Lymphokine-induced production and release of lysosomal enzymes by macrophages

Fate of Mycobacterium tuberculosis inside rat peritoneal macrophages in vitro

Rat peritoneal macrophages in vitro were infected with Mycobacterium tuberculosis and the fate of M. tuberculosis inside macrophages was monitored. Alteration in the levels of nitric oxide (NO) measured in terms of nitrite formed, hydrogen peroxide (H2O2) and lysosomal enzymes such as acid phosphatase, cathepsin-D and beta-glucuronidase in macrophages following M. tuberculosis infection was also studied. Elevation in the levels of nitrite were observed from 72 h of M. tuberculosis infection. Irrespective of the time point, M. tuberculosis infected macrophages produced elevated levels of H2O2. Maximum increase in the level of acid phosphatase was observed from 72 h of M. tuberculosis infection, whereas maximum elevation in the level of beta-glucuronidase was observed 48 h after M. tuberculosis infection. However these microbicidal agents did not alter the intracellular viability of M. tuberculosis.

Role of lysosomal enzymes in tissue damage during hepatic amoebiasis. An experimental study

Two key lysosomal enzymes, N-acetyl-beta-glucosaminidase and beta-glucuronidase of Kupffer cells and blood monocytes were studied in guinea pigs infected intramesenterically with E. histolytica. The animals were sacrificed on days 0, 2, 5 and 8 post-infection. The enzyme levels in the cell lysate and supernatants of both Kupffer cells and blood monocytes were significantly higher (P less than 0.01) in the infected animals compared with the controls. This increase was more marked on the 5th and 8th days post infection (P less than 0.001). The alteration in enzyme levels was higher in Kupffer cells than in blood monocytes (P less than 0.05). The enzyme levels increased exponentially with the severity of the hepatic lesions. A direct correlation was observed between the enzyme levels and the severity of the hepatic lesions (P less than 0.01). Hence, the role of lysosomal enzymes, released by activated mononuclear phagocytic cells, in the pathogenesis of hepatic amoebiasis is postulated.

Evidence for a dentin-derived inhibitor of macrophage spreading

The ability of macrophages to spread in vitro on mineralized and non-mineralized tissues extracted with guanidium hydrochloride (GuHCl) was studied in order to establish morphologic evidence for an extractable inhibitor of macrophage spreading present within dentin. Macrophages were seeded onto dentin, demineralized dentin, predentin and hyaline cartilage extracted with different concentrations of GuHCl. Macrophages were also seeded onto unextracted tissues. The results were evaluated with scanning electron microscopy after varying incubation periods. Macrophages readily attached and spread on extracted and unextracted dentin, extracted demineralized dentin, predentin, and hyaline cartilage. Cells seeded onto unextracted demineralized dentin, predentin, and hyaline cartilage attached, but showed no signs of spreading. It was concluded that an extractable inhibitor of macrophage spreading is present in the organic, non-collagenous component of dentin. This inhibitor may be responsible for the resistance of predentin and dentin to resorption.

Secretion of an articular cartilage proteoglycan-degrading enzyme activity by murine T lymphocytes in vitro

Destruction of articular cartilage is the hallmark of inflammatory arthritides. Enzymes elaborated by mononuclear cells infiltrating the synovium mediate, in part, the degradation of the cartilage extracellular matrix. Since mononuclear cells are the dominant cell type found in chronic inflammatory synovitis, we investigated whether interaction of immune mononuclear cells with antigen initiated the synthesis and secretion of a proteoglycan-degrading enzyme activity. Proteoglycan-degrading enzyme activity was monitored by the capacity of murine spleen cell conditioned medium to release [3H]serine/35SO4 incorporated into rabbit cartilage proteoglycan monomer fraction (A1D1), and by the relative change in specific viscosity of bovine nasal cartilage proteoglycan monomer. The results demonstrated that both virgin and immune mononuclear cells spontaneously generated proteoglycan-degrading enzyme activity and that cellular activation and proliferation induced by the antigen keyhole limpet hemocyanin or the mitogen phytohemagglutinin was not required. Kinetic studies demonstrated stable release of the enzyme activity over 72 h. Cell separation studies showed that T lymphocytes, a thymoma line, and macrophages separately produced proteoglycan-degrading enzyme activity. The enzyme activity has been partially characterized and appears to belong to a class of neutral pH metal-dependent proteinases. These observations, the first to demonstrate that T lymphocytes secrete an enzyme capable of degrading cartilage proteoglycan, raise the possibility that this enzyme activity contributes to cartilage extracellular matrix destruction in vivo. Moreover, these data support the conclusion that production of this enzyme by T lymphocytes is independent of an antigen-specific stimulus.

