Effects of human interferon preparations on neutrophil function

Modulation by interferons of human neutrophilic granulocyte migration

The effect of various interferons (IFN) on neutrophilic granulocyte (PMN) random and directed migration is incompletely understood. We, therefore, investigated PMN migration with a novel micropore membrane technique. No chemotactic effect of either 10-10000 U/ml IFN-alpha or IFN-beta, or 1-1000 U/ml IFN-gamma was observed on PMN isolated from normal human venous blood. However, when present on both sides of the micropore membrane, all the IFN (1000 U/ml IFN-alpha and IFN-beta, 100 U/ml IFN-gamma) inhibited both random and directed migration toward zymosan-activated serum (ZAS). IFN-gamma was the most potent inhibitory agent and produced an inhibition of about 30%. When the bacterial peptide fMLP was used as a chemoattractant, IFN-gamma also depressed chemotaxis. Taking the reduced random migration of IFN-gamma treated cells into account, however, chemotaxis per se-toward both ZAS and fMLP-was not significantly affected. Random migration and directed migration assessed simultaneously with PMN from the same donor were clearly correlated for both control and IFN-gamma treated cells, suggesting that a general antimotility effect of IFN-gamma might explain both reduced random migration and chemotaxis. The antimotility effect of IFN-gamma was not dependent on protein synthesis or on tyrosine kinase activity. In fact, inhibition of tyrosine kinase with herbimycin A increased the ZAS-stimulated motility of both control and IFN-gamma-inhibited PMN. In conclusion, our data indicate that IFN depress both random and directed PMN migration by mechanisms that do not involve protein synthesis or protein tyrosine kinase activity.

"Discordant" influence of equine recombinant interferon-beta 1 on the cytotoxic capacity of equine polymorphonuclear neutrophils and peripheral blood mononuclear cells in vitro and in vivo

The influence of recombinant equine interferon-beta 1 (rEqIFN-beta 1) on mononuclear cells of peripheral blood (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) was tested under in vitro and ex vivo conditions. Treatment of equine PBMC with IFN in vitro enhanced the antibody-independent cytotoxicity (AICC) and antibody-dependent cytotoxicity (ADCC) while there was no significant effect on the cytotoxic capacity of PMN treated with rEqIFN-beta 1 in vitro. Ex vivo there was an increased capacity of AICC and ADCC upon single or multiple application of rEqIFN-beta 1 in PMN, only. Treatment with rEqIFN-beta 1 thus induced an increased cellular cytotoxicity in vitro and in vivo but in different populations of peripheral blood cells. In vivo rEqIFN-beta 1 causes a pronounced activation of PMN but not of PBMC as cytotoxic effector cells. This might be achieved indirectly, e.g., by cytokines produced by IFN-sensitive cells.

Further studies of the defective stimulus-response coupling for the oxidative burst in neutrophils in polycythemia vera

We have previously reported that the chemiluminescence (CL) response of neutrophils (PMN) from patients with polycythemia vera (PV) was abnormally low when induced by surface receptor-dependent stimuli, fMLP and leukotriene B4, but normal when elicited by phorbol myristate acetate (PMA). This study documents that this discrepancy of the CL response to fMLP and PMA remained over a wide range of stimuli concentrations, was not due to iron-deficient PV cells and was also observed with the nitroblue tetrazolium assay. Moreover, another surface receptor-dependent agonist, platelet-activating factor, conferred a significantly lower CL response in PV PMN relative to controls. Treatment with alpha interferon or GM-CSF, to increase fMLP receptors, resulted in a similar enhancement of fMLP-induced CL in PV and controls. CL was normal when induced by a number of non-surface receptor-dependent stimuli. Release of lactoferrin in response to fMLP (and PMA) was normal (as was previously reported fMLP-induced chemotaxis and adherence). Thus, this defect is highly specific for oxidative metabolism, and localized to discrete step(s) of the stimulus-response coupling for fMLP, leukotriene B4 and PAF, but conceivably not due to impairment of the dynamic interaction of fMLP with its receptor.

Recombinant human leukocyte interferon modulates neutrophil function in vitro

Recombinant human interferon-alpha 2 (rIFN-alpha A) was evaluated as a modulator of neutrophil functions. Neutrophils treated with rIFN-alpha A for 1 h in vitro showed reduced chemiluminescence (CL) and aggregation in response to phagocytosis. In contrast, when certain soluble stimuli [f-met-leu-phe (fMLP) or leukotriene B4] were used, rIFN-alpha A treatment conferred a doubling of CL. This was paralleled by a similar increase in superoxide anion production and a 56% increase of release of beta-glucuronidase and lysozyme. The NBT test showed that IFN treatment did not increase the number of responding neutrophils. However, there was a significant increase in the displaceable binding of fML[3H]P. Enzyme release, aggregation, and CL in response to other soluble stimuli, the ionophore A23187 and phorbol myristate acetate were unaffected by IFN treatment. Likewise, chemotaxis was not affected. Thus, phagocytosis-associated events and aggregation were hampered by rIFN-alpha A whereas secretory responses to receptor-dependent soluble stimuli were augmented. The mechanism for the latter is most likely dependent on the observed modulation of binding of fMLP to its receptor.

