Experiemental and clinical studies on muramidase (lysozyme). I. Muramidase activity of normal human blood cells and inflammatory exudates

Intracytoplasmic Lysozyme in Malignant Hematologic Disorders: An Immunoperoxidase Study

Intracytoplasmic lysozynie was studied by the peroxidase antiperoxidase (PAP) and protein A-peroxidase methods in 130 cases of various myeloproliferative and lymphoproliferative disorders and 21 lymph nodes and bone marrow metastases from solid primary tumors. This marker, which can be identified in formalin or Zenker-fixed tissues, as well as in peripheral blood and bone marrow smears, proved useful to distinguish malignant myeloid and histiocytic tumors from malignant lymphoid and undifferentiated epithelial metastases. The diagnostic application of these findings are discussed.

Bacterial and Polymorphonuclear Leukocyte Contribution to Middle Ear Inflammation in Chronic Otitis Media with Effusion

Bacteria can be cultured from approximately one third of chronic middle ear effusions, yet the contribution of these bacteria to the pathogenesis of chronic otitis media with effusion (OME) is not clear due to the absence of signs and symptoms of acute infection in most children with this disease. To explore the role of bacteria in chronic OME, lysozyme, lactoferrin, serum complement factors C3 and C5a, and polymorphonuclear leukocyte (PMNL) chemotaxin content was measured in 21 chronic middle ear effusion samples. Concentrations of lysozyme, lactoferrin, and chemotaxin were significantly higher in culture-positive than in sterile effusions. Lysozyme appeared to be contributed by both PMNL and non-PMNL sources in the middle ear space. These non-PMNL sources, presumably middle ear epithelial cells, accounted for 50% to 80% of the lysozyme variation in middle ear effusion. Although C3 and C5a were present in effusion, chemotaxin content correlated poorly with the C3 and C5a content, suggesting that chemotaxins were derived from bacterial peptides rather than from complement activation products. These results suggest that bacteria contribute to chronic middle ear inflammation with effusion. The eradication of bacteria from chronic middle ear effusion might disrupt the host responses which maintain chronic OME.

Lactoferrin, lysozyme, and beta 2-microglobulin levels in cerebrospinal fluid: differential indices of CNS inflammation

The CSF levels of lactoferrin, lysozyme, and beta 2-microglobulin (beta 2 mu) were measured in patients with evident, probable, or possible inflammatory CNS reactions and compared to those found in neurologically apparently healthy patients. Patients with viral CNS infections had significantly raised beta 2 mu and lysozyme levels but normal lactoferrin levels, indicating a local activation of lymphocytes and monocytes but not of granulocytes. Patients with bacterial CNS infections had significantly raised levels of all three cell markers, but the increase of lysozyme and lactoferrin was relatively more pronounced than that of beta 2 mu, indicating that the inflammatory response to bacterial agents is dominated by monocytes and granulocytes. Patients with primary or secondary malignant brain tumors were characterized by a moderate increase of beta 2 mu and a considerable increase in both lysozyme and lactoferrin, i.e., the same protein pattern as observed in bacterial CNS infection. The lysozyme levels were moderately increased in half the patients with benign cerebral tumors while the levels of beta 2 mu and lactoferrin were normal, indicating that benign and malignant brain tumors induce different local inflammatory CNS reactions. Half the patients with pituitary gland adenoma had elevated beta 2 mu and lysozyme levels but normal lactoferrin levels, suggesting that immunological mechanisms are associated with the adenoma development. Patients with MS had moderately but significantly raised CSF levels of beta 2 mu and lysozyme and a third of them also had raised levels of lactoferrin, a protein pattern suggesting a low-active inflammatory process in CNS involving mononuclears and granulocytes. A similar protein pattern was found in Guillain-Barré syndrome. In cerebrosarcoidosis we noted considerably increased lysozyme and beta 2 mu but normal lactoferrin levels, consistent with the idea that the sarcoid granuloma mass is dominated by monocytic inflammatory cells. The data obtained indicate a clinical value of lactoferrin, lysozyme, and beta 2 mu as differential indices of inflammatory cell reactions taking place in various CNS processes.

