Association of lactoferrin with lysozyme in granules of human polymorphonuclear leukocytes

Lipopolysaccharide-Deficient Acinetobacter baumannii Due to Colistin Resistance Is Killed by Neutrophil-Produced Lysozyme

Acinetobacter baumannii causes nosocomial infections due to its multidrug resistance and high environmental adaptability. Colistin is a polypeptide antibacterial agent that targets lipopolysaccharide (LPS) and is currently used to control serious multidrug-resistant Gram-negative bacterial infections, including those caused by A. baumannii. However, A. baumannii may acquire colistin resistance by losing their LPS. In mouse models, LPS-deficient A. baumannii have attenuated virulence. Nevertheless, the mechanism through which the pathogen is cleared by host immune cells is unknown. Here, we established colistin-resistant A. baumannii strains and analyzed possible mechanisms through which they are cleared by neutrophils. Colistin-resistant, LPS-deficient strains harbor mutations or insertion sequence (IS) in lpx genes, and introduction of intact lpx genes restored LPS deficiency. Analysis of interactions between these strains and neutrophils revealed that compared with wild type, LPS-deficient A. baumannii only weakly stimulated neutrophils, with consequent reduced levels of reactive oxygen species (ROS) and inflammatory cytokine production. Nonetheless, neutrophils preferentially killed LPS-deficient A. baumannii compared to wild-type strains. Moreover, LPS-deficient A. baumannii strains presented with increased sensitivities to antibacterial lysozyme and lactoferrin. We revealed that neutrophil-secreted lysozyme was the antimicrobial factor during clearance of LPS-deficient A. baumannii strains. These findings may inform the development of targeted therapeutics aimed to treat multidrug-resistant infections in immunocompromised patients who are unable to mount an appropriate cell-mediated immune response.

A nutritional supplement containing lactoferrin stimulates the immune system, extends lifespan, and reduces amyloid β peptide toxicity in Caenorhabditis elegans

Lactoferrin is a highly multifunctional glycoprotein involved in many physiological functions, including regulation of iron absorption and immune responses. Moreover, there is increasing evidence for neuroprotective effects of lactoferrin. We used Caenorhabditis elegans as a model to test the protective effects, both on phenotype and transcriptome, of a nutraceutical product based on lactoferrin liposomes. In a dose‐dependent manner, the lactoferrin‐based product protected against acute oxidative stress and extended lifespan of C. elegans N2. Furthermore, Paralysis of the transgenic C. elegans strain CL4176, caused by Aβ1‐42 aggregates, was clearly ameliorated by treatment. Transcriptome analysis in treated nematodes indicated immune system stimulation, together with enhancement of processes involved in the oxidative stress response. The lactoferrin‐based product also improved the protein homeostasis processes, cellular adhesion processes, and neurogenesis in the nematode. In summary, the tested product exerts protection against aging and neurodegeneration, modulating processes involved in oxidative stress response, protein homeostasis, synaptic function, and xenobiotic metabolism. This lactoferrin‐based product is also able to stimulate the immune system, as well as improving reproductive status and energy metabolism. These findings suggest that oral supplementation with this lactoferrin‐based product could improve the immune system and antioxidant capacity. Further studies to understand the molecular mechanisms related with neuronal function would be of interest.

Lactoferrin a multiple bioactive protein: an overview

BACKGROUND

Lactoferrin (Lf) is an 80kDa iron-binding glycoprotein of the transferrin family. It is abundant in milk and in most biological fluids and is a cell-secreted molecule that bridges innate and adaptive immune function in mammals. Its protective effects range from anticancer, anti-inflammatory and immune modulator activities to antimicrobial activities against a large number of microorganisms. This wide range of activities is made possible by mechanisms of action involving not only the capacity of Lf to bind iron but also interactions of Lf with molecular and cellular components of both hosts and pathogens.

SCOPE OF REVIEW

This review summarizes the activities of Lf, its regulation and potential applications.

MAJOR CONCLUSIONS

The extensive uses of Lf in the treatment of various infectious diseases in animals and humans has been the driving force in Lf research however, a lot of work is required to obtain a better understanding of its activity.

GENERAL SIGNIFICANCE

The large potential applications of Lf have led scientists to develop this nutraceutical protein for use in feed, food and pharmaceutical applications. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.

Lactoferrin in human neutrophilic polymorphonuclear leukocytes in relation to iron metabolism

Lactoferrin (LF), the iron-binding protein of external secretions and neutrophilic polymorphonuclear leukocytes (PMN), was studied in 27 patients during granulocytosis caused by acute inflammation and in disorders without granulocytosis (iron deficiency anemia, iron overload and liver diseases). During granulocytosis the LF concentration of PMN was significantly lower than in controls (p less than 0.001). This difference proved to be related to the number of PMN. A relation between the LF concentration of PMN and iron metabolism could be demonstrated: loss of iron by blood donation is accompanied by a significant decrease in the LF concentration in PMN, whereas iron therapy in patients with iron deficiency anemia is accompanied by a significant increase in the LF concentration in PMN.

Immune components of colostrum and milk--a historical perspective

Key developments in the understanding of the immune functions of milk and colostrum are reviewed, focusing on their proteinaceous components. The topics covered include the immunoglobulins, immune cells, immunomodulatory substances, and antimicrobial proteins. The contributions of new technologies and the introduction of fresh approaches from other fields are highlighted, as are the contributions that mammary biology research has made to the development of other fields. Finally, a summary of some current outstanding questions and likely future directions of the field are given.

