Induction of multinucleated giant cell formation from in vitro culture of human monocytes with interleukin-3 and interferon-gamma: comparison with other stimulating factors

Mechanisms of Foreign Body Giant Cell Formation in Response to Implantable Biomaterials

Long term function of implantable biomaterials are determined by their integration with the host's body. Immune reactions against these implants could impair the function and integration of the implants. Some biomaterial-based implants lead to macrophage fusion and the formation of multinucleated giant cells, also known as foreign body giant cells (FBGCs). FBGCs may compromise the biomaterial performance and may lead to implant rejection and adverse events in some cases. Despite their critical role in response to implants, there is a limited understanding of cellular and molecular mechanisms involved in forming FBGCs. Here, we focused on better understanding the steps and mechanisms triggering macrophage fusion and FBGCs formation, specifically in response to biomaterials. These steps included macrophage adhesion to the biomaterial surface, fusion competency, mechanosensing and mechanotransduction-mediated migration, and the final fusion. We also described some of the key biomarkers and biomolecules involved in these steps. Understanding these steps on a molecular level would lead to enhance biomaterials design and improve their function in the context of cell transplantation, tissue engineering, and drug delivery.

Multinucleated Giant Cells: Current Insights in Phenotype, Biological Activities, and Mechanism of Formation

Monocytes and macrophages are innate immune cells with diverse functions ranging from phagocytosis of microorganisms to forming a bridge with the adaptive immune system. A lesser-known attribute of macrophages is their ability to fuse with each other to form multinucleated giant cells. Based on their morphology and functional characteristics, there are in general three types of multinucleated giant cells including osteoclasts, foreign body giant cells and Langhans giant cells. Osteoclasts are bone resorbing cells and under physiological conditions they participate in bone remodeling. However, under pathological conditions such as rheumatoid arthritis and osteoporosis, osteoclasts are responsible for bone destruction and bone loss. Foreign body giant cells and Langhans giant cells appear only under pathological conditions. While foreign body giant cells are found in immune reactions against foreign material, including implants, Langhans giant cells are associated with granulomas in infectious and non-infectious diseases. The functionality and fusion mechanism of osteoclasts are being elucidated, however, our knowledge on the functions of foreign body giant cells and Langhans giant cells is limited. In this review, we describe and compare the phenotypic aspects, biological and functional activities of the three types of multinucleated giant cells. Furthermore, we provide an overview of the multinucleation process and highlight key molecules in the different phases of macrophage fusion.

Mycobacterium tuberculosis Induced Osteoblast Dysregulation Involved in Bone Destruction in Spinal Tuberculosis

Disturbance of bone homeostasis caused by Mycobacterium tuberculosis (Mtb) is a key clinical manifestation in spinal tuberculosis (TB). However, the complete mechanism of this process has not been established, and an effective treatment target does not exist. Increasing evidence shows that abnormal osteoclastogenesis triggered by an imbalance of the receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG) axis may play a key role in the disturbance of bone homeostasis. Previous studies reported that RANKL is strongly activated in patients with spinal TB; however, the OPG levels in these patients were not investigated in previous studies. In this study, we investigated the OPG levels in patients with spinal TB and the dysregulation of osteoblasts caused by Mtb infection. Inhibition of the Mce4a gene of Mtb by an antisense locked nucleic acid (LNA) gapmer (Mce4a-ASO) was also investigated. Analysis of the serum OPG levels in clinical samples showed that the OPG levels were significantly decreased in patients with spinal TB compared to those in the group of non-TB patients. The internalization of Mtb in osteoblasts, the known major source of OPG, was investigated using the green fluorescent protein (GFP)-labeled Mycobacterium strain H37Ra (H37RaGFP). The cell-associated fluorescence measurements showed that Mtb can efficiently enter osteoblast cells. In addition, Mtb infection caused a dose-dependent increase of the CD40 mRNA expression and cytokine (interleukin 6, IL-6) secretion in osteoblast cells. Ligation of CD40 by soluble CD154 reversed the increased secretion of IL-6. This means that the induced CD40 is functional. Considering that the interaction between CD154-expressing T lymphocytes and bone-forming osteoblast cells plays a pivotal role in bone homeostasis, the CD40 molecule might be a strong candidate for mediating the target for treatment of bone destruction in spinal TB. Additionally, we also found that Mce4a-ASO could dose-dependently inhibit the Mce4a gene of Mtb and reverse the decreased secretion of IL-6 and the impaired secretion of OPG caused by Mtb infection of osteoblast cells. Taken together, the current finding provides breakthrough ideas for the development of therapeutic agents for spinal TB.

Macrophage-specific responses to human- and animal-adapted tubercle bacilli reveal pathogen and host factors driving multinucleated cell formation

The Mycobacterium tuberculosis complex (MTBC) is a group of related pathogens that cause tuberculosis (TB) in mammals. MTBC species are distinguished by their ability to sustain in distinct host populations. While Mycobacterium bovis (Mbv) sustains transmission cycles in cattle and wild animals and causes zoonotic TB, M. tuberculosis (Mtb) affects human populations and seldom causes disease in cattle. The host and pathogen determinants underlying host tropism between MTBC species are still unknown. Macrophages are the main host cell that encounters mycobacteria upon initial infection, and we hypothesised that early interactions between the macrophage and mycobacteria influence species-specific disease outcome. To identify factors that contribute to host tropism, we analysed blood-derived primary human and bovine macrophages (hMϕ or bMϕ, respectively) infected with Mbv and Mtb. We show that Mbv and Mtb reside in different cellular compartments and differentially replicate in hMϕ whereas both Mbv and Mtb efficiently replicate in bMϕ. Specifically, we show that out of the four infection combinations, only the infection of bMϕ with Mbv promoted the formation of multinucleated giant cells (MNGCs), a hallmark of tuberculous granulomas. Mechanistically, we demonstrate that both MPB70 from Mbv and extracellular vesicles released by Mbv-infected bMϕ promote macrophage multinucleation. Importantly, we extended our in vitro studies to show that granulomas from Mbv-infected but not Mtb-infected cattle contained higher numbers of MNGCs. Our findings implicate MNGC formation in the contrasting pathology between Mtb and Mbv for the bovine host and identify MPB70 from Mbv and extracellular vesicles from bMϕ as mediators of this process.

The identification of host and pathogen factors contributing to host-pathogen interaction is crucial to understand the pathogenesis and dissemination of tuberculosis. This is particularly the case in deciphering the mechanistic basis for host-tropism across the MTBC. Here, we show that in vitro, M. bovis but not M. tuberculosis induces multinucleated cell formation in bovine macrophages. We identified host and pathogen mechanistic drivers of multinucleated cell formation: MPB70 as the M. bovis factor and bovine macrophage extracellular vesicles. Using a cattle experimental infection model, we confirmed differential multinucleated cell formation in vivo. Thus, we have identified host and pathogen factors that contribute to host tropism in human/bovine tuberculosis. Additionally, this work provides an explanation for the long-standing association of multinucleated cells with tuberculosis pathogenesis.

Distinct macrophage phenotypes skewed by local granulocyte macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF) are associated with tissue destruction and intimal hyperplasia in giant cell arteritis

Objective

To determine the presence and spatial distribution of different macrophage phenotypes, governed by granulocyte macrophage colony‐stimulating factor (GM‐CSF) and macrophage colony‐stimulating factor (M‐CSF) skewing signals, in giant cell arteritis (GCA) lesions.