Serum interferon activity in inflammatory bowel disease. Arachidonic acid release and lipoxygenation activated by alpha-class interferon in human neutrophils

Serum interferon (IFN) of alpha-class was studied in 64 consecutive patients, 26 with Crohn's disease, 38 with ulcerative colitis, and in 34 healthy volunteers. Detectable IFN-alpha in 10 patients was associated with a moderate to severe activity of chronic inflammatory bowel disease (CIBD). However, 19 of 28 patients (68%) with activity in their disease did not have elevated IFN-alpha levels. The three groups, ulcerative colitis, Crohn's disease, and healthy volunteers did not reveal any statistically significant difference in serum IFN-alpha, as four of 34 healthy controls without intercurrent infections had elevated levels as well. Possible effects of alpha, beta, and gamma classes of IFN on endogenous arachidonic acid (AA) release and metabolism in human neutrophils was investigated in a substudy. IFN-alpha caused a dose-dependent release of AA from phospholipids and metabolism of a modest fraction of leukotriene B4 (LTB4) and 5-hydroxyeicosatetraenoic acid (5-HETE) at doses reaching a maximum of 100 IU/ml. IFN of the beta and gamma classes did not exert such effects. Addition of complement 5a to cells activated by IFN-alpha caused induction of increased 5-lipoxygenase activity with unchanged release of AA. As only 16% of all CIBD patients had elevated IFN-alpha levels as compared to 12% among the group of healthy volunteers, IFN-alpha does not seem to be of importance for the perpetuation of the inflammatory reaction in ulcerative colitis or Crohn's disease, and other factors may therefore be responsible for activation of the inflammatory cells to production of LTB4 and 5-HETE.

Modulation of granulocyte oxidative response by recombinant interferon alpha 2 and gamma

Interferon (IFN) has been described to influence various cellular functions. In this study we investigated whether the oxidative response of polymorphonuclear leukocytes (PMN) is also affected by IFN. In order to exclude the possible influence of impurities in IFN preparations, only recombinant human IFN alpha 2 or gamma were used. Lucigenin-dependent chemiluminescence (CL) of PMN was measured to assess the production of oxygen radicals. IFN gamma at a concentration of more than 10 ng/ml elicited a minimal CL response in PMN. When PMN were incubated with IFN gamma for 1 h and then stimulated with chemotactic peptide f-met-phe (FMP), zymosan-activated serum (ZAS), zymosan particles, or phorbol-myristate acetate (PMA), the CL response was increased as consequence of the generally enhanced oxidative metabolism. IFN alpha 2 showed no such effect at any concentration tested. A 5-min pretreatment with IFN gamma decreased the ZAS response but did not affect the reaction to the other stimuli. The possibility of a generation of IFN by PMN during the assay could be excluded as no IFN activity could be detected in an antiviral assay after stimulation of PMN for 6 h with PolyI X PolyC, LPS, ConA, C. parvum, PMA, zymosan, or FMP. The modulation of granulocyte activity by IFN gamma may be important in the regulation of the anti-inflammatory response of PMN.

Granulocyte-activating mediators (GRAM): I. Generation by lipopolysaccharide-stimulated mononuclear cells

We undertook a study to determine whether cytokines exist which are responsible for the activation of polymorphonuclear neutrophilic granulocytes (PMN) besides the already well-known stimuli. Lucigenin-dependent chemiluminescence was used to measure human PMN activation. Addition of supernatants from mononuclear cells stimulated with bacterial lipopolysaccharide produced a long-lasting activation of granulocytes. Induction of chemiluminescence was dose-dependent and inhibitable by superoxide dismutase. Fractionation of mononuclear cells by adherence to plastic dishes or counterflow elutriation proved that monocytes were able to generate granulocyte-activating mediators (GRAM). Production of GRAM was dependent on the dose of the stimulus and appeared to be maximal after 24 h of incubation. Addition of cycloheximide resulted in significantly decreased release of GRAM. Partial characterization of the activity showed GRAM to be heat-labile and sensitive to trypsin, indicating a protein nature of GRAM. The activity fractionated into 2 distinct peaks, one corresponding to 60 kD and another below 10 kD. The interleukin 1 activity did not appear to co-fractionate with GRAM. Evidence presented suggests that the activity corresponds to factors unlikely to have been described previously.

Enhancement of defective monocyte function during immunotherapy with recombinant interferon

The influence of immunotherapy with high dose (50 X 10(6) units/m2) recombinant leukocyte A interferon on blood monocyte functions was studied in eight patients with bronchogenic carcinoma. Monocyte chemotactic responsiveness (MCR) was initially depressed (9.8 +/- 1.6 cells/field) compared to healthy controls (17.6 +/- 5.1 cells/field), P less than 0.01. Recombinant interferon was administered three times weekly, and after 7 days a significant improvement in chemotaxis was observed (16.6 +/- 3.0 cells/field), P less than 0.05. The MCR remained normal until cessation of interferon therapy (greater than 1 month). Phagocytic and candidacidal activities were normal in the patients and were not influenced by treatment with interferon. In conclusion, high dose recombinant interferon given to cancer patients caused a normalization of defective blood monocyte chemotaxis, which persisted for greater than 1 month.