Interferon--a major regulator of natural killer cell-mediated cytotoxicity

Effect of IFNbeta and anti-IFNbeta antibodies on NK cells in multiple sclerosis patients

We analysed longitudinally the numbers of CD3-CD16+ (natural killer cells, NK) and CD3-CD57+ cells (a subset of NK) in 15 IFNbeta1b- and 12 IFNbeta1a-treated relapsing-remitting multiple sclerosis (RRMS) patients. IFNbeta1b (Betaferon)-treated RRMS patients showed a rapid and marked reduction in the number of both NK subsets which started 1 month after therapy initiation, and reached highest significance after 3 months (P=0.000); however, figures reverted to pre-treatment values following the appearance of anti-IFNbeta antibodies. In IFNbeta1a (Avonex)-treated RRMS patients, the decrease in both CD3-CD16+ and CD3-CD57+ cell number was slower but more persistent; anti-IFNbeta antibodies were only rarely detected in these patients, and at lower titers than in IFNbeta1b-treated ones. Our findings suggest that NK cells might be one of the major immunological targets of IFNbeta-based treatments.

The cell and molecular biology of hepatic fibrogenesis. Clinical and therapeutic implications

Much has been learned in the past 2 decades about the cellular and molecular mechanisms underlying hepatic fibrogenesis and about potential therapeutic approaches in patients with liver disease. The central event in fibrogenesis seems to be the activation of hepatic stellate cells. Stellate cell activation is characterized by several important features, including enhanced matrix synthesis and a prominent contractile phenotype, processes that probably contribute to the physical distortion and dysfunction of the liver in advanced disease. It is important to emphasize that the factors controlling activation are multifactorial and complex. The extracellular matrix is a dynamic, active constituent of the fibrogenic response and undergoes active remodeling, including synthesis and degradation. Effective therapy for hepatic fibrogenesis will probably also be multifactorial, based on the basic mechanisms underlying the fibrogenic process. The most effective therapies will probably be directed at the stellate cell. Approaches that address matrix remodeling (i.e., by enhancing matrix degradation or by inhibiting factors that prevent matrix breakdown) may be effective.

Genetic differences in the age-associated decrease in inducibility of natural killer cells by interferon-alpha/beta

Natural killer (NK) cells, which are important in viral infections and anti-tumor activity, show reduced cytotoxicity in aged mice. The mechanism(s) for this age-related decline in NK activity has not been clearly established. We assessed changes in NK cytotoxicity in splenocytes and peripheral blood mononuclear cells after interferon (IFN)-alpha/beta stimulation in adult (6 months) and aged (22-26 months) C57Bl/6, Balb/c, and (Balb/c x C57Bl/6)F1 mice. Aged C57Bl/6 and Balb/c mice had a significantly reduced IFN-alpha/beta-stimulated NK cytotoxicity compared to adult mice. In contrast, adult and aged F1 mice showed similar NK cytotoxicity after IFN-alpha/beta induction. The decreased ability of NK cells of aged mice to respond to induction by IFN-alpha/beta was not due to a requirement for an increased amount of IFN or for a longer period of treatment with IFN. Further, this decreased response did not appear to be the result of suppressive activity of adherent cells or T cells. While the percentage of NK cells (NK1.1+) was similar in adult and aged mice, the (CD8+ NK1.1+) subset of NK cells was significantly increased in aged mice. Importantly, the percentage of CD8+ NK1.1+ cells was inversely related to the cytotoxicity observed after IFN-alpha/beta treatment.

IL-10 enhances NK cell proliferation, cytotoxicity and production of IFN-gamma when combined with IL-18

Previous studies have shown that IL-10 inhibits the accessory cell functions required for production of IFN-gamma by T cells and NK cells. Our results show that although IL-10 did not induce the production of IFN-gamma by NK cells, it did enhance the ability of IL-18 to stimulate NK cell production of IFN-gamma. In addition, IL-10 augmented NK cell proliferation and cytotoxic activity when combined with IL-18. However, IL-10 did not affect the ability of IL-12 to stimulate NK cells to produce IFN-gamma or proliferate, but there was an additive effect with IL-12 to increase NK cell cytotoxic activity. Interestingly, the type I IFN, whose receptors (R) are related to the IL-10R, also enhanced the effects of IL-18 on NK cell production of IFN-gamma and NK cell cytotoxicity. The ability of IL-10 to elevate the production of IFN-gamma appeared to be specific for NK cells since IL-10 had no effect on the production of IFN-gamma by Th1 clones stimulated with IL-18 or IL-12 in the presence of a monoclonal antibody specific for CD3. These latter results correlated with lower mRNA levels for the alpha and beta chains of the IL-10R in Th1 cells than observed in NK cells. Thus, the ability of IL-10 and IL-18 to up-regulate NK cell function, but not Th1 cell activity, appears to be based on expression of the IL-10R.

