A histochemical study of phagocytic and enzymatic functions of rabbit mononuclear and polymorphonuclear exudate cells and alveolar macrophages. I. Survey and quantitation of enzymes, and states of cellular activation

Purification and properties of the cathepsin D types proteinase from beef and rabbit lung and its identification in macrophages

The acid-acting proteinase, cathepsin D (EC 3.4.4.23), was purified from extracts of homogenized rabbit lung and beef lung by autolysis at acid pH, acetone and ammonium sulfate fractionation, column chromatography, and isoelectric focusing. Four isoenzymes were obtained from each source. With acid hemoglobin as the substrate, the proteinase from rabbit lung had a pH optimum of 3.0 and that from beef lung had a pH optimum of 3.6. Their activity was not affected by thiol reagents or by Fe(2+), Mn(2+), or Mg(2+). One isoenzyme from rabbit lung was used to immunize a goat, and one from beef lung was used to immunize a rabbit. In immunoelectrophoresis, each resulting antiserum formed a single precipitin line with its homologous enzyme. They cross-reacted with the other three isoenzymes from the same species, but not with any isoenzyme from the other species. At high concentrations, each antiserum completely inhibited the proteolytic activity of its homologous enzyme. The antiserum against rabbit lung cathepsin D also inhibited the proteolytic activity of rabbit peritoneal and pulmonary macrophages. In limited quantities, this antiserum has now been made commercially available and is being used with labeled antibody techniques to identify under a microscope the presence of cathepsin D in macrophages and to study its role in the pathogenesis of tuberculosis.

Experimental lung injury. I. Bacterial pneumonia: ultrastructural, autoradiographic and histochemical observations

Proteus infection in the rat produces an acute bacterial pneumonia which resolves without necrosis or significant organization within 2 weeks. Ultrastructural changes included widespread damage to type 2 cells and endothelial cells and rapid proliferation of the alveolar epithelial cells, which were the predominant site of labeling with tritiated thymidine. Histochemical staining for lysosomal enzymes showed an initial reduction in type 2 cell reactivity. The majority of proliferating epithelial cells were also unreactive until the normal pattern of staining and morphology returned at 8 to 12 days after infection. The acute inflammatory exudate was reactive, but there was only minimal to moderate staining in the subsequent clusters of alveolar macrophages. These data suggest that resolution with the preservation of the normal architecture of the peripheral airspaces may be correlated with superficial injury and limited reactivity for digestive enzymes.

Enhanced in vitro phagocytic power of macrophages from PPD-stimulated skin sites in human subjects hypersensitive to PPD

By a quantitative Rebuck's skin-window technique human macrophages were collected from individuals either unreactive or hypersensitive to PPD, the latter having recovered from tuberculous infection.

In vitro testing of macrophages with a strain of Paracolonbacter aerogenoides proved that cells from hypersensitive convalescents were provided with increased pagocytic and bactericidal activities. An even higher degree of macrophage activation was attained when cells from hypersensitive individuals had previously been stimulated in vitro with PPD. Changes of macrophage functions such as those mentioned above might well result from the action on macrophages of lympho-kine-like agents released by sensitized lymphocytes coming in contact with PPD.

Inhibition of cathepsin D-type proteinase of macrophages by pepstatin, a specific pepsin inhibitor, and other substances

The macrophage is the main cell participating in chronic inflammation. It contains an acid-acting, cathepsin D-type proteinase with the specificity of pepsin, which may release mediators of the inflammatory process. To find new pharmaceutical inhibitors of this proteinase, we tested a variety of chemical compounds in vitro. For this survey, the possible inhibitor (at a concentration of 0.4 mg/ml) was assayed with partially purified cathepsin D-type proteinase from beef lung (a macrophage-rich tissue) and hemoglobin as the substrate. Diazophenylbutanone, three acetophenones, two barbiturates, a gold salt, a copper chelate of a substituted nicotinic acid, a hexapeptide containing a d-amino acid, and Pepstatin inhibited this enzyme; over 200 other potential inhibitors did not. By far the most active and specific inhibitor found to date is Pepstatin, a pentapeptide with two gamma-NH linkages, two beta-OH groups, and five branched aliphatic side chains. Banyu Pharmaceutical Co., Tokyo, Japan, produces this nontoxic compound for the treatment of peptic ulcers. In vitro, as little as 4 ng of Pepstatin inhibits the acid-acting cathepsin D-type proteinase purified from beef and rabbit lung as well as the similar proteinase of rabbit peritoneal and pulmonary macrophages.

Differentiation of monocytes. Origin, nature, and fate of their azurophil granules

The origin, content, and fate of azurophil granules of blood monocytes were investigated in several species (rabbit, guinea pig, human) by electron microscopy and cytochemistry. The life cycle of monocytes consists of maturation in bone marrow, transit in blood, and migration into tissues where they function as macrophages. Cells were examined from all three phases. It was found that: azurophil granules originate in the Golgi complex of the developing monocyte of bone marrow and blood, and ultimately fuse with phagosomes during phagocytosis upon arrival of monocytes in the tissues. They contain lysosomal enzymes in all species studied and peroxidase in the guinea pig and human. These enzymes are produced by the same pathway as other secretory products (i.e., they are segregated in the rough ER and packaged into granules in the Golgi complex). The findings demonstrate that the azurophil granules of monocytes are primary lysosomes or storage granules comparable to the azurophils of polymorphonuclear leukocytes and the specific granules of eosinophils. Macrophages from peritoneal exudates (72-96 hr after endotoxin injection) contain large quantities of lysosomal enzymes throughout the secretory apparatus (rough ER and Golgi complex), in digestive vacuoles, and in numerous coated vesicles; however, they lack forming or mature azurophil granules. Hence it appears that the monocyte produces two types of primary lysosomes during different phases of its life cycle-azurophil granules made by developing monocytes in bone marrow or blood, and coated vesicles made by macrophages in tissues and body cavities.

