An inhibitor of cell proliferation released by cultures of macrophages

Evidence for the involvement of a macrophage-derived chemotactic mediator in the neutrophil recruitment induced by staphylococcal enterotoxin B in mice

Staphylococcus aureus secretes enterotoxins which are superantigens and the major cause of food poisoning in man. Staphylococcal enterotoxins types A and B can induce neutrophil migration into the peritoneal cavity of mice through sensory C-fiber neuropeptides, lipoxygenase or cyclooxygenase metabolites, nitric oxide, histamine, platelet-activating factor and resident macrophages. In this work, we examined the influence of macrophage-derived products on neutrophil migration during peritonitis induced by staphylococcal enterotoxin type B (SEB) in mice. Macrophages stimulated with SEB released a thermolabile neutrophil chemotactic protein with a molecular weight of 1,000-3,000 (by ultrafiltration). This release was inhibited 30% by dexamethasone (an inhibitor of cytokine synthesis and phospholipase A(2) activity), but not by indomethacin (a cyclooxygenase inhibitor) or BW755C (a dual cyclo- and lipoxygenase inhibitor). Dexamethasone also inhibited (100%) the neutrophil migration induced by the chemotactic protein. Similar inhibition occurred in mice pretreated with BWA4C (lipoxygenase inhibitor; 90%), BW755C (99%), BN52021 (platelet-activating factor-acether receptor antagonist; 93%), cimetidine (histamine H(2) receptor antagonist; 76%), capsaicin (a depletor of sensory C-fiber neuropeptides; 82%) and the neurokinin-1 receptor antagonist SR140333 (71%), but not by indomethacin or the neurokinin(2) receptor antagonist SR48968. These results confirm that macrophages are involved in the neutrophil recruitment induced by SEB, and that the chemotactic protein apparently induces neutrophil migration by a mechanism mediated by platelet-activating factor, histamine H(2) receptors, lipoxygenase products and substance P.

Augmentation of an Antitumor CTL Response In Vivo by Inhibition of Suppressor Macrophage Nitric Oxide

Evidence is provided that inhibition of macrophage NO production can augment in vivo CTL responses. Specifically, administration of NG-monomethyl-l-arginine (NGMMA) via osmotic pumps increases the tumor-specific CTL response against the P815 mastocytoma in the peritoneal cavity of preimmunized mice. Both the magnitude and duration of the CTL response were increased. That the augmented CTL response resulted from inhibition of the NO synthase pathway is supported by the finding that macrophage NO production from NGMMA-treated mice was reduced. Also, in vitro inhibition of NO production by peritoneal exudate cells from P815 tumor-challenged mice augmented the secondary CTL response observed. Cell proliferation was augmented by NGMMA in these cultures, suggesting that macrophage NO may suppress CTL by inhibiting clonal expansion. NO-mediated inhibition was observed in vivo in this experimental system, even though the CTL response is not suppressed, in that tumor rejection occurs. Therefore, the present results are consistent with the conclusion that macrophage NO-mediated inhibition of the CTL response is a side effect of activating macrophages rather than resulting from the action of a distinct subset of what have long been termed suppressor macrophages. Most important, the results indicate that NO-mediated suppressor macrophage activity can be an important CTL immunoregulatory element in vivo.

A dialysis culture system for the study of the production and modulation of growth-regulatory molecules: studies using the P388D1 macrophage cell line

P388D1 macrophage-like cells have previously been shown to produce both mitogenic and inhibitory regulators of porcine smooth muscle cell (pSMC) growth. The mitogenic activity was shown to have a molecular mass of > 10 kDa while the inhibitory activity was in the range of 2–6 kDa. In the present study, we present a novel dialysis culture system where P388D1 cells were grown in dialysis membranes with a 12 kDa cut-off which allowed continuous production of fractions of the culture medium. Using pSMC as target cells, mitogenic activity was found to be retained by the dialysis membrane while the low molecular mass inhibitory activity passed freely through the membrane. The effect of the macrophage-activators phorbol myristate acetate (PMA), concanavalin A (ConA) and interferon-gamma in combination with lipopolysaccharide (IFN gamma/LPS) were investigated in the dialysis culture system. PMA, ConA and IFN gamma/LPS were found to enhance the production of mitogenic activity by P388D1 cells. PMA also increased the production of growth-inhibitory activity, while ConA abolished inhibitor production and IFN gamma/LPS had no effect on the amount of inhibitory activity produced by P388D1 cells. The experiments show that the balance of production of mitogenic and inhibitory activities by macrophages can be modulated by agents that alter the state of activation of the cells. This could be of profound significance in the influence of macrophages on smooth muscle cell growth during the development of atherosclerosis.

The isolation of a fibroblast growth inhibitor associated with perigraft seroma

PURPOSE

Perigraft seroma is a rare complication of reconstructive vascular surgery characterized by a clear, sterile fluid collection confined within a fibrous pseudomembrane around a prosthetic graft. The exact cause of this disease is unknown but involves failure of surrounding connective tissue to incorporate the graft. To understand why this occurs, we studied sera from patients with perigraft seroma for their effect on human fibroblasts. Sera from control subjects, patients with uninfected prosthetic grafts, and patients with prosthetic grafts were tested for comparison.

METHODS

Fibroblast growth was measured by radioactive thymidine uptake and hexosaminidase colorimetric cell proliferation assays. We fractionated sera with gel filtration columns and measured each fraction's effect on fibroblast growth.

RESULTS

Serum samples from patients with perigraft seroma inhibited fibroblast growth in a dose-dependent manner. In contrast, a postseroma sample, normal human sera, and sera from patients with infected and uninfected grafts showed no significant fibroblast inhibition. An inhibitory factor with a molecular weight of 2000 d was isolated from serum of patients with perigraft seroma.

CONCLUSIONS

Perigraft seroma is associated with a fibroblast inhibitor with a molecular weight of 2000 d. Further identification and characterization of this protein may lead to clinical applications in preventing and treating perigraft seroma.

