Immunohistochemical Detection of Interferon-γ: Fake or Fact?

Immunohistochemistry is a widely accepted tool to investigate the presence and immunolocalization of cytokines in tissue sections at the protein level. We have tested the specificity and reproducibility of IFNγ immunohistochemistry on tissue sections with a large panel of anti-IFNγ antibodies. Thirteen different commercially available anti-IFNγ antibodies, including seven advertised and/or regularly applied for immunohistochemistry/-cytochemistry, were tested using a three-step streptavidin–biotin–peroxidase technique and a two-step immunofluorescence (FACS) analysis. Immunoenzyme double staining was used to identify the IFNγ-positive cells. Serial cryostat sections were used of human reactive hyperplastic tonsils, rheumatoid synovium, and inflammatory abdominal aortic aneurysms, known to possess a prominent Th1-type immune response. In vitro phorbol myristate acetate/ionomycin-stimulated T-cells served as positive control; unstimulated cells served as negative control. Cultured T-cells were used adhered to glass slides (immunocytochemistry), in suspension (FACS), or snap-frozen and sectioned (immunohistochemistry). Immunocytochemistry and FACS analysis on stimulated cultured T-cells showed positive staining results with 12 of 13 anti-IFNγ antibodies. However, immunohistochemistry of sectioned stimulated T-cells was negative with all. Unstimulated cells were consistently negative. IFNγ immunohistochemical single- and double staining analysis of the tissue sections showed huge variations in staining patterns, including positivity for smooth muscle cells ( n = 8), endothelial cells ( n = 4), extracellular matrix ( n = 4), and CD138+ plasma cells ( n = 12). Specific staining of T-cells, as the sole positive staining, was not achieved with any of the 13 antibodies. IFNIFNγ-immunohistochemistry appears unreliable because of lack of specificity to stain T-cells in situ. In fact, depending on the type of anti-IFNγ antibody used, a variety of different cell constituents were nonspecifically stained. Consequently, data based on IFNγ-immunohistochemistry must be interpreted with great caution.

Multiple bacteria contribute to intraplaque T-cell activation in atherosclerosis

BACKGROUND

Infection with microorganisms is considered a pathogenic factor in atherogenesis. Several studies have shown the presence of a broad spectrum of bacterial species in atherosclerotic plaques, which could trigger local inflammation. Because T cells contribute to atherosclerotic plaque inflammation, we studied the responsiveness of human plaque derived T-cell cultures to bacteria of different species.

MATERIALS AND METHODS

Primary polyclonal T-cell cultures were generated from both carotid endarterectomy tissue and peripheral blood of nine patients, and the peripheral blood of eight matched controls. The in vitro proliferative responses of the T-cell cultures against H. pylori, N. meningitidis, N. lactamica, S. aureus, S. pneumoniae, S. epidermidis and E. coli were analysed. T-cell proliferation was measured by (3)H-thymidine incorporation and expressed as a stimulation index. Selective outgrowth of intraplaque microbial specific T cells was studied by calculating the ratio of plaque T-cell SI and peripheral blood T-cell SI in each patient.

RESULTS

All patients showed T-cell responsiveness to multiple bacteria in their plaque tissue. Stimulation indices were in the range of 0.3-30, and this degree of reactivity with the different species was heterogeneous among patients. Selective outgrowth (plaque/peripheral blood ratio) of T cells against multiple bacteria was observed in six out of nine patients.

CONCLUSIONS

T cells in atherosclerotic plaques have the capacity to selectively respond to antigens of a wide variety of microbial antigens. This supports the view that such mechanisms could contribute to the atherosclerotic inflammatory response.

Role of plaque inflammation in acute and recurrent coronary syndromes

Inflammation plays an important role in the initiation, development, progression and complications of atherosclerotic vascular disease. Our present knowledge of the elementary role of inflammation for the onset of plaque rupture in atherosclerotic coronary lesions primarily stems from autopsy studies. However, the introduction of directional coronary atherectomy catheters has provided a unique opportunity to directly investigate the role of inflammation in coronary syndromes. In this report we describe the role of coronary plaque inflammation, as determined by immunohistochemistry, on the presentation of coronary syndromes and on the clinical outcome following percutaneous interventions.

