Relationship between ultrastructure and specific functions of macrophages

A mystery revealed: an update on eosinophil and other blood cell morphology of the Argentine black and white tegu (Salvator merianae)

Reptile white blood cell (WBC) morphological features are strikingly variable across species. In the Argentine black and white tegu (Salvator merianae), red tegu (Salvator rufescens), and Savannah monitor (Varanus exanthematicus), previous reports described a WBC type with a single distinct, clear, linear- to ovoid- to crescent-shaped inclusion of presumptive monocytic origin. The objective of this study was to further investigate the origin of this unique WBC type with crescent-shaped inclusions. Blood samples from two Argentine black and white tegus, tegu 1, a 4-year-old female, and tegu 2, a 2-year-old presumed male, were submitted for routine hematological evaluation. Additional blood films were prepared and stained with these cytochemical stains: alkaline phosphatase (ALP; naphthol AS-MX phosphate substrate), alpha-naphthyl butyrate esterase, alpha-chloroacetate esterase, myeloperoxidase, Periodic acid-Schiff, and Sudan black B. Blood films from tegu 1 were also stained with a second ALP stain (5-bromo-4-chloro-3-indoxyl-phosphate and nitroblue tetrazolium substrate), Luna, luxol fast blue, and toluidine blue. The blood from tegu 1 was cytocentrifuged to isolate and fix the buffy coat in glutaraldehyde 2.5% aqueous solution for transmission electron microscopy. Six morphologically distinct WBC types were identified from tegu 1, including heterophils, basophils, monocytes, azurophils, lymphocytes, and the unique WBC type, which were identified as eosinophils with inclusions. WBC types in tegu 2 were similar; however, eosinophils lacked a discernable inclusion. Proper WBC identification will be useful in obtaining accurate hemogram data for this species.

Exploiting the Macrophage Production of IL-12 in Improvement of Vaccine Development against Toxoplasma gondii and Neospora caninum Infections

Toxoplasmosis and neosporosis are major protozoan diseases of global distribution. Toxoplasma gondii is the cause of toxoplasmosis, which affects almost all warm-blooded animals, including humans, while Neospora caninum induces neosporosis in many animal species, especially cattle. The current defective situation with control measures is hindering all efforts to overcome the health hazards and economic losses of toxoplasmosis and neosporosis. Adequate understanding of host-parasite interactions and host strategies to combat such infections can be exploited in establishing potent control measures, including vaccine development. Macrophages are the first defense line of innate immunity, which is responsible for the successful elimination of T.gondii or N. caninum. This action is exerted via the immunoregulatory interleukin-12 (IL-12), which orchestrates the production of interferon gamma (IFN-γ) from various immune cells. Cellular immune response and IFN-γ production is the hallmark for successful vaccine candidates against both T. gondii and N. caninum. However, the discovery of potential vaccine candidates is a highly laborious, time-consuming and expensive procedure. In this review, we will try to exploit previous knowledge and our research experience to establish an efficient immunological approach for exploring potential vaccine candidates against T. gondii and N. caninum. Our previous studies on vaccine development against both T. gondii and N. caninum revealed a strong association between the successful and potential vaccine antigens and their ability to promote the macrophage secretion of IL-12 using a murine model. This phenomenon was emphasized using different recombinant antigens, parasites, and experimental approaches. Upon these data and research trials, IL-12 production from murine macrophages can be used as an initial predictor for judgment of vaccine efficacy before further evaluation in time-consuming and laborious in vivo experiments. However, more studies and research are required to conceptualize this immunological approach.

Cardiac telocytes. From basic science to cardiac diseases. II. Acute myocardial infarction

INTRODUCTION

The purpose of this study was to evaluate the scientific evidence regarding a potential role of telocytes in myocardial infarction.

MATERIALS AND METHODS

To this purpose, we performed a systematic review of relevant scientific literature, indexed in PubMed, Web of Science, and Scopus.

