Primary structures of MCP-1 and MCP-2, natural peptide antibiotics of rabbit lung macrophages

The microbicidal peptides, MCP-1 and MCP-2, of rabbit alveolar macrophages were purified by an improved procedure that employed preparative gel electrophoresis and high performance liquid chromatography. The peptides were arginine- and cystine-rich and lacked free sulfhydryl groups and detectable levels of carbohydrate. Complete sequence determinations revealed that MCP-1 differed from MCP-2 only by the substitution of arginine for leucine at residue 13 from the NH2 terminus and that the molecules were each single chain polypeptides of 33 amino acid residues containing three intramolecular disulfide bonds. The complete amino acid sequences of MCP-1 and MCP-2 are: (sequence in text)

Antibacterial activity of microbicidal cationic proteins 1 and 2, natural peptide antibiotics of rabbit lung macrophages

Microbicidal cationic proteins 1 and 2, peptides derived from rabbit lung macrophages, were tested for bactericidal activity against various bacterial species. Both were highly active against diverse gram-positive and gram-negative organisms under conditions of near-neutral pH (between 7 and 8) and relatively low ionic strength. Susceptible species included Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Listeria monocytogenes, Pseudomonas aeruginosa, Klebsiella pneumoniae, Haemophilus influenzae, Escherichia coli, and Serratia marcescens. Streptococcus agalactiae, type 1A, was less susceptible than the aforementioned organisms or S. agalactiae, type 3. Bordetella bronchiseptica, a common commensal and pathogen of the rabbit respiratory tract, was completely resistant to both peptides.

Specific binding of [3H]phorbol dibutyrate to phorbol diester-responsive and -resistant clones of a human myeloid leukemia (KG-1) line 1

Phorbol diesters induce macrophage-like differentiation in KG-1 and HL-60 human acute myelogenous leukemia cell lines. We developed a cloned subline of KG-1, known as KG-1a, that does not differentiate when exposed to phorbol diesters. Both KG-1 and KG-1a cells have a single class of specific high-affinity receptors for labeled phorbol-12,13-dibutyrate with a mean Kd of 1.47 +/- 0.10 (S.E.) X 10(-8) M and 0.85 +/- 0.20 X 10(-8) M for the sensitive parental KG-1 line and the resistant KG-1a subline, respectively (p less than 0.025). The number of [3H]phorbol-12,13-dibutyrate binding sites (mean +/- S.E.) per cell was 3.85 +/- 0.98 X 10(5) and 3.94 +/- 0.31 X 10(5) on KG-1 and resistant KG-1a cells, respectively. We observed no significant decrease of specific binding with time (down regulation) in either KG-1, KG-1a, or HL-60 cells, suggesting that down regulation of specific phorbol-12,13-dibutyrate binding is not critical to induction of differentiation. Our data also confirm that the presence of specific high-affinity phorbol receptors on leukemic cells does not assure that phorbol diesters can trigger their differentiation.

Assessment of chlorination by human neutrophils

On phagocytosing a microorganism, the neutrophil (polymorphonuclear leukocyte, PMN) consumes oxygen at a sharply elevated rate1. The oxygen is used to kill the microorganism, presumably being used to produce a potent oxidizing agent or agents. Candidates for these bactericidal agents are singlet oxygen, hydroxyl radical and chlorinating agents (that is, species containing 'active' Cl in a formal +1 oxidation state: HOCl, Cl2, N-chloroamides, and so on)1-5. We now report a semiquantitative assay for PMN-generated active chlorine based on its trapping with 1,3,5-trimethoxybenzene (TMB). Using this assay, we have found that at least 28% of the oxygen consumed by stimulated normal human PMNs is converted to active chlorinating agents.

Receptor-mediated regulation of superoxide production in human neutrophils stimulated by phorbol myristate acetate

Human neutrophils contain receptors for phorbol myristate acetate (PMA), a complex lipid that induces them to generate superoxide (O (2)). Binding of PMA to these receptors displays specificity, reversibility, and high affinity. The receptor's apparent KD was approximately 0.29 nM and multiple copies (approximately 2.1 +/- 0.6 x 10(5)) were present per neutrophil. We found that the timing and magnitude of the neutrophil's respiratory burst were set independently. The onset of O (2) production occurred after a lag that was inversely proportional to the initial concentration of added PMA. The extent (rate) of O (2) production was directly proportional to the fractional occupancy of the receptor by PMA. Dual regulatory controls, such as those we noted when neutrophils were stimulated by PMA, could afford metabolic stability in the face of transient or low intensity stimuli without compromising quick and powerful responses to larger disturbances.

