the operational NK effect, should be viewed fundamentally similar to CTL. Analysis of antigen induced cytotoxic systems suggests that the question of "specificity" on the effector level can only be asked if target cells of similar characteristics are used. Specificity at the effector level depends on the panel of targets presented. Cells with inherent sensitivity to the lytic effect of activated lymphocytes (i.e. NK sensitive cells) may be killed even if they are unrelated to the stimulus, and also such NK resistant cells which carry antigens for which the relevant receptor carrying lymphocytes are present in a sufficient number. Lysis of the latter cells can occur due to transactivation. Transactivation means that accompanying the event of antigen specific recognition in a lymphocyte population, additional cells are activated that do not participate in the specific reaction. In patients with solid tumors lymphocytes which recognize autologous tumor biopsy cells and can damage them, have been demonstrated. Auto-tumor-killer lymphocytes have been generated in conventional mixed lymphocyte cultures, using the patient's lymphocytes as responders--probably due to transactivation or in mixed lymphocyte cultures containing lymphocytes and autologous tumor cells.     

Effect of indomethacin on in vitro T- and B-cell activation and cell-mediated lysis.

The effect of indomethacin, an inhibitor of prostaglandin synthetase, on lymphocyte blast transformation induced by T- or B-cell activators has been studied. Simultaneously adding indomethacin (0.03-0.3 x 10(-6) M final concentration) and concanavalin A to mouse spleen cell cultures, led to an enhancement of 3H-thymidine uptake, whereas 30 x 10(-6) M indomethacin inhibited this uptake. The stimulation induced by indomethacin was higher when this drug was present in the cultures before the addition of the mitogen. Neither the optimal concanavalin A concentration nor the day on which the maximum of 3H-thymidine uptake occurred were altered by indomethacin. Activation of B lymphocytes induced by bacterial lipopolysaccharide was inhibited by indomethacin at all concentrations tested. However, indomethacin similarly blocked the prostaglandin synthesis as well in lipopolysaccharide- or concanavalin A-stimulated lymphocyte cultures. Indomethacin enhanced the one-way mixed lymphocyte reaction. No significant effect of indomethacin was found on cell-mediated cytotoxicity of 51Cr labeled targets. The results are discussed in terms of differential sensitivity of B and T lymphocytes to this anti-inflammatory drug.     

丹皮总苷体外对三类免疫细胞功能的影响

目的研究丹皮总苷（ＴＧＭ）体外对３类免疫细胞功能的影响。方法采用［３Ｈ］－ＴｄＲ参入法,检测Ｔ淋巴细胞增殖反应和分泌白介素２（ＩＬ－２）活性,Ｂ淋巴细胞增殖反应以及巨噬细胞产生ＩＬ－１。结果ＴＧＭ２～５０ｍｇ·Ｌ－１可明显促进刀豆蛋白Ａ诱导小鼠Ｔ淋巴细胞增殖反应和大鼠Ｔ淋巴细胞产生ＩＬ－２,ＴＧＭ还可促进脂多糖诱导Ｂ淋巴细胞增殖反应以及大鼠腹腔巨噬细胞产生ＩＬ－１,它们的浓度－效应曲线呈钟罩形。结论ＴＧＭ具有浓度依赖性双向免疫调节作用。     

当归多糖组分AP-3对不同淋巴细胞亚群的作用

目的观察当归多糖组分AP-3对不同淋巴细胞亚群的作用。方法免疫磁珠法制备T、B细胞亚群;四甲基偶氮唑蓝(MTT)法检测细胞增殖;流式细胞术观察CD4+T细胞亚群比例的变化。结果在30~300μg/ml范围内,AP-3能显著促进小鼠脾淋巴细胞、巨噬细胞、混合淋巴细胞和T淋巴细胞的增殖反应,而对B细胞增殖有一定的抑制作用;显著增加培养的脾细胞中CD4+T细胞亚群的比例。结论当归多糖具有独特的免疫调节特性,活化巨噬细胞、T细胞以及辅助性T细胞(Th细胞),但对B细胞有一定的抑制作用。     

Pharmacokinetics of a new extended-release nifedipine formulation following a single oral dose, in human volunteers