Faecal lactoferrin as a predictor of positive faecal culture in south Indian children with acute diarrhoea

Faecal lactoferrin, an iron-based glycoprotein found concentrated in secondary granules of neutrophils, may serve as a surrogate marker of inflammation in the intestine. We evaluated the usefulness of faecal lactoferrin as a predictor of infection with invasive enteropathogens in 262 children with diarrhoea. Lactoferrin at a dilution of 1:50 had the highest sensitivity for detection not only of conventionally cultured invasive enteropathogens but also of all other enteropathogens. Neither individual clinical symptoms nor the identification of faecal leucocytes by microscopy significantly predicted isolation of invasive enteropathogens from the faeces of children with diarrhoea. Faecal lactoferrin is a simple test which showed promise in predicting which children with diarrhoea are likely to be infected with invasive pathogens and can be incorporated as a screening test before faecal cultures are undertaken in this population.

Increased levels of lactoferrin in synovial fluid but not in serum from patients with rheumatoid arthritis

Lactoferrin is a multifunctional immunoregulatory protein, stored in specific granules of neutrophil granulocytes, from which it is released following cell activation. As activated neutrophils play a crucial role in the destruction of synovial joints in rheumatoid arthritis, we evaluated lactoferrin concentration in synovial fluid and sera from 21 patients with rheumatoid arthritis and 11 patients with osteoarthritis. We also measured lactoferrin levels in sera from 12 healthy controls. Lactoferrin was measured by a solid-phase inhibition immunoassay. Median lactoferrin levels were significantly higher in synovial fluid from rheumatoid arthritis than from osteoarthritis patients (P = 0.0002). In contrast, no significant difference was found between serum lactoferrin from patients with rheumatoid arthritis or osteoarthritis compared with normal controls. In patients with rheumatoid arthritis, lactoferrin concentrations were higher in synovial fluid than in sera (P = 0.036). In both rheumatoid arthritis and osteoarthritis no correlation was found between serum and synovial fluid lactoferrin (P = 0.51 and P = 0.5, respectively). In synovial fluid from patients with rheumatoid arthritis, lactoferrin concentrations correlated with neutrophil granulocyte count (P < 0.0001), but neither serum nor synovial lactoferrin levels correlated with disease activity (P = 0.32 and P = 0.25, respectively). In conclusion, lactoferrin is a reliable marker of neutrophil activation at sites of inflammation in rheumatoid synovitis, but does not represent a marker of disease activity.

Gingival crevicular fluid lactoferrin levels in adult periodontitis patients

The present study was designed to determine in a cross-sectional study whether there was any relationship between the levels of lactoferrin in gingival crevicular fluid and clinical periodontal parameters. Crevicular fluid was collected from individual sites using standardized filter paper strips (clinically healthy sites, N = 23; periodontitis sites, n = 66) and evaluated for lactoferrin by enzyme-linked immunosorbent assay. The data showed that: (1) the total amounts of lactoferrin were 0.003-0.021 ng (30 second sample) (average 0.009 +/- 0.005 ng) in a clinically healthy periodontium group and 0.016-3.847 ng (30 second sample) (average 0.575 +/- 0.069 ng) in adult periodontitis patients (statistically significantly higher in adult periodontitis patients); and (2) the total amounts of lactoferrin were significantly correlated with clinical parameters, especially a strong positive correlation with gingival crevicular fluid volume (r = 0.85, p < 0.01) and with probing depth (r = 0.71, p < 0.01). These results indicated that quantification of lactoferrin in gingival crevicular fluid may be a more sensitive indicator of periodontal pathology than traditional clinical indices.

Biosynthesis, processing and sorting of neutrophil proteins: insight into neutrophil granule development

Neutrophil granulocytes are specialized phagocytic cells that carry a collection of granules for regulated secretion, each with distinct constituents. The granules can be classified as azurophil (primary), developed first, followed in time by specific (secondary) granules gelatinase granules, and secretory vesicles. Stage- and tissue-specific transcription factors govern the successive expression of genes for granule proteins to allow storage of the gene products in these organelle categories whose packaging is separated in time. Many of the granule proteins, in particular those of the heterogeneous lysosome-like azurophil granules, are subject to extensive post-translational proteolytic processing into mature proteins, most commonly as a post-sorting event. A selective aggregation of proteins destined for storage in granules, as discussed in this review, would facilitate their retention and eliminate a need for distinct sorting motifs on each granule protein. Aggregation of granule proteins, that are often cationic, would be assisted by the anionic serglycin proteoglycans present in neutrophils. The antibacterial granule proteins can serve as models for antibiotics and some of them possess a potentially useful therapeutic ability to bind and neutralize endotoxin. Because aberrant expression of transcription factors regulating the synthesis of granule proteins is often found in leukemia, the clarification of mechanisms regulating the timed expression of granule proteins will shed light on the maturation block in myeloid leukemias.

