Enhancement of phagocytosis by interferon-containing preparations

A Multiparametric and High-Throughput Assay to Quantify the Influence of Target Size on Phagocytosis

Phagocytosis by macrophages represents a fundamental process essential for both immunity and tissue homeostasis. It consists in the uptake of pathogenic or cellular targets larger than 0.5 μm. For the biggest particles, the phagocytic process involves a massive reorganization of membrane and actin cytoskeleton as well as an important intracellular deformation all in a matter of minutes. The study of the role of the size of objects in their phagocytosis has led to contradictory results in the last decades. We designed a method using confocal microscopy, automated image analysis, and databases for fast quantitative analysis of phagocytosis assays. It yields comprehensive data on the cells and targets geometric and fluorescence intensity parameters, automatically discriminates internalized from external targets, and stores the relationship between a cell and the targets it has engulfed. We used two types of targets (solid polystyrene beads and liquid lipid droplets) to investigate the influence of size on the phagocytic uptake of macrophages. The method made it possible not only to perform phagocytic assays with functionalized droplets and beads of different sizes but to use polydisperse particles to further our understanding of the role of size in phagocytosis. The use of monodisperse and polydisperse objects shows that whereas smaller monodisperse objects are internalized in greater numbers, objects of different sizes presented simultaneously are internalized without preferred size. The total surface engulfed by the cell is thus the main factor limiting the uptake of particles, regardless of their nature or size. A meta-analysis of the literature reveals that this dependence in surface is consistently conserved throughout cell types, targets' nature, or activated receptors.

Effects of glycosylated hemoglobin levels on neutrophilic phagocytic functions

It is well established that diabetic patients with poor glycemic control have increased susceptibility to infections, but glucose levels have not been directly associated with this increase. The assessment of the effects of glycosylated hemoglobin (A₁ c) on the body’s ability to fight infections may be useful directly in establishing a link between elevated blood sugar and the risk of infections. A total of 127 subjects in Heart Pilot Study (HPS), sub-study of the Adventist Health Study 2 (AHS-2) completed a lifestyle, medical and food frequency questionnaire (FFQ) at baseline between 2013 and 2014. The A₁ c and phagocytic index (PI) were measured in the same blood sample and their associations were assessed using linear regression. Mean blood glucose (MBG) was estimated based on A₁ c levels using a standard formula. Three levels of MBG were used to compare prediabetic and diabetic ranges to the normal range. The PI is the average number of bacteria in the cytoplasm of 50 neutrophils, manually counted under a light microscope after the whole blood was briefly exposed to a standard dose of bacteria and stained. In multivariable analysis, we found that MBG in the prediabetic (117 to137 mg/dL) and diabetic (>137 mg/dL) ranges were associated with 12.9% (β= −0.129, 95% Cl: −0.30, 0.05) and 20.4% decrease in PI (β= −0.204, 95% Cl: −0.592, 0.184) compared to that, observed among those with normal MBG (p for trend=0.119). Elevated MBG levels contribute a decrease in the PI among those in the prediabetic and diabetic range compared to the normal range. Although our findings were not quite statistically significant due to low power which are clinically relevant in line with observations of an increased infections among diabetics. Further research on larger populations is needed.

Interferons: The pathways of discovery

This article analyzes the conceptual and technological context in which, over a period of 50 years, exploration of the biological and clinical significance of type I interferon has evolved. The elaboration of techniques for production and purification of mouse and human interferons and the establishment of laboratory-size production units have been of crucial importance in this process. Animal experiments have been invaluable for elucidation of mechanisms underlying the in vivo antiviral, anti-tumour and immunomodulatory potential of interferon, but have been of limited help to define the areas of clinical applicability. Proof of principle for applications as they are established today has come from clinical trials performed quite independently of evidence from animal experiments.

The inhibitory effect of Staphylococcus epidermidis slime on the phagocytosis of murine peritoneal macrophages is interferon-independent

The extracellular slime produced by Staphylococcus epidermidis has been shown to interfere with several human neutrophil functions in vitro, such as chemotaxis, degranulation and phagocytosis. Slime production has been suggested as a useful marker for clinically significant infections with coagulase-negative Staphylococcus. Since the main role of macrophages in defense mechanisms is phagocytosis, the effect of slime on the phagocytic activity of macrophages was investigated. The phagocytic activity of murine peritoneal macrophages treated with slime in vitro decreased in a dose-dependent fashion. A similar decrease was also observed in macrophages isolated from mice that had previously received intraperitoneal injection of slime. To investigate whether interferon also plays a role in this process, mice were treated with interferon or an interferon inducer, polyinosinic-polycytidylic acid (poly I:C), together with slime before macrophage isolation. The slime-suppressed phagocytic activity of macrophages was partially relieved by both agents, and the recovery effect of poly I:C in slime-suppressed phagocytosis of macrophages in vivo might be attributed to the increased interferon level in peritoneal fluid and sera. However, when slime was given to poly I:C-pretreated mice, the phagocytic activity remained suppressed. Thus, it appears that slime is able to suppress the phagocytic activity of macrophages regardless of the state of macrophage activation by poly I:C. The results suggest that the inhibition of phagocytosis by S. epidermidis slime may be independent from the activation of interferon.