Lactoferrin, lysozyme, and beta 2-microglobulin in cerebrospinal fluid. Elevated levels in patients with acute cerebrovascular lesions as indices of inflammation

Serial determinations of beta 2-microglobulin, lactoferrin and lysozyme in CSF were performed in 14 patients with acute cerebrovascular lesions. Marked elevations were noted in patients with cerebral bleeding or hemorrhagic infarction. Patients with infarction without signs of bleeding or with cerebrovascular lesions undetectable by computed tomography also had an increase in these proteins. The increases in CSF of beta 2-microglobulin, lactoferrin and lysozyme could not be explained by a damaged blood-brain barrier but was believed to be a local product of the central nervous system. Peak levels of lactoferrin and lysozyme were noted on day 2-3 after onset of symptoms. Lactoferrin then declined while lysozyme remained elevated for another few days. beta 2-microglobulin gradually increased reaching peak levels on day 4-5 and remained elevated even 2 weeks after the onset of symptoms. We suggest that the increases of lactoferrin, lysozyme and beta 2-microglobulin reflect various inflammatory reactions mediated by granulocytes, macrophages and lymphocytes, respectively.

A simple lysoplate method of lysozyme determination with samples dried on filter paper

A simple method for quantifying lysozyme in serum and urine has been established by modifying the procedures of sample application in the lysoplate method reported by Osserman and Lawlor [1]. A strip of filter paper is partially immersed in a liquid sample, dried at room temperature and cut into discs which are later placed on the surface of an agarose gel containing Micrococcus lysodeikticus. The follow-ng procedures for determination are carried out as described in the lysoplate method. There was no statistically significant loss of enzyme activity during the sample preparation. Lysozyme dried on filter paper is so stable that it can be stored at room temperature for at least 13 weeks and can be mailed. The sensitivity of the method is increased by pretreatment of the filter paper with Triton X-100 and consequently corresponds to that of the lysoplate method. The reproducibility of our method is practically good since the variation coefficient of the diameters of lytic zones within assays is around 1%. There is a very close correlation between lysozyme levels determined by this method and by the lysoplate method with serum samples obtained from patients with various hematological diseases (r = +0.994). The method can be utilized for routine clinical determinations of lysozyme.

Lactoferrin content of peripheral blood cells

The peripheral blood of 60 normal adults was separated into plasma, red cells, neutrophils, lymphocytes, monocytes and platelets. Lactoferrin concentrations were measured in the plasma and cell extracts and compared to those of lysozyme. The neutrophil lactoferrin content in males and post-menopausal females was found to be significantly higher than in pre-menopausal females. A small amount of lactoferrin was found in association with monocytes, but not with lymphocytes, erythrocytes and platelets. Neutrophil lysozyme concentrations did not exhibit any variation with sex and age; but the level in monocytes was higher than that in neutrophils. No correlation was observed between individual neutrophil lactoferrin values and the plasma level. Immunofluorescent studies showed neutrophils to have a lobulated pattern suggestive of nuclear staining. Monocytes did not show direct staining, but exhibited a peripheral pattern after prior exposure to lactoferrin--confirming the existence of a surface receptor. Gel chromatography indicated that neutrophil lactoferrin is in a polymerized or complexed form which elutes with the void volume on Sephadex G-200; serum lactoferrin consists of two forms, one of which also elutes with the void volume on Sephadex G-200.

Diagnostic value of lysozyme activity estimation in the feces of infants with acute diarrhoea

The activity of lysozyme in feces was estimated in a control group of 50 healthy infants and in a group of 152 infants with acute diarrhoea. All infants investigated were artificially nourished. In the latter group the activity of lysozyme was estimated twice: a) at the beginning of clinically active phase of the disease and (b) in the convalescence period immediately after withdrawal of clinical symptoms. The range of normal values was 14.9--77.0 (average 44.0) of egg-white lysozyme units/g dry feces. In acute diarrhoea the activity of lysozyme in feces was found to be elevated in 72.4% of cases in the first determinations and in an additional 7.6% of cases in the second determination (i.e. a total of 80% of cases in both determinations). The average elevations of lysozyme activity in the feces and the dynamics of their normalization after withdrawal of clinical symptoms were generally related to the severity of the disease.