This study aimed to define the pharmacokinetics of nifedipine following oral administration of a new extended-release formulation. Twelve healthy volunteers of both sexes, aged 39 +/- 4 years, were treated with a single oral tablet of a new extended-release formulation containing 40 mg of nifedipine. Samples of venous blood were taken before dosing, after 30 min and at 1, 2, 4, 8, 12, 16, 20 and 24 h after administration. Nifedipine concentration was measured by means of a high-performance liquid chromatography method. Noncompartmental pharmacokinetics parameters were then calculated. The plasma concentration of nifedipine increased slowly and in seven subjects biphasic peaks occurred. The mean values were as follows: t(max): 8.5 +/- 1.2 h; C(max): 36.55 +/- 6.76 ng/ml; AUC: 347.06 +/- 51.61 ng/h/ml; AUC 409.99 +/- 61.08 ng/h/ml; A(half-life): 2.26 +/- 0.36 h; D(half-life): 2.43 +/- 0.44 h; E(half-life): 4.62 +/- 0.79 h. Twenty-four hours after administration nifedipine was still detectable (3.17 +/- 0.67 ng/ml). Arterial blood pressure decreased and heart rate increased concurrently and proportionally to the increase in nifedipine concentration. Extended-release nifedipine formulations have better tolerability profiles than immediate-release formulations, which are at present not recommended in the treatment of hypertension, hypertensive crises or myocardial infarction. This new extended-release formulation has interesting pharmacokinetic parameters and may be effective in conditions in which dihydropyridine calcium channel blockers are indicated.     

Chronic administration of verapamil, ketoconazole and carbamazepine: impact on immunological parameters

Inhibitors of P-glycoprotein (P-gp) (verapamil) or cytochrome P-450 (ketoconazole) may reduce IL2 production and T lymphocyte proliferation in vitro. We have examined the effects of chronic oral administration of these drugs and of the cytochrome P450 inductor, carbamazepine, on the hematological and immunological parameters of mice. We found no changes after giving the mice 0.12 mg verapamil, 0.85 mg ketoconazole, or 0.514 mg carbamazepine per mouse for 4 weeks (5 days/week). But giving the drugs for an additional 7 weeks at 0.6 mg (verapamil), 4.25 mg (ketoconazole) or 2.57 mg/mouse (carbamazepine), resulted in significant decreases in monocytes in the verapamil treated group (-51%) and in CD4+ cells in the carbamazepine group (-35%). Chronic oral administration of these drugs reduced the lymphocyte counts of mice by 10-18% and their NK counts by 10-16%. These changes could be due to changes in P-gp function in the transport of IL2, with decreases caused by verapamil and ketoconazole.     

The inhibitory effect of phenothiazines on NK-mediated cytolysis of tumor cells

Non-toxic concentrations of fluphenazine caused a marked (90%) inhibition of NK-mediated cytolysis of YAC-1 tumor cells. The biologically inactive sulphoxide derivative was not inhibitory and the efficacy of inhibition of other compounds was directly correlated (r = -0.96, p less than 0.02) with their reported affinities for calmodulin. Fluphenazine may act on the earliest stages of the target-effector interaction since conjugate formation between CBA effectors and YAC target cells decreased from 20% to 6% (p less than 0.02) upon pre-treatment with fluphenazine. However, fluphenazine was not selective for NK cells since cytotoxic T lymphocytes, derived from both mixed lymphocyte culture and by concanavalin A stimulation, revealed depressed cytolytic activity against P815 tumor targets after fluphenazine treatment. Tumoricidal activity by activated macrophages and effectors of antibody-dependent cell-mediated cytotoxicity was also blocked. Fluphenazine inhibition was reversible, since addition of 1.25-5 micrograms/ml of the calcium ionophore A23187 to fluphenazine-treated effectors restored NK binding and cytolytic functions to normal levels. Calmodulin was isolated from NK-enriched populations by affinity chromatography on sepharose-fluphenazine columns. Pre-treatment of effector cells with [3H]fluphenazine and isolation of calmodulin by immunoprecipitation and SDS-polyacrylamide gel electrophoresis showed that fluphenazine entered the cells and bound a calmodulin-like molecule. These data are compatible with the suggestion that fluphenazine inhibits NK function by inactivating the calcium-calmodulin complex and thereby altering binding events in the target-effector interaction. Other actions of the phenothiazines are also possible.     