Methods

Temporal artery biopsies (TABs, n = 11) from treatment‐naive GCA patients, aorta samples from GCA‐related aneurysms (n = 10) and atherosclerosis (n = 10) were stained by immunohistochemistry targeting selected macrophage phenotypic markers, cytokines, matrix metalloproteinases (MMPs) and growth factors. In vitro macrophage differentiation (n = 10) followed by flow cytometry, Luminex assay and ELISA were performed to assess whether GM‐CSF and M‐CSF are drivers of macrophage phenotypic heterogeneity.

Results

A distinct spatial distribution pattern of macrophage phenotypes in TABs was identified. CD206⁺/MMP‐9⁺ macrophages were located at the site of tissue destruction, whereas FRβ⁺ macrophages were located in the inner intima of arteries with high degrees of intimal hyperplasia. Notably, this pattern was also observed in macrophage‐rich areas in GCA aortas but not in atherosclerotic aortas. Flow cytometry showed that GM‐CSF treatment highly upregulated CD206 expression, while FRβ was expressed by M‐CSF‐skewed macrophages, only. Furthermore, localised expression of GM‐CSF and M‐CSF was detected, likely contributing to macrophage heterogeneity in the vascular wall.

Conclusions

Our data document a distinct spatial distribution pattern of CD206⁺/MMP‐9⁺ macrophages and FRβ⁺ macrophages in GCA linked to tissue destruction and intimal proliferation, respectively. We suggest that these distinct macrophage phenotypes are skewed by sequential GM‐CSF and M‐CSF signals. Our study adds to a better understanding of the development and functional role of macrophage phenotypes in the pathogenesis of GCA and opens opportunities for the design of macrophage‐targeted therapies.

Cellular, Molecular, and Immunological Characteristics of Langhans Multinucleated Giant Cells Programmed by IL-15

Langhans multinucleated giant cells (LGCs) are a specific type of multinucleated giant cell containing a characteristic horseshoe-shaped ring of nuclei that are present within granulomas of infectious etiology. Although cytokines that trigger macrophage activation (such as IFN-γ) induce LGC formation, it is not clear whether cytokines that trigger macrophage differentiation contribute to LGC formation. Here, we found that IL-15, a cytokine that induces M1 macrophage differentiation, programs human peripheral blood adherent cells to form LGCs. Analysis of the IL-15‒treated adherent cell transcriptome identified gene networks for T cells, DNA damage and replication, and IFN-inducible genes that correlated with IL-15 treatment and LGC-type multinucleated giant cell formation. Gene networks enriched for myeloid cells were anticorrelated with IL-15 treatment and LGC formation. Functional studies revealed that T cells were required for IL-15‒induced LGC formation, involving a direct contact with myeloid cells through CD40L-CD40 interaction and IFN-γ release. These data indicate that IL-15 induces LGC formation through the direct interaction of activated T cells and myeloid cells.

Cytokines and Bone: Osteoimmunology

Cytokines and hematopoietic growth factors have traditionally been thought of as regulators of the development and function of immune and blood cells. However, an ever-expanding number of these factors have been discovered to have major effects on bone cells and the development of the skeleton in health and disease (Table 1). In addition, several cytokines have been directly linked to the development of osteoporosis in both animal models and in patients. In order to understand the mechanisms regulating bone cells and how this may be dysregulated in disease states, it is necessary to appreciate the diverse effects that cytokines and inflammation have on osteoblasts, osteoclasts, and bone mass. This chapter provides a broad overview of this topic with extensive references so that, if desired, readers can access specific references to delve into individual topics in greater detail.

[Histological differential diagnosis of granulomatous lung diseases (part I)]

Granulomatous diseases are a heterogeneous group of the diseases of different etiology, which are manifested by a variety of clinical syndromes and variants of tissue changes, by non-uniform sensitivity to therapy, and by the predominance of the common dominant histologic sign - the presence of granulomas that determine the clinical and morphological essence of each disease. Granuloma is a chronic inflammatory response, which involves macrophages and other inflammatory cells. After exposure to an antigen, T-lymphocytes, macrophages, epithelioid cells, and multinucleated giant cells are activated, resulting in the formation of granulomas. Granuloma also includes the extracellular matrix produced by fibroblasts, which can demarcate and isolate the antigen. According to etiology, granulomatous diseases are classified as infectious and non-infectious. However, recent investigations demonstrate that pathogenic microorganisms can cause granulomas in diseases previously considered non-infectious. In some cases, it is very difficult to classify a granulomatous process as infectious and non-infectious. The aim of this paper is to draw the attention of readers to the diversity of granulomatous diseases, to describe the key points of pathological and anatomical manifestations of various non-infectious diseases, as well as to determine an approach to the differential diagnosis of granulomatoses.

Experimental models of sarcoidosis

PURPOSE OF REVIEW

Sarcoidosis is a disease caused by a complex combination of genetic susceptibility, immune networks and infectious and/or environmental agents. The onset and phenotypic variability of sarcoidosis remain poorly elucidated, not only due to the lack of clearly identified causes, but also because it is widely considered that no reliable model of this disease is available. In this review, we discuss the various models of granulomatous diseases in order to challenge this assertion.

RECENT FINDINGS

A large number of models of granulomatous diseases are available, both cellular models used to study the natural history of granulomas and experimental animal models mostly developed in rodents.

SUMMARY

Although none of the available models fully reproduces sarcoidosis, most of them generate various data supporting key concepts. Selected models with a high level of confidence among those already published may provide various pieces of the sarcoidosis jigsaw puzzle, whereas clinical data can provide other elements. A 'systems biology' approach for modelling may be a way of piecing together the various pieces of the puzzle. Finally, experimental models and a systemic approach should be considered to be tools for preclinical evaluation of the efficacy of drugs prior to testing in clinical trials.

Horizontal alignment of 5' -> 3' intergene distance segment tropy with respect to the gene as the conserved basis for DNA transcription

AIM

To study the conserved basis for gene expression in comparative cell types at opposite ends of the cell pressuromodulation spectrum, the lymphatic endothelial cell and the blood microvascular capillary endothelial cell.

METHODS

The mechanism for gene expression is studied in terms of the 5' -> 3' direction paired point tropy quotients (prpT_Qs) and the final 5' -> 3' direction episodic sub-episode block sums split-integrated weighted average-averaged gene overexpression tropy quotient (esebssiwaagoT_Q).

RESULTS

The final 5' -> 3' esebssiwaagoT_Q classifies an lymphatic endothelial cell overexpressed gene as a supra-pressuromodulated gene (esebssiwaagoT_Q ≥ 0.25 < 0.75) every time and classifies a blood microvascular capillary endothelial cell overexpressed gene every time as an infra-pressuromodulated gene (esebssiwaagoT_Q < 0.25) (100% sensitivity; 100% specificity).

CONCLUSION

Horizontal alignment of 5' -> 3' intergene distance segment tropy wrt the gene is the basis for DNA transcription in the pressuromodulated state.

A high-content imaging assay for the quantification of the Burkholderia pseudomallei induced multinucleated giant cell (MNGC) phenotype in murine macrophages

BACKGROUND

Burkholderia pseudomallei (Bp), a Gram-negative, motile, facultative intracellular bacterium is the causative agent of melioidosis in humans and animals. The Bp genome encodes a repertoire of virulence factors, including the cluster 3 type III secretion system (T3SS-3), the cluster 1 type VI secretion system (T6SS-1), and the intracellular motility protein BimA, that enable the pathogen to invade both phagocytic and non-phagocytic cells. A unique hallmark of Bp infection both in vitro and in vivo is its ability to induce cell-to-cell fusion of macrophages to form multinucleated giant cells (MNGCs), which to date are semi-quantitatively reported following visual inspection.