Correlation of lactoferrin with neutrophilic inflammation in body fluids

We have reported that lactoferrin, a 77-kDa iron-binding glycoprotein found in secondary neutrophil granules, provides a useful marker of fecal leukocytes in fecal specimens from patients with inflammatory diarrhea (R. L. Guerrant, V. Araujo, E. Soares, K. Kotloff, A. A. M. Lima, W. H. Cooper, and A. G. Lee, J. Clin. Microbiol. 30:1238-1242, 1992). In order to determine the usefulness of this marker of neutrophilic inflammation in different body fluids, we examined blood, gingival swabs, sputum, and saliva using antilactoferrin antibodies (lactoferrin latex agglutination [LFLA]). LFLA titers in whole blood samples were < or = 1:4 in all eight samples from patients with neutropenia (absolute neutrophil count [ANC] = < 150 polymorphonuclear cells [PMNs] per microliter), < or = 1:8 in samples from 13 individuals with moderate leukocyte counts (ANC = 150 to 8,000), and 1:8 to 1:32 in samples from six patients with neutrophilia (ANC > 8,000). While the overlap precludes a useful role in the identification of neutropenia, these data confirm that lactoferrin titers of > 1:100 indeed indicate inflammation in fluid specimens. On quantitative elution of lactoferrin from gingival swabs, all 7 patients with dental plaque had titers of 1:200 to 1:400; 9 of 12 patients with clinical gingivitis had LFLA titers of 1:200 to 1:1,600, while all 7 individuals with healthy gums and teeth and 4 edentulous patients had LFLA titers of < or = 1:100. Eight purulent sputum samples had titers of > or = 1:400 (7 were 1:1,600) while 11 normal saliva samples showed titers of < or = 1:100. Lactoferrin titers in sputum, gingival swabs, and whole blood correlate with the presence of neutrophils or inflammation in these specimens and may offer a convenient rapid test for inflammatory processes.

Immunochemical detection of human lactoferrin in feces as a new marker for inflammatory gastrointestinal disorders and colon cancer

We have developed a new immunochemical test for fecal lactoferrin (LF) utilizing an enzyme-linked immunosorbent assay (ELISA). The ELISA had a sensitivity of about 10 micrograms/L of lactoferrin and the measurable range was 10.0-1000.0 micrograms/L (1.0-100.0 micrograms LF/g feces). The stability of lactoferrin in feces was greater than that of myeloperoxidase and leucocyte elastase. The fecal concentration of lactoferrin (mean +/- SD) in 35 normal subjects was 0.75 +/- 0.83 microgram/g feces, whereas that in 24 patients with colon cancer was 74.4 +/- 88.3 micrograms/g feces. The fecal lactoferrin concentration of 38 patient with active ulcerative colitis was 307.4 +/- 233.9 micrograms/g feces, and that in 36 patients with active Crohn's disease was 191.7 +/- 231.1 micrograms/g feces. The ELISA for human fecal lactoferrin might be useful in the diagnosis of colon disease.

Host enzymes in gingival crevicular fluid as diagnostic indicators of periodontitis

Host responses to periodontal infections include the production of several families of enzymes that are released by stromal, epithelial or inflammatory cells. Study of these enzymes in gingival crevicular fluid may lead to insights into pathogenesis and may provide a rational basis for the development of novel diagnostic tests. However, analogous to other diagnostic interventions in dentistry and medicine, validation of host enzymes as diagnostic indicators is dependent on clear-cut demonstrations of the identity of the enzyme, reproducibility, diagnostic accuracy and clinical utility. The enzyme of interest should be readily measured over a broad range of disease severity and in varied clinical settings. Ideally, the enzyme should also be an essential component of proposed pathogenic mechanisms. In this context, the connective tissue matrix degrading enzymes elastase, collagenase and gelatinase are promising because of their apparently central role in periodontal attachment loss and disease progression. Sensitive and specific assays are also available to quantify these enzymes. Other work on enzymes associated with cell death (aspartate aminotransferase, lactate dehydrogenase) and several neutrophil lysosomal enzymes (beta glucuronidase, arylsulphatase, cathepsins) has demonstrated positive associations between enzyme levels and attachment loss and inflammation. While numerous cross-sectional studies have indicated that the levels of hydrolytic enzymes in gingival crevicular fluid parallel the severity of periodontal lesions, there are much less data on reproducibility, diagnostic accuracy and clinical utility in longitudinal studies. As appropriate study design is an essential prerequisite for establishing the efficacy of host enzymes as diagnostic tests, future clinical investigations should include: (1) individuals who would most likely benefit by early diagnosis, i.e., rapidly progressive and recurrent periodontitis cases; (2) longitudinal, cohort study designs to show that attachment loss is temporally linked with large increases in enzyme activity; (3) the use of a battery of tests to overcome intrinsic problems of low predictive values when prevalence of active disease is low. In the final analysis, the utility of host enzymes as diagnostic indicators will need to be examined in randomized controlled trials in which the question is asked: are patients better off as a result of testing?

Evaluation of a New Latex Agglutination Test for Fecal Lactoferrin in Travelers' Diarrhea

The detection and diagnosis of travelers' diarrhea by fecal culture method, often insensitive, expensive, and time consuming, could well be replaced with the latex agglutination test to detect fecal lactoferrin. As an initial screening, this test could be useful to differentiate between those patients who are more likely to have an invasive enteropathogen and those patients requiring antidiarrheal chemotherapy only. Fecal samples from 92 patients with travelers' diarrhea were tested for occult blood, fecal leukocytes, and fecal lactoferrin at stool dilutions of 1:50 and 1:200. The results were compared with findings from fecal cultures for enteropathogens. Statistical analyses were performed measuring the performance of the latex agglutination test for fecal lactoferrin to calculate its sensitivity, specificity, and positive and negative predictive values. Invasive pathogens were identified in 36 (39%), and a noninvasive pathogen was found in 18, or 20%, of the cases. At the stool dilution of 1:50, fecal lactoferrin showed more sensitivity than did leukocytes or occult blood in detecting the presence of invasive enteropathogens and, with a negative predictive value of 94%, was superior in predicting their absence. At the 1:200 dilution, a lower sensitivity of 55%, but a higher specificity of 82%, compared to 55% with the 1:50 dilution, was demonstrated. The determination of fecal lactoferrin might prove to be more useful and less expensive and time consuming as an initial screening for patients presenting with travelers' diarrhea. Further evaluation and antibacterial treatment could, therefore, be reserved for those with a positive lactoferrin test.