A small molecular mass inhibitor of growth of 3T3 cells and porcine aortic smooth muscle cells released from the macrophage cell line P388D1

Murine peritoneal macrophages and the macrophage-like cell line, P388D1, were found to release both mitogenic and inhibitory modulators of growth of cells in culture. These growth factors were effective against both murine Swiss 3T3 fibroblasts and porcine aortic smooth muscle cells as assessed by [3H]thymidine incorporation into DNA and by measurement of cell number. Partial characterisation of the inhibitory activity demonstrated it to be lost on dialysis using a membrane with a 10 kDa cut-off, trypsin sensitive, heat stable, and slightly sensitive to freeze-thawing. The inhibitory activity not only affected cell growth but was found to change the morphology of porcine aortic smooth muscle cells. Gel permeation studies showed an estimated molecular mass in the range 2.5 to 6.5 kDa. The inhibitory activity could be partially purified using ion-exchange chromatography. Experiments with a neutralising antibody against transforming growth factor beta (TGF-beta) showed that TGF-beta is not responsible for the activity observed. Indomethacin had no effect on the production of inhibitor suggesting that it is not an inhibitory prostanoid. The inhibitory activity was not due to a non-specific toxic mechanism as confirmed by a [3H]adenine release assay. Incubation of P388D1 cells with cycloheximide prevented the release of inhibitory activity.

Suppression of interleukin-2 production and activity by factor(s) released by peripheral blood mononuclear cells during papillomavirus infections

Supernatant fluids from cultured peripheral blood mononuclear cells (PBMC) obtained from patients with extensive papillomavirus infections such as condyloma acuminatum (CA) and epidermodysplasia verruciformis (EV) depressed the proliferative responses of T cells to phytohemagglutinin-P (PHA-P) and the production of interleukin-2 (IL-2) from those preparations. Fluids from the same cultures also inhibited the mitogenic activity of IL-2 on CTLL-2 cells as IL-2-dependent target cells. These soluble suppressor factors (SSF) from PBMC were present in significantly higher concentrations in fluids from cultured PBMC from patients in comparison to healthy controls. A soluble suppressor factor was characterized also from cultured rabbit PBMC after the rabbits had been infected with Shope papillomaviruses. This suppressor factor likewise inhibited IL-2 production and IL-2 activity.

Idiopathic pulmonary fibrosis: cellular and molecular pathogenesis

Diffuse involvement of the pulmonary interstitium with abnormal fibrous tissue is a process that occurs in many settings. There are many possible etiologies for pulmonary fibrosis, but in the majority of individuals, a clear cause cannot be determined and a diagnosis of idiopathic pulmonary fibrosis (IPF) results. Despite limited knowledge concerning the etiology, recent advances in biomedical technology offer great promise for increasing our understanding of IPF. This review will focus on current concepts of the pathogenesis and therapy of IPF.

The activation of calcium/phospholipid dependent protein kinase and the association with interleukin-2 production

The thymic leukemia cell line EL4 has been shown to produce the lymphokine Interleukin-2 (IL-2) following stimulation with phorbol ester (PMA). We investigated intracellular enzyme pathways triggered by phorbol stimulation using an EL4 cell line which responds to PMA with IL-2 synthesis (EL4r) and one which does not produce IL-2 following stimulation (EL4nr). By comparing these two cell lines we hoped to establish which enzyme activities were associated with IL-2 synthesis. The enzyme pathways studied included calcium/phospholipid dependent protein kinase (C-kinase) activity, the induction of polyamine synthesis, RNA, DNA and protein synthesis and finally IL-2 production. Our results indicate that both EL4 cell lines have a receptor for PMA, which can activate the C-kinase enzyme. Further, in both cell lines PMA activates the nuclear synthesis of polyamines as demonstrated by ornithine decarboxylase induction. Both RNA and protein synthesis measured by 3H-uridine and 3H-leucine uptake respectively appear comparable between EL4r and EL4nr. The only difference in cellular responsiveness between EL4r and EL4nr was in the 3H-thymidine uptake, and IL-2 production. IL-2 production or lack of production was established by 3H-uridine and 3H-thymidine incorporation as well as viable cell count using the IL-2 dependent cell line CTLL-2. We, therefore, conclude that EL4r and EL4nr cells show similar intracellular responses to phorbol ester except for 3H-thymidine uptake and detectable IL-2 production. Our results suggest that failure of PMA-stimulated EL4nr cells to produce IL-2 is either due to inability of this cell line to synthesize IL-2 or the production of defective IL-2. It is not due to failure of PMA to activate C-kinase or the subsequent nuclear events.

A biochemical study of the carrageenan-induced granuloma in the rat lung

Intralobular injection of carrageenan in the rat lung induced a chronic granulomatous response, characterized by a prolonged accumulation of macrophages within the affected lobe. This was accompanied by moderate but significant increases in lysosomal beta-acetyl glucosaminidase, cathepsin B1, and neutral protease activity. Beta-acetyl glucosaminidase and cathepsin B1 activities peaked on day 16 post carrageenan injection and cathepsin B1 activity peaked again on day 112. These enzyme peaks correlated with previous morphological findings that numerous PMNs and carrageenan-containing macrophages were present in the alveoli on day 16 and on day 112. Lymphocytes and plasma cells were present in the alveoli on day 112 in addition to the numerous carrageenan-filled large macrophages. The caseinolytic enzyme activity was significantly elevated over controls throughout the duration of the experiment but no distinct peaks of activity were observed. Based on determinations of total collagen, insoluble collagen, salt-soluble collagen, acid-soluble collagen, protein, total proline, and specific activity of proline and hydroxyproline, there was biochemical evidence of increased collagen synthesis or collagen accumulation in the inflamed lobes on days 4 to 32 as compared to the control lobes. No evidence was found to indicate an increase of collagen or collagen synthesis after day 32 in the experimental lobes. These results differ from our earlier histological and ultrastructural findings which reported that no increased collagen deposition was observed on any day in this system, even 500 days post carrageenan injection. Lung to body weight ratios of experimental animals were significantly elevated over controls on all days studied.