RESULTS

In this study we report the development of an automated high-content image acquisition and analysis assay to quantitate the Bp induced MNGC phenotype. Validation of the assay was performed using T6SS-1 (∆hcp1) and T3SS-3 (∆bsaZ) mutants of Bp that have been previously reported to exhibit defects in their ability to induce MNGCs. Finally, screening of a focused small molecule library identified several Histone Deacetylase (HDAC) inhibitors that inhibited Bp-induced MNGC formation of macrophages.

CONCLUSIONS

We have successfully developed an automated HCI assay to quantitate MNGCs induced by Bp in macrophages. This assay was then used to characterize the phenotype of the Bp mutants for their ability to induce MNGC formation and identify small molecules that interfere with this process. Successful application of chemical genetics and functional reverse genetics siRNA approaches in the MNGC assay will help gain a better understanding of the molecular targets and cellular mechanisms responsible for the MNGC phenotype induced by Bp, by other bacteria such as Mycobacterium tuberculosis, or by exogenously added cytokines.

Localized AL amyloidosis: a suicidal neoplasm?

Although AL amyloidosis usually is a systemic disease, strictly localized AL deposits are not exceptionally rare. Such case reports form a considerable body of published articles. Although both AL amyloidosis types are formed from an N-terminal segment of a monoclonal immunoglobulin light chain, a typical localized AL amyloid differs from the systemic counterpart by the morphological appearance of the amyloid, and presence of clonal plasma cells and of giant cells. In this article it is pointed out that localized AL amyloidosis ('amyloidoma') represents a true plasma cell neoplasm and not a pseudotumor. The pathogenesis of localized AL amyloidosis may differ from that of the systemic type, a suggestion underlined by the fact that localized AL amyloidosis of kappa type is as common as that of lambda origin, in contrast to the systemic form where lambda chains constitute the overwhelming majority of cases. It is suggested that oligomeric assemblies of the produced immunoglobulin light chain are toxic to plasma cells, which in this way commit suicide.

The CD40-CD40L axis and IFN-γ play critical roles in Langhans giant cell formation

The presence of Langhans giant cells (LGCs) is one of the signatures of systemic granulomatous disorders such as tuberculosis and sarcoidosis. However, the pathophysiological mechanism leading to LGC formation, especially the contribution of the T cells abundantly found in granulomas, has not been fully elucidated. To examine the role of T cells in LGC formation, a new in vitro method for the induction of LGCs was developed by co-culturing human monocytes with autologous T cells in the presence of concanavalin A (ConA). This system required close contact between monocytes and T cells, and CD4+ T cells were more potent than CD8+ T cells in inducing LGC formation. Antibody inhibition revealed that a CD40-CD40 ligand (CD40L) interaction and IFN-γ were essential for LGC formation, and the combination of exogenous soluble CD40L (sCD40L) and IFN-γ efficiently replaced the role of T cells. Dendritic cell-specific transmembrane protein (DC-STAMP), a known fusion-related molecule in monocytes, was up-regulated during LGC formation. Moreover, knock-down of DC-STAMP by siRNA inhibited LGC formation, revealing that DC-STAMP was directly involved in LGC formation. Taken together, these results demonstrate that T cells played a pivotal role in a new in vitro LGC formation system, in which DC-STAMP was involved, and occurred via a molecular mechanism that involved CD40-CD40L interaction and IFN-γ secretion.

Granulocyte macrophage colony-stimulating factor enhances the modulatory effect of cytokines on monocyte-derived multinucleated giant cell formation and fungicidal activity against Paracoccidioides brasiliensis

Multinucleated giant cells (MGC) are cells present in characteristic granulomatous inflammation induced by intracellular infectious agents or foreign materials. The present study evaluated the modulatory effect of granulocyte macrophage colony-stimulating factor (GM-CSF) in association with other cytokines such as interferon-gamma (IFN-γ), tumour necrosis factor-alpha, interleukin (IL)-10 or transforming growth factor beta (TGF-β1) on the formation of MGC from human peripheral blood monocytes stimulated with Paracoccidioides brasiliensis antigen (PbAg). The generation of MGC was determined by fusion index (FI) and the fungicidal activity of these cells was evaluated after 4 h of MGC co-cultured with viable yeast cells of P. brasiliensis strain 18 (Pb18). The results showed that monocytes incubated with PbAg and GM-CSF plus IFN-γ had a significantly higher FI than in all the other cultures, while the addition of IL-10 or TGF-β1 had a suppressive effect on MGC generation. Monocytes incubated with both pro and anti-inflammatory cytokines had a higher induction of foreign body-type MGC rather than Langhans-type MGC. MGC stimulated with PbAg and GM-CSF in association with the other cytokines had increased fungicidal activity and the presence of GM-CSF also partially inhibited the suppressive effects of IL-10 and TGF-β1. Together, these results suggest that GM-CSF is a positive modulator of PbAg-stimulated MGC generation and on the fungicidal activity against Pb18.

Molecular and cellular mechanisms of mammalian cell fusion

The fusion of one cell with another occurs in development, injury and disease. Despite the diversity of fusion events, five steps in sequence appear common. These steps include programming fusion-competent status, chemotaxis, membrane adhesion, membrane fusion, and post-fusion resetting. Recent advances in the field start to reveal the molecules involved in each step. This review focuses on some key molecules and cellular events of cell fusion in mammals. Increasing evidence demonstrates that membrane lipid rafts, adhesion proteins and actin rearrangement are critical in the final step of membrane fusion. Here we propose a new model for the formation and expansion of membrane fusion pores based on recent observations on myotube formation. In this model, membrane lipid rafts first recruit adhesion molecules and align with opposing membranes, with the help of a cortical actin "wall" as a rigid supportive platform. Second, the membrane adhesion proteins interact with each other and trigger actin rearrangement, which leads to rapid dispersion of lipid rafts and flow of a highly fluidic phospholipid bilayer into the site. Finally, the opposing phospholipid bilayers are then pushed into direct contact leading to the formation of fusion pores by the force generated through actin polymerization. The actin polymerization generated force also drives the expansion of the fusion pores. However, several key questions about the process of cell fusion still remain to be explored. The understanding of the mechanisms of cell fusion may provide new opportunities in correcting development disorders or regenerating damaged tissues by inhibiting or promoting molecular events associated with fusion.

A Novel in vitro Human Macrophage Model to Study the Persistence of Mycobacterium tuberculosis Using Vitamin D(3) and Retinoic Acid Activated THP-1 Macrophages

Mycobacterium tuberculosis (Mtb) replicates within the human macrophages and we investigated the activating effects of retinoic acid (RA) and vitamin D(3) (VD) on macrophages in relation to the viability of intracellular Mtb. A combination of these vitamins (RAVD) enhanced the levels of DC-SIGN and mannose receptors on THP-1 macrophages that increased mycobacterial uptake but inhibited the subsequent intracellular growth of Mtb by inducing reactive oxygen species and autophagy. RAVD also enhanced antigen presenting and chemotactic receptors on THPs suggesting an activated phenotype for RAVD activated THPs. RAVD mediated activation was also associated with a marked phenotypic change in Mtb infected THPs that fused with adjacent THPs to form multinucleated giant cells (MNGCs). Typically, MNGCs occurred over 30 days of in vitro culture and contained non-replicating persisting Mtb for more than 60 days in culture. Latent tuberculosis occurs in over a third of mankind and we propose that RAVD mediated induction of persistent Mtb within human macrophages provides a novel model to develop therapeutic approaches and investigate pathogenesis of latency.