Effects of interferon-alpha, beta, and gamma on the function of differentiated leukemic HL-60 cells induced by 1,25-dihydroxyvitamin D3

The differentiation of HL-60, a human leukemic cell line, into monocyte-like cells (D3-HL-60 cells) is induced by 1,25-dihydroxyvitamin D3 (D3). We examined the effects of interferon (IFN) treatment of D3-HL-60 cells on the expression of cell surface antigens, the phagocytic activity for fluorescent beads, production of oxygen radicals, and intracellular growth of Legionella pneumophila. Activation of D3-HL-60 cells with IFN-gamma, Beta, and alpha for 24 h significantly increased expression of CD16, CD36, CD71, and HLA-DR antigens. IFN-gamma markedly enhanced the phagocytic activity of beads in D3-HL-60 cells. There was no significant difference in phagocytic activity between cells exposed to IFN-alpha or beta and untreated D3-HL-60 cells. IFN-alpha, beta, and gamma enhanced production of oxygen radicals, including superoxide, by D3-HL-60 cells. Superoxide production was enhanced to the greatest degree by IFN-gamma, followed by IFN-beta and then IFN-gamma. Intracellular growth of L. pneumophila in D3-HL-60 cells was inhibited by interferons (IFN-gamma > beta > gamma). Similar results were obtained in human mononuclear cells. These data indicate that interferons can act as biologic response modifiers not only in human mononuclear cells but also in differentiated leukemic cells. Our results may have implications for the development of differentiation therapy for treatment of leukemia.

Treatment of Waldenstrom's macroglobulinemia with very low doses of alpha interferon

Waldenström's macroglobulinemia (WM) is a differentiated B-cell malignancy which is usually less responsive to standard chemotherapy because of low-proliferating cells. Interferon alpha has been shown to possess a therapeutic action in numerous B-cell malignancies including the early stage of chronic lymphocytic leukemia, multiple myeloma, follicular lymphoma and hairy cell leukemia. Fourteen patients with progressive WM were included in a pilot study using very low dose of interferon alpha-2a (1 Million Units 3 times a week). The mean duration of treatment was 10.3 months (range 2-44). Six of 14 (42%) patients presented an increase in the hemoglobin level (> or = 0.9 g/dL) and 4/14 (28%) had a substantial decrease of the monoclonal component (> or = 20% of reduction). Only two patients presented both types of response, while the others with an increase in the hemoglobin level had a slight decrease in the monoclonal component (MC) (1 patient), a stable MC (1 patient) or a slight increase of MC (1 patient). One additional patient had a 15% decrease of the MC with a stable hemoglobin level. Response was observed within 3 months with a median duration of 6 months. Treatment was stopped for 3 patients because of flu-like symptoms (2 patients), or thrombocytopenia (1 patient). Follow up was possible in 12 patients lasting up to a maximum of 30 months after discontinuing treatment. Seven patients died, including 4 with progressive disease, two of infection and one of cardiac failure. In the view of these results, very low dose of interferon alpha may constitute a new approach for treatment of some cases of WM.

Interferon-gamma induces phosphorylation of multiple small-molecular-weight proteins in U937 cells

This study examines the hypothesis that interferon-gamma (IFN-gamma) induces protein phosphorylation as part of the signal transduction pathway used to activate U937 cells. U937 cells labeled with 32Pi were treated with IFN-gamma, proteins were separated by two-dimensional polyacrylamide gel electrophoresis, and the pattern of protein phosphorylation was determined by autoradiography and computer-assisted two-dimensional densitometry. IFN-gamma (100 U/ml) induced phosphorylation of multiple proteins between 15 and 60 min, and the proteins were all dephosphorylated by 120 min. The pattern of proteins phosphorylated in the presence of ionomycin or PMA differed from that of IFN-gamma. Inhibition of protein kinase C activity by 1-(5-isoquinolinesulfonyl)2-methyl piperazine (H-7), inhibition of calcium-calmodulin-dependent protein kinase by N-(6-aminohexyl)-5-chloro-naphthalenesulfonamide (W-7), and inhibition of calcium redistribution by 8-(diethylamino)-octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) did not inhibit the majority of IFN-gamma-induced protein phosphorylation. These data indicate that IFN-gamma induces protein phosphorylation in U937 cells by activation of a kinase different from, or in addition to, protein kinase C or calcium-calmodulin-dependent kinase.

Clinical studies on cell-mediated immunity in patients with urinary bladder carcinoma: blastogenic response, interleukin-2 production and interferon-gamma production of lymphocytes

Patients with advanced malignant neoplasms have a variety of abnormal lymphocyte functions. We examined the PHA blastogenic response, interleukin-2 (IL-2) production and interferon-gamma (IFN-gamma) production of lymphocytes in 39 bladder cancer patients and 20 control subjects. Correlation between these parameters was also studied. IL-2 production was measured by 3H-thymidine-labelled CTLL-2 assay, and IFN-gamma production was measured by immunoradiometric assay using 2 mouse monoclonal antibodies. As a result, in high stage bladder cancer patients, the PHA blastogenic response, IL-2 production and IFN-gamma production were impaired. However, these parameters were not significantly different between low stage bladder cancer patients and control subjects. There was a significant correlation between the PHA blastogenic response and IL-2 production but no significant correlation between the PHA blastogenic response and IFN-gamma production.

Differential effect of alpha-interferons on CD4- and CD8-positive lymphocytes in chronic hepatitis B virus carriers

alpha-Interferons are an effective therapy in a proportion of chronic hepatitis B virus (HBV) carriers. The mode of action is almost certainly dependent upon immune modulation in addition to direct antiviral effects but the precise mechanism is unknown. To investigate whether the aberrant T-cell activation present in HBV carriers was responsive to interferons, we have studied the in vitro effect of alpha-interferons on Tac antigen expression and DNA synthesis as early and late markers of T-cell activation, respectively. At a concentration of 1000 U/ml the effect of alpha-interferons on Tac expression was contrasting in the two major T-cell subsets; there was enhancement of Tac expression on CD4-positive T-cells but inhibition of the CD8-positive subset. However, there was no overall effect on lymphocyte proliferation, perhaps as a consequence of the differential effect of alpha-interferons on the early T-cell activation marker. At higher concentration, however, the enhancement of T-cell activation was less clear, indicating that the concentration range that supports T-cell activation is narrow. Such subtle differential effects on T-cell activation may be accompanied by more profound effects on immune function and this may be one way in which alpha-interferons are of value in chronic HBV infection.