Isolation of plasma membrane from human blood monocytes. Subcellular fractionation and marker distribution

The isolation of plasma membrane from human peripheral blood monocytes is described. Monocytes were isolated by centrifugal elutriation, to eliminate an adherence step, thus minimizing functional and surface antigenic alterations to the cells. Monocytes were surface-labelled with a radiolabelled monoclonal antibody, 125I-WVH-1, and then disrupted by nitrogen cavitation. Membranes were separated according to equilibrium buoyant density by isopycnic centrifugation on a sucrose gradient. The subcellular membranes were localized using marker enzymes for the plasma membrane, 5'-nucleotidase and leucine 2-naphthylamidase (leucine aminopeptidase), and for intracellular membranes: galactosyltransferase (Golgi), arylsulfatase C (endoplasmic reticulum), monoamine oxidase (mitochondria), catalase (peroxisomes), beta-hexosaminidase and beta-glucuronidase (lysosomal vesicles) and lactate dehydrogenase (cytosol). The monoclonal antibody 125I-WVH-1 was shown to label the plasma membrane, as judged by known markers, and represents a highly specific trace label, applicable to the use of plasma membrane as an immunogen for monoclonal antibody production. The NAD-splitting enzyme, NAD+ nucleosidase, was detected and its presence on the plasma membrane was demonstrated. The subcellular localization of non-specific esterase in human mononuclear phagocytes is controversial. No evidence was found for alpha-naphthyl acetate esterase activity on the plasma membrane or in lysosomal vesicles. However, a membrane-bound esterase in fractions with properties similar to the smooth endoplasmic reticulum was detected.

Effects of piroxicam on mononuclear cells. Comparison with other antiarthritic drugs

Piroxicam and other antiarthritic drugs were compared with respect to their effects on T-lymphocyte/monocyte/rheumatoid synovial cell interactions leading to inflammatory mediator production. Piroxicam inhibited PGE2 formation by blood mononuclear cells, but was less potent than indomethacin. Both drugs enhanced suboptimal phytohemagglutinin (PHA)-stimulated tritiated thymidine (3H-TdR) incorporation by mononuclear cells, although optimal responses were less affected. Exogenous interleukin-2 (IL-2) enhanced suboptimal but not optimal PHA responses, and the effects of the cyclo-oxygenase inhibitors were overcome by exogenous PGE2. Thus piroxicam and indomethacin prevented the inhibition by endogenous monocyte-derived PGE2 of IL-2 secretion and activity. Other antiarthritic drugs, including antimalarials, immunosuppressive agents and gold salts, inhibited PHA-induced lymphocyte proliferation regardless of the level of stimulation. Mepacrine and chloroquine were more effective in inhibiting the release of mononuclear cell factor (MCF) that stimulated PGE2 synthesis by synovial cells. Cyclosporin-A, azathioprine and 6-mercaptopurine were more potent as antiproliferative agents than as inhibitors of mediator release. Sodium aurothiomalate and aurothioglucose selectively interfered with lymphocyte-mediated amplification of MCF release, whereas auranofin inhibited spontaneous production of monocytes and the action of MCF on synovial cells. In rheumatoid synovial cells, piroxicam and indomethacin inhibited PGE2 production but not collagenase release. Suppression of MCF release could lead indirectly to reduction of IL-2 and collagenase as well as PGE2 production and consequently to more profound inhibition of immunologically-mediated inflammation.

