Formation of multinucleated giant cells from human monocyte precursors. Mediation by a soluble protein from antigen-and mitogen-stimulated lymphocytes

Mini-TrpRS is essential for IFNγ-induced monocyte-derived giant cell formation

Truncated tryptophanyl-tRNA synthetase (mini-TrpRS), like any other aminoacyl-tRNA synthetases, canonically functions as a protein synthesis enzyme. Here we provide evidence for an additional signaling role of mini-TrpRS in the formation of monocyte-derived multinuclear giant cells (MGCs). Interferon-gamma (IFNγ) readily induced monocyte aggregation leading to MGC formation with paralleled marked upregulation of mini-TrpRS. Small interfering (si)RNA, targeting mini-TrpRS in the presence of IFNγ prevented monocyte aggregation. Moreover, blockade of mini-TrpRS, either by siRNA, or the cognate amino acid and decoy substrate D-Tryptophan to prevent mini-TrpRS signaling, resulted in a marked reduction in expression of the purinergic receptor P2X 7 (P2RX7) in monocytes activated by IFNγ. Our findings identify mini-TrpRS as a critical signaling molecule in a mechanism by which IFNγ initiates monocyte-derived giant cell formation.

An insight into the cannibalistic behavior of giant cell granulomas of the jaws

Background:

Cellular cannibalism is defined as a large cell engulfing a smaller one within its cytoplasm. It is predominantly a feature of aggressive malignancies but has recently been demonstrated in giant cell (GC) lesions such as GC tumor of tendon sheath, central GC granuloma (CGCG) and peripheral GC granuloma (PGCG).

Aim:

The aim of the study is to assess the cannibalistic GCs in CGCG and PGCG and correlate with aggressiveness of the lesion.

Settings and Design:

Archival data of histopathologically confirmed cases of CGCG (n = 40) and PGCG (n = 25) were studied in the Department of Oral Pathology, Maulana Azad Institute of Dental Sciences.

Materials and Methods:

Quantification of cannibalistic cells was performed using H&E stain on microscopic sections. One hundred GCs were examined in each slide, and the number of cannibalistic cells was expressed in percentage.

Results:

GC cannibalism was observed in all cases. The mean number of cannibalistic GCs in CGCG was 44.67 which was significantly higher (P = 0.028) than PGCG (mean 28.04). In aggressive (n = 18) CGCG, the mean number of cannibalistic GCs was 51.27 which was significantly higher (P = 0.019) than cannibalistic GCs in nonaggressive (n = 22) CGCG (mean 39.27). No significant difference was observed between the number of cannibalistic cells in recurrent (mean = 52.9) and nonrecurrent (mean = 49.2) cases of CGCG (P > 0.05). Two of the nine cases treated initially by steroid showed fewer and smaller cannibalistic GCs with vesicular nuclei.

Conclusion:

There was a clear distinction in the mean cannibalistic count between aggressive and nonaggressive CGCG. Hence, the aggressiveness of the lesion could be assessed following which appropriate treatment modality can be constituted.

Induction of Pulmonary Granuloma Formation by Propionibacterium acnes Is Regulated by MyD88 and Nox2

Sarcoidosis is characterized by noncaseating granulomas with an unknown cause that present primarily in the lung. Propionibacterium acnes, an immunogenic commensal skin bacterium involved in acne vulgaris, has been implicated as a possible causative agent of sarcoidosis. Here, we demonstrate that a viable strain of P. acnes isolated from a patient with sarcoidosis and instilled intratracheally into wild-type mice can generate pulmonary granulomas similar to those observed in patients with sarcoidosis. The formation of these granulomas is dependent on the administration of viable P. acnes. We also found that mice deficient in the innate immunity adapter protein MyD88 had a greater number and a larger area of granuloma lesions compared with wild-type mice administered P. acnes. Early after P. acnes administration, wild-type mice produced proinflammatory mediators and recruited neutrophils into the lung, a response that is dependent on MyD88. In addition, there was an increase in granuloma number and size after instillation with P. acnes in mice deficient in CybB, a critical component of nicotinamide adenine dinucleotide phosphate oxidase required for the production of reactive oxygen species in the phagosome. Myd88^-/- or Cybb^-/- mice both had increased persistence of P. acnes in the lung, together with enhanced granuloma formation. In conclusion, we have generated a mouse model of early granuloma formation induced by a clinically relevant strain of P. acnes isolated from a patient with sarcoidosis, and, using this model, we have shown that a deficiency in MyD88 or CybB is associated with impaired bacterial clearance and increased granuloma formation in the lung.

Understanding the pathophysiology of the human TB lung granuloma using in vitro granuloma models

Tuberculosis remains a major human health threat that infects one in three individuals worldwide. Infection with Mycobacterium tuberculosis is a standoff between host and bacteria in the formation of a granuloma. This review will introduce a variety of bacterial and host factors that impact individual granuloma fates. The authors describe advances in the development of in vitro granuloma models, current evidence surrounding infection and granuloma development, and the applicability of existing in vitro models in the study of human disease. In vitro models of infection help improve our understanding of pathophysiology and allow for the discovery of other potential models of study.

Giant Cell Lesions of Lungs: A Histopathological and Morphometric Study of Seven Autopsy Cases

INTRODUCTION

Macrophages undergo fusion to form multinucleated giant cells (MGC) in several pathologic conditions. The exact mechanism of their generation is still unclear. MGC are a common feature of granulomas that develop during various inflammatory reactions.

AIM

To study the histopathological features of giant cell lesions in lungs and correlate the characteristics of giant cells with other histopathological findings. Also, to determine the utility of morphometry to differentiate foreign body and Langhans MGC.

MATERIALS AND METHODS

Seven cases were analysed. Specimen of lungs was grossed, sectioned and processed. Routinely, tissue sections were stained by Haematoxylin and Eosin (H&E) stain. Polarizing microscopy and special stains were employed in selected cases. Granulomas and MGC were counted and measured. Several other parameters like location, distribution, type and number of MGC, associated predominant inflammatory component and nature of granulomas were analysed.