Exercise and cellular innate immune function

Epidemiological evidence suggests a link between the intensity of exercise and infectious and neoplastic disease. One likely way by which exercise exerts its effect on cancer and infection is by altering the function of the immune system. Cells of the innate immune system (i.e., macrophage [Mphi], natural killer [NK] cell, and polymorphonuclear neutrophils [PMN]) are first-line defenders against cancer and infectious disease by nature of their phagocytic, cytolytic, and antimicrobial properties. The purpose of this review is to define the role of cells of the innate immune system (i.e., Mphi, PMN, and NK cells) in infection and cancer, present current information regarding the effects of acute and chronic exercise on the quantification and functional activities of these cells, and briefly to discuss potential mechanisms as to how exercise affects these cells and describe how these changes may potentially affect susceptibility to infection and cancer. The effects of exercise on the number, functions, and characteristics of cells of the innate immune system are complex and are dependent several factors, including 1) the cell function or characteristic being analyzed; 2) the intensity, duration and chronicity of exercise; 3) the timing of measurement in relation to the exercise bout; 4) the dose and type of immunomodulator used to stimulate the cell in vitro or in vivo; and 5) the site of cellular origin. Further studies are needed to determine whether the exercise-induced changes in immune function alter incidence or progression of disease. Likewise, the mechanisms as to how exercise alters innate immune function are as yet unresolved.

Natural killer cell activity in patients with Graves' disease and Hashimoto's thyroiditis

Natural killer (NK) cell activity of peripheral blood lymphocytes (PBL) against k562 human tumor cell targets was studied in patients with Graves' disease and Hashimoto's thyroiditis. NK activity was measured in a standard 4-hour 51chromium (Cr) release assay. Cytotoxicity was expressed as lytic units (LU)/10(6) PBL. Significantly decreased NK cell activity was demonstrated in both groups of patients, with mean (+/- SE) lytic units of 10.3 (+/- 9.1) and 13.3 (+/- 10.3) for patients with Graves' disease and Hashimoto's thyroiditis, respectively, compared with 36.0 (+/- 26.3) for age- and sex-matched normal subjects. When patients with Graves' disease were analyzed according to their thyroid status; NK activity was significantly depressed in (1) hyperthyroid patients before treatment; (2) hyperthyroid patients receiving antithyroid therapy; and (3) euthyroid patients receiving antithyroid therapy, compared with normal subjects. Graves' disease patients who were hypothyroid after radioactive iodine therapy or thyroidectomy had normal NK activity. No significant differences between hyperthyroid and euthyroid patients or between hypothyroid patients and normal subjects were demonstrated. NK activity in patients with Graves' disease did not correlate with serum levels of thyroxine, the presence or severity of ophthalmopathy, or titers of serum thyroid antibodies. In patients with Hashimoto's thyroiditis there was no correlation between NK activity and goiter size, titers of antithyroid antibodies, or thyroid status. These findings suggest that depression of NK activity in both disorders is secondary to abnormalities of thyroid hormone secretion, although an effect of the underlying autoimmune reactions has not been excluded.

Enhancement of the anti-tumor immune response using a combination of interferon-gamma and B7 expression in an experimental mammary carcinoma

In recent years, tumor immunotherapy has begun to exploit the emerging knowledge of the mechanisms of T cell activation to enhance the immune responses to tumors. However, many tumors, despite genetic modification to express co-stimulatory molecules or cytokines, are not readily rejected due to their inherently poor immunogenicity. In the present study, we tested whether expression of the co-stimulatory ligand B7-1 and the immunostimulatory cytokines interferon gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) by a mammary carcinoma (SM1) would sufficiently augment its immunogenicity to obtain rejection and immunity. Our findings demonstrate that expression of B7, IFN-gamma, or GM-CSF alone, or co-expression of B7 and GM-CSF did not result in rejection of SM1. However, co-expression of B7 and IFN-gamma was sufficient to result in regression of SM1 tumors by a CD8+ T cell-dependent mechanism. Rejection of the B7/IFN-gamma-expressing SM1 tumor resulted in protection from rechallenge not only with the unmodified SM1 tumor but with another syngeneic mammary tumor. Our data support the idea that although B7 expression alone may not be sufficient for rejection of certain tumors, the immune system may be stimulated to mount an effective anti-tumor immune response by the co-expression of both the co-stimulatory ligand and a cytokine.