Mechanism of enhanced humoral response in rodents by a synthetic polymer

We previously reported that administration of a low molecular weight (MW=800) synthetic polymer, NED 137, significantly increases humoral and cellular immune responses in the rat. The effect of NED 137 on the murine humoral response to T-dependent (TD) and T-independent (TI) antigens was studied in C57 BL/6, CBA/J and Balb/c mice. The TD antigens (SRBC, DNP-DA with adjuvant) or TI antigen (DNP-Ficoll) were administered simultaneously with NED 137. The polymer significantly increased the direct PFC response to all antigens tested in normal mice. However, it could not restore the PFC response to SRBC in athymic (nu/nu) mice. The effect of NED 137 on accessory cells was studied by the assessment of the in vitro response to SRBC in normal and macrophage-depleted rat spleen cultures. The polymer stimulated both, the primary and secondary IgM response and its immunopotentiating activity was the greatest in macrophage-depleted spleen cell preparations. The lack of effect of NED 137 in systems devoid of functional T cells, dependency on and specificity for a sensitizing antigen and its ability to stimulate a secondary response suggest that this polymer does not act as a "conventional" B-cell polyclonal activator.

Cell detachment and metastasis

Cancer cell detachment in three distinct and critical parts of the metastatic cascade is discussed. The detachment of cancer cells from their parent tumors is an initial early event in metastasis. The site of detachment with respect to proximity to blood vessels may determine the initial dissemination route. Many factors affect cell detachment; we specifically consider the effects of growth-rate, necrosis, enzyme activity, and stress on cell release in terms of metastasis-promoting mechanisms. Detachment is also discussed in relation to active cancer cell locomotion, where localized detachment from the substratum is a prerequisite for translatory movement. The importance of active cell movement in tissue invasion has only recently been assessed, and, in the case of at least some human malignant melanomas, a zone of actively moving cancer cells is believed to precede the growing body of the tumor. The secondary release of cancer cells from temporary arrest sites at the vascular endothelium consequent upon intravascular dissemination is also a major area of investigation. Circulating cancer cells arrest at vascular endothelium or are impacted in small vessels, however, most are released into the circulation and subsequently perish. The blood stream is a hostile environment, and it is probable that cancer cells are sufficiently damaged in translocation by hemodynamic trauma and humoral factors such that they easily detach or are 'sheared-off' the vascular endothelium by blood flow. Another possibility is that in some cases they are processed by 'first organ encounters' and perish before or shortly after arriving in a second organ. Animal studies have shown that, following intravenous injection, 60-100% of the injected dose of viable cancer cells are initially arrested in the lungs, but very few remain after 24 hr. As it is only those retained cells which produce tumors, the mechanisms involved in this secondary release, which occurs in all organs so far examined, are critical to any understanding of the metastatic cascade and metastatic inefficiency. The arrest of cancer cells at the vascular endothelium and their subsequent release have been associated with the presence of platelets, and the deposition of fibrin and manipulation of platelet-aggregating mechanisms and fibrinolysis are discussed in terms of their antimetastatic effects. The role of the reticuloendothelial system, natural killer cells, and polymorphs is discussed in relation to cancer cell clearance from blood vessels and also to inherent cancer cell properties which may act to inhibit their metastasis. Although detachment of cancer cells from a primary tumor may be regarded as metastasis promoting, secondary release of cancer cells may be associated with inhibition of metastasis.