Modulation of in vitro immune reactions by platelet activating factor and a platelet activating factor antagonist

Platelet activating factor (PAF) was found to suppress primary and secondary mixed lymphocyte reactions and BN52021, a naturally occurring PAF antagonist, blocked PAF-mediated suppression and enhanced the mixed lymphocyte reactions. The effect of delayed addition of PAF or BN52021 24 h or later after the initiation of cultures reduced the suppressive and enhancing effects, respectively. The removal of the antagonist BN52021 from mixed lymphocyte cultures up to 72 h after their initiation also was found to eliminate the potentiating effect of this antagonist. The continuous presence of PAF in mixed lymphocyte cultures used to generate cytotoxic lymphocytes suppressed the generation of effector cells while the addition of BN52021 elicited an enhanced level of cell-mediated cytotoxicity in such cultures. BN52021 enhanced the cytotoxic activity in such cultures irrespective of the presence of exogenous interleukin-2, suggesting that the antagonist-mediated enhancement is not due to the enhanced production of interleukin-2 by cells in the mixed cultures. The experiments reported here provide evidence for a role of PAF in modulating the complex interactions that take place in the initiation of cellular immune reactions. Furthermore, the results of these experiments indicate that the immunoregulatory action of PAF can be modulated by an antagonist that exerts its action independently of the production of the lymphocyte growth factor, interleukin-2.     

Cocaine administration increases CD4/CD8 lymphocyte ratio in peripheral blood despite lymphopenia and elevated corticosterone

The CD4/CD8 lymphocyte ratio in peripheral blood is used in the diagnosis of HIV infection, autoimmune disorders or susceptibility to infections. The present experiment aimed to evaluate the lymphocyte subsets, their distribution and CD4/CD8 ratio in blood after repeated, intravenous administration of cocaine. Adult male Wistar rats received three daily, in 30 min intervals, intravenous infusions of cocaine hydrochloride (5 mg/kg) or saline for 14 consecutive days. After each infusion the locomotor-activating effects of cocaine were assessed. Blood samples were collected 30 min after the last daily infusion on the 1st, 7th and 14th day of treatment. Total leukocyte numbers, percentages of leukocyte subpopulations, and T, B, NK, T CD4⁺, and T CD8⁺ lymphocyte subsets, IFN-γ, and plasma corticosterone were determined. Repeated cocaine treatment resulted in an increase in neutrophil numbers and a significant decrease in total leukocyte and lymphocyte numbers involving a significant reduction in numbers of T, B, and NK lymphocyte subsets. T CD4⁺ and T CD8⁺ lymphocyte numbers were reduced but with a considerably smaller decrease in T CD4⁺ number. Cocaine treatment altered proportions between the lymphocyte subsets by decreasing the percentages of T CD8⁺, B, and NK cells but increasing a percentage of T CD4⁺ cells. Destabilization in proportions between T CD4⁺ and T CD8⁺ was manifested as an elevated CD4/CD8 ratio that occurred despite increased plasma corticosterone and the lymphocytopenia. Cocaine did not affect the concentration of IFN-γ. The results suggest that although cocaine induced lymphopenia, it did not suppress the overall immune activity in terms of the CD4/CD8 ratio.     

Role of tachykinin NK2-receptor activation in the allergen-induced late asthmatic reaction, airway hyperreactivity and airway inflammatory cell influx in conscious, unrestrained guinea-pigs.

1. In a guinea-pig model of allergic asthma, we investigated the involvement of the tachykinin NK2 receptors in allergen-induced early (EAR) and late (LAR) asthmatic reactions, airway hyperreactivity (AHR) after these reactions and inflammatory cell influx in the airways, using the selective non-peptide NK2 receptor antagonist SR48968. 2. On two different occasions, separated by a 1 week interval, ovalbumin (OA)-sensitized guinea-pigs inhaled either vehicle (3 min) or SR48968 (100 nM, 3 min) at 30 min before as well as at 5.5 h after OA provocation (between the EAR and LAR) in a random crossover design. 3. SR48968 had no significant effect on the EAR, but significantly attenuated the LAR by 44.2+/-16.4% (P<0.05) compared to saline control. 4. The NK2 receptor antagonist did not affect the OA-induced AHR to histamine after the EAR at 5 h after OA challenge (3.59+/-0.59 fold increase in histamine reactivity vs 3.79+/-0.61 fold increase in the controls, NS), but significantly reduced the AHR after the LAR at 23 h after OA challenge (1.59+/-0.24 fold increase vs 1.93+/-0.15 fold increase, respectively, P<0.05). 5. Bronchoalveolar lavage studies performed at 25 h after the second OA provocation showed that SR48968 significantly inhibited the allergen-induced infiltration of neutrophils (P<0.05) and lymphocytes (P<0.01) in the airways. 6. These results indicate that NK2 receptor activation is importantly involved in the development of the allergen-induced late (but not early) asthmatic reaction and late (but not early) AHR to histamine, and that NK2 receptor-mediated infiltration of neutrophils and lymphocytes in the airways may contribute to these effects.     