Some biochemical aspects of the immune macrophage

Some of the biochemical properties of mouse peritoneal macrophages immune to Corynebacterium ovis were characterised. Total cellular protein of immune cells exceeded that of normal phagocytes by 1·85 times. The activities of 7 hydrolytic enzymes, acid phosphatase, β-glucuronidase, Cathepsin D, lysozyme, BPN-ase, MN esterase and aryl sulphatase were measured in lysed cell suspensions and monolayer cultures. Immune macrophages possessed substantially higher levels of these enzymes than did normal cells. No one enzyme was significantly more associated with the development of cellular immunity than another. Resting immune macrophages consumed significantly less oxygen than normal cells required but were twice as active in glycolysis. ATP levels, in agreement, were 5 times higher in normal macrophages whereas ATP-ase activities were equivalent. Normal macrophages were approximately twice as active in protein synthesis measured by the in vitro incorporation of ¹⁴C L-glycine by monolayer cultures than were immune cells. These results were considered in the light of known morphological differences between the 2 cells noted at the ultrastructural level.

The distributions of some granule-associated enzymes in guinea-pig polymorphonuclear leucocytes

1. Homogenates of guinea-pig polymorphonuclear leucocytes were separated by differential centrifugation into six particulate fractions and a soluble fraction. 2. The distributions in these fractions of protein, DNA, succinate dehydrogenase, beta-glucuronidase, peroxidase, alkaline phosphatase, acid phosphatase (against p-nitrophenyl phosphate and beta-glycerophosphate), cathepsin, and catalase were compared. 3. Almost all of the DNA sedimented in the first two pellets, indicating that the nuclei were relatively intact. 4. The four hydrolases and peroxidase showed different distribution patterns, although these activities were previously reported to be localized mainly in the single ;granule' fraction isolated from leucocytes. 5. The particles containing peroxidase, acid phosphatase and alkaline phosphatase all exhibited latency. Maximum activity for each enzyme was obtained at roughly similar concentrations of Triton X-100. 6. The acid phosphatase of these cells was distributed between two populations of particles that differed in both sedimentation characteristics and density. The acid phosphatase(s) of the two populations showed slightly different substrate specificities. This bimodal distribution was not an artifact of the procedure used to elicit the cells. 7. Catalase was recovered almost entirely in the soluble fraction and showed no latency in freshly prepared homogenates. No urate oxidase was detected. 8. We conclude that the ;granule' fraction of the polymorphonuclear leucocyte, as isolated by previous workers, contains at least three, probably more, populations of particles with different enzyme contents, and that these cells probably do not contain peroxisomes.

Cellular hypersensitivity and cellular immunity in the pathogensis of tuberculosis: specificity, systemic and local nature, and associated macrophage enzymes

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Serum and urinary lysozyme (muramidase) in monocytic and monomyelocytic leukemia

Markedly increased quantities of lysozyme have been found in the serum and urine (ranging to 2.6 g per day) of ten consecutive cases of monocytic and monomyelocytic leukemia. The enzyme has been isolated from the urine of several cases and physicochemically and immunochemically characterized. It is apparently identical to the lysozyme of normal tears, saliva, leukocytes, and serum, but structurally different from the lysozyme of hen's egg white. The activity of the human enzyme assayed with M. lysodeikticus organisms is 3 to 12 times greater than egg white lysozyme at equivalent concentrations. An agar plate method has been developed for quantitating lysozyme activity in small samples (approximately 25 microl) of serum, urine, or other biological fluids. The range and reproducibility of this method were found to be superior to previously available lysozyme assay procedures. Present evidence indicates that lysozyme is the principal, if not the sole, product of the proliferating monocytes in monocytic and monomyelocytic leukemia, and quantitation of serum and urine lysozyme should be a useful diagnostic procedure for these leukemias.

Metabolism of Alveolar Cells: Histochemical Evidence and Relation to Pulmonary Surfactant

Large alveolar cells of normal dog lung are rich in enzymes concerned with oxidative and synthetic pathways. In three experimental situations where ability of the lung to produce surfactant was impaired, the enzyme-rich cells were lacking or absent. Findings support the concept that these cells are sites of active metabolism, possibly including production of surfactant.

PHAGOCYTOSIS OF BACTERIA BY HETEROPHIL LEUKOCYTES: ACID AND ALKALINE PHOSPHATASE CYTOCHEMISTRY

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AMINOPEPTIDASE ACTIVITY IN MYOCARDIAL INFARCTION OF MAN. A HISTOCHEMICAL STUDY

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