Macrophage fusion and multinucleated giant cells of inflammation

Macrophages undergo fusion with other macrophages to form the hallmark multinucleated giant cells of chronic inflammation. However, neither the existence of distinct morphological types of giant cells, the signaling pathways that induce their formation, the molecular mechanism(s) of macrophage fusion, nor the significance of macrophage multinucleation at chronic inflammatory sites are well understood. Our efforts have been focused on these unknowns, particularly as they relate to the foreign body-type giant cells that form on implanted biomaterials and biomedical devices. We have pursued the discoveries of human macrophage fusion factors (interleukin-4, interleukin-13, α-tocopherol) with emphasis on foreign body giant cells, and identified adhesion receptors and signaling intermediates, as well as an adhesion protein substrate (vitronectin) that supports macrophage fusion. Studies on the molecular mechanism of macrophage fusion have revealed it to be a mannose receptor-mediated phagocytic process with participation of the endoplasmic reticulum. Further phenotypic and functional investigations will foster new perspectives on these remarkable multinucleated cells and their physiological significances in multiple inflammatory processes.

IL-3 inhibits human osteoclastogenesis and bone resorption through downregulation of c-Fms and diverts the cells to dendritic cell lineage

IL-3 is an important cytokine that regulates hematopoiesis and functions as a link between the immune and the hematopoietic system. In this study, we investigated the role and mechanism of IL-3 action on human osteoclast formation and bone resorption using PBMCs. PBMCs differentiate into functional osteoclasts in the presence of M-CSF and receptor activator of NF-kappaB ligand as evaluated by 23c6 expression and bone resorption. We found that IL-3 dose-dependently inhibited formation of 23c6-positive osteoclasts, bone resorption and C-terminal telopeptide of type I collagen, a collagen degradation product. The inhibitory effect of IL-3 on bone resorption was irreversible. To investigate the mechanism of IL-3 action, we analyzed the effect of IL-3 on the receptor activator of NF-kappaB and c-Fms receptors and c-Fos, PU.1, NFAT cytoplasmic 1, and RelB transcription factors essential for osteoclastogenesis. IL-3 significantly inhibited c-Fms and downregulated both PU.1 and c-Fos at both mRNA and protein level. Furthermore, IL-3-treated cells showed increased expression of dendritic cell markers CD1a and CD80 and decreased expression of monocyte/macrophage marker CD14. Interestingly, IL-3 inhibited formation of human osteoclasts derived from blood monocytes and bone marrow cells of osteoporotic individuals. Thus, IL-3 may have therapeutic potential as an antiosteolytic agent in treatment of osteoporosis.

Lymphocyte adhesion and interactions with biomaterial adherent macrophages and foreign body giant cells

To characterize the effects of adherent macrophages and biomaterial surface chemistries on lymphocyte adhesion and activation, lymphocytes were co-cultured with monocytes alone and together, directly and separated by a porous membrane transwell on hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic biomaterial surfaces. Surface adherent cells were quantitatively analyzed after 3 days utilizing immunofluorescence and phase contrast imaging. After periods of 3, 7, and 10 days, secreted interferon-gamma (IFN-gamma) was quantified by ELISA. Limited direct biomaterial-adherent lymphocytes were identified regardless of the presence of macrophages or foreign body giant cells (FBGC). The majority of adherent lymphocytes, which were T cells (>95%) rather than natural killer cells, predominantly interacted with adherent macrophages and FBGCs; greater than 90% were interacting on surfaces with higher levels of adherent macrophages and FBGCs and greater than 55% were interacting on surfaces with lower levels of macrophages and FBGCs. The hydrophilic/anionic surface promoted higher levels of macrophage- and FBGC-adherent lymphocytes but was nonselective for lymphocyte subtype interactions. The hydrophilic/neutral surface was selective for CD4+ T lymphocyte interactions while the hydrophobic surface was selective for CD8+ T lymphocyte interactions. IFN-gamma was produced in direct and indirect co-cultures but not in lymphocyte- and monocyte-only cultures suggesting that lymphocytes are activated via macrophage-derived cytokines rather than direct biomaterial contact. Direct lymphocyte interactions with adherent macrophages/FBGCs enhanced IFN-gamma production relative to indirect co-cultures. These results suggest that lymphocytes prefer interactions with adherent macrophages and FBGCs, resulting in lymphocyte activation, and these interactions can be influenced by biomaterial surface chemistries.

Multi-nucleated giant cell formation from human cord blood monocytes in vitro, in comparison with adult peripheral blood monocytes

Multi-nucleated giant cells (MGCs; Langhans-type cell), formed from macrophage fusion, are recognized as a hallmark histological feature in chronic inflammation. However, their precise pathological role is still poorly understood, especially for microorganism pathogens in the neonatal immune system, which are capable of surviving intracellularly in phagocytes. To conduct a partial evaluation of the monocyte function of neonates, we investigated the ability of human cord blood monocytes to form MGCs in vitro by stimulating various cytokines and comparing them with adult peripheral blood monocytes. Monocytes from cord blood and adult peripheral blood were isolated and cultured for 14 days with cytokines known to induce MGC in vitro. The fusion index in experiments with a combination of interleukin (IL)-4 and macrophage colony-stimulating factor (M-CSF) and a combination of IL-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) was significantly lower in cord blood than in adult blood monocytes (P = 0.0018 and P = 0.0141, respectively). The number of nuclei per MGC was significantly lower in cord blood than in adult blood monocytes in experiments with IL-4 alone, the combination of IL-4 and M-CSF, and the combination of IL-4 and GM-CSF (P < 0.0001). These results suggest the possibility that the susceptibility of newborns to mycobacterium infection is due partly to impaired MGC formation.

Langhans giant cells from M. tuberculosis-induced human granulomas cannot mediate mycobacterial uptake

Tuberculosis is characterized by a tight interplay between Mycobacterium tuberculosis (M. tb) and host cells within granulomas. These cellular aggregates restrain M. tb spreading but do not kill all bacilli, which persist for years. A more detailed investigation of the interaction between M. tb and granuloma cells is needed to improve our understanding of this persistence and to explain the physiopathology of tuberculosis. In the present study, a recently developed in vitro human model of tuberculous granulomas has been used to analyse the modulation of granuloma cell differentiation by M. tb, in comparison to poorly virulent mycobacteria, which do not persist. It is reported that whilst all mycobacteria species induce granuloma formation, only M. tb triggers the differentiation of granuloma macrophages into very large multinucleated giant cells (MGCs) that are unable to mediate any bacterial uptake. This loss of function is not due to cell quiescence, as MGCs still display NADPH oxidase activity, but it correlates with decreased expression of phagocytosis receptors. This phenomenon is specific for the virulent species of M. tuberculosis complex, as poorly virulent species only induce the formation of small multinucleated cells (MCs) with conserved mycobacterial uptake ability, which never reach the MGC differentiation stage. The phenotype of MGCs thus strongly resembles mature dendritic cells with a loss of microbial uptake ability, despite conserved antigen presentation. In M. tb-induced granulomas, MGCs thus seem to be devoted to the destruction of bacilli that have been ingested in previous differentiation stages, ie in macrophages and MCs.