Recurrent unstable angina after directional coronary atherectomy is related to the extent of initial coronary plaque inflammation

OBJECTIVES

This study was performed to evaluate the relationship between plaque inflammation of the initial culprit lesion and the incidence of recurrent angina for one year after directional coronary atherectomy (DCA).

BACKGROUND

A positive correlation between coronary plaque inflammation and angiographic restenosis has been reported.

METHODS

A total of 110 patients underwent DCA. Cryostat sections were immunohistochemically stained with monoclonal antibodies CD68 (macrophages), CD-3 (T lymphocytes) and alpha-actin (smooth muscle cells [SMCs]). The SMC and macrophage contents were planimetrically quantified as a percentage of the total tissue area. T lymphocytes were counted as the number of cells/mm2. The patients were followed for one year to document recurrent unstable angina pectoris (UAP) or stable angina pectoris (SAP).

RESULTS

Recurrent UAP developed in 16 patients, whereas recurrent SAP developed in 17 patients. The percent macrophage areas were larger in patients with recurrent UAP (27 +/- 12%) than in patients with recurrent SAP (8 +/- 4%; p = 0.0001) and those without recurrent angina (18 +/- 14%; p = 0.03). The number of T lymphocytes was also greater in patients with recurrent UAP (25 +/- 14 cells/mm2) than in patients with recurrent SAP (14 +/- 8 cells/mm2; p = 0.02) and those without recurrent angina (14 +/- 12 cells/mm2; p = 0.002). Multiple stepwise logistic regression analysis identified macrophage areas and T lymphocytes as independent predictors for recurrent UAP.

CONCLUSIONS

There is a positive association between the extent of initial coronary plaque inflammation and the recurrence of unstable angina during long-term follow-up after DCA. These results underline the role of ongoing smoldering plaque inflammation in the recurrence of unstable angina after coronary interventions.

Unstable atherosclerotic plaques contain T-cells that respond to Chlamydia pneumoniae

OBJECTIVE

Atherosclerotic lesions are characterized by an immune mediated chronic inflammation. Seroepidemiological studies support a relationship between atherosclerotic disease and infection with C. pneumoniae; an association further endorsed by immunocytochemical and DNA directed studies. However, the question arises whether C. pneumoniae acts as a causal antigen, or is merely a bystander. For this reason we have analyzed the T lymphocyte population of carotid atherosclerotic plaques of symptomatic patients for their response against C. pneumoniae.

METHODS

T cell lines were generated from carotid endarterectomy tissues obtained from eight patients with symptomatic disease. The response of these T cell lines against C. pneumoniae elementary bodies was analyzed by 3H-thymidine incorporation. T cell clones were generated by limiting dilution from the cell lines of three patients and tested for antigen specificity in the same manner. Furthermore, cytokine profiles (Th1/Th0/Th2) were established by measuring the production of IFN-gamma and IL-4.

RESULTS

Of the eight T-cell lines five responded to C. pneumoniae. Eighteen of 69 CD4-positive clones, generated from three patients with a positive T cell lines response, responded to C. pneumoniae also. The majority (17/18, 96%) of these clones showed a Th1 cytokine profile.

CONCLUSION

These results show that in a subpopulation of symptomatic patients C. pneumoniae can activate T cells within atherosclerotic plaques suggesting that a C. pneumoniae enhanced proinflammatory Th1 response contributes to plaque destabilization in these patients.

Metallothionein in human atherosclerotic lesions: a scavenger mechanism for reactive oxygen species in the plaque?