RESULTS AND DISCUSSIONS

We found six articles containing relevant studies aimed at liking myocardial infarction and telocytes. The studies that were analysed in this review failed to show, beyond a reasonable doubt, that telocytes do actually have significant roles in myocardial regeneration after myocardial infarction. The main issues to be addressed in future studies are a correct characterization of telocytes, and a differentiation from other cell types that either have similar morphologies (using electron microscopy) or similar immunophenotypes, with emphasis on endothelial progenitors, which were previously shown to have similar morphology, and functions in cardiac regeneration after myocardial infarction.

Fundamental aspects of arm repair phase in two echinoderm models

Regeneration is a post-embryonic developmental process that ensures complete morphological and functional restoration of lost body parts. The repair phase is a key step for the effectiveness of the subsequent regenerative process: in vertebrates, efficient re-epithelialisation, rapid inflammatory/immune response and post-injury tissue remodelling are fundamental aspects for the success of this phase, their impairment leading to an inhibition or total prevention of regeneration. Among deuterostomes, echinoderms display a unique combination of striking regenerative abilities and diversity of useful experimental models, although still largely unexplored. Therefore, the brittle star Amphiura filiformis and the starfish Echinaster sepositus were here used to comparatively investigate the main repair phase events after injury as well as the presence and expression of immune system and extracellular matrix (i.e. collagen) molecules using both microscopy and molecular tools. Our results showed that emergency reaction and re-epithelialisation are similar in both echinoderm models, being faster and more effective than in mammals. Moreover, in comparison to the latter, both echinoderms showed delayed and less abundant collagen deposition at the wound site (absence of fibrosis). The gene expression patterns of molecules related to the immune response, such as Ese-fib-like (starfishes) and Afi-ficolin (brittle stars), were described for the first time during echinoderm regeneration providing promising starting points to investigate the immune system role in these regeneration models. Overall, the similarities in repair events and timing within the echinoderms and the differences with what has been reported in mammals suggest that effective repair processes in echinoderms play an important role for their subsequent ability to regenerate. Targeted molecular and functional analyses will shed light on the evolution of these abilities in the deuterostomian lineage.

Osteonecrosis of the Jaw-a Bone Site-Specific Effect of Bisphosphonates

A known complication that can occur in patients using bisphosphonates (BPs) is osteonecrosis of the jaw (ONJ). ONJ features bone exposure that may be associated with severe pain, swelling, local infection, and pathological fracture of the jaw. Current literature indicates that a complex combination of factors is necessary to induce ONJ. Several hypotheses about the pathophysiology of ONJ were previously reported. Here, we review these hypotheses and introduce new ideas and suggestions on this topic, focusing on bone site-specific cells, and the effect that BPs and other anti-resorptive drugs have on those cells. Gaining more insight into bone site-specific effects may help to better understand the pathogenesis ONJ, and contribute to the development of new bone site-specific anti-resorptive drugs.

Evolutionary implication of B-1 lineage cells from innate to adaptive immunity

The paradigm that B cells mainly play a central role in adaptive immunity may have to be reevaluated because B-1 lineage cells have been found to exhibit innate-like functions, such as phagocytic and bactericidal activities. Therefore, the evolutionary connection of B-1 lineage cells between innate and adaptive immunities have received much attention. In this review, we summarized various innate-like characteristics of B-1 lineage cells, such as natural antibody production, antigen-presenting function in primary adaptive immunity, and T cell-independent immune responses. These characteristics seem highly conserved between fish B cells and mammalian B-1 cells during vertebrate evolution. We proposed an evolutionary outline of B cells by comparing biological features, including morphology, phenotype, ontogeny, and functional activity between B-1 lineage cells and macrophages or B-2 cells. The B-1 lineage may be a transitional cell type between phagocytic cells (e.g., macrophages) and B-2 cells that functionally connects innate and adaptive immunities. Our discussion would contribute to the understanding on the origination of B cells specialized in adaptive immunity from innate immunity. The results might provide further insight into the evolution of the immune system as a whole.