Antituberculosis drug-induced hepatotoxicity. The role of hepatitis C virus and the human immunodeficiency virus

Until recently it was thought that age greater than 35 yr was the main risk factor for the development of drug-induced hepatitis (DIH) in patients receiving antituberculosis therapy. We conducted a study to determine whether infection with either the hepatitis C virus or the human immunodeficiency virus (HIV) were significant risk factors for the development of DIH in patients receiving antituberculosis therapy. Our study consisted of two parts. In the first part, 134 consecutive patients admitted for the treatment of tuberculosis (TB) were followed for the development of DIH. All of these patients were also screened for the presence of hepatitis C and HIV. In the second part of the study, those patients who were hepatitis C positive and who developed DIH on repeated reintroduction of the anti-TB drugs were offered a liver biopsy. If active inflammation, which may be suggestive of hepatitis C infection, was present on the biopsy specimen, treatment with alpha-interferon was begun and the anti-TB drugs were subsequently reintroduced. During the 18 mo of the study, 22 patients developed DIH. The relative risk of developing DIH if the patient was hepatitis C or HIV positive was fivefold and fourfold, respectively (p < 0.05). If a patient was coinfected with both hepatitis C and HIV the relative risk of developing DIH was increased 14.4-fold (p < 0.002). In the treatment part, four patients were treated with alpha-interferon, and all were able to undergo the reintroduction of anti-TB therapy without reoccurrence of DIH. Infection with hepatitis C and HIV are independent and additive risk factors for the development of DIH during TB therapy. The treatment of hepatitis C with alpha-interferon may allow the reintroduction of anti-TB agents in those who previously developed DIH when exposed to these drugs.

Alpha interferon treatment in myasthenia gravis: effects on natural killer cell activity

The efficacy of recombinant interferon-alpha (rIFN alpha), on natural killer (NK) cell cytotoxic activity, CD3+, CD4+, CD8+, CD56+, HLA-DR+ lymphocyte counts, anti-acetylcholine receptor antibody (AChR Ab) levels, single fibre electromyography findings (SFEMG) and clinical course were evaluated in patients with myasthenia gravis (MG). During the IFN alpha treatment (3 mu, subcutaneous, 3 times a week), NK cell cytotoxicity and CD4+/8+ ratio increased, NK cell count remarkably decreased, and no significant clinical or SFEMG changes were observed. This preliminary open study in MG patients has demonstrated enhanced NK activity per unit NK cell after IFN alpha therapy. Although lymphocyte phenotypes and NK function approached normal levels during therapy, a higher dose of IFN alpha may be required for a significant clinical response. It has been also concluded that 6 months of IFN alpha therapy seems to be safe in MG, though in patients with malignancy, IFN alpha may cause increased autoimmunity, AChR positivity and MG.

Protective effects of a novel quinone derivative, E3330, on mouse hepatitis virus (MHV)-induced chronic hepatitis in athymic nude mice

In this experiment, we examined the protective effects of a novel quinone derivative, E3330, on MHV-2cc-induced chronic hepatitis in athymic nude mice for up to 3 weeks after virus infection. The daily dose of 25 mg/kg b.w. suppressed the viral replication in the liver and the progression of hepatic lesions. The expansion of small focal lesions at 1 week after viral inoculation (WAI) was suppressed at 2 WAI, and the lesions were still small at 3 WAI in E3330-administered group, whereas small focal lesions at 1 WAI were expanded at 2 WAI to fuse with each other at 3 WAI in the control group. E3330 therefore showed protective effects on MHV-2cc-induced chronic hepatitis in athymic nude mice, but further studies are needed to analyze the mechanism.