RESULTS

Five patterns of lesions were observed in seven cases. Aspiration pneumonia was seen in three cases (42.85%) and constituted the most common pattern. However, aspiration pneumonia as the only cause of MGC was seen in only one case (14.28%). Pulmonary tuberculosis and asteroid bodies constituted two cases (28.57%) each. Cryptococcal pneumonia and cholesterol clefts constituted one case (14.28%) each. Crypococci were demonstrated to be positively birefringent by polarized microscopy on Ziehl-Neelsen stained sections. Based on statistical analysis of morphometric data, a new index (NP index) was proposed to statistically categorize MGC into foreign body type and Langhans type. NP index value of ≤0.016 was found to be statistically significant (p<0.005) in foreign body MGC. It had high sensitivity and efficacy.

CONCLUSION

MGC may not be always associated with granulomas. The mechanisms that lead to the occurrence of MGC, independent of granuloma needs to be elucidated. Morphometry may serve as a useful aid. But a pathologist has to rely on the morphological details to categorize MGC.

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.

An in vitro model of Mycobacterium leprae induced granuloma formation

Background

Leprosy is a contagious and chronic systemic granulomatous disease caused by Mycobacterium leprae. In the pathogenesis of leprosy, granulomas play a key role, however, the mechanisms of the formation and maintenance of M. leprae granulomas are still not clearly understood.

Methods

To better understand the molecular physiology of M. leprae granulomas and the interaction between the bacilli and human host cells, we developed an in vitro model of human granulomas, which mimicked the in vivo granulomas of leprosy. Macrophages were differentiated from human monocytes, and infected with M. leprae, and then cultured with autologous human peripheral blood mononuclear cells (PBMCs).

Results

Robust granuloma-like aggregates were obtained only when the M. leprae infected macrophages were co-cultured with PBMCs. Histological examination showed M. leprae within the cytoplasmic center of the multinucleated giant cells, and these bacilli were metabolically active. Macrophages of both M1 and M2 types co-existed in the granuloma like aggregates. There was a strong relationship between the formation of granulomas and changes in the expression levels of cell surface antigens on macrophages, cytokine production and the macrophage polarization. The viability of M. leprae isolated from granulomas indicated that the formation of host cell aggregates benefited the host, but the bacilli also remained metabolically active.

Conclusions

A simple in vitro model of human M. leprae granulomas was established using human monocyte-derived macrophages and PBMCs. This system may be useful to unravel the mechanisms of disease progression, and subsequently develop methods to control leprosy.

Stereological estimation of average cell volume in monolayer culture by combined light and electron microscopy

In order to convert stereological ratio estimates into 'absolute' values ('per cell' values) the average cell volume must be estimated. The present paper describes a stereological method based on well-known point counting procedures for the estimation of average cell volumes in monolayer cultures fixed in situ. This method involves estimation of the average attachment area per cell by light microscopy combined with estimation of the attachment membrane surface density by electron microscopy. There is no need for any assumption as to cellular or nuclear shape. The method has been tested on an established cell line, NHIK 3025, and shows a good accuracy. It has also been used to analyse the volume changes that take place in human monocytes during monolayer culture, demonstrating a 28-fold increase of the average cell volume over 10 days.

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.

An in vitro model of the leukocyte interactions associated with granuloma formation in Mycobacterium tuberculosis infection

The principal defense of the human host against a Mycobacterium tuberculosis infection is the formation of granulomas, organized collections of activated macrophages, including epithelioid and multinucleated giant cells, surrounded by lymphocytes. This granuloma can sequester and contain the bacteria preventing active disease, and if the granuloma is maintained, these bacteria may remain latent for a person's lifetime. Secretion of a variety of chemoattractant cytokines following phagocytosis of the bacilli by the macrophage is critical not only to the formation of the granuloma but also to its maintenance. To investigate this process of early granuloma formation, we developed an in vitro model composed entirely of human cells. Combining blood lymphocytes and autologous macrophages from healthy purified protein derivative skin test-negative individuals and mycobacteria resulted in the formation of small, rounded aggregate structures. Microscopic examination found macrophage-specific CD68(+) epithelioid macrophages and small round CD3(+) lymphocytes that in complex resembled small granulomas seen in clinical pathology specimens. Acid-fast staining bacteria were observed between and possibly within the cells composing the granulomas. Supernatants from the infected cells collected at 24 and 48 h and 5 and 9 days after infection were analyzed by a multiplexed cytokine bead-based assay using the Luminex 100 and were found to contain interleukin (IL)-6, IL-8, interferon-gamma and tumor necrosis factor-alpha, cytokines known to be involved in human granuloma formation, in quantities from two-fold to 7000-fold higher than supernatants from uninfected control cells. In addition, chemotaxis assays demonstrated that the same supernatants attracted significantly more human peripheral blood mononuclear cells than those of uninfected cells (P<0.001). This model may provide insight into the earliest stages of granuloma formation in those newly infected.

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.

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.

Granulomatous lung diseases in the tropics

International travel, changing immigration patterns, and political upheavals have transformed the epidemiological picture of many tropical granulomatous disorders [53]. These diseases are seen with an increasing frequency in the United States, Europe, and other developed countries. Physicians must now become familiar with illnesses that were previously regarded as being "exotic" because of this increasing prevalence. Accurate diagnosis is important because therapy is significantly different for infectious granulomatous disorders than for non-infectious diseases.

Foreign body giant cell induction in the CSF-1-deficient osteopetrotic (op/op) mouse

The osteopetrosis (op) mutation in mice is characterized by generalized skeletal sclerosis; reduced numbers of osteoclasts, macrophages, and monocytes; and failure to be cured by bone marrow transplantation. This mutation has been shown to result from an absence of colony-stimulating factor-1 (CSF-1) and reported to be cured by treatment with CSF-1. Macrophage polykaryons are known to be formed by fusion of mononuclear precursors and the presence of subcutaneous implants can elicit the formation of macrophage polykaryons. In order to determine if recruitment of foreign body giant cells is also impaired in osteopetrotic mice, tissue reactions to subcutaneously implanted polyvinyl sponges were studied and compared with normal mice. Our result showed that, in the op mouse, recruitment of macrophages and foreign body giant cells in response to the implants was quantitatively not different from that of normal mice. However, these cells were smaller and did not migrate as deeply into the implant as those seen in normal littermates. In contrast, resident macrophages obtained by peritoneal lavage were significantly reduced in op mice. These data indicate that there is a deficiency in the ability of op mice to mount a foreign body giant cell response to an implanted sponge characterized by a deficiency in the recruitment of precursor cells that are capable of either full development and spreading or migration into the implanted sponge. These data add to the emerging appreciation of the regional differences among macrophage populations in their dependence on CSF-1 for differentiation and survival.

