Biochemical properties of polymorphonuclear neutrophils from venous blood and peritoneal exudates of rabbits

Measurement of circulating red cell volume using biotin-labeled red cells: validation against 51Cr-labeled red cells

BACKGROUND

Anemia is a serious problem in the fetus and preterm infant. To investigate the physiology and pathophysiology of anemia and to assess responses to blood transfusions or erythropoietin therapy, measurement of circulating red cell volume would be useful. Because the standard 51Cr method exposes the subject to radiation, a method of measuring circulating red cell volume without radiation exposure, sufficiently sensitive for use in fetuses and infants, was developed.

STUDY DESIGN AND METHODS

In 10 healthy adults whose body mass ranged from 56.8 to 115.9 kg, aliquots of autologous red cells were labeled with biotin or with 51Cr, mixed, and transfused intravenously. Circulating red cell volume was measured in posttransfusion blood by quantitating the in vivo dilution of biotinylated red cells. Biotinylated red cells were detected by two methods: 1) 125I-streptavidin and 2) fluorescein-labeled avidin with flow cytometry.

RESULTS

Circulating red cell volume measured by 125I-streptavidin detection agreed well with that measured by 51Cr (slope = 1.07, y-intercept = -97, correlation = 0.987). Similarly, circulating red cell volume measured by flow cytometry agreed well with that measured by 51Cr (slope = 1.05, y-intercept = -20, correlation = 0.987).

CONCLUSIONS

Circulating red cell volume measured by the use of biotin with either 125I-streptavidin or flow cytometry agrees with that measured by 51Cr. Each system provides a method of performing these studies without exposing the subject to radiation.

[14C]cyanate labeling of sheep red cells: covalent binding to hemoglobin continues in vivo for a day

The sheep is a useful model to study fetal and newborn physiology including perinatal erythropoiesis and red cell kinetics. A practical, economical method for measuring red cell survival (RCS) in sheep would be very valuable. However, 51Cr is unsatisfactory, and suitable alternatives have not been published. In the course of investigating [14C]cyanate as a label for sheep red cells, we observed continued covalent labeling over 24 h in vivo that was great enough to introduce a substantial artifact into two commonly used parameters of RCS: posttransfusion recovery (PTR24) and time to 50% decrease (T50) when referenced to time zero. In a simulation of in vivo conditions, the amount of 14C bound to Hb increased 26 +/- 6% (mean +/- 1 SD, n = 11) over 24 h. To investigate the mechanism of the increasing 14C bound, acid-acetone extraction, molecular sieve chromatography, and density gradient separation were used separately or in combination to quantitate intracellular free 14C and 14C covalently bound to intracellular proteins. Free 14C decreased as protein-bound [14C]cyanate increased. These studies provide evidence that covalent binding of [14C]cyanate to intracellular Hb continues in vivo for the first 24 h and that the source of the increase is intracellular free [14C]cyanate. We conclude that 1) PTR24 cannot be accurately determined by [14C]cyanate unless labeled red cells are incubated before infusion to allow the cyanate reaction to approach completion and 2) RCS by [14C]cyanate should be referenced to blood concentrations at 24 h.

Effects of stilbenes isolated from medicinal plants on arachidonate metabolism and degranulation in human polymorphonuclear leukocytes

Studies were made on the effects of stilbene derivatives isolated from medicinal plants on arachidonate metabolism and degranulation in human polymorphonuclear leukocytes (PMN-L). Resveratrol (3,4',5-trihydroxystilbene) isolated from the roots of Reynoutria japonica was found to inhibit the 5-lipoxygenase products 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid (5,12-diHETE) and leukotriene C4(LTC4); its concentrations for 50% inhibition (IC50) were 8.90 x 10(-6) M, 6.70 x 10(-6) M and 1.37 x 10(-6) M, respectively. The IC50 of 5-HETE, 5,12-diHETE and LTC4 formations of synthetic 3,3',4-trihydroxystilbene were 5.90 x 10(-6) M, 6.30 x 10(-7) M and 8.80 x 10(-7) M, respectively. Moreover, they inhibited the release of lysosomal enzyme such as lysozyme and beta-glucuronidase induced by calcium ionophore A 23187 from human PMN-L at 10(-3)-10(-4) M.