Both human alpha/beta and gamma interferons upregulate the expression of CD48 cell surface molecules

We have established a cDNA library from interferon (IFN)-treated human lymphoblastoid Daudi cells and made use of differential screening to search for yet unidentified IFN-regulated genes. In the course of these studies, we have isolated a human cDNA coding for the glycosyl-phosphatidylinositol-linked (GPI) membrane glycoprotein CD48 (TCT-1, Blast-1). Various studies demonstrated that the murine CD48 is the predominant counterreceptor for the mouse CD2 and is involved in the regulation of T cell activation. Since the murine CD48 is functionally homologous to the human CD2 ligand LFA-3 (CD48), the function of the human CD48 remains unknown. In this report, we show that both Hu-IFN-alpha/beta and Hu-IFN-gamma increase the level of CD48 mRNA and upregulate the expression of CD48 proteins at the surface of various cultured human cell lines. However, the IFN have no effect on the expression of LFA-3. In addition, we show that IFN increase CD48 expression on peripheral blood mononuclear CD3+, CD14+, and CD19+ subpopulations. These data suggest that in addition to modulation of the conventional MHC class I and class II-restricted interactions, the IFN might promote MHC-unrestricted interactions of target cells with the immune cells by inducing the expression of the cell surface CD48 molecule.

An evaluation of the accuracy of four ELISA methods for measuring natural and recombinant human interferon-g

We describe an evaluation of four ELISA methods, including three commercial kits, for measuring recombinant and natural human interferon-g (hIFN-g). Using a panel of samples, including well-characterized reference standards, we compared relative quantification between assays, within assays and, where possible, the absolute accuracy of quantification as compared to other analytical methods. The four assays generated markedly different results; up to an almost 60-fold difference between the highest and lowest values for one sample. The differences between assays were not necessarily predictable. No single correction factor could be determined to correct results from one method to another across the panel of samples tested. We conclude that investigators should be diligent to revalidate commercial methods before depending on such methods and resultant data.

Elevated peripheral blood natural killer cells are effectively downregulated by immunoglobulin G infusion in women with recurrent spontaneous abortions

PROBLEM

We investigated the hypothesis that elevated peripheral blood natural killer cells (NK) are decreased by immunoglobulin G infusion (IVIg) therapy in women with recurrent spontaneous abortions (RSA) and elevated NK cells.

METHODS

Seventy-three women with RSA and elevated NK cells received IVIg therapy (400 mg/Kg/day for 3 days ever 4 wks) and anticoagulation treatment. Peripheral blood immunophenotype assay by flow cytometry was done prospectively prior to and 7 days after first IVIg therapy, every 2 wks until 20 wks gestation and then monthly. Controls were 95 women with RSA and normal NK cells who received anticoagulation treatment.

RESULTS

(1) 86.3% of women with elevated NK cells who received the IVIg and anticoagulation therapy had a successful pregnancy outcome; (2) Peripheral blood CD56+ NK cells and CD56+/16+ NK cells were significantly suppressed 7 days post IVIg infusion (P < 0.0005); (3) Pre-IVIg infusion levels of other lymphocyte subsets were not different as compared with those of 7 days post-IVIg therapy; (4) Women who delivered a liveborn infant with IVIg therapy demonstrated downregulation of peripheral blood NK cells (CD56+, CD56+/16+) during early pregnancy when compared to women who miscarried the index pregnancy (P < 0.05); (5) Women with normal NK cells who miscarried while on anticoagulation therapy demonstrated significantly elevated CD56+ NK cells during early pregnancy as compared with that of women who delivered a liveborn infant (P < 0.05); (6) CD19+ B cells were significantly downregulated during pregnancy in women with anticoagulation and IVIg therapy when compared to women with anticoagulation therapy (P < 0.05).

CONCLUSION

Downregulation of NK cells in women with RSA is associated with a favorable pregnancy outcome. Peripheral blood NK cells (CD56+, CD56+/16+) are effectively suppressed after IVIg therapy. Women with RSA and high NK cells benefit from IVIg therapy and experience suppression of CD56+ and CD56+/16+ NK cells.