Heightened ability of monocytes from sarcoidosis patients to form multi-nucleated giant cells in vitro by supernatants of concanavalin A-stimulated mononuclear cells

The main immunocompetent cells in sarcoidal lesions are epithelioid cells and multi-nucleated giant cells (MGC), both of which are derived from monocyte-macrophage lineage cells. To understand further the relevance of monocytes in sarcoidosis, we examined in vitro MGC formation using monocytes from sarcoidosis patients, patients with other granulomatous diseases (OGD) and healthy control subjects. The supernatant of concanavalin A-stimulated peripheral blood mononuclear cells (conditioned medium) generated Langhans type-MGC and foreign body type-MGC from monocytes. Conditioned medium from any three groups had the same ability to form MGC from normal monocytes. On the other hand, MGC were more highly formed using monocytes from sarcoidosis patients than from other groups. When macrophages induced by treatment of monocytes with macrophage colony-stimulating factor (M-CSF) were used, the rate of MGC formation in sarcoidosis patients was about threefold or fourfold as much as that in OGD patients or healthy controls, respectively. Oxidized ATP inhibited MGC formation in all groups. The susceptibility of monocytes cultured in conditioned medium for 24 h to 2'- and 3'-o-(4-benzoyl-benzoyl)ATP-mediated cytolysis was significantly higher in sarcoidosis patients than other groups. These findings suggest that the ability of monocytes to form MGC through P2x7 receptors is enhanced in sarcoidosis patients.

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.

Interferon-gamma and tumor necrosis factor-alpha specifically induce formation of cytomegalovirus-permissive monocyte-derived macrophages that are refractory to the antiviral activity of these cytokines

Monocytes/macrophages are key cells in the pathogenesis of human cytomegalovirus (HCMV). Although HCMV infection in monocytes is restricted to early events of gene expression, productive infection has been demonstrated in differentiated macrophages in vitro. We examined the cellular and cytokine components that are essential for HCMV replication in Concanavalin A-stimulated monocyte-derived macrophages (MDM). By negative selection, depletion of CD8+ T lymphocytes, but not CD4+ T lymphocytes, CD19+ B cells, or CD56+ NK cells, resulted in a 60-70% reduction in the number of HCMV-infected MDM, and a 4 log decrease in virus production. Neutralization of IFN-gamma and TNF-alpha, but not IL-1, IL-2, or TGF-beta, decreased production of virus by 4 logs and 2 logs, respectively. Subsequently, addition of recombinant IFN-gamma or TNF-alpha to purified monocyte cultures was sufficient to produce HCMV-permissive MDM. While IFN-gamma and TNF-alpha possess antiviral properties, addition of these cytokines to permissive MDM cultures did not affect production of HCMV. Thus, rather than inhibiting replication of HCMV, IFN-gamma and TNF-alpha specifically induce differentiation of monocytes into HCMV-permissive MDM, which are resistant to the antiviral effects of these cytokines.

A case of multicentric reticulohistiocytosis, systemic sclerosis and Sjögren syndrome

We report the case of a 42-year-old Japanese woman who developed multicentric reticulohistiocytosis (MR) complicated by systemic sclerosis (SSc) and Sjögren syndrome (SS). The patient complained of tender nodules on the left hand, polyarthralgia in the finger joints and knees, and xerostomia. The skin nodules were distributed mainly on her hands and fingers with skin sclerosis. The serum anti-nuclear test revealed anti-centromere antibody and the discrete speckled pattern of anti-nuclear antibody. The biopsy specimens from the finger nodule and the sclerotic finger skin showed a perivascular infiltration of multinucleated giant cells with ground-glass cytoplasm and dermal thick collagen proliferation, respectively. The lip biopsy and sialography specimens showed periductal lymphocyte infiltration and apple tree-like changes. Systemic corticosteroid treatment improved the polyarthritis, xerostomia, and skin sclerosis rapidly but suppressed the nodular lesions only gradually. This is the first report of a combined case of MR, SSc and SS. This multiple autoimmune complication suggests the involvement of an immunological disturbance in the pathogenesis of MR.

Formation of Multinucleated Giant Cells In Vitro Is Dependent on the Stage of Monocyte to Macrophage Maturation

Multinucleated giant cells (MGC) are a common feature of granulomas that develop during various inflammatory reactions. MGC originate from fusion of monocytes or macrophages, but the exact mechanism of their generation is still unclear. In the present study, we investigated the influence of monocyte to macrophage maturation on the ability of human monocytes/macrophages to fuse with each other. MGC were generated in vitro by stimulation of human peripheral blood monocytes with cytokine containing supernatants. With freshly isolated monocytes, fusion rates of up to 90% were obtained. When monocyte to macrophage maturation was induced by culturing the cells in human serum, fusion rates gradually decreased with advancing time of the preceding culture (corresponding to the stage of differentiation) and almost no MGC formation could be obtained with 8-day-old macrophages. In contrast, fusion rates did not decrease when monocytes had been cultured under serum free conditions before stimulation. When freshly isolated monocytes were added to 1-week cultured macrophages, which had been membrane-labeled with a fluorochrome, fusion between the two populations could be induced. Because the ability for intracellular killing of certain pathogens is reduced in macrophages, fusion with monocytes (newly arriving at the site of inflammation) may represent an attempt to restore this capacity.

Diagnosis and management of iris juvenile xanthogranuloma

BACKGROUND

Juvenile xanthogranuloma is a benign, self-limiting cutaneous disorder most commonly encountered during infancy. Approximately 10% of cases may develop ocular or adnexal involvement, most commonly in the iris.

METHODS

We review clinical and morphological features of four cases of iris juvenile xanthogranuloma that reflect the diagnostic and therapeutic spectrum.

RESULTS

Tissue diagnosis was confirmed in all cases; in one case, the disease was diagnosed with a skin biopsy and treated with local and systemic steroids, and its persistence in the iris was confirmed with a second tissue specimen obtained five months after systemic steroid treatment.

CONCLUSION

The diagnosis and treatment of juvenile xanthogranuloma may be straightforward, particularly in cases when the ocular lesion receives early attention and responds well to topical steroids, and when there is no hyphema. However, in other instances, this entity may be difficult to manage and may necessitate iris biopsy for diagnosis and radiation therapy for treatment.