Effect of recombinant mouse interferon-beta on acute and latent herpes simplex infection in mice

The antiviral effect of recombinant mouse interferon-beta (rMuIFN-beta) on herpes simplex virus type 1 (HSV-1) in experimentally infected mice was examined at several stages of infection as a model for the treatment of human HSV infection. Recombinant MuIFN-beta protected mice from lethal intraperitoneal challenge with virulent HSV-1 strains. The in vitro reactivation of HSV from latently infected trigeminal ganglia was also suppressed by treatment with rMuIFN-beta. Thus, rMuIFN-beta was effective against HSV-1 during acute infection and during in vitro reactivation of latent HSV. However, rMuIFN-beta was not effective in preventing the establishment of latent infection, or in eliminating a previously established latent infection.

Disseminated Kaposi's sarcoma in AIDS: histogenesis-related populations and influence of long-term treatment with rIFN-alpha A

Lesions (n = 19) of cutaneous Kaposi's sarcoma in different stages of development were obtained from 13 patients with acquired immunodeficiency syndrome (AIDS), and studied by light and electron microscopy. Six additional biopsies from 4 patients treated with recombinant alpha A interferon were obtained after treatment. Varying amounts of two proliferating cell populations were found: (1) Large cells showing cytologic and histochemical characteristics of endothelial cells. They were seen in close proximity to normal vessels, forming new vascular structures and large aggregates found in papular and nodular lesions. (2) Smaller spindle-shaped cells, probably of pericytic origin. They appeared in bundles and fascicles in the papillary dermis of the cutaneous Kaposi's sarcoma lesions and, in part, gave origin to thin-walled, bizarre-shaped vessels that show incomplete lumina proliferating from the upper to the deep dermis and are surrounded by extravasate erythrocytes and siderophages. After long-term systemic treatment with recombinant alpha A interferon, the endothelial type of tumor cell aggregates mostly disappeared, whereas most of the spindle-shaped pericytic-like cells were still present. Our findings lead us to suggest that some cellular product may, as a promoter factor, induce the proliferation and growth of endothelial cells. This factor may be blocked by alpha A interferon and cause regression of endothelial cell proliferation observed in AIDS patients undergoing long-term systemic therapy.

Interferon-induced protein synthesis inhibits endocytosis of bacteria in epithelial cells

Previous studies have shown that human leukocyte interferon (IFN), IFN-gamma, and recombinant (r) IFN-alpha-A protect cultured human cells against the invasiveness of salmonellae, shigellae, and enteroinvasive Escherichia coli. To differentiate between effect on endocytosis and adhesiveness, HEp-2 cells were pretreated with cytochalasin B to block endocytosis, and thereafter treated with IFN. Although a significant reduction of adhesion of bacteria to HEp-2 cells was observed, this reduction was far too small to explain the total reduction of bacterial invasiveness. Thus, the anti-invasive effect of IFN on HEp-2 cells is due mostly to inhibition of endocytosis. The IFN effect was not expressed at 4 degrees C, and the ribosomal 60S subunit inactivators, cycloheximide, abrin, and shigella toxin, completely blocked the expression of the IFN-induced anti-invasive state of the cell. Thus, the IFN effect is dependent on continuous ribosomal activity. Our results indicate that the major effect of IFN on bacterial invasiveness is on endocytosis, and that the action is mediated through the effect of IFN-induced protein synthesis.

The effect of recombinant interferon-gamma on human monocyte-derived macrophages

The effect of recombinant interferon-gamma (rIFN-gamma) on human macrophage functions was studied, using monocytes which had matured to macrophages within hydrophobic containers. Following exposure to rIFN-gamma, the number of surface-expressed specific IgG-binding sites was increased. This increase was restricted to high-affinity Fc receptors (FcR), however; low-affinity FcR were not increased in number. Exposure to rIFN-gamma led to an enhanced chemiluminescence (CL) signal in the presence of luminol and a variety of respiratory burst stimuli, such as zymosan, phorbol 12-myristate 13-acetate or IgG-sensitized sheep erythrocytes (EA). In contrast, phagocytosis of EA was markedly depressed in rIFN-gamma-treated cells. Both increase in CL response and decrease in phagocytic activity were manifest after 1 day of treatment and were more pronounced after 2 days. While 5 U/ml of rIFN-gamma was an insufficient dose, 50 to 5000 U/ml yielded significant dose-dependent changes in both functional assays. Thus, using rIFN-gamma as a biological response-modifier, FcR expression and FcR-mediated CL can be dissociated from FcR-mediated phagocytosis.

Mechanism of differences in pathogenicity between two variants of a laboratory strain of herpes simplex virus type 1

The mechanisms responsible for the difference in neurovirulence to inbred mice between two variants of the Miyama strain of herpes simplex virus type 1 (HSV-1) were studied. After intraperitoneal (i.p.) inoculation, the +GC (LPV) variant reached the spinal cord and the brain, and caused death. Conversely, the -GCr variant lacked the ability to gain access to the central nervous system (CNS) after the same route of infection and failed to kill susceptible mice. The initial virus growth after i.p. inoculation, as indicated by the number of infective centers (ICs) produced by the peritoneal exudate cells (PECs), was compared between these two variants. The virulent +GC (LPV) strain induced much more ICs than the attenuated -GCr variant. When the attenuated variant was preinoculated i.p. 24 hr before the challenge inoculation with the virulent variant by the same route, the production of ICs by the pathogenic variant was highly inhibited, and growth of this variant did not occur in the CNS. Thus, mice were protected from lethal infection by the virulent variant by preinoculation with the attenuated one. Moreover, the ability of mice to resist i.p. infection by HSV-1 was shown to be age-dependent.