Activated macrophages in human periodontitis

Fifteen patients, eight males and seven females, ranging from 30 to 88 years of age with advanced periodontal disease were selected for this study. Biopsies and blood samples were taken of both normal and inflamed gingival tissues, and processed for detection of nonspecific esterase and acid phosphatase activity in monocytes and macrophages. Activated macrophages, as indicated by their intense reaction to acid phosphatase and nonspecific esterase, were found in the gingival epithelium, lamina propria, perivascular tissues and in the blood vessels in human chronic periodontitis. Blood smears of monocytes showed variability of stain intensity suggesting that their activation occurred in blood vessels where they marginate and emigrate into the perivascular tissues in chronic periodontitis. They then appear as macrophages that migrate through the connective tissue, penetrate the basement membrane and continue through the epithelium. The nonspecific esterase stain identified T-cells, by a singular dot-like granule, and plasma cells by multiple granules in the cytoplasm. Lymphocytes containing multiple cytoplasmic nonspecific esterase positive granules commonly were found only in the perivascular connective tissue and may represent B-cell differentiation to plasma cells. The plasma cell predominance, the presence of T-cells and activated macrophages indicated both humoral and cell-mediated responses are operative in human chronic periodontitis.

Corynebacterium parvum treatment of P388 tumor-bearing mice. I. Lysosomal enzyme levels in adherent peritoneal cells and peritoneal lavage fluid

BDF1 mice treated with Corynebacterium parvum (C. parvum) 2 days before an implant of 106 P388 leukemic cells had up to an 110% increase in survival time above control; Bacillus Calmette-Guérin (BCG) treatment was ineffective. Acid phosphatase and beta-glucuronidase were measured in adherent peritoneal lavage cells and beta-glucuronidase in peritoneal lavage fluid form mice treated with C. parvum or BCG 2 days before the implant of P388 cells. In the presence of the tumor, adherent peritoneal cells from C. parvum-treated animals had a 250-300% increased specific lysosomal enzyme activity above control values (cells form animals receiving tumor implant alone). Peak enzyme activity which occurred on day 3 was not present in adherent cells from BCG-treated tumor-bearing animals or the control animals. The beta-glucuronidase activity in peritoneal lavage fluid was elevated by the tumor cells, BCG, or C. parvum. Peak levels occurred on day 5 regardless of the treatment with an additive effect present on day 5 in animals receiving the combination of tumor with C. parvum. The evidence indicated the development of a different pattern of enhanced lysosomal enzyme activity if the immunopotentiator protected against the P388 tumor vs one that did not. Protection was associated with an increase in lysosomal enzyme activity in adherent cells with no increase in lavage fluid in the presence of tumor cells. Changes in cellular enzyme activity may prove to be diagnostic for antitumor activity by an immunostimulant.

Effect of muramyldipeptide, a synthetic bacterial adjuvant, on enzyme release from cultured mouse macrophages

Monolayer cultures of macrophages obtained by peritoneal lavage of normal or thioglycollate-stimulated mice spontaneously secreted lysosomal enzymes into the culture medium. When the elicited macrophages were cultured in the presence of muramyldipeptide (MDP), a 20-30% increase in the release of beta-glucuronidase was consistently observed and the intracellular activity decreased to about 45% of that of control cells after 6-8 days' culture. A stimulatory effect of MDP on lysozyme secretion, though less profound, was also observed. In contrast, release of neither enzyme was stimulated in resident macrophages by the addition of MDP. A neutral alpha-glucosidase, which has recently been found to localize also in granules of macrophages, remained inside the cells and neither its activity nor its release was affected by the addition of MDP to either type of macrophages. A large amount of lactic dehydrogenase was released only when the resident, not the elicited, macrophages were cultured for 3-4 days and then phagocytosed zymosan.

Exocytosis by macrophage polykarya: an ultrastructural study

Macrophage polykarya selectively secrete their lysosomal contents directly into the extracellular space or into the intracytoplasmic membranous labyrinth. Fusion of the lysosomal membrane with the plasmalemma or with the cytoplasmic labyrinth results in the release of the lysosomal contents. The labyrinth, however, was shown to be essentially similar to the plasmalemma, hinting that comparable mechanisms are involved in both instances. The process of secretion is unrelated to motility and phagocytosis and may be important in the extracellular degradation of biological material.

