Inhibition of human lymphocyte proliferation and cleavage of interleukin-2 by Pseudomonas aeruginosa proteases

This study was undertaken to determine the effect of Pseudomonas aeruginosa alkaline protease (AP) and elastase (ELA) on human lymphocyte function. AP at 50 micrograms/ml and ELA at 12 micrograms/ml caused a 50% inhibition of phytohemagglutinin-induced proliferation. There was no difference in the effect of proteases on CD4- and CD8-positive cells. To determine the effect of proteases on interleukin-2 (IL-2)-induced cell proliferation, the proteases and IL-2 were added to the IL-2-dependent CTLL-2 cell line. AP and ELA inhibited the proliferation of these cells. When IL-2 was added in excess, the inhibition was partly reversed. ELA at 10 micrograms/ml cleaved IL-2, as judged by size chromatography of a reaction mixture containing 125I-labeled IL-2 and the proteases. The ELA-digested IL-2 exhibited a reduced binding capacity to IL-2 receptors on the lymphocytes. Furthermore, treatment of phytohemagglutinin-stimulated lymphocytes with AP and ELA resulted in inhibition of binding of intact IL-2 to IL-2 receptors on the stimulated lymphocytes. These results indicated that P. aeruginosa-derived enzymes are able to interfere with human lymphocyte function in vitro and that this effect might be due to cleavage of IL-2.

Cell-mediated immunity to Plasmodium falciparum infection: evidence against the involvement of cytotoxic lymphocytes

Blood mononuclear cells (PBMC) recognizing soluble malaria antigens (SPag) are present in the peripheral blood of individuals clinically immune to malaria, and they proliferate after exposure to such antigens. To test whether these cells have effector activity against Plasmodium falciparum, we stimulated PBMC from malaria-immune donors by SPag and purified protein derivative (PPD) in culture for 7 days. The PBMC were then co-incubated with P. falciparum for 48 h, and parasitaemia was determined by microscopy. Parasite growth was only significantly impaired after incubation with PBMC stimulated by either SPag or PPD in the presence of immune serum. Studies on subpopulations of PBMC indicated that the inhibitory cells resided among the adherent cell fraction. Furthermore we tested PBMC for cytotoxic activity against P. falciparum-infected autologous or heterologous erythrocytes. Experiments were done both in the absence and the presence of immune serum. Neither fresh PBMC nor PBMC activated by SPag or PPD for 7 days prior to assay were cytotoxic, indicating that cytotoxic T cells, natural killer (NK) cells, and K cells did not possess cytotoxic activity directed against parasitized erythrocytes. These data support the hypothesis that activated monocytes are the most important effector cells in the peripheral blood of malaria immune individuals.

The in vivo effect of triethylphosphine gold (auranofin), sodium aurothiomalate and azathioprine on lymphocyte subsets of patients with rheumatoid arthritis

The percentages of CD5+ (pan T), CD8+ (mainly T suppressor) and CD4+ (mainly T helper) cells were studied in 80 patients with rheumatoid arthritis (RA), grouped according to medication into four groups: 1) controls, not receiving remission-inducing therapy, 2) patients on oral gold (triethylphosphine gold, auranofin), 3) patients on parenteral gold (sodium aurothiomalate) and 4) patients on azathioprine. The total number of lymphocytes was not influenced by treatment with auranofin or sodium aurothiomalate, while the number of lymphocytes was depressed in the azathioprine-treated group (P less than 0.01). Neither treatment with azathioprine or parenteral gold, nor treatment with azathioprine influenced the CD4+/CD8+ ratio.