Macrophages are unsuccessful in clearing aggregated alpha-synuclein from the gastrointestinal tract of healthy aged Fischer 344 rats

With age, alpha-synuclein (α-SYNC) misfolds and forms insoluble deposits of protein in the myenteric plexus, leading presumably to dystrophy and degeneration in the circuitry controlling gastrointestinal (GI) function. The present experiment examined aggregates of α-SYNC in the aging small intestine and investigated how macrophages in the wall of the GI tract respond to these aberrant deposits. Groups of adult and aged Fisher 344 rats were studied. Whole mounts of duodenal, jejunal, and ileal smooth muscle wall, including the myenteric plexus, were prepared. Double labeling immunohistochemistry was used to stain α-SYNC protein and the phenotypic macrophage antigens CD163 and MHCII. Alpha-synuclein accumulated in dense aggregates in axons of both postganglionic and preganglionic neurons throughout the small intestine. Staining patterns suggested that deposits of protein occur initially in axonal terminals and then spread retrogradely toward the somata. Macrophages that were adjacent to dystrophic terminal processes were swollen and contained vacuoles filled with insoluble α-SYNC, and these macrophages commonly had the phenotype of alternatively activated phagocytes. The present results suggest that macrophages play an active phagocytotic role in removing α-SYNC aggregates that accumulate with age in the neural circuitry of the gut. Our observations further indicate that this housekeeping response does not clear the protein sufficiently to eliminate all synucleinopathies or their precursor aggregates from the healthy aging GI tract. Thus, accumulating deposits of insoluble α-SYNC in the wall of the GI tract may contribute, especially when compounded by disease or inflammation, to the age-associated neuropathies in the gut that compromise GI function.

Immunology and probiotic impact of the newborn and young children intestinal microflora

Human body has developed a holistic defence system, which mission is either to recognize and destroy the aggressive invaders or to evolve mechanisms permitting to minimize or restore the consequences of harmful actions. The host immune system keeps the capital role to preserve the microbial intestinal balance via the barrier effect. Specifically, pathogenic invaders such as, bacteria, parasites, viruses and other xenobiotic invaders are rejected out of the body via barriers formed by the skin, mucosa and intestinal flora. In case physical barriers are breached, the immune system with its many components comes into action in order to fence infection. The intestine itself is considered as an "active organ" due to its abundant bacterial flora and to its large metabolic activity. The variation among different species or even among different strains within a species reflects the complexity of the genetic polymorphism which regulates the immune system functions. Additionally factors such as, gender, particular habits, smoking, alcohol consumption, diet, religion, age, gender, precedent infections and vaccinations must be involved. Hormonal profile and stress seems to be associated to the integrity microbiota and inducing immune system alterations. Which bacterial species are needed for inducing a proper barrier effect is not known, but it is generally accepted that this barrier function can be strongly supported by providing benefic alimentary supplements called functional foods. In this vein it is stressed the fact that early intestinal colonization with organisms such as Lactobacilli and Bifidobacteria and possibly subsequent protection from many different types of diseases. Moreover, this benefic microflora dominated but Bifidobacteria and Lactobacilli support the concept of their ability to modify the gut microbiota by reducing the risk of cancer following their capacity to decrease β-glucoronidase and carcinogen levels. Because of their beneficial roles in the human gastrointestinal tract, LAB are referred to as "probiotics", and efforts are underway to employ them in modern nutrition habits with so-called functional foods. Members of Lactobacillus and Bifidobacterium genera are normal residents of the microbiota in the human gastrointestinal tract, in which they developed soon after birth. But, whether such probiotic strains derived from the human gut should be commercially employed in the so-called functional foods is a matter of debate between scientists and the industrial world. Within a few hours from birth the newborn develops its normal bacterial flora. Indeed human milk frequently contains low amounts of non-pathogenic bacteria like Streptococcus, Micrococcus, Lactobacillus, Staphylococcus, Corynebacterium and Bifidobacterium. In general, bacteria start to appear in feces within a few hours after birth. Colonization by Bifidobacterium occurs generally within 4 days of life. Claims have been made for positive effects of Bifidobacterium on infant growth and health. The effect of certain bacteria having a benefic action on the intestinal ecosystem is largely discussed during the last years by many authors. Bifidobacterium is reported to be a probiotic bacterium, exercising a beneficial effect on the intestinal flora. An antagonism has been reported between B. bifidum and C. perfringens in the intestine of newborns delivered by cesarean section. The aim of the probiotic approach is to repair the deficiencies in the gut flora and restore the protective effect. However, the possible ways in which the gut microbiota is being influenced by probiotics is yet unknown.