Disease patterns and tissue cytokine profiles in giant cell arteritis

OBJECTIVE

To determine whether clinical heterogeneity in patients with giant cell arteritis (GCA) is correlated with different patterns in the tissue-specific inflammatory response.

METHODS

Twenty-three patients with typical histomorphologic findings of GCA were grouped according to the presence or absence of jaw claudication and/or visual abnormalities, fever, concomitant polymyalgia rheumatica (PMR), and histologic evidence of giant cell formation. The inflammatory response in temporal artery biopsy specimens was characterized by semiquantification of cytokine messenger RNA (mRNA) transcripts using reverse transcriptase-polymerase chain reaction, followed by oligonucleotide hybridization with cytokine-specific probes. Clinical patterns were then correlated with profiles of tissue cytokines.

RESULTS

Inflammatory cytokines were expressed in all temporal artery tissues. In situ synthesis of interleukin-2 (IL-2), interferon-gamma (IFN gamma), and IL-1 beta mRNA, but not of IL-10 and IL-12 mRNA, distinguished different patterns of inflammation, and these patterns correlated with clinical manifestations of the disease. Patients with evidence of ischemic symptoms, indicated by jaw claudication and/or visual symptoms, typically expressed higher concentrations of IFN gamma mRNA (P = 0.008) and IL-1 beta mRNA (P = 0.02). Presence of fever was correlated with lower copy numbers of IFN gamma (P = 0.02). Formation of giant cells in the granulomatous infiltrates was associated with the local synthesis of IFN gamma mRNA (P = 0.003). Tissue from GCA patients with concomitant PMR contained higher levels of IL-2 mRNA transcripts (P = 0.001).

CONCLUSION

Variations in the clinical presentation of GCA were correlated with cytokine mRNA expression in the affected temporal arteries. Differences in the effector functions of tissue-infiltrating T cells distinguished disease patterns in which either local ischemic symptoms or systemic involvement was dominant, or in which there was co-occurrence of PMR. Definition of different patterns of inflammation in GCA might, therefore, facilitate the design of differentiated therapeutic approaches.

Interleukin-4-induced macrophage fusion is prevented by inhibitors of mannose receptor activity

A potential role for the macrophage mannose receptor in human monocyte-derived macrophage fusion was explored by testing the effects of previously described inhibitors of its activity on the formation of interleukin-4-induced foreign body giant cells in vitro Giant cell formation was prevented or reduced in the presence of alpha-man-nan and synthetic neoglycoprotein conjugates according to the following pattern of relative inhibition: mannose-bovine serum albumin (BSA) > N-acetylgucosamine-BSA congruent to glucose-BSA. Laminarin (beta-glucan) or galactose-BSA were not inhibitory. Swainsonine and castanospermine, inhibitors of glycoprotein processing that interfere with the arrival of newly synthesized mannose receptors at the cell surface, also attenuated macrophage fusion and the formation of giant cells, whereas another glycosidase inhibitor, deoxymannojirimycin, was without effect. Mannose receptors were confirmed to be specifically up-regulated by interleukin-4 in this culture system and also demonstrated to be present and concentrated at macrophage fusion interfaces. These data suggest that the macrophage mannose receptor may be an essential participant in the mechanism of interleukin-4-induced macrophage fusion and implicate a novel function for this endocytic/phagocytic receptor in mediating foreign body giant cell formation at sites of chronic inflammation.

T- and B-lymphocyte-independent formation of alveolar macrophage-derived multinucleated giant cells in murine Pneumocystis carinii pneumonia

Multinucleated giant cells developed in Pneumocystis carinii-diseased gene disruption mutant mice deficient in major histocompatibility complex class II molecules, T-cell receptor alpha beta cells, or all mature T and B lymphocytes. These findings demonstrate lymphocyte-independent fusion of alveolar macrophages under morbid conditions. Pulmonary parasite burden seems to be a decisive factor in multinucleation.

Monocyte aggregation and multinucleated giant-cell formation in vitro in Crohn's disease. The effect of cell adhesion molecules

BACKGROUND

Multinucleated giant-cell (MGC) formation is a common histopathologic feature of various granulomatous diseases, including Crohn's disease (CD).

METHODS

We have investigated monocyte aggregation and subsequent MGC formation by in vitro culturing peripheral monocytes from 25 CD patients, 15 ulcerative colitis (UC) patients, and 10 healthy controls. The effect of cell adhesion molecules on the monocyte aggregation and MGC formation in CD patients was investigated by using anti-beta 2 integrin and anti-ICAM-1 antibodies.

RESULTS

The monocyte aggregation and MGC formation were significantly higher in CD than those seen in UC and controls (p < 0.05). In CD, antibody to beta 2 integrin could inhibit not only the monocyte aggregation but also the subsequent MGC formation. In contrast, the antibody to ICAM-1 could inhibit the monocyte aggregation; however, it could not inhibit the MGC formation.

CONCLUSIONS

Monocyte aggregation and MGC formation are increased in CD. beta 2 Integrin may play an important role in the monocyte aggregation and MGC formation of CD patients.

Cell membrane labeling with fluorescent dyes for the demonstration of cytokine-induced fusion between monocytes and tumor cells

Fusion between monocytes and tumor cells has been suggested as a cause for tumor metastasis. The aim of the present study was to establish an in vitro fusion model representing the in vivo situation as close as possible. For this purpose fusion between cells was induced by cytokine containing conditioned medium. In order to prove that hybrid formation between tumor cells and monocytes occurs, a two-color-fusion-assay based on membrane labeling with the fluorochromes PKH 2 (green) and PKH 26 (red) was established. These fusion experiments were analyzed by microscopy and, in addition, by flow cytometry. The attempt to induce fusion between monocytes and several tumor cell lines of hematopoietic origin revealed quite diverse results. The most extensive hybrid formations were seen with TALL, a T-lymphocytic tumor line. The monocytic tumor line HL60 and the B-lymphocytic tumor line BL41 also clearly yielded hybrids with monocytes but in smaller numbers. With some other hematopoietic tumor lines no evidence for hybrid formation was detected. These studies indicate that fusion of normal monocytes with certain tumor cells may be induced under conditions that may occur in comparable manner in vivo.