Production of macrophage-activating and migration-inhibition factors in vitro by serologically selected and cloned Listeria monocytogenes-specific T cells of the Lyt 1+2- phenotype

Lyt-selected Listeria-immune T lymphocytes from peritoneal exudates and cloned T cells were cocultured with heat-killed listeriae and peritoneal macrophages from nonimmune donors. Supernatants were assayed for: activation of macrophages for tumoristatic and tumoricidal activity via macrophage-activating factors and migration-inhibition factor activity. Peptone-induced peritoneal macrophages were activated by incubation with the supernatants for 24 h. For examination of cytocidal activity, 51Cr-labeled EL4 tumor cells were subsequently added, and 51Cr release was determined. Cytostatic activity was measured by adding unlabeled EL4 tumor cells to the pretreated macrophages and determining [3H]thymidine incorporation 24 h later. Migration-inhibition factor production was examined in an agar microdroplet assay. Only Listeria-specific T cells of the phenotype Lyt 1+2- proved active in these assays, whereas T cells of the phenotype Lyt 1-2+ were not active. When T-cell clones were used, a single clone was capable of inducing macrophage-activating and migration-inhibition factor production at cell concentrations of ca. 10(3)/ml.

In vivo assessment of tumor-induced nonspecific suppression of contact sensitivity. II. Regulation by cytokines and T cells via adoptive transfer

Normal BALB/c mice were assessed for 2,4-dinitrofluorobenzene (DNFB)-induced contact sensitivity following adoptive transfer of macrophages (Mo). T cells, or their derived products, from normal or tumor-bearing hosts (TBH). Contact sensitivity (CS) was measured by a quantitative radioisotopic ear assay, a total in vivo system based on localization of IP-injected iodinated human serum albumin [( 125I]HSA) in the DNFB-challenged ear. Adoptive transfer of low or high doses of TBH T cells or their derived supernatants into normal recipients suppressed their responsiveness, while Mo supernatants enhanced it. Moreover, in all cases adoptive transfer of TBH cells or supernatants resulted in a lower CS response than did their normal counterparts. These results further corroborate our previous in vitro data indicating that T cells, or Mo and T cell soluble products, possess immunoregulatory capabilities in vivo.

Immunodepression in Giardia muris and Spironucleus muris infections in mice

Infections with the intestinal flagellates Giardia muris and Spironucleus muris are accompanied by a depression in the ability of mice to mount an immune response to a thymus-dependent antigen (sheep red blood cells) but not to a thymus-independent antigen (TNP-lipopolysaccharide). The number of splenic IgM plaque-forming cells and haemagglutination titres, of both IgM and IgG, to sheep red blood cells decreased between days 10 and 21, which correlated with the time of maximal trophozoite levels in the small intestine. The number of background IgM plaque-forming cells to sheep red blood cells or DNP was not significantly different from controls in either infection. No evidence for systemic macrophage activation was associated with these infections. In fact, adherent peritoneal exudate cells (PEC) from infected mice were slightly less cytostatic against target tumour cells than adherent PEC from normal mice, at a time when the parasites were being eliminated from the small intestine.

Mechanism of immunosuppression in leprosy: presence of suppressor factor(s) from macrophages of lepromatous patients

Human peripheral blood mononuclear cell proliferation induced by Mycobacterium leprae could be inhibited by the suppressor factor in the lysate of the macrophages of lepromatous leprosy patients. Macrophages from normal subjects and tuberculoid patients did not show production of a suppressor factor. Inhibition occurred only when the factor was present in the initial stages of lymphocyte culture. The factor is heat stable and nondialyzable. Proliferation induced by some mycobacteria and concanavalin A could also be blocked by the factor. Interestingly, blastogenic response by a few other antigens and phytohemagglutinin could not be inhibited by the suppressor factor. Mononuclear cells pretreated with such lysate from lepromatous macrophages for 24 h could induce suppressive activity in the cells in vitro in an autologous system. Treatment of these cells with carbonyl iron after the induction phase, to remove phagocytic cells, did not abolish their suppressive activity. The lepromatous macrophage lysate also generated suppressive activity in a T-lymphocyte-enriched population of normal subjects. These studies are interpreted to indicate that immunosuppression in lepromatous patients is produced by both macrophages and T lymphocytes. The exact phase in which either of these cells acts as a suppressor may be different. Specific suppression by macrophages to M. leprae can be an early event, and nonspecific suppression by T lymphocytes may be a later event in the course of lepromatous leprosy.

An ultrastructural study of the macrophages of the carrageenan-induced granuloma in the rat lung

The intralobular injection of 0.17 ml of 2 per cent. carrageenan into the rat lung induced an inflammatory granulomatous response. This inflammation was characterized in the early stages by immediate polymorphonuclear (PMN) leucocyte infiltration into the alveoli. Within 2 days the PMN's began to disappear and were replaced by carrageenan-containing macrophages. Alveolar macrophages actively phagocytised the injected carrageenan and were the dominant cell type in he alveoli for the length of this study (365 days). These low-turnover alveolar macrophages, which with light microscopy stained pinkish-red metachromatically with toludine blue due to their carrageenan content, underwent changes in vacuole morphology as well as changes in size and shape. Throughout the course of this inflammation, these macrophages had carrageenan-containing vacuoles which could be seen undergoing fusion to form larger vacuoles which at times constituted half the size of the entire macrophage cytoplasm. The carrageenan in the vacuoles was an amorphous flocculent appearing material for the initial 14 days but changes to a more fine filamentous form for the remainder of the study. This was probably due to its partial digestion by lysosomal enzymes. The general composition of the cytoplasm remained fairly constant during the 365 days. Pinocytotic vesicles and free ribosomes were abundant and the many mitochondria were small and rounded. Smooth endoplasmic reticulum lysosomes, and Golgi apparati, although not prominent, were present but the most striking feature of the cytoplasm was the presence of numerous lamellar bodies (phagocytosised surfactant). Some of the macrophages increased greatly in overall size (five to seven times) compared to their initial size. A few isolated macrophages could be seen degenerating but no general necrosis was seen. Except for one isolated case, no epithelioid cells were observed in this carrageenan inflammation. Fibrosis, if present at all, was very localised and was only evident at day 340 post-injection. This fibrosis generally involved one or two carrageenan-containing macrophages encapsulated by a few collagen fibres. No widespread fibrosis was ever observed in this study which confirmed earlier histological and biochemical investigations.