The biochemistry and in vitro activity of soluble factors of activated lymphocytes

Activated lymphocytes release numerous products which are either synthesized de novo or in increased amounts; some of these products play a role in the regulation of the immune response and are designated as mediators of cellular immune reactions or lymphokines. The first lymphokine described was the macrophage migration inhibitory factor (MIF) which has been studied most extensively with regard to its chemical and biological properties. Using sensitive radiolabelling techniques and an antiserum against highly purified fractions of MIF we were able to identify several products of activated guinea pig lymphocytes with different molecular weights of 15.000, 30.000, 45.000, 60.000 which all had an isoelectric point of 5.2 and were all inhibitory to macrophage migration. It is suggested, that these molecules are oligomers of a common subunit of molecular weight 15.000. It was further shown, that molecules of the same physical-chemical and serological characteristics are produced by activated B-cells, L2C leukemia cells and growing fibroblasts, thus further substantiating earlier reports on the production of MIF by lymphoid and non-lymphoid cells. The described molecules were also shown not to contain determinants of the major histocompatibility complex and to be distinct from lymphotoxin, another lymphocyte activation product. It is concluded, that MIF is not a single molecule but rather a system of structurally related molecules. Their interaction with macrophages and possible relationships to macrophage activating factor is discussed.

Antigen-antibody complexes stimulate the synthesis and release of prostaglandins by mouse peritoneal macrophages

Antigen-antibody complexes (Ag/Ab) formed at equivalence stimulate the release of arachidonic acid and synthesis of prostaglandin E2 and 6-keto-prostaglandin F1 alpha by resident mouse peritoneal macrophages. Prostaglandin synthesis and secretion is stimulated by submicrogram quantities of Ag/Ab which increases in a dose-dependent manner. This release is time-dependent and occurs in the absence of any loss of cell viability as indicated by increased cellular levels of lactate dehydrogenase without concomitant loss of this activity to the media and the continued secretion of a constitutive cellular product, lysozyme. The stimulated synthesis of prostaglandins by Ag/Ab is inhibited by indomethacin and physiological levels of antiinflammatory glucocorticoids.

Antigen- or mitogen-provoked spleen cells produce factors that stimulate the secretion of macrophages of a neutral proteinase degrading cartilage proteoglycans

Soluble products released by rabbit spleen cells on stimulation with either mitogen or antigen markedly stimulate the secretion of a proteoglycan-degrading neutral proteinase by rabbit bone-marrow macrophages.

Breakdown of articular cartilage proteoglycans by lymphokine-activated macrophages

Lymphokine supernatants (LE) prepared from antigen sensitive lymphocytes caused an inhibition of migration of macrophages from capillary tubes. Control supernatants (LC) had no effect. The lymphokine supernatants, when added to macrophage cultures (the equivalent of 60 x 10(6) lymphocytes added to 40 x 10(6) macrophages), activated the macrophages so that they secreted the enzyme collagenase after 48 h and 72 h of culture. No collagenase was detected before 48 h or from macrophage supernatants to which LC was added. The macrophage supernatants (LE but not LC) also contained factors (probably enzymes) that, when added to a piece of articular cartilage in medium, caused a partial loss of the hexosamine content of the articular cartilage. These changes were seen as early as after 24 h of culture. Activated macrophages therefore release enzymes that can completely destroy cartilage. Both collagenase and a proteoglycan-hydrolyzing enzyme are released which in vivo might be responsible for the cartilage damage that is found in diseases such as rheumatoid arthritis.

Acid hydrolases in monocytes from patients with inflammatory bowel disease, chronic liver disease, and rheumatoid arthritis

A sensitive technique was used to estimate two acid hydrolases--N-acetyl-beta-glucosaminidase (N.A.G.) and beta-glucuronidase (B.G.)--produced by peripheral-blood monocytes. Enzyme levels were measured after in-vitro incubation of monocytes with or without stimulation by zymosan and endotoxin. Compared with controls, enzyme production and release in inflammatory bowel disease, chronic liver disease, and rheumatoid arthritis were markedly raised. It is suggested that various stimuli, including immunological ones, may be responsible for the release of such enzymes from monocytes and that such release may be a factor in the production of the chronic inflammation seen in these disorders.