Increased content of microbicidal cationic peptides in rabbit alveolar macrophages elicited by complete Freund adjuvant

We measured the microbicidal peptides MCP-1 and MCP-2 in rabbit alveolar macrophages (AM), comparing rabbits pretreated with complete Freund adjuvant with untreated control animals. Levels of MCP-1 increased from 4.7 +/- 0.6 microgram/10(7) resident AM to 13.2 +/- 0.1 microgram/10(7) complete Freund adjuvant-elicited AM. MCP-2 levels rose from 1.8 +/- 0.1 microgram/10(7) resident AM to 7.3 +/- 0.4 microgram/10(7) complete Freund adjuvant-elicited AM. The activities of five lysosomal hydrolases (beta-D-glucuronidase, beta-D-galactosidase, acid phosphatase, N-acetyl-beta-D-galactosaminidase, and N-acetyl-beta-D-glucosaminidase) were 44 to 96% higher in complete Freund adjuvant-elicited AM, and lysozyme activity was three- to fourfold higher. As MCP-1 and MCP-2 are major constituents of rabbit AM and exhibit potent antibacterial and antifungal properties, they may contribute to the expression of microbicidal activity in both resident and activated states.

Microbicidal cationic proteins of rabbit alveolar macrophages: amino acid composition and functional attributes

We purified two microbicidal cationic proteins, MCP-1 and MCP-2, from rabbit alveolar macrophages. MCP-1 was remarkably rich in arginine (25.5 mol%) and half cystine (18.7 mol%) residues and constituted approximately 1.5% of the total protein content of Freund adjuvant-elicited alveolar macrophages. MCP-2 was approximately half as abundant as MCP-1 and contained relatively less arginine (14.9 mol%) and half cystine (9.8 mol%). The amino acid compositions of MCP-1 and MCP-2 resembled those reported for the lysosomal cationic proteins of rabbit granulocytes, but were distinct from those of any known histone. MCP-1 (1 microgram/ml) killed 99.6% of Candida albicans in 20 min, whereas MCP-2 killed approximately 80% under similar conditions. Both proteins rapidly suppressed O2 consumption by C. albicans and induced a rapid loss of intracellular 86Rb+. Although more information is needed about the biological origin, distribution, and roles of macrophage microbicidal proteins, it seems likely that MCP-1 and MCP-2 contribute to the microbicidal efficacy of rabbit alveolar macrophages.

NAD(P)H oxidase activity in human neutrophils stimulated by phorbol myristate acetate

Phorbol myristate acetate activated in normal human neutrophils a single enzymatic entity that was dormant in unstimulated cells, optimally active at pH 7.0, and capable of oxidizing either NADH or NADPH, producing NAD(P)+ and superoxide (O27). Comparative fluorometric and spectrophotometric measurements supported the stoichiometry NAD(P)H + 20(2) leads to NAD(P)+ + 20(27) + H+. the seemingly considerable NAD(P)+ production at pH 5.5 and 6.0 was due largely to nonenzymatic oxidation of NAD(P)H by chain reactions initiated by HO27 (perhydroxyl radical), the conjugate acid of O27. This artifact, responsible for earlier erroneous assignments of an acid pH optimum for NAD(P)H oxidase, was prevented by including superoxide dismutase in fluorometric assays. NAD(P)H oxidase was more active towards NADPH (Km = 0.15 +/- 0.03 mM) than NADH (Km = 0.68 +/- 0.2 mM). No suggestion that oxidase activity was allosterically regulated by NAD(P)H was seen. Phorbol myristate acetate-induced O27 production was noted to be modulated by pH in intact neutrophils, suggesting that NAD(P)H oxidase is localized in the plasma membrane where its activity may be subject to (auto) regulation by local H+ concentrations.

Preparation of rabbit alveolar macrophages in high purity and yield

We describe methods that permit large numbers of viable and functional alveolar macrophages (greater than or equal to 5 x 10(8)/rabbit), substantially free of granulocyte contamination, to be recovered. Such populations are especially well suited for biochemical analyses demanding cell purity.