Immunoregulation of the mixed lymphocyte reaction by macrophage-derived factors: functional and biochemical separation of enhancing and inhibitory factors

Positive and negative immunoregulation of the mixed lymphocyte reaction (MLR) occurred through release of macrophage(MO)-derived, soluble enhancing and inhibitory factors. Macrophages, sonicated or cultured in low concentrations, produced nondialyzable, soluble factor(s) capable of enhancing the MLR; but the culture supernatant had no biologically detectable levels of Interleukin 1, Interleukin 2, or interferon. Production of enhancing supernatants was not affected by pretreatment of MO with trypsin or anti-Thy 1 antibody plus complement. In contrast, MO cultured in high concentrations yielded an inhibitory supernatant factor(s) which suppressed MLR reactivity even when MO were cultured in the presence of indomethacin. Culturing MO with proteolytic enzyme inhibitors increased the yields of the inhibitory and enhancing factors. Both factors were precipitable with ammonium sulfate and could be separated into several biologically active fractions using anion exchange chromatography.

The effect of rheumatoid synovial fluid macrophages on DNA, glycosaminoglycan and collagen synthesis by synovial fibroblasts

The effects of soluble factors secreted by peripheral blood monocytes and rheumatoid synovial fluid macrophages were tested on human synovial fibroblast cultures. Both monocytes and macrophages liberated factors which reduced DNA synthesis (3H-thymidine incorporation) by synovial fibroblasts. Monocyte and macrophage factors stimulated hyaluronic acid synthesis. The activation obtained with rheumatoid synovial macrophages was considerably greater than that with monocytes. Foetal bovine serum was found to have a clear stimulatory effect on the synthesis of collagen and other proteins by fibroblasts. The effects of monocyte and macrophage factors on protein synthesis in synovial fibroblasts were small: collagen synthesis was slightly increased relative to other extracellular proteins.

Kinetics and genetics of herpes simplex virus-induced antibody formation in mice

The kinetics of antibody synthesis was investigated after intraperitoneal, subcutaneous, and footpad infection of various strains of mice with herpes simplex virus. Immunoglobulin M antibodies appeared 5 days after and immunoglobulin G antibodies appeared 10 to 12 days after intraperitoneal infection with herpes simplex virus type 1. The major histocompatibility complex and the background genome of inbred mice were not found to have a systematical influence on antibody synthesis. Female mice, however, consistently produced more antibodies than did male if the infection was done intraperitoneally, but not if it was done subcutaneously or into footpads. Castration considerably increased the amount of antibodies produced by male mice. The difference in antibody formation between females and males could be abolished by injection of silica; moreover, antibody titers were enhanced by this treatment. This has also been found by immunization with a Formalin-inactivated herpes simplex virus vaccine. The effect of silica in enhancing antibody formation could be observed up to 12 days after infection. Infectious virus could be detected up to 2 days after infection, and herpes simplex virus type 1 antibody-stimulating antigens could be detected up to 4 days in ultrasonicates of macrophages. The assumption is made that androgen-sensitive cell populations, including macrophages and their soluble products, are involved in antibody-depressing mechanisms.

Deoxycytidine excretion by mouse peritoneal macrophages: its implication in modulation of immunological functions

Pyrimidine excretion by macrophages was studied in order to identify the potential immunoregulatory effector molecules. Deoxycytidine was found in the culture medium of thioglycollate-elicited mouse peritoneal macrophages, along with thymidine, which was shown by others to be a possible immunoregulatory substance. The identification of deoxycytidine was based on: (1) cochromatography with the authentic compound in four different solvents, (2) UV absorption spectral analysis, and (3) the enzymatic peak shift method. Phagocytosis of nucleated chicken erythrocytes, but not enucleated sheep erythrocytes, increased deoxycytidine excretion. The macrophages lacked both deoxycytidine kinase and deoxycytidine deaminase, which is consistent with their excretory pattern. Since it has been known that deoxycytidine can protect cells against cytotoxic effects of thymidine, we propose that deoxycytidine has a role in preventing immunosuppression by thimidine. In patients with adenosine deaminase deficiency, however, immunosuppression caused by combined toxicity of thymidine and deoxyadenosine may not be adequately prevented by deoxycytidine.

Mechanisms of action of Mycobacterium bovis BCG-induced suppressor cells in mitogen-induced blastogenesis

Spleen cells from Mycobacterium bovis BCG-infected C57B1/6 mice when cultured in vitro for 72 h elicited soluble suppressor mediators capable of nonspecifically suppressing the mitogen-induced blastogenesis of normal splenocytes. Maximal production of suppressor mediators occurred during the first 24 h in culture, and their production ceased after 72 h. Attempts to isolate the mediators from fresh nonincubated splenocytes failed. After incubation, a strong residual suppressive activity was constantly detected in cell preparations used for production of suppressor factors. Supernatants prepared from cultures of spleen cells of mice infected 14 days earlier possessed higher suppressive activity than did those obtained 28 days after infection. In contrast, the residual cellular suppressive activity increased during the course of the infection. Although the activity of soluble factors was not inhibited, the residual activity of incubated cells was highly depressed by the presence of mouse erythrocytes in the cultures. Thus, the incubated cells appear to act through a direct cell-to-cell contact with the mitogen-responding cells. Finally, the results of depletion experiments suggest that the two populations of BCG-induced suppressor cells, namely, T lymphocytes and macrophage-like cells, are able to elicit suppressor mediators and to retain thereafter suppressive activity.