Enhanced production of gamma-interferon by therapy with parenteral OK-432 and alpha-interferon in patients with head and neck cancer

Although the drug OK-432 can induce the release of gamma-interferon (IFN-gamma), the serum concentrations of IFN-gamma produced are very low. We studied the effects of combining OK-432 with alpha-interferon (IFN-alpha) on the endogenous production of IFN and the postoperative courses of patients with oral cavity cancers. Forty patients operated on for head and neck cancers were studied. Each patient was given an injection of OK-432 1 week after surgery. Between 10 and 14 days later, a combination of OK-432 and IFN-alpha was given to assess the effects of the concomitant use of IFN-alpha on IFN production. In 18 of the 30 patients given a large dose of IFN-alpha (3 or 5 X 10(6) IU/mg protein), IFN production induced by OK-432 was enhanced. A small dose of IFN-alpha (7 X 10(3) IU) did not enhance the action of OK-432. OK-432 also induced the release of both endogenous IFN-gamma and IFN-alpha, and the production of both types of IFN was enhanced by the concomitant administration of parenteral IFN-alpha. Next, 50 patients operated on for oral cavity cancers were given OK-432 or a combination of OK-432 and IFN-alpha for 4 months, and their postoperative courses were followed for 2-5 years. The clinical courses were better in the combined therapy group than in the group given OK-432 alone.

A sensitive radioimmunoassay for alpha-interferon: circulating alpha-interferon-like substance in the plasma of healthy individuals and rheumatoid arthritis patients

A radioimmunoassay for circulating alpha-interferon (IFN alpha) has been developed using lymphoblastoid IFN alpha. The assay was specific for IFN alpha, and did not cross-react with IFN beta, IFN gamma, or ACTH, while it was specifically inhibited by recombinant IFN alpha. The radioimmunoassay (y) correlated linearly with the virus inhibition assay (x), with a regression line of y on x of y = 0.659x + 245 (u) (P less than 0.01). alpha-Interferon-like substance (IFN alpha-LS) was extracted and concentrated from plasma either by silicic acid or by antibody immunoadsorption. Serial dilutions of plasma and extracted samples of plasma showed dilution curves identical to those of standard IFN alpha, suggesting the presence of endogenous IFN alpha in human plasma. The circulating IFN alpha-LS of healthy individuals aged 20 to 45 was 0.207 +/- 0.055 ng/ml in males (n = 48) and 0.172 +/- 0.076 ng/ml in females (n = 34). Gel filtration studies on a Sephadex G-75 column suggested that circulating IFN alpha-LS exists in a fragmented form, inactive in virus inhibition assays, in the plasma of healthy individuals. The finding may help explain why biological IFN alpha is often undetectable in the plasma of healthy donors, yet is detectable by radioimmunoassay. Circulating IFN alpha-LS in the plasma of healthy individuals declined gradually with age. IFN alpha-LS was significantly decreased in the plasma of rheumatoid arthritis patients, when compared with the value found in the age and sex-matched healthy controls and in osteoarthritis patients (P less than 0.0001). The decrease was related neither to treatment nor to disease activity. IFN alpha-LS was, however, not decreased in the plasma of vasculitis patients. Decreased IFN alpha-LS in rheumatoid arthritis may be important from pathogenetic and therapeutic standpoints.

Aspartate-assisted immune stimulation: its importance in antitumor and antiviral protection

Immune stimulators such as Corynebacterium parvum (CP) are useful for antitumoral and antiviral therapy. However, the immune trigger cannot be reactivated without adversely affecting the disease. We have tried to amplify the results yielded by a single injection of CP by using either interleukin-2 (IL2) or aspartate salts (ASP). In the present report, we show that IL2 has no detectable clinical effect. In contrast, the addition of an ASP salt increases the antiviral and antitumoral protection afforded by the CP-induced trigger. Moreover, treatment using only ASP slightly protects against tumor development and significantly increases antiviral resistance during experimental encephalomyocarditis (EMC) infection. This ASP-assisted CP immune stimulation improves antitumoral resistance even when ascitic tumors have already developed. In the latter case, tumor regression can even be detected. Since ASP increases T-cell cytotoxicity in vitro and aggravates spontaneous T-cell lymphomas in AKR mice, the involvement of T-cell-mediated immunity may explain antitumoral and antiviral effects. We propose the use of this therapeutic model for human cancer therapy, and possibly for treating AIDS.

Role of interferon in streptococcal infection in the mouse

In previous studies, we have shown the rapid in vitro induction of IFN gamma from human T cells by highly purified peptic extracts of M proteins from Streptococcus pyogenes. The present report extends these in vitro studies and shows that a mixture of both alpha/beta and gamma IFN were present in spleen cell homogenates after in vivo treatment with M protein wild-type (M+) or mutant (M-) S. pyogenes strains. The levels of bacterial-induced IFN were found to be greater in M+ treated animals. Additional studies in vivo showed that pretreatment of mice with heat-killed M+ S. pyogenes organisms significantly protected mice to pneumococcal infection compared to similarly treated M- or control animals (P less than 0.001). Further, antibodies to mouse IFN alpha/beta and antibodies specific to a synthetic N-terminal peptide of mouse IFN gamma enhanced the death of animals due to pneumococcal infection and blocked the protection observed in animals previously treated with heat-killed M+ organisms. Most importantly, treatment of mice with either type of IFN alone enhanced the survival of mice to levels similar to that observed by treatment with M+ organisms (P less than 0.05). The results strongly suggest that IFN can play a crucial role, directly or indirectly, in controlling infection by Streptococcus pneumoniae and perhaps other streptococci.