Modulation of natural killer cell activity in peripheral blood by physical exercise

The present study was designed to examine the effect of physical exercise on human natural killer (NK) cells. Six healthy volunteers underwent two different acute physical exercise tests with an interval of at least 1 week: (1) 60 min bicycle exercise at 80% of maximal oxygen uptake (VO2max) and (2) 60 min back-muscle training at up to 29% of VO2max; blood samples were collected before and during the last few minutes of exercise, as well as 2 h and 24 h afterwards. The NK cell activity (lysis/fixed number of mononuclear cells) increased during bicycle exercise, dropped to a minimum 2 h later and returned to pre-exercise levels within 24 h. Back-muscle exercise did not significantly influence NK cell activity. Plasma levels of adrenaline, noradrenaline, and cortisol were elevated during bicycling, but not during back-muscle exercise, indicating that exercise intensity is a determinant of NK cell activity. During bicycle exercise the NK cell subset (CD16- cells) of mononuclear cells increased significantly. Furthermore an improved interleukin 2 (IL-2) boosting of the NK cell activity was found during work as compared to IFN-alpha and indomethacin-enhanced NK cell activity. These results indicate that NK cells with a high IL-2 response capacity are recruited to the peripheral blood during exercise. The decreased NK cell activity demonstrated 2 h after work was probably not due to fluctuations in size of the NK cell pool, since the proportion of CD16+ cells was normal. The finding that indomethacin fully restored the suppressed NK cell activity in vitro and the demonstration of a twofold increase in monocyte (CD20+ cells) proportions 2 h after work, strongly indicate that prostaglandins released by monocytes during the heavy physical exercise are responsible for the down-regulation of the NK cells.

Impaired release of natural killer cytotoxic factor in patients with primary Sjögren's syndrome

The impaired natural killer (NK) cell activity against K562 target cells of patients with primary Sjögren's syndrome (primary SS) was re-examined in a 2-year follow-up study of 10 patients and 10 normal controls. The ability of blood mononuclear cells (BMNC) to form effector/target cell conjugates and to release NK cytotoxic factor (NKCF) were studied. NK cell activity of the patients was unchanged low (P less than 0.01) compared with the controls. The number of effector/target cell conjugates did not differ between patients and controls, whereas NKCF-release from interferon-stimulated BMNC was significantly (P less than 0.01) reduced in the patients with primary SS and positively correlated to the reduced NK cell activity (r = 0.85, P = 0.0002). The permanently low NK cell activity of patients with primary SS appears therefore, at least in part, to be due to an impaired release of NKCF and not to a defective ability of effector cells to recognize and/or adhere to target cells.

Down-regulation of natural killer cell activity by autologous polymorphonuclear leucocytes. Role of indomethacin

It has been recently reported that neutrophils are involved in the regulation of NK cell activity. However, the mechanism of such regulation is unclear. The present study was designed to investigate the mechanisms involved in the regulation of NK cytotoxicity by human neutrophils. The role of indomethacin, an anti-inflammatory drug, in this interaction was studied. NK cells were purified from peripheral blood obtained from normal individuals. NK cell cytotoxicity was tested on K 562 cell line by Cr release assay. Autologous neutrophils obtained from peripheral blood were stimulated by opsonized zymosan either in the presence or absence of indomethacin. The role of neutrophil supernatant containing oxygen radicals and prostaglandins on NK cytotoxicity was examined. It was shown that supernatants from stimulated neutrophils significantly inhibited (P less than 0.05) the autologous NK cell cytotoxicity. The presence of indomethacin in the in vitro reaction mixture, or given orally to donors, partially or completely abolished the inhibitory effect of neutrophil supernatant. Indomethacin inhibited prostaglandin E2 release, and luminol-enhanced, myeloperoxidase-mediated chemiluminescence of activated PMN. Diafiltration of neutrophil supernatant showed that the inhibitory activity was present in the fraction containing molecules lower than 5,000 daltons. In conclusion, our findings indicate that down-regulation of NK cytotoxicity is mediated by prostaglandins produced by stimulated neutrophils and possibly by oxygen radicals.

Enhancement of human natural cytotoxicity by Plasmodium falciparum antigen activated lymphocytes

Mononuclear cells (MNC) isolated from malaria immune donors and from donors never exposed to malaria were stimulated in vitro with soluble purified Plasmodium falciparum antigens (SPag) or PPD. After 7 days of culture the proliferative response and the cytotoxic activity against the natural killer cell (NK cell) sensitive cell line, K562, were measured. It was found that SPag stimulation enhanced cytotoxic activity of MNC from donors whose lymphocytes exhibited a strong proliferative response to the antigen. MNC with low proliferative responsiveness showed increased cytotoxic activity if the MNC were preincubated with interleukin 2 (IL-2) for one hour before the start of the cytotoxic assay. SPag activation did not enhance the cytotoxic activity of MNC which did not respond to the antigen in the proliferation assay, and preincubation of these cells with IL-2 did not increase the activity. PPD stimulation enhanced the cytotoxic activity and induced strong proliferative responses in all MNC preparations. The role of NK cells in the protection against malaria is unknown, but they play a role in the protection against virus infection and in the immune surveillance against cancer. Our findings indicate that malaria antigens either directly or through the activation of immunoregulatory cells enhance the NK cell activity.