Possible role of macrophage-like suppressor cells in the anti-tumour activity of BCG

The i.v. injection of high doses (3 mg) of BCG into C3H mice bearing a transplantable 3-methylcholanthrene-induced fibrosarcoma caused the regression of a significant proportion. This effect was most evident when the BCG was injected on the day of the graft, or 7 days later. The injection of this agent either 14 days before the graft, or in low doses (0.1 or 0.5 mg), or directly into the tumour (i.t.) only prolonged the survival of the animals. Spleen cells from systemic high-dose BCG-treated mice were found to exert a strong nonspecific cytostatic effect in vitro that was not an artefact of the test conditions, and was not expressed by cells from low-dose animals. The cytostatic effect was shown to be caused by cells with the characteristics of macrophages, i.e. they were strongly adherent, unaffected by treatment with anti-Thy 1.2 + C', radioresistant but heat-sensitive, and were detected in BCG-treated "B" mice. The spleens of high-dose BCG-treated mice also contained suppressor cells that were capable of inhibiting the in vitro reactivity of normal T cells to PHA. Like the cytostatic effect, this suppressor activity was not detected in low-dose mice, and the cells responsible had the properties of macrophages; the effect was lost after the removal of adherent cells by sequential exposure to plastic and colloidal iron, but was conserved after treatment with anti-Thy 1.2 + C'. T-cell-deprived animals, such as "B" or nude mice, also developed suppressor-cell activity when treated with systemic high-dose BCG. Close parallels became evident between the in vivo anti-tumour activity of BCG, the in vitro cytostatic effect, and the suppressor-cell activity. We here discuss the possible role of suppressor cells in the mechanism of action of this agent.

Monocyte-induced cell cycle synchronization of a leukemic cell line in vitro

Human monocytes cultured in vitro exert cytostatic activity against neoplastic cell lines. The cytostatic effect was examined on the nonadherent human leukemic cell line K-562. After 24 hours of co-culture between monocytes and K-562 cells (in a ratio of 10: 1), the K-562 cells were removed and their DNA-synthesis and DNA-content were examined by methyl-3H-thymidine incorporation and flow cytofluorometry. Cell proliferation curves were obtained. A partial and reversible cell cycle block in the G0/G1-phase was observed. After removal of the target cells from the monocyte monolayers, the target cells regained their normal proliferation rate during the following 1 to 3 days, with a maximal number of cells in S-phase at 7 to 9 hours after separation of target cells from the monocytes. The most marked effect was induced by monocytes cultured in vitro for 12 days, and with monocytes stimulated with lymphokine, i.e. supernatants from BCG-exposed lymphocyte cultures.

Opposing changes in electrokinetic potential of spleen cells induced by factors from different tumour supernatants

Tumour supernatants were tested on normal spleen cells electrophoretic mobility. In the case of two tumours, characterized by a fast growth rate (RV2 and VFM1), supernatants produced an increase in the mean electrophoretic mobility. For the two other tumours, characterized by a slow growth rate (VMM2 and VMM1), supernatants produced a decrease in the mean electrophoretic mobility. Electrophoretic mobility analysis of mouse spleen cells showed that after treatment with RV2 tumour supernatant, the percentage of 'slow' cells decreased by about 20%. VMM2 supernatant produced an increase in 'slow' cells of about 20%. The effect of dialysed supernatants (with mol. wt cutoff 12,000) was different. VMM2 and VMM1 dialysed supernatants modify spleen cells mobility as VMM2 and VMM1 undialysed supernatants. RV2 and VFM1 dialysed supernatants induced a significant slowing in the mobility in regard to RV2 and VFM1 undialysed supernatants. RV2 and VMM2 tumour supernatants were fractionated into four fractions on Sephacryl S-300. Fraction II (mol. wt of about 400,000) from VMM2 supernatant was found to reduce significantly the spleen cells' mobility. In contrast, fraction IV (mol. wt less than 12,000) from RV2 supernatant increases significantly the mobility, and fraction IV (mol. wt less than 12,000) from VMM2 supernatant reduced the mobility significantly. These different charge changes in spleen cells after contact with supernatants from slow and fast growth rate tumours might influence the contact between tumour and lymphocytes.

Human monocytes induce a reversible inhibition of cell cycle progression in the leukemic cell line K-562 during co-culture in vitro

Human monocytes cultured in vitro exert cytostatic activity against the non-adherent human leukemic cell line K-562. K-562 cells in asynchronous growth were added as target cells to adherent mononuclear blood cells, either freshly isolated or cultured in vitro for 4 and 12 days. After 24 hours of co-culture, the non-adherent cells were gently removed and incubated further. Target cell DNA-synthesis and cellular DNA content were examined by methyl-3H-thymidine incorporation and by flow cytofluorometry, respectively. Cell-proliferation curves were obtained. Monocytes cultured in vitro exert a reversible cytostatic activity, which is a partial cell cycle block in the G0/G1 phase. Target cells exposed to freshly isolated monocytes also showed accumulation of cells in the G0/G1 phase. These target cells did not regain their normal proliferation rate before day 3 after removal from the monocyte cultures. This effect may, however, to some extent be due to loosely adherent mononuclear blood cells removed from the monocyte cultures together with the target cells.