Giant cell formation in Hodgkin's disease

The identity of Reed-Sternberg cells in Hodgkin's disease has remained an unresolved issue, though many studies have addressed this question. Giant cells are usually formed either by endomitosis without cytoplasmic division or by cell fusion through cytokines or viruses. Growing evidence associates Epstein-Barr virus (EBV) with Hodgkin's disease, a major issue being whether EBV is a passenger virus or has an aetiological role. This communication describes experimental conditions enabling observation of giant cell cytogenesis from peripheral blood mononuclear cells in culture. Mononuclear cells were isolated from autologous peripheral blood and cocultured with a single-cell suspension obtained from Hodgkin's lymph nodes in a culture chamber where the two cell populations are isolated by a microporous membrane that allows only cytokines and viruses to pass through. Under these experimental conditions, giant cells are formed in the peripheral blood mononuclear cell fraction; some of them appear morphologically indistinguishable from Reed-Sternberg cells and their mononuclear variant, while others much resemble Langhans giant cells. Some of these giant cells are positive for EBV DNA by in situ hybridization. These results suggest that an EBV-dependent biological activity is responsible for giant cell cytogenesis originating from lymphocytes and monocytes, induced either by EBV and/or cytokines.

Theoretical analysis of in vivo macrophage adhesion and foreign body giant cell formation on strained poly(etherurethane urea) elastomers

Quantitative description of foreign body giant cell (FBGC) formation on poly(etherurethane urea) (PEUU) surfaces as a function of time can conceivably predict the effects of polymer characteristics on cellular responses in vivo. In the present study, the formation of FBGCs on strained and unstrained PEUUs was quantified with two parameters: the density of adherent macrophages present initially that participate in FBGC formation (d(o)) and the rate constant for cell fusion (k); both kinetic parameters were used to calculate the time-dependent FBGC density (dfc). Relationships were sought between results of the cellular analysis and the extent of environmental stress cracking (ESC), as characterized by scanning electron microscopy. Surface degradation was semiquantified with percent light transmittance. The materials used were: base PEUU, base PEUU with 1% Santowhite antioxidant powder, base PEUU with 5% Methacrol 2138F antifume agent, and base PEUU with both 1% Santowhite and 5% Methacrol 2138F. A comparison of unstrained base PEUU with base PEUU strained to 400% elongation indicated that the rate of cell fusion, but not d(o) and dfc, increased in the presence of strain. In all strained samples, additives that strongly affected the ESC also influenced FBGC kinetic parameters. Strained PEUU containing Santowhite had the lowest d(o), the slowest rate of cell fusion, and lowest dfc, and the least incidence of ESC. The results suggest that the incidence of ESC in PEUU was decreased in the presence of Santowhite, which also lowered the number of adherent macrophages participating in FBGC formation, the rate of FBGC formation and the subsequent FBGC density. These studies also indicate that strain in PEUUs does not directly modulate the adherent macrophage and FBGC density. Further studies are necessary to delineate the relationship between PEUU strain and adherent macrophage and FBGC activation, which leads to the exocytosis of degrading agents and the observed incidence of biodegradation.

Chorioretinal, iris, and ciliary body infiltration by juvenile xanthogranuloma masquerading as uveitis

Juvenile xanthogranuloma is a benign cutaneous disorder which occasionally involves the eye, orbit, and ocular adnexa in children. Iris and ciliary body manifestations are commonly seen, but retinal and choroidal lesions are exceedingly rare. We report a unique case of retinal, choroidal, iris, and ciliary body infiltration in a 12-year-old patient diagnosed by excisional biopsy of the iris. The diagnosis was confirmed by routine histology and oil-red-o staining. Immunohistochemistry revealed predominantly macrophages, monocytes, and T-helper lymphocytes. Unusual features of this case include the late age at diagnosis, posterior pole involvement, and lack of cutaneous lesions. The presence of cellular adhesion molecules and T lymphocytes implicate a lymphocyte-driven inflammatory process. Apolipoprotein A was the predominant apolipoprotein present within the foamy histiocytes. We also present a critical review of the literature.

Mycobacterium tuberculosis alters expression of adhesion molecules on monocytic cells

The host response to Mycobacterium tuberculosis is characterized by interactions between mononuclear cells, with recruitment and fusion of these cells culminating in granuloma formation. In addition, the host response to M. tuberculosis requires CD4+ T-cell reactivity, mediated by antigen-independent as well as antigen-dependent mechanisms. Thus, we hypothesized that cell adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1; CD54) would participate in the response to infection with M. tuberculosis. Exposure of THP-1 cells derived from a monocyte/macrophage cell line to M. tuberculosis (1:1 bacterium/cell ratio) elicited a sustained increase (660% +/- 49% above resting level) in the expression of ICAM-1 that continued for at least 72 h. Neither the expression of vascular cell adhesion molecule 1 (VCAM-1; CD106) nor that of the integrins lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) or CR3 (CD11b/CD18) was increased to a similar extent at corresponding time points. The increase in ICAM-1 protein expression was accompanied by an increase in steady-state mRNA (Northern [RNA] analysis). Neutralizing monoclonal antibodies directed against tumor necrosis factor alpha but not interleukin 1 alpha or interleukin 1 beta substantially abrogated the response to M. tuberculosis consistent with a paracrine or autocrine response. Continuous upregulation of the expression of ICAM-1 on mononuclear phagocytes induced by M. tuberculosis may mediate the recruitment of monocytes and enhance the antigen presentation of M. tuberculosis, thus permitting the generation and maintenance of the host response.

Simian immunodeficiency virus SIVsmmPBj 1.9 induces multinucleated giant cell formation in human peripheral blood monocytes

SIVsmmPBJ 1.9 is an extremely virulent clone of the simian immunodeficiency virus SIVsmmPBj 14 that causes an acute lethal disease in pigtail macaques, with death occurring 6 to 8 days after infection. The disease is characterized by bloody mucoid diarrhea, lymphoid hyperplasia, and giant cell pneumonia. We have developed an in vitro model for the production of multinucleated giant cells (MGCs) in which peripheral blood monocytes rapidly fuse to form MGCs when cultured in lymphocyte-conditioned medium and antibody against class II MHC. We have tested the effect of SIVsmmPBj on monocytes in our MGC model system. Peripheral blood mononuclear cells (PBMCs) from normal healthy human subjects, when cultured in the presence of anti-class II MHC monoclonal antibody and SIVsmmPBj 1.9, but not either alone, resulted in the formation of MGCs within 4 days. Experiments using Transwell chambers indicated that such MGCs are formed by fusion of monocytes, not by virus-induced fusion of lymphocytes. SIVsmmPBj 1.9 is unique in inducing MGC formation in that other SIV and HIV isolates do not induce MGCs. Whereas SIVsmmPBj 1.9 grown in PBMCs was a potent inducer of MGCs in the presence of anti-class II MHC antibody, SIVsmmPBj 1.9 grown in CEMx174 failed to do so. Antibodies against IFN-gamma and TNF-alpha significantly inhibited SIVsmmPBj/anti-class II-induced formation of MGCs. These results indicate that cytokines released in response to SIVsmmPBj 1.9, in conjunction with antibodies to class II MHC, caused fusion of monocytes.