Multinucleate giant cells and the control of chemokine secretion in response to Mycobacterium tuberculosis

Multinucleate giant cells (MGC) are characteristic of tuberculous granulomas, but their function is not well understood. In a comparative study, we investigated regulation of chemokine secretion by MGC generated using 5 microg/ml ConA and 1000 IU/ml IFN-gamma. After 72-h differentiation of MGC cultures, CXCL8, CCL2 and CCL3 concentrations were 9540+/-110 pg/ml, 11190+/-2210 pg/ml and 19440+/-440 pg/ml respectively all significantly higher than in MDM (P<0.01). There was associated increased chemokine gene expression. M.tb stimulation of MGC, MDM and monocytes increased CXCL8 secretion. M.tb increased monocyte CCL2 secretion, whereas MGC and MDM secreted CCL2 constitutively. CXCL10 secretion was induced in M.tb-stimulated MDM and constitutive in MGC. All cell types responded to M.tb with CCL3 secretion. Monocyte chemokine secretion was associated with increased gene expression, whereas M.tb-stimulated MGC principally upregulated CCL3 gene expression. In summary, differentiating MGC express genes for and secrete chemokines which regulate cell influx to sites of infection. Established MGC will contribute to cell recruitment to granuloma, but this may not depend on exposure to the pathogen.

B-1 cells are pivotal for in vivo inflammatory giant cell formation

The mechanisms that govern giant cell (GC) formation in inflammatory, neoplastic and physiologic conditions are far from being understood. Here, we demonstrate that B-1 cells are essential for foreign-body GC formation in the mouse. GCs were analysed on the surface of glass cover slips implanted into the subcutaneous tissue of the animals. It was demonstrated that GCs are almost absent on cover slips implanted into the subcutaneous tissue of BALB/c or CBA/N X-linked immunodeficient mice. As these animals do not have B-1 cells in the peritoneal cavity, they were reconstituted with B-1 cells obtained from cultures of adherent mouse peritoneal cells. Results showed that in B-1-reconstituted animals, the number of GCs on the implant surface surpassed the values obtained with preparations from wild animals. In animals selectively irradiated (pleural and peritoneal cavities) to deplete these cavities of B-1 cells, GCs were also not formed. Enriched suspensions of B-1 cells grown in culture were labelled with [(3)H]-tymidine and injected into the peritoneal cavity of naive mice before implantation of glass cover slips. After 4 days, about 17% of mononuclear cells had their nuclei labelled, and almost 70% of GCs had one or more of their nuclei labelled when analysed by histoautoradiographic technique. A few GCs expressed an immunoglobulin M when analysed by immunostaining and confocal microscopy. Overall, these data demonstrate that B-1 cells are pivotal in the mechanisms of foreign-body GC formation in the mouse.

The role of osteopontin in foreign body giant cell formation

Foreign body giant cells (FBGCs) are a hallmark of the foreign body reaction caused by biomaterial implantation and are thought to contribute to biomaterial degradation and the duration of the response. Osteopontin (OPN) is a secreted, acidic matricellular protein with multiple phosphorylation sites that is highly expressed at sites of inflammation. OPN wildtype and knockout mice were implanted with poly(vinyl alcohol) sponges and explanted at 14 days. OPN knockout mice had more foreign body giant cells but fewer macrophages surrounding the implants than their wildtype counterparts. In an in vitro human FBGC assay, addition of soluble OPN was found to reduce macrophage fusion to giant cells. These are the first studies to show a direct inhibitory role of OPN in FBGC formation in response to implantation.

Inhibitory influences of xanthine oxidase inhibitor and angiotensin I-converting enzyme inhibitor on multinucleated giant cell formation from monocytes by downregulation of adhesion molecules and purinergic receptors

BACKGROUND

Allopurinol, a xanthine oxidase inhibitor, and captopril, an inhibitor of angiotensin I-converting enzyme, are widely used for hyperuricaemia and hypertension, respectively. There have been reported cases showing that these two agents are effective for the treatment of granulomatous diseases such as sarcoidosis, although the mode of action is not elucidated.

OBJECTIVES

We examined the in vitro effects of these agents on the formation of multinucleated giant cells (MGC) from human monocytes by concanavalin A-stimulated mononuclear cell supernatants (conditioned medium).

METHODS

We cultured monocytes with conditioned medium and each agent and compared the rate of MGC formation as well as the expression of adhesion molecules and P2X7 receptor, which are involved in MGC formation.

RESULTS

The addition of 25 or 100 microg mL(-1) allopurinol or 0.125-1.0 microg mL(-1) captopril inhibited MGC formation. Monocytes treated with these agents exhibited less expression of intercellular adhesion molecular-1 (ICAM-1) than untreated monocytes. The susceptibility of monocytes cultured in conditioned medium for 24 h to 2'-and 3'-o-(4-benzoyl-benzoyl)adenosine triphosphate-mediated cytolysis was significantly lower in monocytes treated with these agents than in untreated monocytes.

CONCLUSIONS

Allopurinol and captopril have a therapeutic effect on granulomatous disorders by a direct action on monocyte/macrophage lineage cells partly through downregulation of ICAM-1 and P2X7 receptor.

Foreign body-type multinucleated giant cell formation is potently induced by alpha-tocopherol and prevented by the diacylglycerol kinase inhibitor R59022

Multinucleated foreign body giant cells (FBGCs) form by monocyte-derived macrophage fusion on implanted biomedical devices and are believed to mediate oxidative damage to biomaterial surfaces. Our in vitro system of human macrophage culture and interleukin (IL)-4-induced FBGC formation was developed to study the macrophage fusion mechanism and the physiological significance of FBGCs on implanted biomaterials and at other sites of chronic inflammation. Here, we demonstrate that the antioxidant vitamin E (90% alpha-tocopherol) moderately induces macrophage fusion and increases IL-4-induced FBGC formation. Moreover, purified alpha-tocopherol, but not beta-, gamma-, or delta-tocopherol, most remarkably induces macrophage fusion, leading to cultures of confluent FBGCs below normal plasma concentrations. This is not observed with the similar antioxidants probucol or Trolox, suggesting that the alpha-tocopherol effects on FBGC formation are independent of its antioxidant activity. Consistent with the reported activation of diacylglycerol kinase by alpha-tocopherol, the diacylglycerol kinase inhibitor R59022 completely abrogates FBGC formation. R59022 inhibition of IL-4-induced FBGC formation is reversed by alpha-tocopherol, suggesting that FBGC formation involves diacylglycerol kinase activation. This study suggests a novel role for diacylglycerol kinase in the mechanism of macrophage fusion/FBGC formation at sites of chronic inflammation and reveals that the pleiotropic lipophilic compound, alpha-tocopherol, is a highly potent macrophage fusion factor.

Impaired hepatic granuloma formation in mice deficient in C-C chemokine receptor 2

Granulomas are characterized histologically by a nodular collection of macrophages with occasional admixture of epithelioid cells, multinucleate giant cells, and other immunocompetent cells. Chemokines are considered to play an important role in the recruitment of these constituent cells of granulomas. The present study has examined the effect of a deficiency of C-C chemokine receptor-2 (CCR2) on hepatic granuloma formation induced by a single injection of Zymosan A. In CCR2+/+ mice, the number and the size of granulomas gradually increased until they reached peak values at 10 days after the injection. In contrast, both the number and the size of granulomas were smaller in CCR2-/- mice than in CCR2+/+ mice from days 5 to 21. They showed low peaks at day 5, after which the number and the size of the granulomas gradually decreased. Immunohistochemical analysis of the constituent granuloma cells using cell type-specific monoclonal antibodies revealed rapid accumulation of blood monocytes, with subsequent differentiation to macrophages, in CCR2+/+ mice during days 2-10. This process was greatly impaired in CCR2-/- mice and granulomas remained small. At all time points, the percentage of polymorphonuclear cells in granulomas was higher in CCR2-/- mice than in CCR2+/+ mice. Interestingly, multinucleate giant cells were frequently observed in granulomas in CCR2-/- mice, whereas they rarely appeared in CCR2+/+ mice. Profiles of liver cytokine RNA levels as well as serum cytokine levels revealed reduced expression of the Th1 cytokine IFN-gamma in CCR2-/- mice. These data clearly indicate that signalling through CCR2 has many effects on the normal growth and development of hepatic granulomas.