Bovine neutrophils recruited by endotoxin to a teat cistern continuously produce oxygen radicals and show increased phagocytosis and extracellular chemiluminescence

Bovine neutrophils were harvested from a teat cistern following endotoxin infusion and were compared with blood neutrophils by measurements of chemiluminescent and phagocytic activity towards C3- and IgG-opsonized and unopsonized yeast particles. Both phagocytosis and luminol-dependent chemiluminescence elicited by all three particles were enhanced in the teat cells. The increase in the luminol-dependent chemiluminescence towards C3- and IgG-opsonized particles was due to an enhanced extracellular release of myeloperoxidase. The observed increase in phagocytosis of unopsonized yeast was shown to reflect the interaction between up-regulated CR3 receptors on the surface of the teat neutrophils and the yeast particles. A high chemiluminescent activity of the teat neutrophils in both the luminol- and lucigenin-dependent systems in the absence of a phagocytic prey indicated that the NADPH oxidase was permanently active and that myeloperoxidase was continuously released by the cells. Treatment of neutrophils with cytochalasin B showed that the chemiluminescence and phagocytosis of teat neutrophils were less sensitive to this drug than that of blood neutrophils. These results indicate that the teat neutrophils have up-regulated their receptors for IgG- and C3-opsonized and unopsonized yeast on the cell surface by the action of actin. The cells also have a permanently active NADPH oxidase dependent on the association with actin and show a higher tendency than blood neutrophils to secrete the content of their primary granules during phagocytosis.

Characterization of arachidonic acid metabolism, superoxide production, and bacterial killing by bovine alveolar neutrophils elicited with leukotriene B4 and zymosan-activated plasma

Leukotriene B4 (LTB4) and zymosan-activated plasma (ZAP) were each instilled into the lungs of steers to elicit alveolar neutrophils for subsequent functional analysis. Prior to instillation of either agent, bronchoalveolar lavage cell populations consisted of 95.8 +/- 0.4% macrophages (mean +/- SEM). Four hours after instillation of LTB4 or ZAP, the lavage cell populations consisted of 75.0 +/- 8.8% and 90.7 +/- 0.7% neutrophils, respectively. Alveolar neutrophils elicited with LTB4 and stimulated with the calcium ionophore A23187 released diminished amounts of LTB4 and increased amounts of 5-hydroxyeicosatetraenoic acid (5-HETE) as compared to circulating neutrophils. Release of superoxide anion was decreased for LTB4-elicited alveolar neutrophils as compared to circulating cells, while bacterial killing was unchanged. ZAP-elicited alveolar neutrophils released diminished amounts of LTB4 when stimulated with A23187 as compared to circulating neutrophils. There were no differences observed in 5-HETE levels between the two cell populations. In addition, release of superoxide anion was diminished among ZAP-elicited alveolar cells, while bacterial killing was unchanged. Incubation of circulating neutrophils with LTB4 did not influence the release of arachidonate metabolites, superoxide anion, or bacterial killing. However, incubation of circulating neutrophils with ZAP, followed by A23187 resulted in a reduction in the release of LTB4, as compared to control cells. Prior exposure to ZAP did not influence the release of superoxide anion or bacterial killing by the circulating neutrophils.

Inhibitory effects of methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl- 2H-pyrazolo[3,4-d]pyrimidine-2-carboxylate (AA-2379) on lysosomal enzyme and arachidonic acid release from rat polymorphonuclear leukocytes and its mode of action