[Studies of lysozyme activity in serum, urine and blood smears from patients with haematological diseases]

Lysozyme activity was studied in blood smears, serum, and urine of patients suffering from leukaemia or other haematological diseases. Increased enzyme activity was found in myelocytic, myelomonocytic and monocytic leukaemia and equally in secondary granulocytosis and polycythaemia vera. Reduced rates were found in lymphocytie leukaemia, malignant lymphoma with bone marrow involvement, and myelophthisic conditions. A rise in urinary lysozyme occurred when the serum level exceeded 50 microgram/ml. Abundant activities were found in myelomonocytic and monocytic leukaemias. Using the bacteriolytic method in blood smears, no enzyme activity was demonstrated in cells of acute or chronic lymphocytic leukaemia, in monocytic leukaemia however, almost all cells show strong reaction. In acute myelocytic or myelomonocytic leukaemia, the portion of positive cells changes from case to case depending on the degree of cell differentiation and maturation. In chronic myelocytic leukaemia there was no difference as compared to enzyme activity of myelocytes in bone marrow of control cases. Thus the bacteriolytic demonstration of lysozyme in blood smears may additionally contribute to distinction of different types of blastic leukaemias, and serum lysozyme also may allow more reliable insight into granulocytic and monocytic myelopoiesis than morphologic studies of blood or bone marrow smears can do, e.g. in agranulocytosis and pancytopenia.

Factors influencing lysozyme determinations by the lysoplate method

Some factors influencing the lysoplate method have been investigated. The influences of pH, ionic strength and temperature of the gel medium can be explained by considering the influence of these factors upon the diffusion rate rather than upon the enzymatic properties of lysozyme. Salts and proteins present in a sample probably affect the results in a similar way. Although the method has a variation coefficient around 10% and thus an acceptable precision, its accuracy is variable and doubtful. The method could be clinically interesting, by discriminating lysozyme isoenzymes, or by indirectly detecting proteins associated with some disease states.

Lactoferrin and lysozyme levels in synovial fluid: differential indices of articular inflammation and degradation

Lysozyme and lactoferrin levels were measured in 71 synovial fluids (SF) of patients with traumatic effusions, osteoarthritis, rheumatoid arthritis, pseudogout, septic arthritis, and gout, as well as in 91 synovial fluids graded according to their neutrophil count. Elevated lysozyme levels were found in all the inflammatory arthritides and also in osteoarthritis. Lactoferrin levels were not increased in osteoarthritis but displayed a close correlation to the extent of the inflammatory response as judged by SF neutrophilia. The ratio of lysozyme to lactoferrin decreased progressively with increasing SF neutrophilia. In vitro experiments showed that lactoferrin is released from neutrophils isochronously with lysozyme and beta-glucuronidase. Lactoferrin was not found in hyaline cartilage, a tissue known to contain lysozyme. These results are consistent with belief that SF lysozyme has a major derivation from both cartilage and neutrophils, and that lactoferrin arises only from neutrophils. These findings indicate that the simultaneous measurement of lysozyme and lactoferrin provides a potentially useful index of both joint inflammation and cartilage degradation.

Serum lysozyme, antinuclear factors and antibody to native DNA

This work was done in order to investigate the previously reported antinuclear property of lysozyme (LZM). Addition of human or hen egg white lysozyme (hLZM or eLZM) to normal serum and to 11 sera with different types of antinuclear factors (ANF) produced no consistent changes in ANF titre or type. Likewise, absorption of LZM from the sera with bentonite failed to influence ANF titre and, finally, hLZM and eLZM were incapable of binding native DNA (nDNA). Elevated serum lysozyme levels in rheumatic diseases are therefore unlikely to produce false-positive results in tests for antinuclear antibodies.

Granulocyte release of vitamin B12-binders in vivo and in vitro in leukaemia and non-neoplastic leucocytosis

The unsaturated vitamin B12-binding capacities of the 'large molecular size vitamin B12-binding protein' (LBP) and the 'small molecular size vitamin B12-binding protein' (SBP) were determined by a Sephadex G 150 gel filtration method in 9 patients with chronic myelocytic leukaemia (CML), 5 patients with blast cell leukaemia and 12 patients with non-neoplastic leucocytosis. EDTA plasma and serum separated after 20 min and after 120 min were examined. In the 20 min EDTA plasma samples, the mean LBP value was 8,009 pg/ml in CML, 2,468 in blast leukaemia, 175 in non-neoplastic leucocytosis, and 57 in normal controls. The in vitro release of LBP into serum was much smaller in the leukaemias than in non-neoplastic leucocytosis. No correlation was found between the LBP values and the white blood cell counts or lysozyme values, but lysozyme was correlated to white cell count in CML. It is suggested that the plasma LBP levels reflect the fraction of LBP decay taking place at sites, e.g. the spleen, from which the released LBP can enter the circulation.