The role of interferon gamma in the pathogenesis of Crohn's disease

To investigate the role of interferon gamma in the pathogenesis of Crohn's disease, we examined the interferon gamma levels of serum, supernatant of cultured peripheral blood mononuclear cells activated by phytohemagglutinin, and medium of organ culture of colonic mucosa in Crohn's disease. Serum interferon gamma levels in Crohn's disease, especially in active or non-resected Crohn's disease, were more elevated than those in normal subjects. In contrast, the production of interferon gamma by peripheral blood mononuclear cells was reduced in Crohn's disease. In some patients, interferon gamma levels of organ culture medium of colonic mucosal tissue specimens were elevated. When peripheral blood mononuclear cells were preincubated for 72 hours, interferon gamma production in Crohn's disease increased from 23.8% to 62.3% in comparison to levels in healthy controls. These results indicate that elevated serum interferon gamma in Crohn's disease may originate from the intestine, and interferon gamma may be related to the immune reaction and inflammation in the intestine.

Time course of lipid-laden pulmonary macrophages with acute and recurrent milk aspiration in rabbits

High levels of lipid-laden macrophages (LLM) in bronchial washings have been associated with food aspiration. We studied the time course of appearance and clearance of LLM in rabbits undergoing either a single milk instillation, five weekly milk instillations or saline (control) instillations into the airways. Cells were obtained by bronchoalveolar lavage of intubated rabbits at uniform time intervals following the single or the last of five milk/saline instillations. LLM semi-quantitative indexes were derived using oil-red-O staining. Significantly elevated indexes were found in both milk groups 6 hr after milk instillation. In the single saline and milk instillation groups the indexes were not different beginning on the 4th day, and indexes from 8 of 9 rabbits had returned to baseline by the 6th day. However, indexes remained significantly elevated up to 17 days in the group receiving weekly milk instillations. Indexes from all rabbits in the repeat milk instillation group remained elevated for 12 days or longer. This group also developed increased numbers of binucleated macrophages. Quantitation of LLM in this model appears to be a sensitive indicator of recurrent lipid aspiration, these cells remaining in the airways for several days after the last aspiration event.

Temporal artery morphology and morphometry in giant cell arteritis

Paraffin sections and more than 7,000 plastic cross-sections of temporal arteries from 27 patients with a clinical diagnosis of polymyalgia rheumatica (PMR), 16 patients with a clinical diagnosis of temporal arteritis (TA) and 18 age- and sex-matched postmortem controls were studied using light microscopy. A new method was developed to permit a morphometric comparison between biopsies and autopsy specimens. Two stages of inflammation were discerned in TA. In atrophic arterial segments there was a focal, foreign-body, giant-cell reaction to the calcified internal elastic membrane (IEM) with a spatially correlated, mononuclear cell infiltration. Isolated giant cells were also found to attack the IEM in these cases. The majority of the biopsies displayed a different picture with a diffuse macrophage attack on media and intima with numerous and apparently macrophage-derived giant cells, which did not attack calcifications. The latter arteries were significantly widened (p less than 0.02), which indicates that this phase is the later one. Non-inflamed segments of PMR vessels displayed a significant, non-reactive media atrophy compared with controls (p less than 0.03) and their IEM calcifications were significantly larger (p less than 0.02). The circumference was smaller in atrophic PMR arteries than in inflamed TA arteries (p less than 0.006), which contradicts post-inflammatory scarring.

An evaluation of the putative human mammary tumour retrovirus associated with peripheral blood monocytes

The primary aims of this study were purification and molecular cloning of a putative retrovirus designated human mammary tumour virus (HMTV). However, our preliminary unpublished data of negative reverse transcriptase (RT) activity in ostensibly 'infected' cells led us to re-examine the evidence for this virus; namely multinucleate giant cell (MNGC) formation and RT activity in cultured blood monocytes from breast cancer patients versus benign breast tumour and normal control subjects. MNGCs from by fusion of monocytes and we estimated the total number of cell fusions which had occurred after 10 days of culture in vitro by counting cells with two, three, four and five or more nuclei (n) and by measuring the density of adherent mononuclear cells for each subject studied. We found no clear-cut difference in MNGC formation between the three subject groups. Moreover, a substantial number of cultures, encompassing the three groups, showed far more MNGCs per 10(5) monocytes than previously reported. Various parametric and nonparametric statistical analyses were performed on the multinucleate cell data and only one parametric test, which utilised the density of monolayers as a co-variate, showed a statistically significant difference at the 5% level between the breast cancer and the normal subject groups. We observed marked subject-to-subject variation in multinucleate cell formation and we suggest that the evidence for a difference between the breast cancer and the normal groups is marginal. Further, MNGC formation by breast cancer monocytes may not be attributed to the presence of a retrovirus since 5'-Azacytidine (AZA), an agent known to stimulate replication of latent retroviruses showed no effect on the MNGC formation. In addition, culture supernatants from the three groups were assayed for RT activity and no test sample gave a significant signal above background. Preliminary transmission electron microscopy analysis failed to identify viral particles in MNGCs.