AA-2379 (methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl- 2H-pyrazolo [3,4-d]pyrimidine-2-carboxylate) has antiinflammatory, analgesic, and antipyretic activities, and inhibits the type III allergic (Arthus) reaction. In the studies reported here, we investigated the effect of AA-2379 on rat polymorphonuclear leukocyte (PMN) functions to clarify the mechanism of the antiinflammatory and antiallergic actions of AA-2379. AA-2379 at 10(-4) M inhibited lysozomal enzyme release. AA-2379 inhibits formyl methionyl-leucyl-phenylalanine (fMLP)- and C5a-induced arachidonic acid release; their 50% inhibitory concentrations were 2.8 x 10(-5) and 3.8 x 10(-5) M, respectively. Because dibutyryl cAMP, a cAMP analogue, and 3-isobutyl-1-methylxanthine, a cAMP phosphodiesterase inhibitor, inhibited fMLP-induced arachidonic acid release, and AA-2379 inhibited cAMP phosphodiesterase and increased cAMP content in PMNs, it is likely that AA-2379 inhibited arachidonic acid release by increasing cAMP content in rat PMNs. Furthermore, from the studies of fMLP-induced arachidonic acid release in Ca free medium it is suggested that AA-2379 inhibits the process which depends on Ca concentration in the medium. These results suggest that the inhibitory effect of AA-2379 on inflammation and allergic reactions such as the Arthus reaction is partly exerted by inhibiting PMN functions such as arachidonic acid and lysozomal enzyme release.

Comparative studies on the leukotriene D4-metabolizing enzyme of different types of leukocytes

1. The leukotriene (LT) D4-metabolizing enzyme which catalyzes the conversion of LTD4 to LTE4, was investigated in various types of leukocytes from guinea pigs and humans. 2. In guinea pigs, the enzyme activity was present in macrophages but was hardly present in neutrophils, lymphocytes and eosinophils. 3. In humans, neutrophils, lymphocytes and macrophages all possessed the enzyme activity. However, enzyme activity varied with cell types and macrophages showed the highest enzyme activity among the leukocytes. 4. The subcellular localization of the LTD4-metabolizing enzyme was studied and leukocytes were divided into two groups: one which has the enzyme activity exclusively on the cell surface and the other which has the activity both on the cell surface and in the granules of leukocytes. 5. The enzyme activity was remarkably inhibited by o-phenanthroline and dithiothreitol and the inactivated enzyme was considerably reactivated by Co2+ and Zn2+, suggesting that the LTD4-metabolizing enzyme of leukocytes is a metalloenzyme.

Effect of vitamin K3 on macrophage functions and intracellular calcium

1. The effect of vitamin(vit) K3 on guinea-pig macrophage functions was studied. 2. Vit K3 inhibited macrophage locomotion, phagocytosis and lysosomal enzyme release. 3. Vit K3 inhibited the rise in the intracellular free calcium level induced by stimuli at the concentration at which vit K3 suppressed functions. 4. These results suggest that vit K3 inhibits macrophage functions through the interference with the mobilization of intracellular calcium.

Effects of a phagocytosis-stimulating factor derived from polymorphonuclear neutrophils on the functions of macrophages

The effects of phagocytosis-stimulating factor (PSF) derived from polymorphonuclear neutrophils on macrophage functions were studied. PSF enhanced the initial rate of phagocytosis of serum-opsonized zymosan particles by macrophages, whereas it did not affect the phagocytosis of immunoglobulin G-sensitized and inert zymosan particles. Kinetic studies showed that PSF accelerated the ingestion step, but not the attachment step, of phagocytosis by macrophages. On the other hand, PSF did not affect the other macrophage functions such as O2- generation, chemotaxis, adherence, and enzyme release. These results suggest that PSF may specifically modulate the complement receptor function of macrophages. Immunoblot assay showed the absence of components in macrophage which reacted with purified antibodies against polymorphonuclear neutrophil-derived PSF, and an extract from phagocytosing macrophages had no phagocytosis-stimulating activity, indicating that the macrophages did not produce PSF-like substances.