Iron uptake mechanisms of pathogenic bacteria

Most of the iron in a mammalian body is complexed with various proteins. Moreover, in response to infection, iron availability is reduced in both extracellular and intracellular compartments. Bacteria need iron for growth and successful bacterial pathogens have therefore evolved to compete successfully for iron in the highly iron-stressed environment of the host's tissues and body fluids. Several strategies have been identified among pathogenic bacteria, including reduction of ferric to ferrous iron, occupation of intracellular niches, utilisation of host iron compounds, and production of siderophores. While direct evidence that high affinity mechanisms for iron acquisition function as bacterial virulence determinants has been provided in only a small number of cases, it is likely that many if not all such systems play a central role in the pathogenesis of infection.

Human neutrophil granules and secretory vesicles

The traditional classification of neutrophil granules as peroxidase-positive (azurophil, or primary) and peroxidase-negative (specific or secondary) has proven to be too simple to explain the differential exocytosis of granule proteins and incorporation of granule membrane into the plasma membrane which is an important aspect of neutrophil activation. Combined subcellular fractionation and immunoelectron microscopy has revealed heterogeneity among both peroxidase-positive and peroxidase-negative granules with regard to their content, mobilization and time of formation. Peroxidase-negative granules may be classified according to their content of lactoferrin and gelatinase: 15% of peroxidase-negative granules contain lactoferrin, but no gelatinase. 60% contain both lactoferrin and gelatinase. The term specific or secondary granule should be reserved for these two subsets. In addition, 25% of peroxidase-negative granules contain gelatinase but no lactoferrin. These should be termed gelatinase granules or tertiary granules. Gelatinase granules are formed later than specific granules and mobilized more readily. In addition, a distinct, highly mobilizable intracellular compartment, the secretory vesicle, has now been recognized as an important store of surface membrane-bound receptors. This compartment is formed in band cells and segmented cells by endocytosis. This heterogeneity among the neutrophil granules is of functional significance, and may also be reflected in the dysmaturation which is an important feature of myeloproliferative and myelodysplastic disorders.

Measurement of fecal lactoferrin as a marker of fecal leukocytes

While diarrheal illnesses are extremely common in communities and hospitals throughout the world, an etiologic diagnosis may be expensive and cost-ineffective. Although the presence of fecal leukocytes are helpful in the diagnosis and specific therapy of inflammatory diarrheas, this requires prompt microscopic examination of fecal specimens (preferably obtained in a cup rather than a swab or diaper) by a trained observer. We developed a simple, sensitive test for the detection of leukocytes in fecal specimens using antilactoferrin antibody. Whereas radial immunodiffusion detected 0.02 micrograms of lactoferrin (LF) per microliter or greater than or equal to 2,000 leukocytes per microliter, latex agglutination (LA) readily detected greater than or equal to 0.001 micrograms of LF per microliter or greater than or equal to 200 leukocytes per microliter added to stool specimens. Despite the destruction or loss of morphologic leukocytes on storage for 1 to 7 days at 4 degrees C or placement of specimens on swabs, measurable LF remained stable. Initial studies of stool specimens from six patients with Salmonella or Clostridium difficile enteritis were positive and those from three controls were negative for LF by LA. Of 17 children in Brazil with inflammatory diarrhea (greater than or equal to 1 leukocyte per high-power field), 16 (94%) had LF titers of greater than 1:50 by LA, whereas only 3 of 12 fecal specimens with less than 1 leukocyte per high-power field on methylene blue examination and none of 7 normal control specimens had an LF titer of greater than 1:50 by LA. Of 16 fecal specimens from patients with C. difficile diarrhea (cytotoxin titers, >/= 1:1,000), 95% (n = 15) had detectable LF by LA (in titers of 1:100 to 1: 800). Finally, of 48 fecal specimens from healthy adult U.S. volunteers before and after experimental shigellosis and of 29 fecal specimens from children with documented shigellosis and hospitalized controls in northeastern Brazil, fecal LF titers ranged from 1:200 to >/= 1:5,000 in 96% (25 of 26) samples from patients with shigellosis (and reported positive for fecal leukocytes), while 51 controls consistently had fecal LF titers of </= 1:200. We conclude that fecal LF is a useful marker for fecal leukocytes, even when they are morphologically lost swab specimens or when they are destroyed on transport or storage or by cytotoxic fecal specimens.

Ovine lactoferrin: isolation from colostrum and characterization

Highly purified lactoferrin was isolated from ovine colostrum by sequential purification on CM-Sephadex C-50 and Blue-Sepharose, with overall yield of 55%. The ovine lactoferrin was characterized by SDS-PAGE, its amino acid composition and N-terminal sequence to residue 30. Homology with bovine and human lactoferrins was greater than 80 and 50% respectively. Antibodies to ovine lactoferrin were raised in rabbits and used to develop an enzyme-linked immunosorbent assay (ELISA). The antiserum was not cross reactive with other colostrum proteins.