Role of alveolar macrophage- and lung T cell-derived mediators in pulmonary sarcoidosis

The process of granuloma formation in the lung is mediated by an intimate interaction between macrophages and T cells, and this interaction provides the appropriate environment for granuloma formation and the development of fibrosis. Much of this process of granuloma formation and fibrosis appears to be triggered by the release of immune mediators by alveolar macrophages and lung T cells.

In vitro effects of lymphoblastoid interferon on lymphocyte activation and cell-mediated cytolysis in patients with chronic hepatitis B virus infection

In addition to a direct anti-viral effect, interferons have important immunological properties including effects on cell-mediated immunity and antibody production as well as cell-mediated cytolysis. In chronic hepatitis B virus infection the host immune system is important for the elimination of replicating virus and in addition to directly inhibiting hepatitis B virus replication, interferons may affect host immune responses. We investigated the effect of lymphoblastoid interferon in vitro on lymphocyte activation and cell-mediated cytolysis in patients with chronic hepatitis B virus infection. The proliferative response to the mitogen PHA was significantly impaired in patients compared to controls. In addition supernatants of cultured mononuclear cells from patients stimulated with PHA contained less interleukin-2 activity than controls while the proportion of stimulated mononuclear cells expressing the interleukin-2 receptor was also reduced in patients. Prior incubation with 10(3) U ml-1 lymphoblastoid interferon increased both interleukin-2 activity and interleukin-2 receptor expression in patients and controls, although in patients the response was less marked. In contrast the proliferative response was unaffected. Natural killer cell activity against K562 cells was similar in patients and controls which in both groups was significantly augmented by prior incubation with 10(3) U ml-1 lymphoblastoid interferon; the increase was inversely proportional to baseline activity. In contrast incubation of target or effector cells with interferon did not augment T-cell cytotoxicity against autologous hepatocytes. The effects of lymphoblastoid interferon in vitro, were modest, but subtle changes in immunological status in addition to a direct effect on viral replication may be relevant to eventual clearance of the hepatitis B virus.

Streptococcus pneumoniae cocultured with fibroblasts enhances both interferon production and cytotoxic activity by lymphocytes

Cell-mediated cytotoxicity against normal human fibroblasts was dependent on treatment of the fibroblasts with Streptococcus pneumoniae. Both spontaneous and interferon (IFN)-enhanced lymphocytes killed human foreskin (HFS) or skin muscle cells cocultured with S. pneumoniae five- to eightfold more than control nontreated cells. Based on Percoll gradient centrifugation, the cytotoxic effector cell migrated like a large granular lymphocyte. The human IFN produced from mixtures of HFS cells, lymphocytes, and S. pneumoniae was observed to be both a mixture of IFN-alpha and IFN-gamma and in an amount 500 times greater than that observed with lymphocytes on HFS cells alone, and it was in an amount 12 times greater than when lymphocytes and bacteria were cultured together. A mixture of antibodies to IFN-alpha and -gamma added to cocultures of fibroblasts and bacteria blocked the killing of fibroblast targets by lymphocytes (47 versus 13%). Thus, endogenously produced IFN was essential for the effective killing of the fibroblasts. Treatment of HFS cells with IFN before bacterial treatment protected the HFS cells from lysis by lymphocytes. The observation that normal diploid cells exposed to bacteria can be killed by lymphocytes suggests that natural cytotoxic cells are active at the site of bacterial infection and conceivably play roles in defense or pathogenesis.

Interferon affects the formation of adhesion plaques in human monocyte cultures

When monocytes isolated from human blood adhere to glass substratum, actin- and vinculin-containing punctate plaques rapidly appear at the ventral surface of the cells. We show here that highly purified human leukocyte interferon (IFN) can inhibit formation of these adhesion plaques in a dose-dependent manner. Complete inhibition was obtained when 300 IU/ml IFN were added into the cell-seeding medium. Plaques already formed in the absence of IFN were only partially affected by subsequent addition of IFN into the culture medium. Prevention by IFN of the formation of the adhesion plaques was associated with loosened attachment of the cells to the substratum. Effect of IFN on cellular morphology was complex. At higher doses, IFN added to the cultures within 24 h of seeding almost completely inhibited the differentiation of monocytes to macrophages and most of the cells remained rounded. At lower doses, however, an enhancement of the bipolar spreading was seen and the end result was a culture with predominantly elongated fibroblastoid cells. The latter cells, unlike the fibroblastoid cells in untreated monocyte-macrophage cultures, were completely devoid of the actin plaques, while the reorganization of vimentin-type intermediate filaments took place in a normal manner. These results further support the view that the actin- and vinculin-containing plaques have a role in mediating firm adherence of human monocytes to growth substratum.