Platelet-activating factor modulates phospholipid acylation in human neutrophils

The present study showed that platelet-activating factor (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, PAF), but not lysoPAF (1-O-hexadecyl-sn-glycero-3-phosphocholine) rapidly (within 15 sec) stimulated the incorporation of both [1-14C]arachidonate and [1-14C]docosahexaenoate into phosphatidylinositol (PI) and phosphatidylcholine (PC) in human neutrophils. Concomitantly, it inhibited the formation of labeled phosphatidic acid from both fatty acids. The magnitude of stimulation (percentage of control) was greater in PI than in PC for the incorporation of arachidonate and vice versa for the incorporation of docosahexaenoate. It reached a maximum at 10(-7) M and started to decline at 10(-6) M. Extracellular Ca2+ was not essential for the action of PAF on phospholipid acylation. The distribution of labeled arachidonate in the molecular species of PC was not altered by PAF after 1 min incubation, suggesting that the increased formation of arachidonyl-PC during the early stage of neutrophil-PAF interaction was not originated from the added PAF. No measurable changes in the mass of each phospholipid were detected in neutrophils challenged by PAF from 15 sec to 2 min. The data suggest that the increased incorporation of extracellular fatty acids into PI and PC elicited by PAF may be secondary to increased deacylation of these phospholipids, and the magnitude of stimulation reflects the specificity of acyltransferase catalyzing the acylation of lysoPI and lysoPC by fatty acyl-CoA.

Impaired function of polymorphonuclear leukocytes exuded into bronchoalveolar spaces infected with Pseudomonas aeruginosa in steroid-treated rabbits

Steroid-treated and untreated rabbits were infected transbronchially with Pseudomonas aeruginosa. The polymorphonuclear leukocytes (PMN) exuded into the bronchoalveolar spaces were obtained by lavage 18 hr later, superoxide (O2-) production and chemotactic activity were studied. In the steroid-treated group, there was a heightened susceptibility to the infection, as compared to findings in the untreated group. The lung exudate PMN in the steroid-treated group showed a significant decrease (p less than 0.05) in O2- production, and somewhat depressed chemotactic activity. In the untreated group, both O2- production (p less than 0.01) and chemotactic activity (p less than 0.001) of lung exudate PMN doubled, compared with findings in blood PMN. There was, however, no significant difference between lung exudate PMN and blood PMN in the steroid-treated group. Impaired PMN function in the steroid-treated group was also observed in case of casein-induced lung exudate PMN. These results suggest that the antibacterial function of PMN exuded in the infected lung may be impaired in steroid-treated hosts, hence an enhanced susceptibility to lung infection.

Fungicidal activity of murine inflammatory polymorphonuclear neutrophils: comparison with murine peripheral blood PMN

A characteristic of inflammation is the influx of polymorphonuclear neutrophils (PMN) from peripheral blood to the inflammatory reaction. We report on metabolic alterations and alterations in fungicidal activity in PMN elicited intraperitoneally with different inflammatory agents. The fungicidal activity of murine peripheral blood PMN (PB-PMN) against phagocytosable Candida albicans and nonphagocytosable Blastomyces dermatitidis was compared to that of murine inflammatory PMN. PMN elicited with sodium caseinate exhibited enhanced killing of B. dermatitidis (93 +/- 3%) compared to PB-PMN (38 +/- 11.7%). In contrast, thioglycollate medium elicited PMN had significantly less ability to kill B. dermatitidis (3 +/- 5%) than PB-PMN. Incubation of caseinate PMN with thioglycollate medium for 1 h significantly reduced their ability to kill B. dermatitidis (95% vs 25%). This effect was not due to cytotoxicity of thioglycollate medium for PMN. Candidacidal activity of inflammatory PMN (caseinate or proteose peptone-elicited) was not significantly greater than that of peripheral blood PMN. However, inflammatory PMN had significantly greater candidacidal activity than thioglycollate-elicited PMN.

Localization of leukotriene D4-metabolizing metalloenzyme on the cell surface of human neutrophils

The localization of leukotriene D4-metabolizing enzyme on the cell surface was examined using human neutrophils. Intact neutrophils rapidly converted leukotriene D4 to leukotriene E4. However, when neutrophils were modified chemically by diazotized sulfanilic acid, a poorly permeant reagent which inactivates cell surface enzymes selectively, the leukotriene D4-metabolizing activity of neutrophils decreased significantly without any inhibition of the cell viability or marker enzymes of cytosol, granules, microsome and mitochondria. The leukotriene D4-metabolizing enzyme activity of the membrane fraction was inhibited by modification to the same extent as that of Mg2+-dependent ATPase, a cell-surface marker enzyme. Among various enzyme inhibitors examined, a metal chelator, o-phenanthroline, strongly suppressed the leukotriene D4-metabolizing activity of intact neutrophils and the o-phenanthroline-inactivated enzyme activity was fully reactivated by Co2+, Mn2+ and Zn2+. These results would suggest that some metalloenzyme located on the cell surface is involved in the conversion of leukotriene D4 to leukotriene E4 by neutrophils.