Stimulation of fibroblast chemotaxis by human recombinant tumor necrosis factor alpha (TNF-alpha) and a synthetic TNF-alpha 31-68 peptide

Macrophages are a major source of fibrogenic factors that promote healing of injured tissue. The recruitment of fibroblasts to sites of tissue injury is a prerequisite for optimal repair of tissue damage. In the present study, human recombinant tumor necrosis factor alpha (hrTNF-alpha), a major macrophage-derived cytokine, was demonstrated to be a potent fibroblast chemoattractant, inducing migration at picomolar concentrations. Anti-hrTNF-alpha monoclonal antibody neutralized most of the fibroblast chemotactic activity generated during short-term culture of human peripheral blood monocytes stimulated with bacterial lipopolysaccharide, suggesting that TNF-alpha is a major monocyte-derived fibroblast chemoattractant. The portion of the human TNF-alpha molecule responsible for its chemotactic stimulation of fibroblasts appears to reside in residues 31-68. This region is highly conserved between TNF-alpha and lymphotoxin. This peptide is not only itself chemotactic but is also able to block the chemotactic response of fibroblasts to hrTNF-alpha and vice versa, suggesting that they each mediate fibroblast migration through similar mechanisms. These data further underscore the potential importance of TNF-alpha in modulating a variety of fibroblast functions, including chemotaxis and synthesis of collagen, glycosaminoglycans, interleukin 1 alpha (IL-1 alpha) and -beta, human histocompatibility leukocyte antigen A and B antigens, collagenase, prostaglandin E2, and IL-6.

Anti-RMA, a murine monoclonal antibody, activates rat macrophages: II. Induction of DNA synthesis and formation of multinucleated giant cells

Anti-RMA is a murine anti-rat monoclonal antibody that binds to a 120-kD surface membrane antigen expressed primarily by alveolar macrophages. Saline-lavaged alveolar macrophages (AM) formed clusters after incubation with anti-RMA. Anti-RMA produced multinucleated giant cells (MGC) in approximately 15% of adherent AM, and the F (ab')2 fragment of anti-RMA yielded MGC in approximately 9% of AM. The Fab fragment of anti-RMA did not promote MGC formation, nor did the murine anti-rat monoclonal antibodies OX41 and W3/25 (anti-CD4). Although anti-RMA produced a tenfold increase in [3H]thymidine incorporation by AM, it yielded a minimal increase in the number of AM. Autoradiography of AM stimulated with anti-RMA showed heterogeneous labeling of nuclei in MGC, suggesting that 3H-labeled AM may fuse with AM that are not actively synthesizing DNA. These findings suggest that binding of anti-RMA to AM may activate DNA synthesis, and promote clustering and fusion of AM, leading to MGC formation.

Cytokine-induced generation of multinucleated giant cells in vitro requires interferon-gamma and expression of LFA-1

Multinucleated giant cells (MGC), which are a common feature of various pathologic states, were generated in vitro by cytokine-stimulation of human peripheral blood monocytes. As expected, conditioned medium, i.e. the supernatant of concanavalin A-stimulated peripheral blood mononuclear cells, readily caused generation of MGC. Addition of a monoclonal antibody (mAb) against interferon-gamma (IFN-gamma) completely abrogated this effect. IFN-gamma alone, however, had a much smaller effect than the conditioned medium. All other cytokines tested [including interleukin (IL)2, IL4 and tumor necrosis factor-alpha, which are known to activate monocytes] did not induce MGC nor did they enhance the effect of IFN-gamma. Formation of MGC could almost entirely be inhibited by mAb to the alpha or beta chain of LFA-1 and to a lesser extent by relatively high concentrations of a mAb against ICAM-1, one of the ligands of LFA-1. In contrast to the anti-IFN-gamma mAb that had no significant effect on the formation of monocyte clusters, mAb against LFA-1 inhibited clustering very efficiently. Antibodies directed to a number of different antigens present on the surface of monocytes (alpha chains of CR3 and CR4, HLA class I and II molecules, CD14 and CD16 antigens) had little or no effect on the generation of MGC. IFN-gamma, but not the concanavalin A-induced supernatant clearly enhanced expression of LFA-1 and ICAM-1 on monocytes. The results indicate that cytokine-induced generation of MGC is not possible without IFN-gamma, but most probably additional factor(s) enhance this effect. The mechanism(s) by which IFN-gamma promotes monocyte fusion apparently includes, among others, up-regulation of LFA-1 whose expression seems to be necessary but not sufficient for fusion.

Characterization of the binucleated giant cells generated in the autologous mixed leucocyte reaction from patients with rheumatoid arthritis

Binucleated giant cells several times larger than lymphocytes or monocytes were generated in an autologous mixed leucocyte reaction (AMLR) independent of DNA synthesis in patients with rheumatoid arthritis (RA). The AMLR giant cells with multiple cytoplasmic granules were non-specific esterase-staining positive, phagocytic, non-adherent, HLA-DR+, CD11b+, CD14+, 4F2+, CDW29+, and anti-transferrin receptor positive, but negative for T, B, or NK markers. RA patients aged less than 60 years from more giant cells: 12.6 +/- 13.5% (n = 33) as compared with 0.4 +/- 1.5% in age- and sex-matched normals (n = 38, (P less than 0.001). More giant cells were seen over age 60 in both groups: RA 20.1 +/- 15.5% (n = 5) and healthy controls 3.0 +/- 3.2% (n = 8) (P less than 0.01). Neither disease activity nor treatment appear to influence the result in RA. The giant cells that are probably derived from monocytes in AMLR may explain the formation of the giant cells in rheumatoid granulation tissues.

Lymphocyte subsets in granulomas of human tuberculosis: an in situ immunofluorescence study using monoclonal antibodies

The immunophenotypic characteristics of lymphocyte subpopulations in tissue lesions of human tuberculosis were investigated in 18 cases. Frozen sections of affected cervical lymph nodes were stained with a panel of monoclonal antibodies using avidin-biotin immunofluorescence technique. The mean percentage of cells staining with different antibodies was as follows: CD3 44%; CD4 43%; CD8 36%; HLA-DR 86%; and IgM 29%. The mean CD4/CD8 ratio was 1.3:1. Leu7 and CD1 staining cells were very sparsely distributed in the granulomas. Thus, infection with tuberculosis is associated with a predominantly T cell infiltrate in lesional tissues. The proportion of CD4 positive (helper/inducer) cells at these sites is much lower than that seen (i) in the normal circulation, (ii) in reactive lymph nodes and (iii) at the site of purified protein derivative (PPD) injection in healthy tuberculin-responsive individuals.