The detection of intracellular antigens in human leucocytes by immunoperoxidase staining

An immunoperoxidase procedure is described for staining intracellular leucocyte antigens in peripheral blood and bone marrow smears. Brief exposure of cell smears to a buffered formol acetone mixture was found to give optimal fixation, combining good cellular morphology with preservation of antigenic reactivity. The immunoperoxidase method is superior to immunofluorescence in that it provides a permanent preparation which can be counterstained with orthodox reagents and viewed by conventional light microscopy. In addition the technique is considerably more sensitive than immunofluorescence procedures. Immunoglobulin was demonstrated in plasma cells, Türk cells and a minority of peripheral blood lymphocytes. Lysozyme was found in cells of the neutrophil series from promyelocytes to mature granulocytes. Monocytes stained for lysozyme but the reaction was less intense than in neutrophils and some monocytes were devoid of activity. Lactoferrin stained strongly in mature neutrophil polymorphs and metamyelocytes, but was weak or absent in earlier myeloid cells. These reaction patterns are in keeping with previous reports on the distribution of these antigens in human leucocytes. In the case of immunoglobulin and lysozyme it was possible to abolish leucocyte staining by incubation of the specific antisera with the appropriate purified antigen, providing additional proof of the specificity of the reactions. Anti-ferritin antisera stained granulocytes and myeloid precursors strongly, and reached weakly with a minority of monocytes. These latter observations are not entirely in accordance with published data on the leucocyte distribution of ferritin and may be attributed to antibody activity of unknown specificity in the anti-ferritin antiserum.

Inhibition by lysozyme of growth of the spherule phase of Coccidioides immitis in vitro

Development of mature endosporulating spherules from an endospore inoculum was markedly inhibited by human or hen egg-white (HEW) lysozyme at 5 mug/ml. Mature spherules formed in medium containing 5 mug per lysozyme per ml (3.3 x 10(-7) M) were approximately 50% smaller than control spherules. In addition, lysozyme induced a large portion of the endospore inoculum to revert to the mycelial growth phase. Increasing lysozyme concentrations to 10 or 20 mug/ml prompted a nearly complete reversion of the inoculum to the mycelial phase. Mature endosporulating spherules removed from growth medium and resuspended in a solution of human or HEW lysozyme at 18 mug/ml in distilled water prompted leakage of four to five times as much of materials absorbing maximally at 260 nm into the supernatant as untreated control spherules during 90 min of incubation. This four- to fivefold increase in nucleotide loss was evident at 4, 25, and 37 C. The permeability of 1-day-old immature spherules and 8-day-old endospores was considerably altered by lysozyme treatment of cells suspended in distilled water. Large amounts of potassium and nucleotides were rapidly lost by each type of cell when treated with 20 mug of lysozyme per ml. After 270 min of exposure to lysozyme, 98% of the immature spherules and 25% of the endospores were nonviable. Lysozyme adsorption by formalin-killed spherules in the presence of varying concentrations of calcium ion and the rapid alteration of permeability seen after lysozyme treatment suggested that the cell membrane was damaged as a result of binding lysozyme.

Effects of lysozyme and chitinase on the spherules of Coccidioides immitis in vitro

Spherules of Coccidioides immitis strain Silveira produced in vitro were treated with chitinase and lysozyme. The walls of merthiolate-killed mature endosporulating spherules were degraded by chitinase (500 mug/ml) and by lysozyme (100 and 500 mug/ml). Thus, as was visible through the light microscope, the spherule wall was reduced in thickness from 1 to 2 mum to less than 0.5 mum. The degradation was evident also by release of N-acetylglucosamine, three times as much N-acetylglucosamine being released by chitinase in 12 h as was released by lysozyme in 3 days. However, the effect of lysozyme on living mature spherules was in marked contrast to the effect of chitinase in that treatment with lysozyme led to marked reduction in viability. Exposure to lysozyme (500 mug/ml) for 48 h permitted survival of only 0 to 0.2% of spherules. Thinning of the walls was observed only in the larger spherules (25-35 mum) treated with lysozyme. By contrast, chitinase (500 mug/ml) led to complete dissolution of the walls of living mature spherules but the viability of the liberated endospores was unaffected during contact with chitinase for 48 h. Living non-endosporulating immature spherules and free endospores were also rendered nonviable by lysozyme but not by chitinase.