Neutrophil activity in abscess-bearing mice: comparative studies with neutrophils isolated from peripheral blood, elicited peritoneal exudates, and abscesses

Intraabdominal abscesses were induced in mice by intraperitoneal inoculation of Bacteroides fragilis and Escherichia coli plus bran as the abscess-potentiating agent. Six- or seven-day-old abscesses were mechanically disaggregated in buffer, and the cells obtained were fractionated on discontinuous Percoll density gradients. Neutrophil populations of different density, each approximately 90% pure, were isolated. When the abscess-derived neutrophils were subsequently incubated with normal serum in vitro under aerobic conditions, the viability of the gram-negative bacteria that had been phagocytosed within the abscess did not change significantly. This anergy to intracellular bacteria (on subsequent incubation in vitro under optimal conditions for phagocytic killing) was also found for neutrophils that had been obtained from abscesses induced by a mixture that included Proteus mirabilis plus B. fragilis and from those induced by E. coli plus P. mirabilis. While unable to significantly kill intracellular organisms that had been phagocytosed in vivo, the abscess-derived neutrophils could engulf and kill organisms to which they were exposed in vitro. Neutrophils from abscesses induced by P. mirabilis only plus bran killed that organism introduced in vitro significantly more effectively than the organisms that had been engulfed in vivo. In contrast, neutrophils from abscesses induced by the gram-positive organism Staphylococcus aureus plus bran were able to kill their intracellular organisms on subsequent incubation in vitro as effectively as they could kill added S. aureus. Neutrophils isolated from the peripheral blood and from induced peritoneal exudates of abscess-bearing mice were able to phagocytose and kill organisms in vitro with greater efficiency than abscess-derived neutrophils. The mechanism whereby neutrophils from abscesses induced by the gram-positive organism S. aureus can kill the organisms phagocytosed in vivo on subsequent in vitro incubation, in contrast to the relative anergy to their intracellular organisms displayed by neutrophils derived from abscesses induced by combinations of gram-negative bacteria, is not known.

Comparison of blood and peritoneal neutrophil activity in rabbits with and without peritonitis

The neutrophil (polymorphonuclear cell, or PMN) function is an essential component of the host defense against infection. However, infection itself may alter PMN activity. To investigate both the effects of infection on PMN activity and PMN activity on survival, we evaluated control and infected blood and peritoneal PMN phagocytosis, chemotaxis, and superoxide anion production in rabbits with and without peritonitis. Control blood and peritoneal PMNs were obtained from noninfected rabbits which were subjected to intraperitoneal infusion of sterile hypertonic saline. Infected blood and peritoneal PMNs were obtained from rabbits which had undergone appendiceal devascularization and ligation 18 hr earlier. Phagocytosis was similar in all groups except for a threefold increase in normal peritoneal PMNs. Chemotaxis was inhibited by infection in the blood and peritoneal PMNs. Normal peritoneal PMNs also had decreased chemotaxis. Superoxide anion production was comparable in the infected and control blood; however, both control and infected peritoneal PMNs had elevated superoxide anion production. Of the infected rabbits, four died in 5 days or less. Of the six that lived, two developed intraabdominal abscesses. Blood and peritoneal PMN activity was similar in all rabbits despite their outcome. We conclude that (1) blood and peritoneal PMNs have different basal activities and responses to infection; (2) the milieu of the peritoneal cavity appears to alter the PMNs present; and (3) PMN activity did not predict morbidity or mortality.