The G protein alpha o subunit alters morphology, growth kinetics, and phospholipid metabolism of somatic cells

The physiological role of the alpha o subunit of guanine nucleotide-binding (G) protein was investigated with a murine adrenal cell line (Y1) transfected with a rat alpha o cDNA cloned in a retroviral expression vector. The parental cell line lacked detectable alpha o subunit. Expression of the alpha o cDNA in transfected cell lines was confirmed by Western blot (immunoblot) analysis. The rat alpha o subunit interacted with murine beta and gamma subunits and associated with cell membranes. Y1 cells containing large amounts of alpha o subunit had altered cellular morphology and reduced rate of cell division. In addition, GTP-gamma S-stimulated release of arachidonic acid from these cells was significantly increased compared with that in control cells. The alpha o subunit appears directly or indirectly to regulate cellular proliferation, morphology, and phospholipid metabolism.

The G protein alpha o subunit alters morphology, growth kinetics, and phospholipid metabolism of somatic cells

The physiological role of the alpha o subunit of guanine nucleotide-binding (G) protein was investigated with a murine adrenal cell line (Y1) transfected with a rat alpha o cDNA cloned in a retroviral expression vector. The parental cell line lacked detectable alpha o subunit. Expression of the alpha o cDNA in transfected cell lines was confirmed by Western blot (immunoblot) analysis. The rat alpha o subunit interacted with murine beta and gamma subunits and associated with cell membranes. Y1 cells containing large amounts of alpha o subunit had altered cellular morphology and reduced rate of cell division. In addition, GTP-gamma S-stimulated release of arachidonic acid from these cells was significantly increased compared with that in control cells. The alpha o subunit appears directly or indirectly to regulate cellular proliferation, morphology, and phospholipid metabolism.

Potential mechanisms for coordinate gene activation in the rheumatoid synoviocyte: implications and hypotheses

Evidence is reviewed to support the concept that synovial cells in rheumatoid arthritis have undergone distinctive alterations at the cellular and subcellular level that result in their taking on some of the characteristics that are also manifest by transformed cells. These phenotypic modulations could be indirectly driven by cytokines in a paracrine or autocrine fashion. Specific regional patterns of cell phenotype modulation were used to argue against a simple widely diffusing direct inductive effect to cytokines and in favor of microenvironmental determinants. It is hypothesized that these extracellular factors induce novel activation in a coordinate manner by acting through master regulatory genes operating in cells with specific microenvironmental interactions. Two of these regulatory genes, fos and jun, are discussed in detail because of their induction by growth factors and their central role in the transactivation of genes which have been implicated in rheumatoid synovitis. A model for gene activation in the rheumatoid synovium is proposed based on the premise that fos and jun are an important link in the intracellular transduction pathways used by cytokines to induce cellular phenotypic changes.

Temporal arteritis: cell composition and the possible pathogenetic role of cell-mediated immunity

A biopsy specimen exhibiting the typical morphologic characteristics of temporal arteritis was studied by using light immunofluorescent, and electron microscopy and immunohistochemical techniques. The granulomatous lesion consisted of clusters of macrophages, epithelioid cells, giant cells, and the peripheral lymphocyte mantle, and was localized mainly in the media. Neutrophils were rare, and fibrinoid necrosis was absent. In immunofluorescent and immunohistochemical studies, no significant deposition of immunoglobulins or complement was observed. Immunohistochemical study with monoclonal antibodies to leukocyte surface antigens demonstrated that the central aggregated granulomatous infiltrate consisted of OKTM1+, Leu-M3+, HLA-DR+ epithelioid macrophages and multinucleated giant cells, whereas OKT8+, HLA-DR+ (suppressor/cytotoxic) T cells predominated in the peripheral lymphocyte mantle. These findings suggest that cell-mediated immunity, especially T cell-regulated granulomatous reaction, may play an important role in the pathogenesis of temporal arteritis. By electron microscopy, smooth muscle cells often exhibited closely attached macrophages, epithelioid cells, and giant cells, and displayed a variety of cell injuries. It therefore seems likely that smooth muscle cells are a primary target of the granulomatous reaction.

Macrophages: current views on their differentiation, structure, and function

Macrophages are large mononuclear phagocytes that represent the major differentiated elements of the mononuclear phagocytic system. They arise from distinct progenitors in the bone marrow, and their immediate precursors, the monocytes, emigrate from the vascular compartment into many tissues and organs where they develop into mature macrophages. The latter display diverse morphological and functional characteristics, depending on the environmental stimuli that they receive. This phenotypic heterogeneity is, therefore, the final consequence of a series of down-regulation of some cellular processes and the up-regulation of others. The kinetics of the production of macrophages and their participation in various physiological and pathological phenomena is the subject of this review.

Occurrence of multinucleated giant cells in the appendix of clinically healthy rabbits

The spontaneous formation of multinucleated giant cells was observed in the appendix of clinically healthy adult rabbits that were free of infection with intestinal viruses, pathogenic bacteria, fungi and parasites. Giant cells occurred singly and in aggregates. They were of the foreign body and of the Langhans' type, but intermediate forms were also noticed. Ultrastructurally, the hallmark of these appendiceal polykaryons were large phagolysomal fields harbouring amorphous debris and remains of cytoplasmic organelles and bacteria. The bacteria in the appendiceal tissues were neither of a special type nor acid-fast. The aetiology and significance of appendiceal giant cells remains to be clarified.

Paracoccidioidomycosis: a sequential histopathologic study of lesions in experimentally-infected rats

Female albino rats were used for the sequential histopathological study of experimental paracoccidioidomycosis. The animals were inoculated intraperitoneally with a strain of Paracoccidioides brasiliensis in the yeast-like phase, and sacrificed at given intervals from 1 to 168 days after inoculation; each animal received an inoculum of 4 x 10(6) cells in 0.8 ml of saline. The control group received saline containing scrapings of the culture medium. Tissue from the inoculation site was examined. The cellular population, the extracellular matrix, and the presence and characteristics of fungi were analysed in the inflammatory granulomatous process by light microscopy. The results allowed to separate the kinetic of the inflammatory response into three stages: 1) neutrophilic or macrophagic-neutrophilic; 2) pre-granulomatous; 3) granulomatous. Synthesis of the extracellular matrix began with the depositing of fibrin-like material, and increased gradually with deposits of collagen, proteoglycans, and glycoproteins. Parasites were present in all of the examined periods. Recurrences of the disease were clearly shown through the concurrence of recently-formed granulomas with older granulomas, implying that this type of granulomatous process does not eliminate the disease, nor is it able to limit fungal dissemination over a prolonged period of time.