Monocyte-derived multinucleated giant cells and sarcoidosis

Multinucleated giant cells (MGC) are characteristic cells in granulomatous disorders such as sarcoidosis and also formed in vitro from peripheral blood mononuclear cells by stimulation with cytokines, including interferon-gamma (IFN-gamma), interleukin-3 (IL-3), IL-4, IL-13, and granulocyte-macrophage-colony stimulating factor. In addition to such inflammatory mediators, a factor derived from the pathogens of granulomatous disorders may be necessary for MGC formation. Muramyl dipeptide (MDP), a peptidoglycan portion of bacterial cell walls present in sarcoidal lesions, is one of the candidates and can preferentially induce Langhans-type cells (LGC) in in vitro MGC formation system. Although the exact mechanisms of in vitro MGC formation remains unknown, receptors such as P2X(7), integrins, CD98, and macrophage fusion protein are considered to be involved in cell-to-cell adhesion and subsequent fusion process. Monocytes from sarcoidosis patients expressed higher levels of P2X(7) and had a higher ability to induce MGC than those from healthy controls. Attributable cells for the formation were CD14(++)CD16(-) monocytes. Therefore, CD14(++)CD16(-) monocytes may infiltrate into sarcoidal lesions and be fused to form LGC by inflammatory mediators and MDP derived from the pathogens of the disorder. Effective agents for sarcoidosis such as tranilast, allopurinol, and captopril inhibited in vitro MGC formation through inhibiting the expression of adhesion molecule and purinergic receptor. Thus, an in vitro MGC formation model would be a useful tool to understand the relevance of MGC in granulomatous disorders.

Formation of short-lived multinucleated giant cells (MGCS) from cultured gilthead seabream macrophages

Monocytes/macrophages obtained from the head kidney and peritoneal cavity of gilthead seabream (Sparus aurata) were cultured using plates from three different manufacturers, and were maintained under different conditions. The effects on the morphology and fusion of monocytes/macrophages of initial cell loading, removal of non-adherent cells at different times after plating, and addition of serum and antibiotics were evaluated by light microscopy, and transmission (TEM) and scanning (SEM) electron microscopy. Despite variations in adherence, the behaviour and the morphological changes in kidney monocytes/macrophages were similar in all three types of plates. When foetal calf serum (FCS) was added to the incubation medium, most of the cells resembling monocytes/macrophages were connected by cytoplasmic extensions that formed bridges after 24 hr in culture. After 30 hr, the monocytes/macrophages started to fuse, forming multinucleated giant cells (MGCs) which gradually increased in size until the culture was 4-5 days old. After 5 days the MGCs started to die, and after a week most had disappeared from the cultures. Cells incubated with medium without serum showed changes similar to those fed with FCS, but some cells survived for 3 weeks. The addition of fish serum to the medium appeared to accelerate all processes: the monocytes/macrophages and MGCs died after 3 days in culture. Antibiotics had no apparent effect on the cultures. Removal of non-adherent cells at different times after plating did not appear to affect cell fusion. Coating the wells with extracellular matrix proteins reduced adherence but did not inhibit cell fusion. Curiously, not all macrophages fused with MGCs, and, unlike MGCs, these macrophages phagocytosed sheep red blood cells (SRBCs). Peritoneal macrophages also fused and formed MGCs in culture, similarly to kidney cells.

Systemic administration of antigen-pulsed dendritic cells induces experimental allergic asthma in mice upon aerosol antigen rechallenge

Antigen-pulsed dendritic cells (DCs) have been used extensively as cellular vaccines to induce a myriad of protective immune responses. Adoptive transfer of antigen-pulsed DCs is especially effective at generating Th1 and CD8 immune responses. However, recently this strategy has been shown to induce Th2 cells when DCs are administered locally into the respiratory tract. We sought to address whether systemic rather than local antigen-pulsed DC administration could induce Th2 experimental allergic asthma. We found that OVA-pulsed splenic DCs injected intraperitoneally induced polarized Th2 allergic lung disease upon secondary OVA aerosol challenge. Disease was characterized by eosinophilic lung inflammation, excess mucus production, airway hyperresponsiveness, and OVA-specific IgG1 and IgE. In addition, unusual pathology characterized by macrophage alveolitis and multinucleated giant cells was observed. These data show that systemic administration of antigen-pulsed DCs and subsequent aeroantigen challenge induces Th2 immunity. These findings have important implications for the development of DC-based vaccines.

Bone marrow cells adopt the phenotype of other cells by spontaneous cell fusion

Recent studies have demonstrated that transplanted bone marrow cells can turn into unexpected lineages including myocytes, hepatocytes, neurons and many others. A potential problem, however, is that reports discussing such 'transdifferentiation' in vivo tend to conclude donor origin of transdifferentiated cells on the basis of the existence of donor-specific genes such as Y-chromosome markers. Here we demonstrate that mouse bone marrow cells can fuse spontaneously with embryonic stem cells in culture in vitro that contains interleukin-3. Moreover, spontaneously fused bone marrow cells can subsequently adopt the phenotype of the recipient cells, which, without detailed genetic analysis, might be interpreted as 'dedifferentiation' or transdifferentiation.

Culture at high density improves the ability of human macrophages to control mycobacterial growth

The mechanisms through which granuloma formation helps control mycobacterial infection are poorly understood, but it is possible that the accumulation of macrophages at high density at sites of infection promotes the differentiation of macrophages into cells with improved mycobactericidal activity. To test this possibility, varying numbers of monocytes were cultured in 96-well plates for 3 days, infected with Mycobacterium bovis bacillus Calmette-Guérin, and mycobacterial number was assessed 7 days after infection based on the measurement of luciferase activity expressed by a mycobacterial reporter strain or by counting CFU. Mycobacterial growth was optimal in cultures containing 5 x 10(4) cells/well, but increasing the number of cells to 2 x 10(5) cells/well resulted in complete inhibition of mycobacterial growth. This effect could not be explained by differences in mycobacterial uptake, multiplicity of infection, acidification of the extracellular medium in high density cultures, enhanced NO production, or paracrine stimulation resulting from secretion of cytokines or other proteins. The morphology of cells cultured at high density was strikingly different from that of monocytes cultured at 5 x 10(4) cells/well, including the appearance of numerous giant cells. The bacteriostatic activity of monocyte-derived macrophages was also dependent on cell number, but fewer of these more mature cells were required to control mycobacterial growth. Thus, the ability of human macrophages to control mycobacterial infection in vitro is influenced by the density of cells present, findings that may help explain why the formation of granulomas in vivo appears to be a key event in the control of mycobacterial infections.