The effect of MS14 on innate and cellular immune responses in BALB/c mice

MS14 is an Iranian natural preparation of herbal-marine source with no obvious toxicity in oral administration, which possesses anti-inflammatory and immunomodulatory effects. In this study, the effect of oral administration of MS14 on nitric oxide (NO) production of peritoneal macrophages and lymphocyte Th1 cytokines and delayed-type hypersensitivity (DTH) test in BALB/c mice were investigated. Peritoneal macrophages were cultured and NO production was measured by Griess method. Viability of macrophages was assayed by MTT (3-(4,5-dimethy-2-lthiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) test. Interleukin-2 (IL-2) and INFγ levels in supernatant of spleen lymphocytes culture were assayed by enzyme-linked immunosorbent assay kit. For DTH test the mice were immunized with sheep red blood cell and DTH was measured 24 h after the last immunization of mice. NO production of macrophages has been diminished significantly in MS14 treated group (about 40%) at the presence or absence of stimulators. Macrophage viability had no significant alteration after MS14 administration. However, interferon-γ production of lymphocytes was significantly decreased in MS14 group both at the absence or presence of concanavalin A (ConA; about 50%); IL-2 production declined about 20% at the presence of ConA. In comparison with the control group, MS14 had no statistically significant effect on DTH test. The results have pointed that MS14 may have immunomodulatory potentials at least through its decreasing effect on NO production of macrophages and level of Th1 cytokine pattern.

Phagocytosis and antigen presentation in dendritic cells

Like macrophages and neutrophils, dendritic cells (DCs) are considered professional phagocytes. Even if the three cell types phagocytose parasites, bacteria, cell debris, or even intact cells very efficiently, the functional outcomes of the phagocytic event are quite different. Macrophages and neutrophils scavenge and destroy phagocytosed particles, a critical step in innate immunity. DCs, in contrast, have developed means to 'preserve' useful information from the ingested particles that serve to initiate adaptive immune responses. Thus, both phagosomal degradation and acidification are much lower in DCs than in macrophages or neutrophils. Reduced degradation results in the conservation of antigenic peptides and in their increased presentation on major histocompatibility complex class I and II molecules. In this article, we review the mechanisms that control this delicate equilibrium between phagosomal degradation/cytotoxicity and antigen presentation in the different families of phagocytes.

Modulation of macrophage structure and function by low level He-Ne laser irradiation

Studies have shown that He-Ne laser irradiation can affect the biological functions of macrophages. The aim of the present study was to investigate the effect of He-Ne laser irradiation on the various functional parameters of macrophages and look for possible correlations in the effects to understand the mechanisms involved. Mice peritoneal macrophages were irradiated with a He-Ne laser (632.8 nm, approximately 10 W m(-2)) at energy densities ranging from 100 to 600 J m(-2) and the activities of lysozyme and cathepsin, phagocytosis, and cell spreading (markers of cell activation), as well as changes in NAD(P)H autofluorescence, were monitored. He-Ne laser irradiation was observed to lead to significant changes in all the parameters investigated. While lysozyme activity and spreading of the peripheral membrane were found to increase with the irradiation dose over the dose range investigated, the phagocytotic activity of macrophages, the activity of cathepsin, the observed decease in cell membrane fluidity and the observed increase in NAD(P)H level showed a peak at 200 J m(-2). Possible reasons for and the significance of the observed correlations are discussed.