Effect of human gamma interferon on invasiveness of Salmonella typhimurium in HEp-2 cell cultures

The effect of human gamma interferon (HuIFN-gamma) on the invasiveness of Salmonella typhimurium, Shigella flexneri and Yersinia enterocolitica serotype 0:3 in HEp-2 cell cultures was examined. The intracellular and extracellular bacteria were identified by a combination of Nomarski differential interference contrast microscopy and UV incident light microscopy applied on the same microscope. Pretreatment of HEp-2 cells with HuIFN-gamma reduced in a dose dependent manner the number of S. typhimurium bacteria per cell and the proportion of cells containing bacteria. Maximum inhibitory effect was observed with approximately 10 units per ml of HuIFN-gamma. The inhibitory effect of interferon as well as the antiviral effect was eliminated when the preparation was neutralized with monoclonal anti-interferon globulin and was acidified to pH 2. Murine gamma interferon did not influence invasiveness of S. typhimurium. No effect of interferon was observed when the bacteria were incubated in cell cultures at 4 degrees C. Invasiveness of S. flexneri and Y. enterocolitica was not influenced by treatment of cells with HuIFN.

Interferon enhances the susceptibility of virus-infected fibroblasts to cytotoxic T cells

Interferon (IFN) pretreatment of low-passage mouse embryonic fibroblasts (MEF) infected with lymphocytic choriomeningitis virus or vaccinia virus rendered these cells two to three times more susceptible to lysis by H-2 restricted, virus-specific cytotoxic T lymphocytes (CTL) than control, virus-infected MEF. The increased sensitivity to lysis correlated with increased expression of surface H-2 antigens, but not viral antigens. Continuous cell lines already highly sensitive to CTL-mediated lysis and already expressing high levels of surface H-2 antigens were unaffected by IFN pretreatment. These results suggest that IFN treatment, by increasing surface H-2 levels, may result in increased association of surface H-2 and virus antigens, leading to enhanced recognition and lysis by virus-specific CTL.

Effects of interferon-alpha/beta and interferon-gamma preparations on phagocytosis by mouse peritoneal macrophages

The influence of murine alpha/beta-interferon (Mu IFN-alpha/beta) and murine gamma-interferon (Mu IFN-gamma) preparations on the attachment and ingestion phase of phagocytosis by mouse peritoneal macrophages (MPM) was studied. A non-opsonized strain of Escherichia coli, IgG-opsonized E. coli, and sheep erythrocytes opsonized with IgG (E-IgG) and IgM plus complement factor C3b (E-IgMC) were used as test particles. Pretreatment of MPM with 10(2)-10(3) U/ml of Mu IFN-alpha/beta for 24 h enhanced both attachment and ingestion of bacteria or erythrocytes mediated by the non-specific receptor, the Fc receptor, or the C3b receptor. Higher concentrations had no such effects. In contrast, treatment of MPM with 10(1)-10(2)U/ml of Mu IFN-gamma suppressed attachment and ingestion of non-opsonized and IgG-opsonized E. coli and of E-IgG by 10-40%. Mu IFN-gamma did not influence attachment and ingestion of E-IgMC. The effects were neutralized by specific anti-IFN antiserum. The data indicate that the IFN effect on phagocytic activity is, at least to a large extent, due to modifications of the surface receptors.

Functions of human neutrophilic granulocytes after in vivo exposure to interferon alpha

The ability of neutrophilic granulocytes to phagocytize yeast particles and to reduce Nitro Blue Tetrazolium at rest and on activation with bacterial stimuli was monitored in 32 patients receiving treatment with human interferon alpha. The ability of these cells to attach to and ingest yeast particles was not altered to any major extent during 1 year of interferon treatment. In most patients, the Nitro Blue Tetrazolium-reducing activity increased after the first injection of interferon. During prolonged treatment with interferon alpha, 1 week to 1 year, granulocytes activated with bacteria exhibited a reduced Nitro Blue Tetrazolium activity in most patients.

Influence of interferon on human monocyte to macrophage development

The effect of interferon-alpha (Wellferon) on human monocyte to macrophage maturation in vitro has been investigated. Cell volume and three markers, acid phosphatase, leucine aminopeptidase, and phagocytosis, which increase with maturation, have been studied employing recently developed flow cytofluorometric techniques. The increase in cell volume and in the expression of all three markers was inhibited in a dose-dependent manner in monocyte cultures given 50-300 U/ml of interferon within 2 hr of culture initiation. An initial dose of 300 U/ml of interferon, removed from the cultures after 24 hr, was as effective in inhibiting the development of each of the markers as three 100 U pulses on three consecutive days, and as effective as 300 U interferon left in throughout the culture period. Histogram analysis of marker expression indicated that all monocytes, and not a subpopulation, were affected by the interferon. Cytotoxic activity of freshly isolated monocytes rapidly decayed when the cells were cultured under standard maturation conditions. The addition of interferon to the cultures prevented the loss of this activity while also preventing the development of more mature cells. It appears that maintenance of the cytotoxic state is one influence of interferons; however, it may be that these cells have also been directed toward alternate pathways of macrophage differentiation.

Immunological and chemotherapeutic prevention and control of oncogenic viruses

Computed tomographic (CT) and surgical findings were correlated retrospectively in 51 patients with preoperative diagnoses of prolactin-secreting pituitary microadenomas. Twenty-four had microadenomas at surgery. Twenty-eight had identifiable discrete lesions. Of these, 18 had microadenomas and 10 did not; these two groups could not be distinguished reliably. Six patients with proven microadenomas had normal CT scans. Focal hypodense lesions, sellar floor erosion, infundibulum displacement, gland height greater than 8 mm, and an abnormal diaphragma sellae configuration are neither sensitive nor specific findings of microadenoma. A significant number of patients with proven microadenomas had few or none of these abnormalities. Thus, recognition of prolactin microadenoma is seldom possible by CT alone, even with high-resolution direct coronal imaging.