Microbicidal cationic proteins in rabbit alveolar macrophages: a potential host defense mechanism

Rabbit alveolar macrophages contain two highly cationic microbicidal proteins. These were shown to be distinct from histones and not to arise from granulocyte contamination. The macrophage proteins were especially active against Candida albicans and Candida parapsilosis. Gram-positive bacteria (Bacillus subtilis, Listeria monocytogenes, and Streptococcus faecalis) were also susceptible, whereas Escherichia coli and Salmonella typhimurium appeared more resistant. The proteins may be present in lysosomes, based on their solubilization by dilute acids and their distribution with lysosomal markers on sucrose density gradients. Such microbicidal proteins have not previously been demonstrated in any mammalian macrophage. They may play a significant role in the host-defense functions of the rabbit lung.

Fungicidal activity of rabbit alveolar and peritoneal macrophages against Candida albicans

We tested the ability of rabbit macrophages to kill Candida albicans in vitro. Resident (unstimulated) alveolar macrophages killed 28.1 +/- 1.9% of ingested organisms in 4 h, whereas resident peritoneal macrophages killed only 15.2 +/- 1.3% (mean +/- standard error of the mean, P < 0.01). Peritoneal macrophages obtained from rabbits treated 3 weeks earlier with complete Freund adjuvant showed enhanced candidacidal activity relative to normally resident peritoneal cells (28.2 +/- 3.1%, P < 0.01). Candidacidal activity by alveolar macrophages recovered from such treated animals was slightly enhanced relative to untreated alveolar macrophages (32.9 +/- 2.3%). Candidacidal activity by peritoneal and alveolar macrophages was not decreased by several agents (cyanide, azide, sulfadiazine, and phenylbutazone) that inhibit the ability of human blood monocytes to kill C. albicans. In contrast, candidacidal activity by alveolar macrophages was greatly diminished by iodoacetate, an ineffective inhibitor of this function in human monocytes. We conclude that rabbit macrophages kill C. albicans by a fungicidal mechanism distinct from the peroxidase-H2O2 mechanism of human granulocytes and monocytes, and that the fungicidal properties of peritoneal and alveolar macrophage populations are enhanced after nonspecific stimulation with complete Freund adjuvant.

A micromethod for measuring neutrophil candidacidal activity in neonates

We developed a micromethod, requiring but a few drops of blood, for measuring the ability of neutrophils to kill ingested Candida albicans. The neutrophils of 10 normal adults killed 26.2 +/- 9.5% of ingested C. albicans in 2.5 hr in a standard fungicidal assay, and 21.4 +/- 6.5% in our new micromodification. Neutrophils from 14 full term, healthy 30- to 40-hr-old infants, studied with the micromethod, killed 23.2 +/- 6.0% of ingested C. albicans. We conclude that the neutrophils of normal neonates are competent in this sphere of antimicrobial activity.

Severe candidal infections: clinical perspective, immune defense mechanisms, and current concepts of therapy

Disseminated candidiasis has become an important infection, particularly in immunocompromised and postoperative patients. Although serologic tests may, in some settings, facilitate a premortem diagnosis, the disease is usually diagnosed by comprehensive clinical evaluation. Detection of the relatively newly recognized peripheral manifestations of candidemia may be vital to early diagnosis: endophthalmitis, osteomyelitis, arthritis, myocarditis, meningitis, and macronodular skin lesions. Studies in patients with chronic mucocutaneous candidiasis and in-vitro manipulations have begun to elucidate normal immune defense mechanisms against Candida, including serum factors, phagocytosis, intracellular killing mechanisms, and lymphocyte function (particularly T cell). The primary drugs for the treatment of disseminated candidiasis are still amphotericin B or amphotericin B plus 5-fluorocytosine; the mainstay of therapy for chronic mucocutaneous candidiasis is amphotericin B. Other antifungals and immune system-stimulating modalities (transfer factor, thymosin, thymus epithelial cell transplantation, and levamisol) may be useful for chronic mucocutaneous candidiasis in some settings and deserve further evaluation.

Development of amphotericin B-resistant Candida tropicalis in a patient with defective leukocyte function

Emergence, during therapy, of fungi resistant to amphotericin B is purportedly rare, as fungi with altered cell membrane ergosterol content are considered too fragile to survive normal host defenses. Progressive amphotericin B resistance arose in a strain of Candida tropicalis isolated repeatedly from the urine of a patient with pyelonephritis. The most resistant isolate (R-2) lacked cell membrane ergosterol, the usual attachment site for amphotericin B, and was not inhibited by greater than 500 micrograms/ml of the drug. R-2 infected and killed embryonated eggs, but was unable to produce progressive renal infection in steroid-treated mice because of a reduced capacity to produce pseudomycelia. Persistent infection of the patient by this altered fungus was attributed to defective leukocyte candidacidal activity, especially marked in autologous serum, and to defective Candida-related cell-mediated immunity. A literature review suggests that amphotericin B resistance may not be as rare as many authorities have indicated. It is apparent that few laboratories routinely monitor fungi for amphotericin B susceptibility. In patients with defective antimicrobial defenses, amphotericin B-resistant fungi may survive, produce progressive infection, and require alternative chemotherapy for eradication.