Degradation of cartilage proteoglycans by a neutral proteinase secreted by rabbit bone-marrow macrophages in culture

When cultivated together with pieces of cartilage biosynthetically labelled with 35S in their proteoglycans, rabbit macrophages, differentiated in vitro from bone-marrow cells, cause the release of soluble 35S-labelled material into the culture medium. This process is inhibited by killing the macrophages or by cycloheximide treatment, and is due to the secretion by the cells of a metal-dependent neutral proteinase capable of degrading cartilage proteoglycan subunits into fragments of high molecular weight. Enzyme activity is optimum at about pH7, and is inhibited by EDTA, o-phenanthroline, cysteine or serum, but not by di-isopropyl phosphorofluoridate nor by 4-hydroxymercuribenzoate. The effect of EDTA is partially reversed by Co2+ or Zn2+ ions. The enzyme is eluted from Sephadex G-150 columns as a single peak of material (apparent mol.wt. 17000) that contains also most of the proteolytic activity exerted by culture media on Azocoll (denatured collagen) or on casein. The possible role of this metalloproteinase in chronic inflammatory processes is discussed, particularly in connection with joint erosions in rheumatoid arthritis.

Extracellular hydrolytic enzymes of rabbit dermal tuberculous lesions and tuberculin reactions collected in skin chambers

To evaluate extracellular hydrolytic enzymes in an in vivo system, plastic chambers were glued over rabbit dermal BCG lesions in various stages of development, after the central epithelium was removed with a scalpel. They were filled with tissue culture medium and left in place 2 days. The following enzymes in the fluid were assayed: collagenase (an enzyme secreted but not stored in macrophages); lysozyme (both secreted and stored); DNase and RNase (released on cell death and possibly regurgitated but not secreted); and, as a control, lactic dehydrogenase (released only on cell death). Tissue sections were prepared and studied histologically for the type of cell infiltrate, for beta-galactosidase (our marker enzyme for macrophage activation), and for necrosis. At 11 and 18 days of age the BCG lesions were largest and the number of activated macrophages in the chamber beds was highest. At this time the levels of the five enzymes assayed in the chamber fluids reached their peaks, tuberculin hypersensitivity was well developed, and the bacilli components would still be plentiful. In general, the chamber fluids from 11- and 18-day BCG lesions contained higher enzyme levels than chamber fluids from tuberculin reactions. Active collagenase was only detected in fluids from such BCG lesions. Evidently, the serum in the chamber fluids was sufficient to inhibit the lower amounts of collagenase probably released from smaller BCG lesions and tuberculin reactions (and from the 2-week polystyrene lesions that were also evaluated). These studies demonstrate that in chronic inflammatory reactions, both acid-acting and neutral-acting hydrolytic enzymes are released extracellularly. Tissue components would be hydrolyzed locally wherever the acid-acting hydrolytic enzymes encounter a drop in pH and wherever the concentration of neutral-acting hydrolytic enzymes exceeds the concentration of their inhibitors.

The role of macrophage activation in chronic inflammation

The macrophage is the characteristic cell type in chronic inflammatory reactions, in the rheumatoid synovium, as in other sites. When macrophages are activated, considerable synthesis of enzymes and other proteins occurs. Macrophages can be activated by (i) products of activated lymphocytes, (ii) immune complexes and (iii) the complement cleavage product C3b. Among the many consequences of macrophage activation are (i) secretion of hydrolytic enzymes, (ii) cleavage of C3 into C3a, which is cytolytic, and C3b, (iii) production of tissue thromboplastin, a powerful procoagulant, and (iv) formation of polyamine oxidase, which in the presence of appropriate substrates generates factors that lyse or limit the proliferation of tumour cells, lymphocytes and micro-organisms. The relevance of these observations to the pathogenesis of chronic inflammatory reactions is discussed.