Application of X-ray microscopy in analysis of living hydrated cells

Because there is a limit for analysis of fine hydrophilic cell structures of living cells in medium by ordinary techniques, including electron microscopy, the development of a new technology to overcome such limitation is highly desirable. In this regard, soft X-ray microscopy (high-resolution X-ray imaging of structures), which does not require any special procedures for sample preparation, has been developed and applied to analyze structures of biological specimens. In this article, application of two types of X-ray microscopes, which use laser-produced plasma X-rays or synchrotron radiation to image the structure of macrophage cells, is introduced as an example of a novel approach to analysis of biological specimens. Both types of X-ray microscopy show the network of fine fibrillar surface structures on macrophages in medium. Ordinary transmission and scanning electron microscopy and light microscopy also show the presence of such structures, but electron microscopy showed alterations due to sample processing and light microscopy did not show a clear image due to low resolution. Thus, X-ray microscopy has the potential capability to analyze structures of live cells in a hydrated condition and may reveal a function-related structural alignment of cells in their natural form.

Phagosome maturation: aging gracefully

Foreign particles and apoptotic bodies are eliminated from the body by phagocytic leucocytes. The initial stage of the elimination process is the internalization of the particles into a plasma membrane-derived vacuole known as the phagosome. Such nascent phagosomes, however, lack the ability to kill pathogens or to degrade the ingested targets. These properties are acquired during the course of phagosomal maturation, a complex sequence of reactions that result in drastic remodelling of the phagosomal membrane and contents. The determinants and consequences of the fusion and fission reactions that underlie phagosomal maturation are the topic of this review.

Photoreceptor renewal: a role for peripherin/rds

Visual transduction begins with the detection of light within the photoreceptor cell layer of the retina. Within this layer, specialized cells, termed rods and cones, contain the proteins responsible for light capture and its transduction to nerve impulses. The phototransductive proteins reside within an outer segment region that is connected to an inner segment by a thin stalk rich in cytoskeletal elements. A unique property of the outer segments is the presence of an elaborate intracellular membrane system that holds the phototransduction proteins and provides the requisite lipid environment. The maintenance of normal physiological function requires that these postmitotic cells retain the unique structure of the outer segment regions--stacks of membrane saccules in the case of rods and a continuous infolding of membrane in the case of cones. Both photoreceptor rod and cone cells achieve this through a series of coordinated steps. As new membranous material is synthesized, transported, and incorporated into newly forming outer segment membranes, a compensatory shedding of older membranous material occurs, thereby maintaining the segment at a constant length. These processes are collectively referred to as ROS (rod outer segment) or COS (cone outer segment) renewal. We review the cellular and molecular events responsible for these renewal processes and present the recent but compelling evidence, drawn from molecular genetic, biochemical, and biophysical approaches, pointing to an essential role for a unique tetraspanning membrane protein, called peripherin/rds, in the processes of disk morphogenesis.

Role of COPI in phagosome maturation

Phagosomes mature by sequentially fusing with endosomes and lysosomes. Vesicle budding is presumed to occur concomitantly, mediating the retrieval of plasmalemmal components and the regulation of phagosomal size. We analyzed whether fission of vesicles from phagosomes requires COPI, a multimeric complex known to be involved in budding from the Golgi and endosomes. The role of COPI was studied using ldlF cells, that harbor a temperature-sensitive mutation in epsilon-COP, a subunit of the coatomer complex. These cells were made phagocytic toward IgG-opsonized particles by heterologous expression of human FcgammaRIIA receptors. Following incubation at the restrictive temperature, epsilon-COP was degraded in these cells and their Golgi complex dispersed. Nevertheless, phagocytosis persisted for hours in cells devoid of epsilon-COP. Retrieval of transferrin receptors from phagosomes became inefficient in the absence of epsilon-COP, while clearance of the FcgammaRIIA receptors was unaffected. This indicates that fission of vesicles from the phagosomal membrane involves at least two mechanisms, one of which requires intact COPI. Traffic of fluid-phase markers and aggregated IgG-receptor complexes along the endocytic pathway was abnormal in epsilon-COP-deficient cells. In contrast, phagosome fusion with endosomes and lysosomes was unimpaired. Moreover, the resulting phagolysosomes were highly acidic. Similar results were obtained in RAW264.7 macrophages treated with brefeldin A, which precludes COPI assembly by interfering with the activation of adenosine ribosylation factor. These data indicate that neither phagosome formation nor maturation are absolutely dependent on COPI. Our findings imply that phagosomal maturation differs from endosomal progression, which appears to be more dependent on COPI-mediated formation of carrier vesicles.