Murine neutrophils collected from subcutaneously implanted sponges

Polyvinyl sponges implanted subcutaneously in mice were used as a source of murine neutrophils (PMNs). Yield of PMNs from sponges averaged 6.3 X 10(5) PMNs per mouse and viability of sponge PMNs was 96.5%. These results were comparable to the yield and viability of PMNs harvested from peripheral blood. The chemotactic activity of sponge PMNs was significantly greater than the chemotactic activity of peripheral blood PMNs (chemotactic index of 4.78 +/- 1.66 in sponge PMNs versus 2.16 +/- 1.08 in peripheral blood PMNs, P less than 0.001). The difference in chemotactic activity was not attributable to hypotonic injury of PMNs nor the presence of soluble factors in sponge fluids. Phagocytic activity of sponge PMNs was comparable to the activity of blood PMNs (mean of 31.3 +/- 16.4% phagocytic cells for sponge PMNs versus 33.0 +/- 23.9% for blood PMNs). In addition, the number of fluorescent spheres ingested by sponge PMNs was not different (mean of 2.81 +/- 0.86 in sponge PMNs versus 2.65 +/- 0.68 spheres per cell for blood PMNs). These studies indicate that subcutaneously implanted sponges can be used as a source of functioning murine PMNs.

Enhanced oxidative burst in immunologically activated but not elicited polymorphonuclear leukocytes correlates with fungicidal activity

Polymorphonuclear neutrophils (PMN) induced locally in immune mice by intraperitoneal injection of antigen exhibit enhanced fungicidal activity compared with PMN elicited with thioglycolate. The mechanism of the differences in these PMN populations was studied. Sublethal infection was used to produce immunity to Blastomyces dermatitidis. A correlation was sought between the ability of PMN to kill, or not kill, B. dermatitidis and the production of the oxidative burst, as measured by luminol-enhanced chemiluminescence (CL). Although elicited PMN cocultured with Candida albicans produced a burst of CL and were candidacidal, killing did not occur when PMN were cocultured with B. dermatitidis. Lack of killing of B. dermatitidis by elicited PMN correlated with lack of stimulation of a brisk oxidative burst. In contrast to elicited PMN, PMN induced by B. dermatitidis antigen responded to this fungus with a burst of CL and a significant reduction of inoculum CFU (80%). Furthermore, these PMN when cocultured with C. albicans produced an enhanced burst of CL, and killing was enhanced compared with that by elicited PMN, e.g., 86 versus 58%. The CL burst and killing of B. dermatitidis by antigen-induced PMN was abrogated in the presence of catalase, implying a critical role for hydrogen peroxide. Partial but significant depression of CL and killing in the presence of dimethyl sulfoxide, a hydroxyl radical scavenger, identified hydroxyl radical, or its metabolites, as a toxic product(s) responsible for a significant fraction of fungicidal activity. These results indicate that the metabolic activity and microbicidal activity of PMN can be altered (enhanced) at the site of an immunological reaction and thus could constitute an important factor in resistance.

Purification and characterization of a phagocytosis-stimulating factor from phagocytosing polymorphonuclear neutrophils: comparison with granule basic proteins

Phagocytosis-stimulating factor (PSF) was purified by copper chelate chromatography and characterized in comparison with basic proteins in the granule of polymorphonuclear neutrophils. By copper chelate chromatography, PSF was eluted at pH 3.7; whereas cationic protein, lysozyme, and lactoferrin were eluted at pH 5.6, 5.1, and 4.0, respectively. Purified PSF has an approximate molecular weight of 16,000 and an isoelectric point at 8.7, which differ from those of basic proteins, such as cationic protein, lysozyme, and lactoferrin. Anionic substances such as DNA and heparin did not influence the phagocytosis-stimulating activity of PSF, whereas that of the granule basic protein fraction from resting polymorphonuclear neutrophils was abolished. PSF had little bactericidal activity against Escherichia coli and Staphylococcus aureus, whereas the granule basic protein fraction from resting PMNs had strong bactericidal activity against E. coli and weak activity against S. aureus. These results indicate that PSF is a basic protein which is distinguishable from cationic protein, lysozyme, and lactoferrin.