Lysosomes and membrane recycling. A hypothesis

A mechanism for intralysosomal membrane recycling is proposed. After invagination of the lysosomal membrane during autophagy, intralysosomal vesicles are formed. It is suggested that membrane can bleb out from these internal vesicles, probably in the form of very small vesicles, and return to the external lysosomal membrane by membrane fusion. This mechanism would conserve lysosomal membrane during autophay, and is analogous to current models of plasma-membrane recycling. Its relationship to turnover of lysosomal-membrane proteins and other proteins is discussed.

The selective release of lysosomal acid hydrolases from mouse peritoneal macrophages by stimuli of chronic inflammation

The paralelism between the capacity of various agents to elicit chronic inflammatory responses in vivo and to induce the selective release of lysosomal enzymes from cultures of mouse peritoneal macrophages in vitro is discussed. Zymosan elicits an intense inflammatory response when injected i.m. in mice. Chrysotile asbestos produces a response of a similar nature and intensity as is seen with zymosan, while injections of acid-leached asbestos and polystyrene latex are not followed by inflammation. It is also shown that zymosan and asbestos induce a dose-dependent increase in the total enzyme activity of an inflamed muscle. On the other hand latex and acid-leached asbestos caused no significant increases in lysosomal enzyme levels. Agents eliciting inflammatory responses, such as zymosan and chrysotile asbestos induce a selective release of acid hydrolases from cultured macrophages; in contrast agents lacking the capacity to induce inflammation, such as latex and acid-leached chrysotile asbestos, do not induce the release of lysosomal enzymes from cultured macrophages.

Experiments on lymphocyte-mediated cellular immunity in murine histoplasmosis

Peritoneal exudate cells from immunized mice inhibit the intracellular growth of Histoplasma capsulatum. The lymphocyte is the mediator cell of this phenomenon. Lymphocytes from immunized animals are highly activated cells. Supernatants from cultures of immune lymphocytes or from cultures of mitogen-stimulated lymphocytes did not arm macrophages from normal animals to inhibit the intracellular growth of H. capsulatum.

Lymphokine-induced secretion of plasminogen activator by murine macrophages

Thioglycollate-stimulated macrophages are known to release a plasminogen activator (PA) into the medium. In this study it was investigated whether macrophages could be activated to release PA after exposure to lymphokines. Macrophage monolayers obtained by 24 h culture of proteose peptone-elicited murine exudate cells were incubated with lymphocyte culture supernatants. After 48 h the supernatants were replaced by serum-free medium and the macrophages were incubated for another 24-48 h. These supernatants were assayed for PA as measured by the lysis of 125I-labeled fibrin. The following results were obtained: (a) Supernatants of antigen or mitogen-stimulated spleen cells induced PA secretion by macrophages whereas control supernatants were ineffective. The same was found with supernatants of mitogen-stimulated lymph node cells. (b) PA secretion by macrophages seems to be induced by a rather narrow concentration range of lymphokines. (c) Lymphokine-induced PA secretion by macrophages is enhanced after phagocytosis of latex beads. The results show that PA secretion by activated macrophages can be considered as a parameter of immunoactivation.

Partial purification and properties of an antibacterial product of peritoneal exudate cell cultures from BCG-infected guinea pigs

Peritoneal exudates elicited in BCG-infected guinea pigs with caseinate yield cell cultures that have been shown to produce soluble material capable of sterilizing certain bacteria if the cultures are incubated with the specific antigen purified protein derivative or the lectin phytohemagglutinin. This material is now shown to have the following properties: (i) strongly adsorbable to glass; (ii) strongly adsorbable to cation- and not to anion-exchange resins but not elutable with mineral acid or solutions of high ionic strength; (iii) strongly adsorbable to cellulose nitrate membrane filter materials and quantitatively elutable with dilute HCl, providing a convenient method for partial purification; (iv) relatively stable over a wide range of pH and temperature; (v) antagonized by polyanions and by iron ions; (vi) active against the three gram-positive bacilli tested and not against the other organisms tested: (vii) more active in alkaline than in acidic media; and (viii) inactivated by proteolytic enzymes.