Depressed natural killer cell activity in acute myocardial infarction

Natural killer (NK) cell activity against K562 target cells was measured in patients within 24 h of acute myocardial infarction (AMI) and regularly thereafter for 6 weeks. NK cell activity was suppressed on days 1, 3, and 7 (P less than 0.01), day 14 (P less than 0.05) and at 6 weeks (P = 0.05) when compared to controls. Interferon, interleukin 2 and indomethacin enhanced NK cell activity on all days measured, but did not completely restore the defective NK cell activity. Serum from the patients did not suppress the NK cell activity of healthy mononuclear cells. The number of NK cells, identified as large granular lymphocytes (LGL), measured on days 1, 3, and 14 and at 6 weeks was not reduced in comparison to that of controls. Thus, the defective NK cell activity can be characterized as functional.

Increase in natural killer cell activity during diethylcarbamazine treatment of patients with filariasis

Two patients, one with Bancroftian filariasis and the other with onchocerciasis, and two healthy controls were treated with diethylcarbamazine (DEC). The natural killer (NK) cell activity of the two patients increased during DEC treatment to 2.5 and 2.8 times, respectively, while that of the controls remained unchanged. We conclude that the augmentation of baseline NK cell activity, as well as interferon- and interleukin-2-enhanced NK cell activity seen in the patients, is not a direct effect of DEC, but is related to the reaction to DEC in lymphatic filariasis and onchocerciasis.

Selective modulation of the CD4 molecular complex by Pseudomonas aeruginosa alkaline protease and elastase

The binding of monoclonal antibodies against CD4 was specifically inhibited by treatment of human CD4+ cells with either alkaline protease (AP) or elastase (Ela), purified from Pseudomonas aeruginosa. Binding of antibodies against CD3 (pan T), CD5 (pan T), CD8 (T suppressor/cytotoxic), HLA-ABC, HLA-DR, HLA-DQ, HLA-DP/DR, and beta 2 microglobulin was not inhibited by AP or Ela. Heat-inactivation of the proteases at 65 degrees C for 20 min or treatment with the metal chelator EDTA abolished the inhibitory activity of both proteases. These findings may serve to develop novel immunological methods for the isolation and study of the lymphocyte CD4 structure, which plays an important part in the immune response.

Inhibition of human natural killer cell activity by Pseudomonas aeruginosa alkaline protease and elastase

The present study was designed to examine the effect of Pseudomonas aeruginosa alkaline protease (AP) and elastase (Ela) on human natural killer (NK) cell activity in vitro. AP and Ela were found to inhibit NK cell function. Addition of alpha interferon and interleukin-2 did not abolish this inhibition of NK cell activity. Adhesion of effector to target cells was studied in a single-cell agarose assay of monocyte-depleted NK-cell-enriched cell populations. AP and Ela were shown to inhibit effector/target cell conjugate formation. Furthermore, AP and Ela inhibited the binding of the monoclonal antibody Leu-11, which reacts with the Fc receptor of NK cells. The inhibition of NK cell binding to the target cell by P. aeruginosa proteases is most likely due to proteolytic cleavage of the surface receptors involved in the binding of the effector cell to the target cell.

Methylprednisolone pulse therapy in severe acute asthma

In a group comparative double blind pilot study six asthmatic patients with an acute exacerbation of their disease were randomly treated with either methylprednisolone pulse therapy (MPPT) (1000 mg daily for 3 days) (n = 2) followed by placebo tablets, or standard doses of methylprednisolone (MP) (50 mg daily gradually decreased to zero over 3 weeks) (n = 4). The results showed that the effect of MPPT did not differ from that of standard doses of MP. MPPT has, however, the potential of being preferable to standard treatment with MP, because of easy administration and optimal patient compliance.