Synergistic inhibitory effects of interferon-alpha and 5-fluorouracil in meningioma cells in vitro

We have investigated the effects of interferon-alpha (IFN-alpha) and 5-fluorouracil (5-FU) on meningioma cells in two different culture systems, evaluated by the uptake of radiolabelled methionine. With both IFN-alpha and 5-FU an inhibitory effect on the uptake of radiolabelled methionine by the meningioma cells was demonstrated, and we found a synergistic inhibitory effect with a combination of IFN-alpha and 5-FU. To obtain a maximal inhibition of cell metabolism without causing cell toxicity, we were able to decrease the dose of 5-FU by simultaneously adding IFN-alpha. Our results suggest that a combined treatment of IFN-alpha and 5-FU may be a successful alternative for patients with inoperable meningiomas. A novel in vitro positron emission tomography technique was used for the study of metabolic changes in tumour cells caused by drug treatment, which is complementary to conventional cell culture techniques.

Interferon-alpha hybrids

The alpha-interferons (IFN-alpha) belong to a family of polypeptides comprising several subtypes. Using recombinant DNA technology, it has been possible to create IFN hybrids that provide novel combinations of the amino acid residues from the parental protein sequences. They have been used to study structure-activity relationships of IFN-alpha and interactions with the IFN-alpha receptor, and to create analogs of natural IFNs with novel properties for potential therapeutic application. The biological data obtained with these hybrids are now evaluated in terms of the published structural and homology models of IFN-beta and -alpha.

Interferons and other cytokines in head and neck cancer

The use of cytokines in head and neck cancer is increasingly under investigation. Clinical trials have tested the interferons, interleukin-2 and other cytokines as single agents and in various combinations. The addition of interferon to the cisplatin and 5-fluorouracil (5-FU) regimens (with and without leucovorin) has been explored. A randomized international trial comparing cisplatin and 5-FU with cisplatin, 5-FU and interferon-alpha 2b is in progress.

In vitro combined effects of a triazene compound and interferon-beta on natural immunity against lymphoblastoid cells: studies at effector and target cell level

It was shown that Dacarbazine and other triazene compounds render murine leukemias highly immunogenic and susceptible to natural immunity (NI). In addition a pilot clinical study revealed that Dacarbazine can be cytotoxic for bone marrow blasts in patients with acute non-lymphoblastic leukemias through a mechanism that could be, at least in part, of immunological origin. However triazenes depress antigen-dependent responses and NI, whereas interferons, including interferon-beta (IFN), antagonize drug-induced impairment of NI. Therefore the complex interaction between triazenes and IFN on NI effector (i.e. NK) lymphocytes and human target lymphoblastoid cells has been investigated. The results show that: (a) IFN increases NK activity and antagonizes the depressive effects of methyl-triazene-benzoic acid (MTBA, an in vitro active triazene compound) on the NK function; (b) a lymphoblastoid cell line exposed to multiple in vitro treatments with MTBA, shows increased growth rate, augmented chemoresistance to MTBA, and higher susceptibility to NI than parental cells; (c) as expected IFN pretreatment down-regulates the susceptibility of lymphoblastoid cells to NK effectors; (d) however a net "therapeutic gain" was found if the overall influence of MTBA+IFN on target and effector cells is considered.

Drug-mediated changes in the susceptibility of human lymphoblastoid B cells to NK-mediated cytolysis: studies with a triazene compound

Previous studies have shown that treatment of leukemia-bearing mice with triazene compounds results in a profound alteration of the immunological properties of leukemic cells. These cells become highly immunogenic and susceptible to natural immunity (NI). Moreover, in a pilot clinical study, dacarbazine was found to suppress bone marrow blasts in patients with acute non-lymphoblastic leukemias. The cytotoxic mechanism involved could be of biochemical and immunological origin as well. Therefore experiments were carried out to test whether triazenes could influence the susceptibility of blast cells to human NI effector lymphocytes (represented, at least in part, by NK cells). The results obtained with target Epstein-Barr virus (EBV)-immortalized B cells and effector cells of different donors, showed that: (a) multiple in vitro treatments of lymphoblastoid cells with methyl-triazene-benzoic acid (MTBA, a triazene compound active in vitro), gave origin to lines that were more resistant than the parental lines to the antitumor effects of MTBA; (b) MTBA-treated lines were more susceptible (37.5% of cases), or less susceptible (31.2% of cases) to NI than parental cells. Effector lymphocytes of various donors recognized different changes in susceptibility to natural killer (NK)-mediated lysis; (c) treatment of parental or MTBA-treated lines with interferon-beta reduced target cell susceptibility to NK-mediated cytolysis, but increased NK activity and lymphoblast chemosensitivity to MTBA.