Inhibition of bactericidal and bacteriolytic activities of poly-D-lysine and lysozyme by chitotriose and ferric iron

In a previous report from this laboratory (N. J. Laible and G. R. Germaine, Infect. Immun. 48:720-728, 1985), evidence was presented to suggest that the bactericidal actions of both reduced (i.e., muramidase-inactive) human placental lysozyme and the synthetic cationic homopolymer poly-D-lysine involved the activation of a bacterial endogenous activity that was inhibitable by N,N',N"-triacetylchitotriose (chitotriose). In the present investigation however, we found that the bactericidal and bacteriolytic action of poly-D-lysine could be prevented only by some commercially available chitotriose preparations and not by others. Analysis by physical and chemical methods failed to distinguish protective chitotriose (CTa) and nonprotective chitotriose (CTi) preparations. CTi and CTa preparations displayed equal capacities to competitively inhibit binding of [3H]chitotriose by immobilized lysozyme and were indistinguishable in their abilities to block the lytic activity of lysozyme against Micrococcus lysodeikticus cells. Elemental analysis revealed significantly higher levels of phosphorus, calcium, iron, sodium, manganese, and copper in CTa. Removal of metals from CTa by chelate chromatography completely abolished the poly-D-lysine-protective capacity. Of the metals detected, only ferric iron (5 to 10 microM) mimicked the protective action of CTa. A Fe(III) concentration of 50 microM was required to inhibit lysozyme (5 micrograms/ml). Both Fe(III) and CTa (but not CTi) quantitatively blocked the labeling of poly-D-lysine by fluorescamine, suggesting that the primary amino groups of the lysine residues participate in iron binding. Thus, it appears that the poly-D-lysine-protective capacity of certain chitotriose preparations was due not to the chitotriose itself but to contaminating metal ions which interact directly with the polycationic agent. In contrast, Fe(III) cannot account for inhibition of either the bactericidal or bacteriolytic activity of lysozyme by chitotriose.

Purification and antimicrobial properties of three defensins from rat neutrophils

Three cysteine-rich cationic peptides, designated RatNP-1, RatNP-3, and RatNP-4, were purified from an acid extract of rat polymorphonuclear neutrophils, sequenced, and tested for antimicrobial activity. The peptides ranged from 29 to 32 amino acids in length (Mr, 3,252 to 3,825), and each contained all eight invariantly conserved "framework" residues that are characteristic of defensins. Each of the peptides killed Escherichia coli ML-35, Acinetobacter calcoaceticus HON-1, Staphylococcus aureus 502A, and Candida albicans 820 in vitro. RatNP-1, the most cationic rat defensin, was also the most potent. With this report, a total of 13 distinct defensins have been characterized in the polymorphonuclear leukocytes of four mammalian species. The existence of the defensin system in rats should facilitate investigations of the in vivo role of defensins in experimental infections.

Detection of high-risk groups and individuals for periodontal diseases: laboratory markers from analysis of gingival crevicular fluid

Gingival crevicular fluid is regarded as a promising medium for the detection of markers of periodontal diseases activity. The collection protocols are straight forward and non-invasive and can be performed at specific sites of interest in the periodontium. Because the fluid accumulates at the gingival margin, it will contain potential markers derived not only from the host tissues and serum but also the subgingival microbial plaque, and thus an extremely broad range of candidate molecules may be investigated. However, the ability to successfully describe indicators of current disease activity and predictors of future disease is dependent not only upon the choice of the biochemical marker but also on the accurate description of the health status of the sample sites using currently available clinical and radiographic methods. Areas of study which currently show the most promise involve the analysis of host enzyme activities directed against components of the extracellular matrix, the nature of the glycosaminoglycans released into the sulcus and the concentration in gingival crevicular fluid of certain mediators of the inflammatory process, most notably prostaglandin E2.

Plasma lactoferrin reflects neutrophil activation in psoriasis

We used a biotinylated antibody ELISA technique to measure plasma levels of lactoferrin (LF) and the LF content of peripheral blood PMN in 20 patients with psoriasis, 21 with eczema or other inflammatory skin conditions, 19 patients with malignant skin tumours and 20 healthy control individuals. In psoriasis, plasma LF levels were significantly increased compared with levels in the other skin conditions and in the healthy controls (P less than 0.01). Furthermore, in psoriasis the LF content of circulating PMN was decreased. These findings provide further evidence that in psoriasis systemic activation ('priming') of circulating PMN may take place.

Ultrastructural quantitation of peroxidase- and elastase-containing granules in human neutrophils

Previous ultrastructural studies of human neutrophils showed two distinctive granule types, the azurophil (peroxidase-positive) and the specific (peroxidase-negative). By identification of granules with peroxidase activity and those immunopositive for elastase antigen, the authors defined two subpopulations of azurophil granules, one that contained peroxidase activity and no measurable elastase antigen and another that contained elastase antigen associated with a small amount of peroxidase activity. They quantitated the peroxidase-positive as well as the elastase-positive granules in human peripheral blood neutrophils and found an average of 1536 +/- 69 peroxidase-positive granules per neutrophil. Of these, 399 +/- 20 were also elastase-positive. The average elastase concentration per neutrophil was 1.59 pg, and the average concentration per granule was 4 X 10(-3) pg. It is concluded that in normal individuals approximately one-third of the azurophil granules contain elastase antigen. Because neutrophil elastase has been implicated in the pathogenesis of emphysema, quantitation of its distribution within the cell presents an approach that may help define selective azurophil granule release and its relationship to the development of emphysema.