The in vivo effect of triethylphosphine gold (auranofin), sodium aurothiomalate and azathioprine on natural killer cell activity of patients with rheumatoid arthritis

Natural Killer (NK) cell activity was measured in 80 patients with rheumatoid arthritis (RA) grouped according to medication into 1) controls not in remission-inducing therapy, 2) patients treated with oral gold (auranofin), 3) parenteral gold (sodium aurothiomalate) and 4) azathioprine. Baseline, interferon (IF)-enhanced and interleukin 2 (Il-2)-enhanced NK cell activity of patients in the two gold groups did not differ from that of controls, while NK cell activity before and after exposure to IF and Il-2 was significantly suppressed in patients on azathioprine (p less than 0.01). The percentage of Large Granular Lymphocytes did not differ in the four groups while the percentage of Leu 11 positive cells and the total number of lymphocytes were significantly lower in the azathioprine group. Sixty out of 80 patients received nonsteroidal anti-inflammatory drugs (NSAID), whereas 20 did not. A comparison of these two groups showed no influence of NSAID on NK cell activity.

Inhibition of natural killer cell activity by antigen-antibody complexes

The natural killer (NK) cell activity of human peripheral blood mononuclear cells was found to be inhibited by precipitated tetanus toxoid anti-tetanus toxoid complexes (Te/aTe) as well as soluble Te/aTe. Preincubation of the immune complexes with protein A decreased the inhibition of NK cell activity. When mononuclear cells were preincubated with interferon (IF) or interleukin 2 (Il-2) before incubation with Te/aTe, the immune complex-induced inhibition was decreased, while IF or Il-2 added after incubation with the immune complexes had no effect. Using NK cell-enriched suspensions in a single cell agarose assay, the immune complexes were shown to inhibit NK cell activity by inhibiting the formation of effector/target cell conjugates.

Characterization of the in vivo and in vitro effects of indomethacin on human natural killer cell activity

The in vivo and in vitro effects of indomethacin on the natural killer (NK) cell activity against K 562 target cells were studied. In vivo administration of indomethacin, 3 X 50 mg for 7 days to normal donors did not influence baseline NK cell activity, which means that treatment with prostaglandin (PG) inhibitors can be allowed in studies on NK cell activity of persons with normal PG production. The NK cell activity of fresh mononuclear cells was boosted with pharmacological concentrations of indomethacin in vitro, while frozen cells were not. Our results indicate that indomethacin enhances the NK cell activity in vitro by blocking the prostaglandin production of monocytes, since monocyte depleted effector cells were not boosted by indomethacin.

Effects of chloroquine, mefloquine and quinine on natural killer cell activity in vitro. An analysis of the inhibitory mechanism

Natural killer (NK) cell activity against K 562 target cells was inhibited by pharmacological concentrations of chloroquine, mefloquine and quinine. The most potent were mefloquine and quinine. The drug-induced inhibition of the NK cell activity was abolished by addition of alpha-interferon (IF) or interleukin 2 (Il-2); preincubation of mononuclear cells with IF or Il-2 followed by addition of anti-malarial drugs decreased the inhibitory effects of the drugs. The drug-induced inhibition of the NK cell activity was not dependent on the presence of monocytes. Using monocyte depleted Percoll fractionated NK cell enriched populations in a single cell agarose assay, it was shown that the inhibitory effects of mefloquine, but not of chloroquine and quinine were due to an inhibition of the formation of effector/target cell conjugates.

Characterization of the in vitro effect of triethylphosphine gold (auranofin) on human NK cell activity

Pharmacological concentrations of auranofin (oral gold) modulated NK cell activity in a dose dependent biphasic manner. In vitro low doses enhanced NK cell activity, while high doses inhibited the NK cell activity. Sodium aurothiomalate (parenteral gold) had no effect. The effect of auranofin on NK cell function was irreversible and independent of the presence of monocytes. Neither IF nor Il-2 abolished the auranofin-suppressed NK cell activity. When NK cell activity was enhanced by low doses of auranofin, both IF and Il-2 could further boost the NK cell function. Using percoll fractionated NK cell enriched populations in a single cell agarose assays, it was shown that auranofin did not influence effector/target cell conjugate formation. The effect of auranofin on NK cell activity is thus due to an influence on the lytic step.