In vitro proliferation of T lymphocytes from Listeria-infected rodents: assay conditions for rat peritoneal exudate cells and characterization of an inhibitor

Conditions favorable to [(3)H]thymidine incorporation into antigen-stimulated T lymphocytes from Listeria-infected rats have been established. In cultures of peritoneal exudate (T) lymphocytes purified twice with nylon-wool vigorous antigen-specific proliferation was observed within 2 days. Cultures of lymphocytes from nodes draining a subcutaneous Listeria-infection site differed in that back-ground proliferation was higher than for peritoneal exudate lymphocytes, and [(3)H]thymidine incorporation was maximal at day 3. A critical factor for the rate of proliferation was the lymphocyte-to-macrophage ratio; optimal cultures of peritoneal exudate lymphocytes contained 2 to 5% macrophages. Macrophages exceeding a proportion of 10% strongly, if not completely, inhibited [(3)H]thymidine incorporation into antigen-stimulated lymphocytes. Inhibition was associated with mononuclear cells, adherent to plastic or nylon-wool, of the stimulated or unstimulated peritoneal cavity. It was neither attributable to release of cold thymidine from macrophages nor to rapid degradation of particulate antigen by macrophages. The degree of inhibition reflected the metabolic activity of macrophages; on a cell-for-cell basis, heat-killed and glutaraldehyde-fixed macrophages were less inhibitory, and stimulated macrophages were more inhibitory than macrophages from the unstimulated peritoneal cavity.

A histological study of the carrageenan-induced granuloma in the rat lung

Intralobular injection of 0.17 ml of 2% carrageenan, through a ventral slit in the trachea of rats, induced localised areas of inflammation with a high survival rate. This inflammation was characterised by immediate polymorphonuclear leucocyte (PMN) infiltration into the interstitial and alveolar spaces followed in 4 days by replacement of the PMNs by carrageenan-containing macrophages. Between days 10 to 70, the macrophages rapidly increased in size and accumulated numerous large vacuoles which stained for the presence of carrageenan. Several macrophages were so large that they each filled an entire alveolar space. From days 70 to 205, the macrophage appearance was unchanged except that the staining of their carrageenan-containing vacuoles was less metachromatic with toluidine blue. Fibrosis was first noted at day 205 and consisted of several small granulomas located near large airways and blood vessels. These granulomas had a central area filled with macrophages and a peripheral zone consisting of fibroblasts, new collagen, scattered macrophages and blood vessels. The morphology of the macrophages remained essentially unchanged from days 205 to 500 but by day 500, the macrophages were found only in numerous pockets within the inflamed lobe. They still stained positive for the presence of carrageenan at day 500. The extreme longevity of these macrophages and the lack of significant fibrosis may be due to the "un-naturalness", indigestibility, and low toxicity of the irritant, carrageenan. In addition, their size and numerous vacuoles may have inhibited their movement and subsequent removal from the lung. The paucity of significant fibrosis may be due to the lack or inhibition of a "fibroblast stimulating factor" released by the macrophages or possibly the collagen was degraded as soon as it was synthesised. This carrageenan-induced inflammation is a very suitable for the study of alveolar macrophages but appears to be inappropriate for the study of pulmonary fibrosis.

Macrophages as a source of tumoricidal activity (tumor-necrotizing factor)

Macrophage-enriched peritoneal exudate cells from mice infected with Mycobacterium bovis BCG, macrophage-like tumor cells (PU 5-1.8), and peritoneal macrophages propagated in vitro with macrophage growth factor released tumoricidal activity into the culture medium within 2 to 3 h after stimulation with nanogram quantities of bacterial lipopolysaccharide. The cytotoxic activities from each of the macrophage culture supernatants eluted from diethylaminoethyl-Sephacel columns at a sodium chloride concentration of 200 mM exhibited a molecular weight of 50,000 to 60,000 as estimated by gel filtration, were stable at 56 degrees C for 30 min, and were active at a pH range of 6 to 10. A rabbit antiserum directed against serum-derived cytotoxic activity (tumor-necrotizing factor) from BCG-infected and lipopolysaccharide-challenged mice inhibited all of the cytotoxic activities generated in vitro. This suggests that the macrophage-derived cytotoxins are identical with serum-derived cytotoxic factor, which further implies that the macrophage is the cellular source of tumor-necrotizing factor.

Role of adherent cells in graft-versus-host-induced suppression of the humoral immune response

Experiments were performed to investigate the role of adherent (A) cells in graft-versus-host (GVH)-induced immunosuppression. GVH reactions (GVHR) were induced in adult F1 hybrid mice by intravenous injections of parental lymphoid cells. Spleen cells (SC) from mice experiencing a GVHR (GVH mice) were stimulated with phytohaemagglutinin (PHA), concanavalin (Con A), and lipopolysaccharide (LPS). SC taken in the early phase of the GVHR (early GVHR) responded normally to LPS but did not respond to PHA and Con A. SC taken in an advanced phase of the GVHR (advanced GVHR) did not respond to PHA, Con A, or LPS. The influence of A cells from GVH mice (GVH-A cells) on the response of normal non-adherent cells to sheep erythrocytes (SRBC), PHA, and LPS was investigated. A cells from early GVHR, used in appropriate numbers, stimulated the responses to SRBC and to PHA; in excess they inhibited both responses. They had no effect on the response to LPS. A cells from advanced GVHR, even in low numbers, suppressed the responses to SRBC, PHA and LPS. The lymphoregulatory activities of GVH-A cells seemed to be mediated by soluble factors. The results indicate that the GVHR evokes complex non-specific regulatory interactions between A cells and lymphocytes.

A three-dimensional study of the normal human placental villous core. I. The Hofbauer cells

In order to study the three-dimensional ultrastructure of the Hofbauer cells, human placentae from the 6th to the 21st week of gestation and also from the end of pregnancy were cryofractured and observed by scanning electron microscopy. Hofbauer cells were found in the villous core at all the gestation stages examined. Their surface morphology was characterized by lamellipodia, funnel-like structures, blebs and microplicae. This pleomorphic aspect was probably related to functional or environmental conditions. In addition, thin cytoplasmic processes connected the Hofbauer cells with each other and with the components of the villous stroma. Fractured Hofbauer cells revealed large vacuoles in the cytoplasm; the vacuoles were smaller in size both at the beginning and at the end of pregnancy. This study further attests to the macrophagic nature of these cells.