Spatial regulation and surface chemistry control of monocyte/macrophage adhesion and foreign body giant cell formation by photochemically micropatterned surfaces

A long-standing goal of biomedical device development has been the generation of specific, desired host blood and tissue responses. An approach to meeting this design criteria is precise surface modification that creates micropatterns of distinct physicochemical character to direct cell adhesion and behavior. For this study, poly(ethylene terephthalate) films were coated with poly(benzyl N, N-diethyldithiocarbamate-co-styrene) and sequentially exposed to monomer solutions for photoirradiation. A photomask was placed over different regions to generate micropatterned surfaces with graft polymer stripes of three distinct ionic characters. Human monocytes were cultured on these surfaces to ascertain whether adhesion and fusion of monocytes/macrophages could be controlled. Nonionic polyacrylamide greatly inhibited adhesion and induced clumping of the few monocytes that did adhere. Macrophage adhesion and spreading led to high degrees of interleukin-13 induced foreign body giant cell formation on both the anionic poly(acrylic acid), sodium salt, and benzyl N,N-diethyldithiocarbamate portions of the culture surface. In spite of the highest observed levels of monocyte/macrophage adhesion on cationic poly(dimethylaminopropylacrylamide), methiodide, the adherent cells were not competent to undergo fusion to form foreign body giant cells. These results suggest that inflammatory cell responses may be spatially controlled in a manner that may be ultimately exploited to improve the biocompatibility of medical devices.

Modulation of Monocytic Cell Activity and Virus Susceptibility During Differentiation into Macrophages

A major component of innate immune responses relies on monocytes and macrophages, virus infection of which will pose a particular problem for immunological defense. Consequently, the monocytic cell differentiation pathway was analyzed in terms of cellular modulations therein and their relation to monocytotropic virus infection. Differentiation was characterized by down-regulation of CD14, MHC Ags, the monocytic SWC1 marker, and p53; concomitant up-regulation of the SWC9 macrophage marker, a putative porcine CD80 (detected with anti-human CD80 Ab), and acid phosphatase secretion were also characteristic. Elevated phagocytic and endocytic activities as well as endosomal/lysosomal acidification were identified as being important to the macrophage. In contrast, monocytes possessed high accessory activity. This was multifactorial, concomitantly requiring 1) high MHC Ag expression; 2) enzyme activity of esterase, peroxidase, myeloperoxidase, and 5′ nucleotidase in preference to glucosidase, galactosidase, and glucuronidase; and 3) elevated capacity for spontaneous IL-1 production. Only with all parameters was efficient stimulation of Ag-specific lymphocytes possible. These results point to a continuous process during differentiation, involving inter-related characteristics linking the more accessory monocyte to the scavenger macrophage, both in vitro and in vivo. Of particular interest was how these characteristics related to monocytotropic virus infection, and how a particular virus could show a clear preference for the differentiating macrophages. Such results not only further our understanding of porcine immunology, but also provide evidence and a potential model for the determination and characterization of monocytotropic virus-host cell interactions.