Assessment of total immunoreactive lactoferrin in hematopoietic cells using flow cytometry

Cell-associated lactoferrin (Lf) was analyzed using a new method involving cell permeabilization, indirect immunofluorescence staining, and flow cytometry. Statistical techniques to evaluate the results for percentage of positive cells, relative fluorescence and homogeneity of Lf distribution were also devised. Most normal adult neutrophils (97.1 +/- 0.3% (SEM), range 92.7-99.6%, n = 41) had brilliant fluorescence homogeneously distributed among the cells. There was significantly greater homogeneity of neutrophil Lf distribution in post-menopausal than pre-menopausal females. In chronic myelogenous leukemia (n = 13) and cord blood (n = 7), fractions of Lf-positive neutrophils were decreased (77.3 +/- 7.5%, range 13.3-96.3%; 71.4 +/- 9.3, range 32.0-95.6%, respectively). Normal monocyte-rich isolates had moderate fluorescence (28.7 +/- 3.6%, range 9.3-76.8%, n = 22). Among blood lymphocyte-rich preparations, 13.1 +/- 1.3% of cells had weak positivity (range 4.9-26.6%, n = 19); monoclonal B and T lymphocytes had similar parameters. No other cells had detectable Lf. Our results were significantly correlated with those obtained manually (r = 0.98, P less than 0.001), and are consistent with Lf quantity and distribution determined using other methods.

Leukocyte adhesion receptors are stored in peroxidase-negative granules of human neutrophils

Previous studies have suggested that the leukocyte adhesion proteins Mac-1 and p150,95 are stored in a latent intracellular pool in neutrophils, and cellular fractionation studies have shown that Mac-1 is localized primarily in the peroxidase-negative specific granules. To determine the subcellular location of leukocyte adhesion receptors (LAR), we used immunocytochemical techniques on frozen thin sections of human blood leukocytes that had been incubated for peroxidase to mark the peroxidase-positive azurophil granules. To enhance the sensitivity of detection, polyclonal antibodies against immunoaffinity-purified p150,95 were raised in rabbits and absorbed with leukocytes from a patient deficient in this protein. The antiserum reacted with p150,95 and two other antigens with the same beta subunit, Mac-1 and lymphocyte function-associated antigen 1 (LFA-1). In neutrophils, we observed immunogold label for LAR predominantly on the membranes of peroxidase-negative granules, and in smaller amounts on the plasma and perinuclear membranes. In double-label experiments, there was colocalization of LAR with lactoferrin in some of the peroxidase-negative granules. We conclude that the latent pool of LAR resides in the membranes of peroxidase-negative granules. A significant increase in label on the plasma membrane of neutrophils stimulated with PMA is consistent with secretion of LAR to the exterior of the cell during degranulation. While LFA-1 appears very early in neutrophil maturation, it is becoming clear that Mac-1 and p150,95 are upregulated from an intracellular storage pool of peroxidase-negative granules that appear during the myelocyte stage of differentiation. Further studies are indicated to determine the significance of these proteins on the plasma membrane of two other granulocytes, eosinophils and basophils.

Evidence for the presence of lactoferrin in odontogenic keratocyst fluids

Investigations into the possibility that X (an antigen consistently present in aspirated odontogenic keratocysts, but not in most fluids from other cyst types), represented a keratinocyte component failed to identify the antigen as a keratin, involucrin, or one of the blood group substances. Antigen X was detected in human mixed and parotid saliva and in colostrum, as well as in a commercially obtained preparation of colostral IgA. The antigen was similar biochemically to both secretory component and lactoferrin but proved to be identical antigenically with lactoferrin. The origin of lactoferrin in keratocyst fluids remains uncertain, though the lining epithelium seems a more likely source than does the very variable, and often negligible, inflammatory infiltrate found in these lesions.

The effect of oxygen-dependent antimicrobial systems on strains of Legionella pneumophila of different virulence

Four strains of Legionella pneumophila of different virulence as identified by ability to produce pneumonia and death in guinea-pigs infected by a fine-particle aerosol were examined for factors which may intracellularly influence virulence. Possible bactericidal mechanisms possessed by alveolar phagocytes were examined. A relationship could be established between resistance to H2O2, catalase activity and virulence amongst the strains. Virulent strains resisted the bactericidal activity generated by the xanthine oxidase system; avirulent strains did not. Incorporation of various specific inhibitors of the xanthine oxidase system indicated that the main bactericidal activities were associated with the production of H2O2 and hydroxyl radicals (.OH). All strains of L. pneumophila were susceptible to the bactericidal activity generated by the myeloperoxidase-H2O2-halide system, confirming earlier observations that polymorphonuclear neutrophil leucocytes (PMNLS) are able to kill both virulent and avirulent strains of L. pneumophila.

Indicators of periodontal disease activity: an evaluation

It is becoming increasingly apparent that the traditional clinical criteria are inadequate for: determining active disease sites in periodontitis, monitoring quantitatively the response to therapy or measuring the degree of susceptibility to future breakdown. In an attempt to develop objective measures, a wide variety of studies have been undertaken using saliva, blood, plaque and gingival crevicular fluid (GCF) as the specimen source. Examination has included: specific bacteria and their products; host cells and their products (enzymatic and antibacterial, both immunologic and non-immunologic); products of tissue injury derived from local epithelial and connective tissues and bone. Although most of the work to date has failed to provide reliable aids to the clinician, refinements in techniques for sampling and the availability of more sophisticated analytic techniques give cause for optimism. Methods proposed for detection of disease-associated bacteria in subgingival plaque vary in their sensitivity and specificity. Dark field microscopy shows some correlation with existing disease; however, the limited specificity of this method imposes severe restrictions on its usefulness. Highly specific polyclonal and monoclonal antisera to suspected pathogens Bacteroides gingivalis and Actinobacillus actinomycetemcomitans have been developed and improved methods of identification of these microbes in plaque by ELISA immunofluorescence and flow cytometry are under development. With respect to the host response, a strong correlation between antibody patterns to specific bacteria and periodontal disease categories appears to be emerging. Although most studies have focused on serum antibody derived from peripheral blood, a shift to detection of local antibody response appears to be likely. Techniques of measurement that are exquisitely sensitive have been developed for detection of major immune recognition proteins such as antibody and complement in crevicular fluid. Research efforts attempting to correlate local antibody response to local disease activity are underway. Measurement of GCF flow rate, endotoxin, H2S, butyrate and a variety of enzymes (e.g., collagenase, arylsulfatase, B-glucuronidase) show good correlation with levels of gingivitis. In periodontitis, the most promising markers of tissue breakdown are prostaglandins of the E series, the enzymes collagenase and aspartate aminotransferase, sulfated glycosaminoglycans, osteoclastic activating factor and bone resorptive capacity of crevicular cells. Assay of the migration of crevicular leucocytes in vivo can serve as an indicator of a defect in host resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Bactericidal effect of lactoferrin on Legionella pneumophila