A two-signal mechanism for the induction of cytotoxic T lymphocytes

Depletion of adherent cells from stimulator and responder lymphocytes by a single filtration through nylon wool columns led to complete abrogation of the cytotoxic response to the stimulating alloantigen. Cytotoxic responses were restored by adding anti-Thy-1 + complement-greated normal peritoneal exudate cells (PEC) syngeneic or allogeneic to the responding population. Alternatively, the response could be reconstituted with costimulator, a lymphokine obtained by stimulation of spleen cells with concanavalin A. Costimulator was not itself cytotoxic and induced few or no cytotoxic T lymphocytes (CL) in the absence of stimulator cells. Costimulator was also more efficient than allogeneic PEC, which in turn were more efficient than syngeneic PEC, in reconstituting the cytotoxic response. The number of CL produced to the activating alloantigen was shown to increase with increasing concentration of costimulator. More interestingly, in the presence of a relatively high concentration of costimulator, CL were also activated to target cells that differ in H-2 haplotype from the stimulating alloantigen. Lysis of the third-party target cells could not be inhibited by cold targets syngeneic to the activating alloantigen. A clonal assay for cytotoxic precursors was used to confirm that CL for the activating alloantigen and CL for the third-party H-2 antigens were derived from different progenitors. Only about 37% of the cytotoxic clones produced were specific for the activating alloantigen. These observations are explained in terms of a two-signal model of CL activation.

Cytostatic effects of activated macrophages on tumor target cells: inhibition of cytotoxic action of ARA-C

Studies carried out to explore further the cytotoxic effects of activated macrophages from mice treated with Corynebacterium parvum revealed that their effect on the EMT-6 line of tumor target cells was limited solely to cytostasis with no evidence of a cytocidal effect. In additional studies, the cytostatic effects of activated macrophages markedly reduced the cytotoxic effects of the chemotherapeutic agent cytosine arabinoside on EMT-6 target cells.

Alveolar macrophage--induced suppression of the immune response

Alveolar macrophages were shown to suppress the in vitro immune response of rabbit lymphoid cells stimulated with heterologous erythrocytes. Suppression was associated with an adherent, phagocytic cell that was resistant to the effects of irradiation and treatment with anti-thymus serum. Suppression was mediated by a soluble factor whose production was independent of antigen and required an interaction of viable alveolar macrophages and lymphocytes. Suppression was associated with an early event in the induction of the PFC response and appeared to affect lymphocyte proliferation. Suppression could not attributed to cytotoxicity, sequestration of antigen, depletion of nutrients or release of prostaglandins, arginase or thymidine. These results, taken together, provide additional information regarding immunological function of alveolar macrophages and suggest that they play a regulatory role in the immune response.

Alveolar macrophages. III. Studies on the mechanisms of inhibition of T-cell proliferation

Unlike macrophages from the peritoneal cavity or the peripheral blood, rat alveolar macrophages actively inhibit mitogen-induced T-cell proliferation. Studies on the characteristics of this inhibitory activity revealed the following: the macrophages must be live, but mitomycin C does not block their activity; they must be added to lymphocyte cultures soon after the initiation of the cultures, and prolonged pre-incubation of macrophages in vitro diminishes their cytostatic activity; suppressive activity is most obvious in cultures of rapidly proliferating lymphocytes, and the lymphocytes themselves may be syngeneic or allogeneic; the suppressive activity may be duplicated by a low molecular-weight dialysable component of macrophage culture supernatants, and suppression of RNA synthesis is as readily demonstrable as suppression of DNA synthesis in target cells; the cytostatic effects of alveolar macrophages in lymphocyte cultures do not appear to result from target cell destruction. Studies involving repeated endobronchial lavage of rats revealed the presence of two alveolar macrophage subpopulations, one (weakly adherent in vivo) supportive to T-lymphocyte proliferation, and another (strongly adherent) strongly inhibitory; the latter population comprises the majority of alveolar macrophages in normal rats.

Influence of supernatants from polymorphonuclear leucocytes on blastogenesis of syngeneic and allogeneic murine splenocytes

Supernatant was produced from activated peritoneal polymorphonuclear leucocyte-rich cell populations from different strains of mice. These supernatants were studied for their ability to modify spontaneous and mitogen-induced blastogenesis of syngeneic and allogeneic splenocytes. Our results indicate that polymorphonuclear leucocyte-rich cell cultures from two strains of mice, A/J and BALB/c, produced a supernatant that could enhance PHA-induced blastogenesis of syngeneic and allogeneic splenocytes. Cells from a third strain C57B1/6, did not produce an active supernatant. In general, the response by splenocytes from these three strains paralleled the production of active supernatant that we observed. The response to the active supernatant was dependent upon the mitogen stimulation of the splenocytes, the mitogen dilution and the supernatant activity. These functions are believed to be genetically determined.

Antagonistic interactions between enhancing and suppressor factors that regulate the humoral immune response