Inhibitory influences of tranilast on multinucleated giant cell formation from monocytes by supernatant of concanavalin A-stimulated mononuclear cells

Tranilast is an anti-allergic drug that inhibits the release of chemical mediators from mast cells. There have been cases-reports showing that tranilast is effective for the treatment of granulomatous diseases such as granuloma annulare and cutaneous sarcoidosis. Here we examined the in vitro effects of tranilast on the formation of multinucleated giant cells (MGCs) from human peripheral monocytes. Supernatant of concanavalin A (Con A)-stimulated mononuclear cells induced Langhans-type and foreign body-type MGCs and the addition of 10 or 100 microg/ml tranilast inhibited the formation of total MGCs and foreign body-type MGCs. Tranilast decreased the number of MGCs with 16<nuclei and increased that of MGCs with three to five nuclei. Fluorescence-activated cell sorting analysis showed that tranilast-treated monocytes had lower expressions of intercellular adhesion molecule-1 (ICAM-1). These findings suggest that tranilast is effective for cutaneous lesions in some cases of granulomatous disorders partly through a direct effect on monocyte/macrophage-lineage cells.

Inflammatory cytokine production by immunological and foreign body multinucleated giant cells

Multinucleated giant cells (MGC) are a common feature of granulomas. The mechanism of their formation has been studied extensively, but their function has not been completely characterized. A new method for the in vivo production of MGC was developed involving subcutaneous injection of microscopic nitrocellulose particles with adsorbed mycobacterial antigens into the footpads of sensitized BALB/c mice (immune [I]-MGC), or by nitrocellulose administration to non-sensitized mice (foreign body [FB]-MGC). The development of granulomas with a highly enriched MGC population was observed 2 weeks after the nitrocellulose injection. MGC were larger with a greater number of nuclei in I-MGC than in FB-MGC. From days 7-28 after nitrocellulose administration, the production of interleukin-1alpha (IL-1alpha) and tumour necrosis factor-alpha (TNF-alpha) was demonstrated in both MGC types by in situ reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. After 2 months, the MGC had ceased production of IL-1alpha and TNF-alpha, but the expression of transforming growth factor-beta (TGF-beta) was very high, occurring together with extensive fibrosis. These results suggest that MGC are an active source of inflammatory cytokines, which can contribute to the initiation, maintenance and down-regulation of granulomatous inflammation induced by immunological and inert substances.

Giant cell formation in cells exposed to 740 nm and 760 nm optical traps

BACKGROUND AND OBJECTIVE

Optical trapping is becoming a useful and widespread technique for the micromanipulation of cells and organelles. Giant cell formation following optical trapping was studied to detect the potential adverse effects.

STUDY DESIGN/MATERIALS AND METHODS

The nuclei of preselected single CHO cells were exposed to 740 nm and 760 nm laser microbeam generated by a titanium-sapphire tunable laser at 88 and 176 mW and different time exposures. The irradiated single cells were recorded and observed morphologically following exposure. Giant cells were tabulated and photographed.

RESULTS

The irradiated cells either failed to divide, or they underwent nuclear proliferation to form giant cells through endoreduplication.

CONCLUSION

Giant cells were induced by both 740 nm and 760 nm. The frequency of giant cell formation was higher for the longer time exposures and at the higher power densities. The use of an optical etalon to remove intracavity mode beating and high peak powers of the titanium-sapphire laser caused a significant reduction in the formation of giant cells.

Formation of multinucleated giant cells in the mouse lung is promoted in the absence of interleukin-12

The formation of multinucleated giant cells (MGCs) in an in vivo model of pulmonary inflammation was investigated to determine whether these cells are the result of a dominant T helper (Th) 1 or Th2 cytokine environment. We report that knockout (KO) mice with a disrupted interleukin (IL)-12 p40 gene exposed to the helminth Schistosoma mansoni had abundant and very large MGCs (> 50 microm) in their lungs concurrent with extensive eosinophilia and a population of large macrophages. Many of the MGCs and macrophages appeared to have phagocytosed eosinophils as part of a clearance process. The KO mice also had a strongly polarized Th2 immune response as judged by elevated levels in the lungs of messenger RNA (mRNA) transcripts for IL-4, IL-5, IL-6, and IL-13, but decreased levels of mRNA for interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). In addition, cells recovered by bronchoalveolar lavage from the airways of these mice secreted a Th2-biased profile of cytokines upon restimulation in vitro with parasite antigen. In contrast, wild-type C57BL/6 or KO mice treated with recombinant IL-12 had a polarized Th1 phenotype with elevated levels of IFN-gamma and TNF-alpha mRNA in the lungs, and an airway cell population that secreted abundant IFN-gamma. Very few MGCs were detected in these mice, and there was an absence of pulmonary eosinophilia. We conclude that the formation of MGCs in our model is promoted in the absence of IL-12 and is linked instead to the abundance of Th2 cytokines, notably IL-4 and IL-13.

Generation of multinucleated giant cells in vitro by culture of human monocytes with Mycobacterium bovis BCG in combination with cytokine-containing supernatants

Multinucleated giant cells (MGC), a characteristic feature of tuberculous granulomas, form by fusion of monocytes or macrophages, but little is known about the mechanism of the fusion process itself. Several studies report an indirect effect of mycobacteria, i.e., induction of a soluble lymphocyte-derived fusion factor following stimulation by mycobacteria or mycobacterial products. The aim of our study was to determine whether contact with mycobacteria can induce MGC formation from human monocytes in vitro. Stimulation of monocytes with Mycobacterium bovis bacillus Calmette-Guérin (BCG) in combination with cytokine-containing supernatants of herpesvirus saimiri-transformed human T-cell clones (T-SN) led to MGC formation with fusion rates of about 27%. In contrast, stimulation with one component alone induced only low fusion rates of up to 10%. Heat-killed BCG in combination with T-SN induced monocyte fusion to the same extent as live mycobacteria. BCG culture supernatant, BCG lysate, or inert particles in combination with T-SN did not induce MGC formation. Experiments using transwell plates containing a semipermeable membrane revealed that induction of the fusion process is dependent on direct contact of monocytes and mycobacteria. MGC formation induced by BCG plus T-SN could be inhibited by addition of monoclonal antibodies to gamma interferon (but not tumor necrosis factor alpha) as well as to the beta chain (CD18) of beta2-integrins. These results demonstrate that contact with mycobacteria in combination with cytokine-containing supernatants is able to induce human monocytes to form MGC and that membrane-bound molecules of mycobacteria and monocytes are involved in the fusion process.

"Aleukemic" granulomatous leukemia cutis

Aleukemic leukemia cutis is a rare condition characterized by the infiltration of the skin by leukemic cells before their appearance in the peripheral blood. The authors report a case of aleukemic leukemia cutis in a 30-year-old seemingly healthy man who presented with multiple skin papulonodular lesions and lack of peripheral blood involvement. Histopathologically, the skin infiltrates showed prominent granulomatous features that masked the underlying malignant process. Immunophenotypic studies of skin and bone marrow infiltrates revealed the myelomonocytic lineage of the atypical cells, consistent with M4 acute myelomonocytic leukemia. The authors emphasize the value of immunohistochemical studies in diagnosing a cutaneous atypical infiltrate and discuss problems of histopathologic differential diagnosis.