Mechanism of nonspecific macrophage-mediated cytotoxicity: evidence for lack of dependence upon oxygen

Peritoneal macrophages elicited in C3H/HJ mice by the i.p. injection of Corynebacterium parvum were cytotoxic to allogeneic virus-transformed fibroblasts in vitro. Cytotoxicity was demonstrated in a morphologic (plaque) assay, and quantitated by measuring macrophage-mediated inhibition of incorporation of 3H-thymidine by the target cells. The cytotoxic effect was well established by 6 hr of macrophage-fibroblast interaction, and was retained in cultures from which the supernatant was removed before the addition of 3H-thymidine. Cytotoxic activity of macrophages diminished rapidly after 22 hr of cultivation in vitro. Maximal cytotoxic effect could be prolonged by addition of C. parvum, 50 microgram/ml to macrophage monolayers preincubated in vitro for 22 hr. It could neither be retained nor regenerated when C. parvum was added to monolayers greater than 22-hr old. C. parvum-activated macrophages, grown under anaerobic conditions for 8 hr, retained the ability to phagocytize heat-killed Candida albicans and to exclude trypan blue dye. There was a small but significant reduction in the ability of macrophages to inhibit 3H-thymidine incorporation by target fibroblasts under anaerobic conditions. The cytotoxic effect of activated macrophages in air was not altered by the presence of catalase and was enhanced by enzymatically active superoxide dismutase. We conclude that the processes involved in macrophage-mediated cytotoxicity against allogeneic fibroblasts in this system are largely independent of oxygen.

UCLA Conference. Monocytes and macrophages: functions and diseases

The mononuclear phagocyte complex is a widespread system of cells originating in the bone marrow monoblast and promonocyte, passing through the intermediate monocyte stage in the blood, and culminating in the tissue macrophages of the lung, liver, spleen, and pleural and peritoneal spaces. The cells are prominently phagocytic and have a well-developed lysosomal system. They function in host defense reactions against micro-organisms, in interactions with lymphoid cells in immunity, in disposal of cell debris, and possible in the regulation of granulopoiesis. Monocytes and the alveolar macrophage are the most accessible cells of this system for study. Several diseases of mononuclear phagocytes have been identified and characterized. These include microbicidal defects associated with increased susceptibility to infection, enzyme defects leading to storage diseases, and neoplastic diseases in which both cell proliferation and biologically active cell products contribute to the clinical disorder.

A simple microscopic method for identifying and quantitating phagocytic cells in vitro

A simple method is described for distinguishing phagocytic cells from non-phagocytic cells in a mixed population of leukocytes.

Fungicidal properties of a chymotrypsin-like cationic protein from human neutrophils: adsorption to Candida parapsilosis

Human neutrophils contain a chymotrypsin-like cationic protein (CLCP) that binds to the surface of Candida parapsilosis and is preferentially adsorbed by yeasts mixed with unfractionated extracts of neutrophil granules. Adsorption of CLCP to opsonized or nonopsonized yeasts was rapid at pH 4 through 8. Irreversible inhibition of the enzymatic site of CLCP by phenylmethylsulfonylfluoride or N-acetyl-Ala-Ala-Phe-chloromethyl ketone did not affect its adsorption by yeast. Adsorption, highly sensitive to ionic strength, was abrogated by 0.15 M KCl. The number of CLCP molecules adsorbed per yeast cell and the loss of colony-forming units are described by an exponential relationship.

Fungicidal components of mammalian granulocytes active against Cryptococcus neoformans

Citric acid extracts of granule-rich fractions, prepared from rabbit and guinea pig heterophils or human neutrophis, killed Cryptococcus neoformans in vitro. These extracts sere fractionated by micropreparative electrophoresis on polyacrylamide gels. In preparation of rabbit and guinea pig heterophils, cryptococcidal activity was associated predominantely with lysosomal cationic protein complex. Human neutrophils lacked strictly comparable cationic proteins but contained other components that killed C. neoformans. These components appeared to be identical to previously described proteins of the human neutrophil active against Candida parapsilosis.