Effect of maleimide derivatives on superoxide-generating system of guinea-pig neutrophils stimulated by different soluble stimuli

The effect of modification of maleimide derivatives on superoxide production by guinea-pig neutrophils induced by a variety of different soluble stimuli was studied. Pretreatment of neutrophils by showdomycin, a very slowly penetrating-SH reagent, did not affect superoxide production by all of the stimuli used, suggesting no exposure of sulfhydryl groups involved in superoxide-generating system on the cell surface. Pretreatment with N-ethylmaleimide (MalNEt), a considerably penetrating-SH reagent, markedly inhibited superoxide production stimulated by formyl-methionyl-leucyl-phenylalanine (HCO-Met-Leu-Phe), cytochalasin E or digitonin, but not superoxide production stimulated by the ionophore A23187 or sodium fluoride. The oxygen consumption stimulated by HCO-Met-Leu-Phe or cytochalasin E was inhibited by MalNEt pretreatment, whereas the oxygen consumption stimulated by A23187 was not inhibited by MalNEt. The inhibition by MalNEt of superoxide production did not appear to be due to the interference with binding of the affected stimuli, since MalNEt pretreatment did not inhibit the release of lysozyme, granule enzyme, induced by HCO-Met-Leu-Phe, cytochalasin E or digitonin. Particulate fractions from MalNEt-pretreated neutrophils before exposure to the stimulus exhibited the inhibition of the enhancement of NADPH-dependent superoxide production induced by HCO-Met-Leu-Phe, cytochalasin E or digitonin, but not A23187, whereas treatment of neutrophils with MalNEt after activation by these stimuli had no effect on the NADPH oxidase activity in particulate fractions. Direct exposure of particulate fractions from A23187-stimulated neutrophils to MalNEt showed no actual susceptibility of NADPH oxidase to MalNEt inhibition. These findings suggest that the inhibitory effect of MalNEt is caused by the modification of the process of the activation by the affected stimuli of the superoxide system, probably NADPH oxidase and that at least two mechanisms exist for activation of superoxide-generating system in guinea-pig neutrophils on the basis of the susceptibility to MalNEt inhibition.

Incorporation of arachidonic acid and eicosapentaenoic acid into phospholipids by polymorphonuclear leukocytes in vitro

The present study demonstrated that the patterns of the incorporation of [1-14C] arachidonic acid and [1-14C] eicosapentaenoic acid into individual phospholipids by polymorphonuclear leukocytes were similar. However, human leukocytes exhibited higher activity than guinea pig peritoneal leukocytes in the formation of arachidonoyl- and eicosapentaenoyl-phosphatidic acid. Cells from both origins showed a decrease of label in phosphatidylcholine accompanied by an increase of label in phosphatidylethanolamine after a longer period (30-120 min) of incubation, suggesting that part of the arachidonoyl or eicosapentaenoyl moiety in phosphatidylethanolamine may be derived from that of phosphatidylcholine. The observed difference between human cells and elicited cells in the timecourse of the incorporation of both fatty acids into phosphatidylcholine and phosphatidylethanolamine appears to be due to different contents of the diacyl and ether-linked class compositions of these phospholipids in cells from different origins. Both labeled fatty acids were incorporated more rapidly into the diacyl-linked class, but were retained to a greater extent in alkylacyl-phosphatidylcholine and alkenylacyl-phosphatidylethanolamine. The data suggest that, in addition to alkylacylphosphatidylcholine and phosphatidylinositol, alkenylacyl-phosphatidylethanolamine may be an important endogenous source of arachidonic acid and eicosapentaenoic acid in stimulated human leukocytes.