Selective expansion and continuous culture of macrophages from adult pig blood

Macrophages were selectively expanded and continuously cultured from adult pig blood. One-half ml of heparinized adult pig blood was inoculated directly into the medium overlaying a feeder layer of STO mouse fibroblasts. After attachment to the feeder cells for 24 h, the culture was washed several times with the medium to remove most of any unattached blood cells and re-fed. Approximately 7 x 10(4) blood monocytes were initially detected and enumerated by specific binding of DiI-labeled acetylated low density lipoprotein (DiI-Ac-LDL). Macrophage outgrowths appeared in the primary culture after 6-7 days. The macrophages grew to relatively high density in 2-3 weeks (2-3 x 10(6) cells/T25 flask), and the culture was passaged on to fresh STO feeder layers to begin secondary culture. Over 2-3 months of culture the macrophage replication produced as many as 1.4 x 10(9) DiI-Ac-LDL-positive cells. The macrophages grew on top of the feeder cells in two forms: either a semi-attached, round morphology, or a closely adherent, flat ameboid morphology with several extended pseudopods. Electron microscopic examination revealed the cells to be uniformly of macrophage character and that 4-5% were giant cells. The macrophages were phagocytic and expressed CD14 on their surfaces. They also reacted positively with pig macrophage-specific monoclonal antibody (mAb), and were negative for reactivity with pig T- and B-cell-specific mAb. This simple method for isolating and propagating macrophages may indicate the replicative capacity of either adult pig blood monocytes or circulating blood stem cells, and it may be useful in providing macrophages for general research, virological assay, adoptive-immunotherapy models, and somatic gene therapy models.

Induction of human osteoclast-like cells by treatment of blood monocytes with anti-fusion regulatory protein-1/CD98 monoclonal antibodies

We have developed a new and simple system of human osteoclast formation by fusing peripheral blood monocytes with anti-Fusion Regulatory Protein-1 (anti-FRP-1) monoclonal antibody (mAb). When human blood monocytes were cultured in the presence of anti-FRP-1/CD98 mAbs, polykaryocytes began to appear at approximately 15 h and increased in size with time until 3-4 days of incubation with anti-FRP-1 mAb. These fused cells showed positive staining in tartrate-resistant acid phosphatase, possessed numerous calcitonin receptors, and were capable of bone resorption. These results strongly suggest that anti-FRP-1 antibody-induced multinucleated cells are osteoclasts. Furthermore, FRP-1 antigens were detected in osteoclasts isolated from human bone and in the osteoclast-like cells obtained from human giant cell tumors of bone.

Chronic lymphocytic leukaemia with binucleated lymphocytes

Chronic lymphocytic leukaemia (CLL) is a monoclonal proliferation usually involving B cells and composed of mature lymphoid cells. Distinct morphologic subtypes have been recognized according to lymphocyte size, nuclear:cytoplastic ratio and nucleolus. However the presence of characteristically binucleated lymphocytes in patients fulfilling criteria for CLL diagnosis has never been described. We here report immunological and cytogenetic studies of four patients with CLL but with binucleated lymphocytes. Moreover, trisomy 12, known to be associated with atypical morphology in CLL, was detected in two of these four patients. We suggest that this be considered as a possible new entity.

Malignant melanoma masquerading as malignant fibrous histiocytoma

Numerous cytological variants of malignant melanoma (MM) exist. We report two cases of MM resembling malignant fibrous histiocytoma (MFH). Pathologists should be aware of this variant. Possible pitfalls that could lead to an incorrect diagnosis are discussed.

Non-secretory multiple myeloma with multinucleated giant plasma cells

We report a case of non-secretory multiple myeloma with unusual cytological features. The plasma cells were multinucleated and contained up to forty nuclei. All nuclei had regular outlines without multilobulated and convoluted slopes. DNA content measurement demonstrated that all nuclei of uni- and multinucleated cells were diploid. All plasma cells contained cytoplasmic alpha chain but light chains and their corresponding transcripts were absent. There is no clear explanation concerning multinuclearity. In addition, hypotheses regarding non-secretion of immunoglobulin in non-secretory multiple myeloma and in other B-cell neoplasias are discussed.

Adenosine A1 receptor promotion of multinucleated giant cell formation by human monocytes: a mechanism for methotrexate-induced nodulosis in rheumatoid arthritis

OBJECTIVE

To determine why methotrexate (MTX) exacerbates rheumatoid nodules in some patients, despite the effective suppression of synovial inflammation.

METHODS

Phorbol myristate acetate (PMA)-induced differentiation of monocytes into multinucleated giant cells was used as an in vitro model to study the effects of adenosine on nodulosis.

RESULTS

MTX at 200-2,000 nM or the adenosine A1 agonist N5-cyclopentyl adenosine (CPA) (10(-12) to 10(-9) M) or the A2 antagonist 3,7-dimethyl-1-propargylxanthine markedly enhanced giant cell formation, whereas the adenosine A1 antagonist 8-cyclopentyl-dipropylxanthine completely reversed these effects. PMA, CPA, and MTX induced adenosine release by cultured monocytes at concentrations consistent with those associated with predominantly A1 effects. Furthermore, surface expression of A1 receptors was found to remain unchanged on the differentiating cells throughout the culture period.

CONCLUSION

Agents that inhibit adenosine A1 receptors might be useful in the treatment of MTX-induced rheumatoid nodulosis, while still potentiating the A2-mediated antiinflammatory effects of MTX on synovitis.

A case of giant cell reparative granuloma of the petrous bone: demonstration of the proliferative component

BACKGROUND

Giant cell reparative granuloma (GCRG) is an uncommon benign lesion of the bone. It typically arises in the mandible and rarely involves the skull. The cytologic nature and genesis of the involved cells are poorly understood.

METHODS AND RESULTS

We report a case of GCRG in the petrous bone of a 3-year-old girl. One year following gross total removal, the granuloma recurred locally and was resected en bloc at the second surgery. Histologically, the lesion was composed of oval or spindle-shaped stroma cells admixed with a number of multinucleated giant cells. Immunohistochemical study demonstrated that 5.6% of the stroma cells, but none of the multinucleated giant cells, were positive for MIB-1 antibody.

CONCLUSION

These results suggest that this lesion expands by proliferation of the stromal component, with a growth rate roughly between those of the typical benign and malignant brain tumors. The cytologic nature of the cells comprising this uncommon disease remains to be elucidated.

Tumor necrosis factor alpha (TNFalpha) promotes growth of virulent Mycobacterium tuberculosis in human monocytes iron-mediated growth suppression is correlated with decreased release of TNFalpha from iron-treated infected monocytes

The human immune response to Mycobacterium tuberculosis is not well characterized. To better understand the cellular immune response to tuberculosis, a human mononuclear phagocyte culture system using a low-infecting inoculum of M. tuberculosis to mimic in vivo conditions was developed. Using this system, monocytes treated with IFNgamma/TNFalpha/ calcitriol (CytD) were permissive for the growth of virulent M. tuberculosis. In the presence of iron, however, these monocytes suppressed the growth of M. tuberculosis. The enhanced permissiveness of CytD-preincubated monocytes was found to be due to TNFalpha, however, the ability of iron to suppress M. tuberculosis growth also required preincubation with TNFalpha. Iron-mediated growth suppression was correlated with selective suppression of TNFalpha release from infected monocytes. In addition, removal of TNFalpha from CytD-treated monocytes 2 d after infection mimicked the suppressive effect of iron, suggesting that iron may also be decreasing monocyte sensitivity to exogenously added TNFalpha. In the absence of iron, permissive, CytD-treated monocytes formed large infected cellular aggregates. With iron treatment, aggregation was suppressed, suggesting that the iron-suppressive effect on M. tuberculosis growth may be related to suppression of monocyte aggregation and diminished cell-to-cell spread of M. tuberculosis. The results of this study indicate that TNFalpha preincubation is required for human monocytes to exert an iron-mediated suppressive effect on M. tuberculosis growth. In the absence of iron, however, the continued presence of TNFalpha has a growth-promoting effect on M. tuberculosis in human monocytes. Iron may be an important early modulator of M. tuberculosis growth via its effects on TNFalpha.