Arginine-rich cationic proteins of human eosinophil granules: comparison of the constituents of eosinophilic and neutrophilic leukocytes

Several arginine-rich cationic proteins previously isolated from granules of leukemic myeloid cells have been found to reside primarily in human eosinophil leukocytes. The major component has a molecular weight of 21,000 and it contains approximately 2.6 moles of zinc per mole of protein. Velocity centrifugation of cytoplasm from leukocytes of patients with marked eosinophilia showed that this group of proteins is packaged in the crystalloid-containing large eosinophil granules. Approximately 30% of the protein content of eosinophil granules belonged to this group of cationic proteins. Bactericidal or esterolytic activities of the cationic proteins were not detected, nor did they inhibit guinea pig anaphylatoxin or histamine-induced contraction. The basic protein previously demonstrated in guinea pig eosinophils may be analogous to the group of basic proteins of human eosinophils but great differences are found for molecular weight and amino acid composition.

Rubidium release: a rapid and sensitive assay for amphotericin B

A new assay for amphotericin B has been devised with use of the release of a radioactive potassium analogue (86rubidium; 86Rb) from Candida parapsilosis. The 86Rb-release assay is rapid, highly sensitive, and reproducible. Amphotericin B levels of 0.06-2.0 mug/ml can be measured in serum, whereas as little as 0.015 mug of amphotericin B/ml can be detected in spinal fluid. The greater sensitivity of the assay in spinal fluid as compared with that in serum may be the result of binding of the amphotericin molecules by serum components, thus decreasing the amount of amphotericin free to interact with the fungal membrane.

Nonoxidative fungicidal mechanisms of mammalian granulocytes: demonstration of components with candidacidal activity in human, rabbit, and guinea pig leukocytes

Granulocytes from the peripheral blood of normal subjects and a patient with hereditary myeloperoxidase deficiency were homogenized in 0.34 M sucrose. A granule-rich fraction, prepared by sedimentation at 27,000 x g for 20 min, contained components that killed C. parapsilosis in vitro. These were extractable with 0.01 M citric acid and were shown by micropreparative polyacrylamide electrophoresis to be multiple. The candidacidal activity of these neutrophil components was heat stable and they were somewhat more active at pH 5.0 than at pH 7.0. When rabbit or guinea pig heterophils were obtained from sterile peritoneal exudates and similarly fractionated, they also were found to contain components that killed C. parapsilosis in vitro. These were primarily associated with a group of lysosomal cationic proteins lacking direct counterpart in human neutrophils. Among the candidacidal components of the human neutrophil was a protein, more cationic than lysozyme, that exhibited naphthol-ASD acetate esterase activity.

NADPH oxidase deficiency in X-linked chronic granulomatous disease

We measured the cyanide-insensitive pyridine nucleotide oxidase activity of fractionated resting and phagocytic neutrophils from 11 normal donors, 1 patient with hereditary deficiency of myeloperoxidase, and 7 patients with X-linked chronic granulomatous disease (CGD). When measured under optimal conditions (at pH 5.5 and in the presence of 0.5 mM Mn++), NADPH oxidase activity increased fourfold with phagocytosis and was six-fold higher than with NADH. Phagocytic neutrophils from patients with CGD were markedly deficient in NADPH oxidase activity.

The fungicidal mechanisms of human monocytes. I. Evidence for myeloperoxidase-linked and myeloperoxidase-independent candidacidal mechanisms

We tested the ability of human peripheral blood monocytes to kill Candida albicans and Candida parapsilosis. Evidence that multiple fungicidal mechanisms operate in normla monocytes was found. Normal monocytes ingested and killed viable C. albicans, and could iodinate heat-killed C. albicans. Both functions were defective in monocytes from subjects with myeloperoxidase deficiency or chronic granulomatous disease. Methimazole, isoniazid, and aminotriazole inhibited iodination by normal monocytes without impairing their ability to kill C. albicans, indicating that iodination was not essential to the myeloperoxidase-hydrogen peroxide-mediated fungicidal system of the monocyte. C. parapsilosis, an organism killed with supranormal efficacy by monocytes from a patient with hereditary myeloperoxidase deficiency, was selected to examine the myeloperoxidase-independent fungicidal mechanisms of monocytes. Monocytes were obtained from the blood of normal or leukemic subjects and homogenized in 0.34 M sucrose to yield fractions rich in cytoplasmic granules. These fractions were extracted with 0.01 M citric acid and the soluble components were separated by micropreparative polyacrylamide electrophoresis. Monocytes were found to contain cationic proteins, other than myeloperoxidase, that kill C. parapsilosis in vitro.