Induction of human gamma interferon by structurally defined polypeptide fragments of group A streptococcal M protein

The presence of interferon (IFN) has been demonstrated previously (i) in fluids obtained from the middle ears of children with Streptococcus pneumoniae infections, (ii) from the serum of mice injected intraperitoneally with either S. pneumoniae or Streptococcus pyogenes, and (iii) from human lymphoid cell cultures treated with a variety of bacteria. In this study, we showed that highly purified peptic extracts of three different serotypes of group A streptococcal M protein (pep M5, pep M6, and pep M24) stimulated human peripheral leukocytes to produce IFN. IFN production was apparent by 10 h and peaked 24 h after exposure. Dose-response experiments indicated that IFN could be detected in cultures treated with concentrations of M protein as low as 6 micrograms/ml, whereas maximum IFN production occurred at a concentration of 200 micrograms/ml. The IFN had antigenic and physicochemical characteristics of IFN-gamma. Preliminary leukocyte fractionation studies revealed that the IFN-producing cell was a nonadherent lymphocyte with receptors for sheep erythrocytes (T cell). Rabbit antisera specific for these structurally defined polypeptide fragments of streptococcal M protein (pep M5, pep M6, and pep M24) blocked IFN induction by each of the polypeptides. The data suggest that the different serotypes of streptococcal M protein may induce IFN by a common structural determinant shared by each of the polypeptide fragments tested.

Enhancement of base hexose-monophosphate shunt activity of human polymorphonuclear leucocytes by human beta-interferon

The effect of human fibroblast interferon (HuIFN-beta) on the HMP shunt activity of human polymorphonuclear leucocytes (PMNLs) was examined. HuIFN-beta caused an increase in the base level of the HMP shunt activity. No significant increase was observed in the same PMNLs stimulated with opsonized zymosan. The augmentation of this property, generally associated with antimicrobial and cytotoxic properties of the PMNLs, may be of potential importance in host defences against microbial and malignant diseases.

Inhibition of cell division and antibody secretion by murine alpha/beta interferon: effects on plasmacytoma and hybridoma lymphoid cells

Murine alpha/beta interferon (IFN) inhibited the growth of myeloma cells in vitro. Independently of the cell growth inhibition, IFN also reduced the number of antibody secreting myeloma cells as measured by haemolytic plaque assay. The sensitivity of both MOPC 315 plasmacytoma cells and 4F4 hybridoma cells varied, though not to the same extent, depending on the dose of IFN used and the duration of exposure. Inhibition of PFC activity was observed after one day of IFN treatment while inhibition of cell growth was not detected until Day 2 of incubation. A dose of 20 u/ml IFN had no effect on the growth rate of MOPC 315 cells but with 100 u/ml the inhibition of growth was virtually complete. In contrast, an inhibition of PFC activity was observed at all the concentrations tested. The cell growth and PFC activity of 4F4 hybridoma cells, on the other hand, were both inhibited by IFN when used at concentrations as low as 1.25 u/ml. Incubation with higher concentrations of IFN resulted in a progressive reduction in cell growth and PFC activity of 4F4 cells, however to a lesser degree of inhibition compared to that observed with MOPC 315 cells. For example, although virtually 70% of MOPC 315 PFC could be inhibited by culture for two days in the presence of 100 u/ml, it was necessary to use 1,250 u/ml IFN for 4 days incubation before the similar level of PFC inhibition was achieved with 4F4 cells. IFN treatment resulted in an increase in both cellular volume and protein content and this effect was prevented when IFN was previously neutralised by a specific antiserum. IFN-treated cells also showed an inhibition in the incorporation of 3[H]-thymidine but no alteration in the rate of utilization of 35[S]-methionine, when compared with an equal number of control cells.

Interferon--present and future prospects

The interferons are a group of proteins that have inspired a new era of investigation into biological modification. The interferons are now divided into subgroups characterized by chemical means and correspond to different biological responses which can be observed in terms of the inducer used, and the timing of the response. Identified originally as antiviral agents when homologous cell systems were treated prior to infection, new studies have extended these observations to place the interferons in a central role as a strong force in the regulation of immunologic responses. A marriage of interferonology and cell immunology is enlarging both our understanding of the action of these proteins and our ability to follow the course of an illness and eventually to control its outcome . Genetic engineering has provided a way to process quantities of interferon and provided the molecular sequence of all three classes of IFN including a model of the active site for IFN-alpha. The offshot of the technology developed to study the intracellular processes after interferon treatment have already led to increased sensitivity to detect virally treated diseases. Both the variety of the interferon inducers and the scope of parasites in which it can exert its influence provide a frontier of biological investigation which has at the root of its nature the very secret of life. In addition to cellular phenomena, the positive effects on tumor-bearing organisms and the ill effects on infant animals highlight the potential power of the interferons.

Interferon decreases production of hydrogen peroxide by macrophages: correlation with reduction of suppressive capacity and of anti-microbial activity

Mouse peritoneal macrophages (M phi) expressed enhanced tumoricidal activity upon in vitro stimulation either with the lymphokine M phi-activating factor (MAF) or with fibroblast interferon (IFN-beta). In contrast, M phi suppressive activity on lymphoproliferation was not affected by MAF pretreatment, but was drastically reduced or abolished by IFN-beta. Catalase, the enzyme involved in the destruction of hydrogen peroxide (H2O2), did significantly decrease M phi suppressive capacity but had no effect on M phi tumoricidal activity. Analysis of the phagocytosis-dependent H2O2 production by IFN-beta-treated M phi demonstrated a strong impairment of the oxygen metabolite release, which strictly paralleled the decreased M phi suppressive capacity. On the other hand, MAF did not modify H2O2 release by M phi. Studies on M phi antibacterial activity against Salmonella typhimurium, a function thought to depend upon H2O2 production, showed that exposure of M phi to IFN-beta significantly impaired their bactericidal and bacteriostatic capacity, again in close correlation with the decrease in H2O2 production. Thus, IFN-beta appears as modulating both suppressive and antibacterial capacities of M phi through reduction of their oxygen metabolism, whereas regulation of M phi anti-tumour activity is possibly controlled by different mechanisms.