Characterization of mononuclear-phagocyte terminal maturation by mRNA phenotyping using a set of cloned cDNA probes

The terminal step in the maturation of mononuclear cells from circulating monocytes to resident macrophages is accompanied by dramatic changes in cell morphology and physiology. Applying a cultivation system which allows peripheral monocytes to undergo terminal maturation in vitro under absolutely endotoxin-free conditions, we have determined the pattern of expression of a set of eight genes by mRNA phenotyping. The results can be summarized as follows: the two protease inhibitors alpha 1-antitrypsin and alpha 2-macroglobulin show a inverse pattern of expression. alpha 1-Antitrypsin mRNA is repressed, alpha 2-macroglobulin mRNA is strongly induced during maturation to macrophages. Therefore, these two genes are excellent markers of the terminal maturation. In addition, ferritin-light-chain mRNA progressively increases during the course of differentiation, providing a further marker for maturation. Gene expression as a function of activation was studied in mononuclear cells stimulated with bacterial endotoxin (lipopolysaccharide). In monocytes, complement-factor-B, interleukin-1 and interleukin-6 mRNAs are drastically induced upon lipopolysaccharide activation whereas lysozyme RNA is strongly repressed. However, the ability of all four genes to respond to endotoxin was markedly diminished or abolished in mature macrophages, indicating that susceptibility to a certain type of activation may be restricted to a specific stage of maturation. Our data show that mRNA phenotyping is excellently suited for the characterization of the differentiation and activation state of mononuclear phagocytes.

Bacterial antigen immunolabeling in macrophages after phagocytosis and degradation of Bacillus subtilis

After phagocytosis of Bacillus subtilis 168 by bone marrow-derived macrophages, the intracellular pathway followed by different antigens was studied by immunofluorescence and immunoelectron microscopy. Three different rabbit antisera were used: (i) an antiserum to B. subtilis whole cells mainly recognizing the cell wall constituents, (ii) an antiserum to teichoic acid, and (iii) an antiserum to peptidoglycan recognizing the disaccharide tetrapeptide molecules resulting from peptidoglycan degradation. During the first 3 h after phagocytosis of B. subtilis, the three antisera were confined to the same vacuolar compartments, as follows. They were first found in phagosomes gathered in the perinuclear region. Upon bacterial degradation, the three antisera colocalized in an increasing number of small dense vesicles, located in the perinuclear region, that seemed to result from the fragmentation of phagolysosomes. These vesicles correspond to an acidic compartment since they also stained for 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine, a drug known to accumulate in the acidic compartments of cells. At later time points, the antigens recognized by the three antisera followed different pathways. After 18 h, teichoic acid and peptidoglycan were no longer detectable in macrophages whereas an antigen(s) labeled with antiserum to B. subtilis whole cells remained stocked for several days in small acidic vesicles randomly distributed throughout the macrophage. This compartment appeared to be different from the one labeled during the first 3 h after ingestion of bacteria. These results suggest that the transport rate and the compartments implicated in antigen processing differ according to the antigen.

Repression of alpha 2-macroglobulin and stimulation of alpha 1-proteinase inhibitor synthesis in human mononuclear phagocytes by endotoxin

Mononuclear phagocytes are a bone-marrow-derived subgroup of white blood cells which circulate as monocytes and, after differentiation into macrophages, become resident in many tissues. By synthesizing the important proteinase inhibitors alpha 2-macroglobulin and alpha 1-proteinase inhibitor mononuclear phagocytes contribute to the control of proteolysis both in blood and tissues. Applying a culture system which enables human blood monocytes to differentiate into macrophages in vitro, synthesis of alpha 2-macroglobulin and alpha 1-proteinase inhibitor was studied. The normal course of monocyte-macrophage maturation is accompanied by a strong increase of specific alpha 2-macroglobulin synthesis and a concomitant slight decrease of alpha 1-proteinase inhibitor. alpha 2-Macroglobulin can be designated as a marker protein of the monocyte/macrophage differentiation. Endotoxin (Salmonella typhi) in a concentration as low as 100 ng/ml strongly represses alpha 2-macroglobulin synthesis both in monocytes and macrophages. Furthermore, endotoxin completely abolishes the induction of alpha 2-macroglobulin synthesis during the course of normal monocyte in vitro cultivation, indicating that endotoxin is a strong inhibitor of the monocyte-macrophage maturation. In contrast to alpha 2-macroglobulin, alpha 1-proteinase inhibitor synthesis is strongly stimulated by endotoxin in monocytes as well as in macrophages.