In assay cultures of normal mouse spleen cells stimulated with sheep erythrocytes (SRBC) on day 0, the addition on day 2 of murine enhancing factor (MEF), purified from supernatants of mixtures of allogeneic lymphoid cells, resulted in significant non-specific augmentation of the haemolytic plaque response. A different supernatant activity, antibody initiation suppressor factor (AISF), generated by specific anamnestic stimulation of spleen cells from mice immunized 7 days earlier with horse erythrocytes (HRBC), was capable of significant inhibition of the anti-SRBC plaque-forming cell response of similar assay cultures when added simultaneously with SRBC on day 0 of a 5-day culture period. The addition of optimal concentrations of both MEF and AISF to SRBC-stimulated spleen cells at the initiation of culture blocked the inhibitory activity of the suppressive mediator. Similarly, the activity of MEF in enhancing both the AISF-specific (anti-HRBC) and non-specific (anti-SRBC) responses was abrogated in the presence of AISF added in optimal amounts with MEF on day 2 of culture. A similar antagonistic interaction between AISF and MEF was observed when each factor was added, at its respective optimal dilution and time, to SRBC-stimulated splenocytes in vitro. Moreover, AISF, a factor derived from antigen-activated T lymphocytes, failed to replace suppressor T-cell function in assay cultures of T-cell depleted mouse splenic B cells. Paradoxically, AISF markedly enhanced the anti-SRBC haemolytic plaque response of such cultures. The addition of graded numbers of T lymphocytes to AISF-treated B-cell cultures also resulted in an augmented humoral immune response. But the target cell of AISF was the macrophage, since the presence of splenic macrophages in the B-cell cultures reconstituted the suppressive activity of the inhibitor. In addition, AISF dramatically increased the number of macrophage-like colony-forming units in bone marrow cultures in vitro. These data are discussed in terms of the delicate balance and possible interactions between effector molecules which, in part, regulate antibody synthesis.

Requirement for a radiosensitive lymphoid cell in the generation of lipopolysaccharide-induced rejection of a murine tumor allograft

Lipopolysaccharide-initiated rejection of a tumor allograft requires the cooperation of a radiosensitive nonadherent lymphoid cell population and an adherent cell, presumably a macrophage.

Inflammatory and immune cell function in psoriasis: II. Monocyte function, lymphokine production

We have previously confirmed that subjects with psoriasis have an alteration of cell-mediated immune responses. We now report a possible in vitro corollary; the amount of lymphokine (lymphocyte-derived chemotactic factor) released by both antigen-stimulated and control lymphocytes is decreased in psoriatic subjects; 61% of similar values for normal subjects. Monocyte migration to complement-derived chemotactic factors is reported to directly correlate to skin tests; however, in psoriasis the relation is inverse, i.e., a 200% increase in complement factors and 136% increase to lymphocyte-derived chemotactic factor in monocyte migration is noted in psoriatic subjects when compared with normal subjects. This increased migration does not correlate with amount of disease and is still present in "disease-free" subjects. Culturing monocytes from psoriatic subjects in media alone demonstrates they reduce more (205%) nitroblue tetrazolium than do monocytes of normal subjects. These data demonstrate that monocytes from subjects with psoriasis are altered and suggest an apparent inherent metabolic disorder.

The regulation of lymphocyte functions by the macrophage

Macrophages may exert a regulatory influence at various stages in the life of the lymphocyte - they may influence the non-antigen-driven differentiation of lymphocytes - as exemplified by the effects on thymic differentiation; they may establish the mode and form of antigen to be presented or recognized by the lymphocyte; may regulate the lymphocyte's antigen-driven functions. Each of these critical regulatory steps needs explaining in molecular terms and integrated and placed in the context of the other regulatory functions of lymphocytes. The control of secretion of MP is an eloquent example of the molecular complexities and the intricate congrol mechanisms - internal and external - operating at each step of each regulatory process. A final comment concern the question of macrophage heterogeneity. Is the same cell performing all the functions of degradation, presentation, and secretion - or cytotoxicity? Or do we have subpopulation, each with a different role? This issue is not settled. The unitarians argue that the phagocytes pass through different stages of differentiation and that each function may become more or less prominent at each stage. Certainly, the manner in which each macrophage function is assayed can condition the outcome: for antigen presentation, one adds 1 % of macrophages to cultures of spleen cells; for cytotoxic assays, the figure is 50 to 100 macrophages per tumor cell! It is our feeling that until such time as membrane molecules are identified and used as probes for differentiation or for identification of subsets we will not resolve this issue. Along these lines, macrophages have been found to have Ia antigens (Hämmerling et al. 1975, Schwartz et al. 1976) and can be divided into two sets on the basis of the presence or absence of Ia. Dorf and I have found - by cytotoxicity - that only about 35 to 50% of peritoneal macrophages bear Ia molecules (Dorf & Uanue 1977). Exceptionally, some exudates will bear up to 75% positive cells. Neither Ia-positive nor Ia-negative macrophages change significantly after prolonged periods of culture. Whether these results indicate two defined subsets of macrophages is now being investigated.

New concepts in the pathogenesis of primary and secondary amyloid disease

Despite the marked progress obtained in the structural and amino acid sequencing data of amyloid proteins our understanding of the cellular mechanisms causing the deposition of amyloid fibrils is still poor. Some of the questions about the cellular events leading to the synthesis of amyloid fibrils can be approached by evaluating the immune reactivity of animals that develop amyloid after repeated daily casein injections. Recent studies carried out in a mouse model indicate that macrophage activation associated with T-cell suppression and followed by B-cell proliferation appear to be responsible for the immunopathological abnormalities in both primary and secondary amyloid disease.

Injury and repair of the lung: response to intravenous Freund's adjuvant

Tissue from the lungs of rabbits was examined at intervals up to 24 weeks after the animals had received a single intravenous injection of Freund's complete adjuvant. Though this is not a conventional method for damaging the peripheral lung, it had the advantage of producing multiple lesions in which most tissue components were altered for a prolonged period. White blood cells were present within the tissue and air spaces of these damaged areas. They persisted for 6 weeks in large numbers and gradually decreased over the next 12 weeks. There was replacement of type A by type B alveolar lining cells. Basement membranes were displaced and lost. Elastic and collagen fibres were distorted and destroyed. Blood vessels were occluded. Epithelioid cell and foreign body granulomas developed. Interalveolar septa disappeared, and air spaces were compressed. Despite all these changes the lungs regained near normal structure by 24 weeks after the initial injury. These results do not support the importance that has been placed on damage to various structural components of the lung as an explanation for chronic pulmonary disease. They do give some insight into the capacity of peripheral lung tissue for regenerationa following a single injury that induces a prolonged inflammatory response.