The interferons

An overview of the interferons is presented. A description of something of what is known about them is given, including: their genes; their protein structures and characteristics; their mechanisms of actions; and their varied biological effects emphasising particularly their immunomodulatory actions. Finally, a brief summary is made of the current status of human clinical studies that have been conducted with interferons in the oncological and viral fields, mentioning also recent findings in patients who have the acquired immunodeficiency syndrome (AIDS).

Effect of interferon on human neutrophilic granulocytes

The in vitro influence of interferon (IFN) on various functions of human neutrophilic granulocytes was investigated. It was observed that the attachment and engulfment of opsonized yeast particles by human neutrophilic granulocytes were enhanced after preincubation in vitro with IFN for 30 min. The same result was obtained whether the particles were opsonized with fresh normal serum (complement) or with specific antibodies. However, after incubation of the granulocytes with IFN for 3 h the phagocytosis rate was somewhat decreased. Nitroblue tetrazolium (NBT) reduction by resting granulocytes was slightly, although not significantly, increased by preincubation with IFN for 30 min, but their NBT reduction during phagocytosis of E. coli was significantly increased. No major effects of preincubation with IFN were observed on spontaneous or random migration of granulocytes.

Interferon production by leukocytes infiltrating the lungs of mice during primary influenza virus infection

Lung fluids and leukocytes were obtained from unprimed C3H mice by transpleural lavage at intervals after infection with influenza A/Hong Kong/68 virus and were tested for interferon activity. Lavage fluid interferon titers correlated directly with lung virus titers and with initial increases in leukocyte yields from infected lungs. In contrast to cultured lymph node cells from infected animals or leukocytes from lungs of uninfected mice, washed leukocytes obtained from the lungs of mice infected 2 to 6 days earlier produced interferon spontaneously in culture. The physiochemical, biological, and antigenic properties of both the interferon in lavage fluids and that produced by lung lavage leukocytes were similar and characteristics of alpha interferon. Fractionation studies indicated that macrophages and T lymphocytes were primarily responsible for the interferon produced in culture. The early presence and significant numbers of interferon-producing leukocytes in infected lungs suggests that these cells have an early role in defense against influenza virus infection.

Effect of beta-interferon on in vitro spreading of mouse peritoneal macrophages

The influence of a homologous beta-interferon preparation (MuIFN-beta) on in vitro adherence and the early and late phase of spreading of mouse peritoneal macrophages (MPM) was tested. MPM from mice pre-treated with 2 x 10(4) U of MuIFN-beta did not differ in ability to adhere to a glass surface, compared to controls. However, when the early phase of MPM spreading was tested, the percentage of spreading cells from mice injected with MuIFN-beta or Newcastle disease virus was almost doubled as compared to MPM from control mice. To assay the late phase of MPM spreading, MPM from unstimulated mice were seeded on glass surfaces and cultivated with or without MuIFN-beta for 1-24 hours. MuIFN-beta enhanced the spreading of MPM with maximal difference 3-5 hours after seeding. The effect was dose-dependent up to 10(2)U per ml of MuIFN-beta. The effect was also species--specific and neutralized by addition of anti-MuIFN-beta globulin. Morphometric measurements of the spreading of MPM indicated that after 24 hours of MuIFN-beta treatment the mean area occupied was 50 per cent larger than that of controls.

Interferon treatment of murine Meth-A sarcoma cells: effects on the malignant phenotype and expression of tumor-specific and H-2 antigens

A virus-free methycholanthrene-induced sarcoma (Meth-A) in BALB/c mice was grown in culture and treated with purified mouse interferon (alpha and beta mixture) prior to testing for oncogenicity in the host animal. Use of interferon in vitro caused growth inhibition, but not cytotoxic effects; such effects were fully reversible upon interferon removal from the system. There was a significant decrease in tumor incidence in mice challenged with interferon-treated cells, but this could be overcome by sufficiently increasing the number of cells in the inoculating dose. By transplanting these BALB/c sarcoma cells into Sprague-Dawley nude mice, the effects of interferon could be negated. Since these mice have an unaltered activity of NK cells, the results suggest that NK cells do not play a major role in rejection of the Meth-A tumor, but that the reduction in tumor incidence is dependent on the presence of functional T cells. Interferon caused a detectable reduction in the expression of the tumor-specific transplantation antigen (TSTA) associated with Meth-A cells, but increased the expression of H-2 antigens. It has recently been shown that H-2 antigens play a role in host recognition of the TSTA of methylcholanthrene-induced sarcomas. It is suggested that the increased expression of H-2 antigens on interferon-treated Meth-A cells could lead to an increased frequency of recognition by T-cells.

Effect of human leukocyte interferon on phagocytic activity of polymorphonuclear leukocytes

The effect of homologous leukocyte interferon HuIFN on the phagocytic activity of human polymorphonuclear (PMN) leukocytes was examined. The PMN cells were obtained from healthy donors and they were grown on coverslips. Escherichia coli labelled with 32P-orthophosphate was phagocytized in the presence of fresh homologous serum during a 15 min incubation period. PMN cells pretreated with interferon for at least 3 hours ingested more bacteria as compared to untreated controls. This effect was dose dependent, in maximal effect being obtained with 10(3) units per ml. The effect was species specific and it was neutralized by antiinterferon globulin.