Lactoferrin, an iron-binding protein found in mucosal secretions and in specific granules of polymorphonuclear leukocytes, has been shown to be bactericidal for a variety of organisms. In this study, the effect of lactoferrin on Legionella pneumophila was investigated. Purified human apolactoferrin was bactericidal for the Knoxville 1 strain (serogroup 1), with a 4-log decrease in viability within 2 h at 37 degrees C. Killing was dependent on the iron-free state since iron-saturated lactoferrin had no activity. Guinea pig passage of this strain did not affect its sensitivity to lactoferrin. Treatment of the cells with dilutions of the lactoferrin resulted in correspondingly reduced killing. Activity was temperature dependent; there was no loss of viability at 1 or 22 degrees C and slightly enhanced killing at 41 degrees C. Addition of Mg2+ blocked bactericidal activity. In addition, mature human milk, a lactoferrin-containing mucosal secretion, was also bactericidal for L. pneumophila. As demonstrated with the purified lactoferrin, bactericidal activity was lost when the milk was iron saturated.

Chédiak-Higashi syndrome neutrophils are characterized by the absence of both normal azurophilic granules

Neutrophils from two Chédiak-Higashi syndrome brothers were isolated, suspended in heparinized sucrose, lysed, and filtered. The granule-rich filtrate was centrifuged on a sucrose gradient (rho = 1.287-1.10 g/ml) at a mean force of 95,000g for 4 hours. The gradients contained one band at rho = 1.18 g/ml (band C) which was broader than normal and lacked normal bands A, rho = 1.22 g/ml, and B, rho = 1.20 g/ml. Gradient fractions were assayed for enzyme activities and protein. No marker enzymes identified densities normally occupied by bands A and B, and of the enzymes measured, only lysozyme showed peak activity with band C. Thus, only normal specific granules were present. Two azurophil granules, normally present and separable, were absent. Also identified was eosinophil granule peroxidase at rho = 1.24 g/ml (band E). Alkaline phosphatase, not a granule marker, was twice normal at the normal density, rho = 1.14-1.15 g/ml, consistent with an increase in unidentified membranes. A lysate gradient suggested that the giant azurophilic granules were rho = 1.25-1.27 g/ml. These neutrophils contain blue-grey or slate-grey giant granules, which are not truly azurophilic or basophilic, but should continue to be identified as azurophilic to conform to the convention making "azurophilic" and "peroxidase-positive" synonymous. The eosinophils contain normal eosinophil granules as well as giant inclusion granules. In contrast, neutrophils are deficient in both normal azurophilic granules.

Lysozyme-mediated aggregation and lysis of the periodontal microorganism Capnocytophaga gingivalis 2010

The ability of lysozyme to aggregate and lyse the gram-negative capnophilic periodontal microorganism Capnocytophaga gingivalis 2010 was monitored optically at 540 nm. Both hen egg white and chromatographically purified human lysozymes had significant but similar aggregation potentials for both logarithmic- and stationary-phase bacteria. In general, an increase in enzyme concentration resulted in a graded increase in both the initial and maximum changes in turbidity which occurred during the reaction period. The greatest change in turbidity occurred within the initial minutes of interaction of lysozyme and the cells, and the extent of aggregation paralleled a rapid depletion of lysozyme by the suspensions during the first minute of its incubation with the bacteria. Interestingly, the muramidase inhibitors N-acetyl-D-glucosamine and histamine did not block aggregation, whereas maleylation of lysozyme completely inhibited its aggregating ability. Demaleylation, however, restored aggregation activity comparable to the native enzyme, indicating that maleylated lysozyme retained its integrity and that aggregation was primarily dependent on charge. The addition of up to physiological concentrations of NaHCO3 and NaCl to cell aggregates resulted in varying degrees of deaggregation and lysis. Surprisingly, ultrastructural analysis of lysozyme-treated cells revealed morphological changes with or without the addition of salt. Damage appeared to occur at the blunted polar end of the cells where there was a large spherical outpouching bordered by a damaged cell envelope. Damaged cells uniformly contained dense granular cytoplasmic debris. In effect, the cationic enzyme lysed C. gingivalis 2010, which was not apparent in the spectrophotometric assay. The paradoxical finding that during bacterial aggregation there was lysis may be of significance to the further elucidation of lysozyme's antibacterial role in the gingival sulcus.