Activation-induced T cell apoptosis by monocytes from stem cell products.

We recently found that mobilized peripheral blood stem cell (PSC) products (from both cancer patients and normal donors) contain high levels of CD14+ monocytes, which can inhibit the proliferation of allogeneic and autologous T cells. We found in our studies that using CD14+ monocytes from mobilized PSC products (from normal and cancer patient donors), normal apheresis products or normal peripheral blood (PB) can affect lymphocyte function and apoptosis-dependent T cell activation. However, it appears that the apoptosis is dependent on the frequency of monocytes, which is increased by both mobilization and apheresis. Both phytohemagglutinin (PHA)- and interleukin (IL)-2-induced proliferation of steady-state peripheral blood mononuclear cells (PBMC) were markedly inhibited by co-culture with irradiated CD14+ monocytes, although inhibition was significantly greater with PHA than with IL-2 stimulation. IL-2 (predominately CD56+ NK cells) or anti-CD3 monoclonal antibody (mAb) and IL-2-expanded lymphocytes (activated T cells) were inhibited by PSC monocytes to a significantly greater level as compared to steady-state lymphocytes. Indeed, no inhibition of T cell proliferation was observed when lymphocytes were co-cultured in the absence of mitogenic or IL-2 stimulation. In contrast, an increased proliferation was observed in co-cultures of CD14+ monocytes and steady-state or activated lymphocytes without mitogenic stimulation. Cell cycle analysis by flow cytometry revealed a significant increase in hypodiploid DNA, in a time-dependent manner, following co-culture of monocytes and PBMC in PHA, suggesting that T cell apoptosis occurred during PHA-induced activation. These results demonstrate that PSC-derived monocytes inhibit T cell proliferation by inducing the apoptosis of activated T cells and NK cells, but not steady-state cells. This suggests a potential role for monocytes in the induction of peripheral tolerance following stem cell transplantation.     

Immunotoxicity of N,N-diethylaniline in mice: effect on natural killer activity, cytotoxic T lymphocyte activity, lymphocyte proliferation response and cellular components of the spleen

We previously found that N,N-diethylaniline increased the frequency of sister chromatid exchange (SCE) of human lymphocytes to about five times that of the control value, and was as toxic as cyclophosphamide used as a positive control for SCE. To explore whether N,N-diethylaniline affects the function of lymphocytes, we evaluated its immunotoxicity using CBA/N mice. The mice were divided into four groups and received 0, 100, 200, or 400 mg/kg body weight of N,N-diethylaniline by subcutaneous injection. The following items were investigated on days 3 and 7 after injection: body weight, weight of spleen, number of splenocytes, natural killer (NK) and cytotoxic T lymphocyte (CTL) activities, and concanavalin A (Con A)- and lipopolysaccharide (LPS)-stimulated lymphocyte proliferation using splenocytes. The following splenocyte phenotypes were also quantified by flow cytometry: (1) B cells; (2) total T cells; (3) CD4⁺ and CD8⁺ T cells; (4) NK; (5) macrophages and (6) nucleated erythrocytes. The splenic NK and CTL activities in exposed groups significantly decreased compared to the control in a dose-dependent manner and lymphocytes from the 200 and 400 mg/kg groups showed significantly higher spontaneous proliferation. The weight of the spleen and number of splenocytes were significantly higher in exposed groups than in the control. N,N-Diethylaniline also increased the percentages of macrophages, nucleated erythrocytes and B cells in the spleen. On the other hand, N,N-diethylaniline did not affect LPS-stimulated B cell and Con A-stimulated T cell proliferation, or the percentages of NK, total T, and CD4⁺ and CD8⁺ T cells in the spleen or the body weight of mice. The above findings indicated that N,N-diethylaniline selectively inhibited splenic NK and CTL activity and this inhibition was due to decreased NK and CTL functions, but not due to changes in the numbers of splenic NK and T cells.