Comparative studies on the leucine aminopeptidase activity of different types of leukocytes

The distribution of the leucine aminopeptidase activity among different types of leukocytes in a few animals was examined. In guinea-pig, the enzyme activity was detected in all cell types examined but its activity per cell was diverse among leukocytes, i.e. neutrophils and monocyte-macrophage cell lines, so-called "professional" phagocytes, showed higher enzyme activity than other types of leukocytes, lymphocytes and eosinophils. The same distribution pattern of leucine aminopeptidase activity as that in guinea-pig was also observed among leukocytes in human, rat and mouse. When leukocytes were modified with a poorly permeant reagent, diazotized sulfanilic acid to examine the subcellular localization of leucine aminopeptidase in leukocytes, the leucine aminopeptidase activity of the cells was inhibited by 50% without the inhibition of lactate dehydrogenase, a soluble cytoplasmic enzyme, in various types of leukocytes from all animals used here. The possibility was suggested from these observations that higher leucine aminopeptidase activity is distributed on the cell surface of "professional" phagocytes.

Specific and azurophilic granules from rabbit polymorphonuclear leukocytes. I. Isolation and characterization of membrane and content subfractions

The specific and azurophilic granules of rabbit polymorphonuclear heterophils (PMNs) have been isolated and fractionated into membrane and extractable subfractions. Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) revealed several features of the protein composition of the two granules: (a) Whereas each type of granule had 40-60 proteins separable on one-dimensional gradient gels, few of the proteins were common to both granules. (b) The proteins of the extractable fractions (which comprised approximately 98% of the total granule protein) of each granule were distinct from the proteins of the membrane fractions (which comprised approximately 2% of the total granule protein). (c) The extractable proteins co-migrated with those collected from the medium of ionophore-treated, degranulating PMNs and therefore were defined as content proteins. These results were confirmed by radiolabeling studies. Lactoperoxidase-catalyzed iodination of intact granules did not label the content proteins but did label proteins that co-migrated with major granule membrane proteins. Moreover, disruption of the granules before iodination led to labeling of both content and membrane proteins. We conclude that the membranes of specific and azurophilic granules, which arise from different faces of the Golgi complex, are composed of unique sets of membrane proteins some of which are exposed on the cytoplasmic face of the granules.

Effects of a phagocytosis-stimulating factor on the phagocytic process of polymorphonuclear neutrophils

The effect of phagocytosis-stimulating factor (PSF) on phagocytosis was studied in detail. PSF did not affect the Fc receptor-mediated phagocytosis, whereas PSF enhanced the ingestion step, but not attachment step, of C3b receptor-mediated phagocytosis by polymorphonuclear neutrophils (PMNs), suggesting that PSF may specifically modulate the C3b receptor function of PMNs. PSF generated from guinea pig PMNs enhanced phagocytosis by rabbit PMNs, and rabbit PMN-produced PSF accelerated the phagocytosis by guinea pig PMNs, indicating that PSF is not specific for animal species. The effects of PSF on some PMN functions, such as O2- generation, chemotaxis, adherence, and enzyme release, were also studied. Only O2- generation from PMNs was significantly increased in the initial phase of phagocytosis, and this stimulation of O2- generation was completely parallel with the stimulation of phagocytosis by PSF. Resting PMNs hardly generated the superoxide anions by PSF treatment, suggesting that PSF does not affect the O2- forming system directly.

Inactivation during phagocytosis of leucine aminopeptidase, an ecto-enzyme of polymorphonuclear neutrophils

Changes in enzyme activities of the plasma membrane markers were examined during phagocytosis using guinea-pig polymorphonuclear neutrophils. Incubation of neutrophils with fresh serum-opsonized zymosan particles showed a significant reduction in leucine aminopeptidase activity, whereas 5'-nucleotidase and alkaline phosphodiesterase activities remained unchanged. Inactivation of leucine aminopeptidase activity was also observed by exposure of neutrophils to complement-opsonized zymosan particles, but not to non-opsonized zymosan, IgG-coated zymosan or polystyrene latex particles. Pretreatment of neutrophils with cytochalasin B, which prevents phagocytosis but not surface binding of particles, provoked inactivation to the same degree as when the cells were allowed to phagocytose the particles. However, the inactivation during phagocytosis was protected by serine protease inhibitors. These findings suggest that loss of leucine aminopeptidase activity from phagocytosing cells may be mediated by certain serine protease inhibitor-sensitive factor(s) which are probably activated by the attachment of an opsonized zymosan particle to a specific membrane receptor, probably the C3b receptor.