Ingestion and intracellular survival of Brucella abortus in human and bovine polymorphonuclear leukocytes

Bovine polymorphonuclear leukocytes (PMNs) were found to be significantly more bactericidal than human PMNs against a smooth-intermediate strain of Brucella abortus (45/0), whereas there was no difference in bactericidal activity of the two kinds of PMNs against a rough strain of B. abortus (45/20). Electron microscopy of thin sections of PMNs revealed that both strains of B. abortus were readily ingested; however, the extent of degranulation was significantly less than in PMNs incubated with an extracellular parasite, Staphylococcus epidermidis. Amounts of myeloperoxidase and lactoferrin released through exocytosis by PMNs incubated with S. epidermidis were 4.7- and 1.2-fold greater, respectively, than those released from PMNs incubated with B. abortus 45/0. When azurophil and specific granules were isolated after incubation of PMNs with either B. abortus 45/0 or S. epidermidis, results showed that the extent of degranulation by both types of granules was greater in PMNs incubated with S. epidermidis than in those incubated with B. abortus 45/0. Amounts of degranulation by azurophil and specific granules were similar in PMNs incubated with either the smooth-intermediate strain 45/0 or the rough strain 45/20. Degranulation was not stimulated when glutaraldehyde-killed strain 45/0 was substituted for viable cells. These data suggest that B. abortus does not stimulate an effective level of degranulation after ingestion, as observed with extracellular parasites, and that the smooth intermediate strain 45/0 is more resistant to intraleukocytic killing system than the rough strain 45/20.

Nonoxidative antimicrobial reactions of leukocytes

Increasingly abundant evidence supports the hypothesis that PMNs and perhaps alveolar macrophages have antimicrobial mechanisms independent of the presences of molecular oxygen for effective action against an array of bacteria and against some fungi. Eosinophils have mechanisms toxic for schistosomula and Trichinella larvae. In all instances the antimicrobial substances isolated have been cationic proteins and, in PMNs, associated with the azurophil cytoplasmic granules of the PMNs. Several of these substances have thus far demonstrated no enzymic function. Two of these substances are serine proteases but in one, chymotrypsin-like protein, the antimicrobial action depends on the cationic properties of the protein and is independent of the proteolytic action of the substance. In most instances, these proteins are cationic due to relatively large proportions of arginine. In two instances, a large proportion of lysine is present. All have high proportions (about 50%) of hydrophobic amino acid. Such proteins occur in the PMNs of man, rabbit, guinea pig, rat, cow, and chicken. The present view is that they are most active against gram-negative bacteria. At least two of them-37-kd and 57-kd proteins (Shafer and Spitznagel, 1983)-act on S. typhimurium in a manner analogous to that of polymyxin B through binding to lipid A. Currently available results shows that anaerobic PMNs have substantial antimicrobial capacity. Whether this capacity is due to the O2-independent mechanisms discussed in this chapter remains to be established with greater certainty.

An enzyme-linked immunoassay (ELISA) for measurement of lactoferrin

An enzyme-linked immunosorbent assay has been developed for quantitation of lactoferrin (LF) in body fluids. An indirect double-sandwich method was used which allows a sensitivity of 3 ng LF/ml in samples of polymorphonuclear cell lysates and serum. Mean LF content of serum was 0.307 +/- 0.066 micrograms/ml (n = 18). Mean LF content of polymorphonuclear cells was 4.90 +/- 1.48 micrograms/10(6) PMN. Concentrations of LF were similar in serum and in plasma of EDTA anticoagulated blood. Advantages of this method include its rapidity, and radioactivity is not required.

Lysozyme and lactoferrin quantitation in the crevicular fluid

This study was designed to determine if quantitation of lysosomal products in crevicular fluid may be useful as a diagnostic test to evaluate clinical status in periodontal disease. Levels of lysozyme and lactoferrin were quantitated in crevicular fluid from patients with gingivitis, generalized adult periodontitis, localized juvenile periodontitis and normals. Crevicular fluid (CF) was collected from each patient by standardized filter paper strips and evaluated for lysozyme and lactoferrin by rocket immunoelectrophoresis. Levels of lysozyme (micrograms of protein per microliter of CF) were significantly higher in localized juvenile periodontitis patients as compared to gingivitis and adult periodontitis. On the other hand, levels of lactoferrin (micrograms of protein per microliter of CF) did not show significant differences between gingivitis, adult periodontitis and localized juvenile periodontitis. These results indicate that a lysozyme to lactoferrin ratio could be of value as a diagnostic test for localized juvenile periodontitis patients.

A novel type of cytoplasmic granule in bovine neutrophils

We obtained cell preparations containing greater than 95% neutrophils from freshly drawn bovine blood. The cells were suspended in sucrose and disrupted in a Dounce homogenizer, and the postnuclear supernate was fractionated by zonal differential sedimentation and by isopycnic equilibration. The subcellular fractions were characterized biochemically by testing for marker enzymes and other constituents known to occur in azurophil and specific granules of other species, and by electrophoretic analysis of extracts of the particulate material. In addition, each fraction was examined by random-sampling electron microscopy. We found that bovine neutrophils contain in addition to azurophil and specific granules a third type of granule, not known to occur in neutrophils of other species. These novel granules are larger, denser, and considerably more numerous than the two other types. Except for lactoferrin, they lack the characteristic constituents of azurophil granules (peroxidase, acid hydrolases, and neutral proteinases) and of specific granules (vitamin B12-binding protein). Instead, they contain a group of highly cationic proteins not found in the other granules, and they are the exclusive stores of powerful oxygen-independent bactericidal agents. We studied the fate of the large granules in bovine neutrophils exposed to opsonized particles, the ionophore A 23187, or phorbol myristate acetate. The appearance in the cell-free media of antibacterial activity and of the characteristic highly cationic proteins as revealed by electrophoresis was monitored and compared with the release of azurophil and specific granule markers. In addition, changes of the relative size of the large granule compartment induced by phagocytosis were assessed by morphometry. The results show that exocytosis of the large granules occurs following both phagocytosis and exposure to soluble stimuli. Like the specific granules, the large granules appear to be discharged by true secretion under conditions where the azurophil granules are fully retained.