A longitudinal study of the influence of azathioprine on natural killer cell activity

Natural killer (NK) cell activity against K562 target cells was studied in six patients with definite or classical rheumatoid arthritis before and during treatment with azathioprine. Azathioprine induced suppression of NK cell activity, but treatment with azathioprine for 5-8 months was necessary before NK cell activity was completely suppressed. In vitro incubation of mononuclear cells from a healthy donor with azathioprine or 6-mercaptopurine in concentrations not reducing cell viability did not inhibit NK cell activity, nor did sera from patients treated with azathioprine for more than 6 months.

Characterization of the in vitro effects of glucocorticosteroids on NK cell activity

The NK cell activity of mononuclear cells as well as monocyte-depleted, Percoll-fractionated, NK cell-enriched effector cells against K 562 target cells was inhibited by methylprednisolone (MP) and hydrocortisone (HC) in a dose-dependent manner. The effector/target cell conjugate formation was studied in a single cell agarose assay, and it was shown that MP and HC partly inhibited the NK cell activity by inhibition of the adhesion of effector cells to target.

Interleukin 2 augmentation of the defective natural killer cell activity in patients with primary Sjögren's syndrome

Natural Killer (NK) cell activity against K562 target cells was measured in 21 female patients with primary Sjögren's syndrome (primary SS) and in 20 female normal controls matched for age. The in vitro effect of alpha-interferon (IF) and interleukin 2 (IL-2) on NK cell activity was examined and the percentage of large granular lymphocytes (LGL) in blood was measured. Median baseline NK cell activity in primary SS was 15.4% versus 24.4% in the controls (P less than 0.05). Median IF-enhanced NK cell activity in the SS group was 35.5% versus 49.6% in the controls (P less than 0.02). IL-2-enhanced NK cell activity was 35.5% versus 37.6% in the controls (n.s.) The proportion of LGL did not differ in the two groups. Median LGL/lymphocytes was 4.0% in the primary SS patients versus 4.5% in the controls (n.s.). We conclude that the defective NK cell activity in patients with primary SS is functional, as the number of LGL is normal. Further the NK cell activity off SS was restored by IL-2.

Baseline and interferon-enhanced natural killer cell activity in rheumatoid arthritis

Natural killer (NK) cell activity against the leukemia cell line K-562 was tested in 45 patients with rheumatoid arthritis (RA) who either had not received any remission-inducing drugs for more than 6 months or had received penicillamine for at least 6 months. Baseline NK cell activity and interferon (IF)-enhanced NK cell activity did not differ from that observed in 45 controls matched for age and sex, and neither NSAID (non steroidal anti-inflammatory drugs) nor penicillamine influenced NK cell activity. There was no correlation between NK cell activity and acute-phase reactants.

Bambuterol: effects of a new anti-asthmatic drug

Twenty-seven asthmatic outpatients were randomly treated with bambuterol 30 mg administered once daily before going to bed and sustained release terbutaline 10 mg twice daily in a 14 day, double blind cross over study. On all the parameters of bronchodilator effects, namely peak expiratory flow rate (PEF), use of extra beta-agonist puffs, asthma symptom score, and patient preference for one of the treatments, no statistically or clinically significant difference between the two treatments was found. No significant difference between treatments was observed in the number or severity of side-effects. Bambuterol administered once daily appears to be an effective anti-asthmatic treatment.

Methylprednisolone pulse therapy induced fall in natural killer cell activity in rheumatoid arthritis

Natural killer (NK) cell activity was studied in 8 patients with classic or definite rheumatoid arthritis (RA) by investigating the killing of K 562 cells by peripheral blood lymphocytes before, during, and after intravenous methylprednisolone pulse therapy (MPPT). MPPT produced a considerable fall in NK activity and after 3 months NK activity was less than half that before MPPT.