Oxidative stress is important in the genesis of atherosclerotic lesions. The extracellular effects of reactive oxygen species (ROS), such as oxidative modification of lipoproteins and upregulation of matrix degrading enzymes, are considered crucial in this context. The effects of ROS are counteracted by antioxidant scavenging systems; metallothioneins (MTs) may serve as such. This study was designed to see whether MTs occur in human atherosclerotic plaques and which cell types are involved. The immunohistochemical study focuses on smooth muscle cells (SMCs), macrophages, and T cells. MT immunoreactivity was seen only within SMCs, which occurred usually in small clusters and were found mostly near lipid cores and occasionally in the media. Double immunostaining showed MT-positive SMCs and matrix metalloproteinase (MMP)-9 in the same area but not within the same cell. Electron microscopy was done to evaluate the subtype of MT-positive cells and revealed that the majority consisted of synthetic SMCs. Thus, atherosclerotic plaques in humans contain MT known to act as a scavenger for ROS. The observation that MT was expressed only in SMCs, particularly those of synthetic phenotype, suggests that MT plays a role in protecting these active matrix-producing cells.

Plaque inflammation in restenotic coronary lesions of patients with stable or unstable angina

OBJECTIVES

To evaluate immunohistochemically various parameters of inflammation in coronary atherectomy specimens obtained from restenotic culprit lesions of patients presenting with either stable or unstable angina (UA).

BACKGROUND

There is no information regarding the relationship between atherosclerotic plaque inflammation and the severity of the coronary syndromes in patients with restenotic coronary lesions.

METHODS

A total of 37 patients with either stable angina or UA underwent directional coronary atherectomy for restenotic coronary lesions. Cryostat sections of atherectomy specimen were immunohistochemically stained with monoclonal antibodies CD68 (macrophages [MACs]), CD3 (T-lymphocytes) and alpha-actin (smooth muscle cells [SMCs]). Smooth muscle cell contents and MAC contents were planimetrically quantified as the percentage immunopositive tissue area of the total tissue area. T-lymphocytes were counted at 100-X magnification throughout the entire section and expressed as number of cells per mm2.

RESULTS

Restenotic coronary lesions of patients with UA or stable angina showed no significant difference in SMC areas (31.9%+/-16.3% vs. 38.5%+/-18.8%, respectively; p = NS). However, restenotic coronary lesions of patients presenting with unstable angina contained significantly more MACs (24.4%+/-15.1% vs. 10.5%+/-5.8%, p = 0.001) and T-lymphocytes (18.8 cells/mm2+/-15.1 cells/mm2 vs. 8.6 cells/mm2+/-9.8 cells/mm2; p = 0.034) than patients with stable angina.

CONCLUSIONS

These results suggested that inflammation appears to affect plaque instability in restenotic coronary lesions resulting in unstable coronary syndromes.

Extracellular matrix of the human aortic media: an ultrastructural histochemical and immunohistochemical study of the adult aortic media

Aortic distensability is the key to normal aortic function and relates to the lamellar unit in the media. However, the organization of the extracellular matrix components in these lamellar units, which are largely responsible for the distensability, is insufficiently known, especially in the human. We therefore performed a detailed ultrastructural analysis of these components. Thoracic aortas of 56 individuals (age 45-74 years), none of whom suffered from aortic disease, were studied by immunoelectron microscopy of elastin, collagen types I, III, IV, V, and VI, fibronectin, and fibrillin-1, and by ultrastructural histochemistry of proteoglycans, which were further characterized by enzymatic digestion. The elastic lamellae were closely associated with thick collagen fibers containing types I, III, and V collagen. Between these collagen fibers, numerous complex, circumferentially oriented streaks of elastin protruded from the lamellae. In contrast to what is usually reported in the aortas of experimental animals, the smooth muscle cells preferentially adhered to these ill-defined streaks rather than directly to the solid lamellae. Fibrillin-1- and type VI collagen-containing bundles of microfibrils (oxytalan fibers) were also involved in the smooth muscle cell-elastin contact. The smooth muscle cells were invested by basal lamina-like layers connecting them to each other as well as to the oxytalan fibers. Unexpectedly, these layers were abundantly labeled by anti-fibronectin, whereas type IV collagen, a specific basement membrane component, was mainly found in larger, flocculent deposits. The proteoglycans present were collagen-associated dermatan sulfate proteoglycan, cell-associated heparan sulfate proteoglycan, and interstitial chondroitin sulfate proteoglycan. Our observations demonstrate that the extracellular matrix in the human aorta is extremely complex and therefore differs from most descriptions based on experimental animals. They serve as reference for future studies on aortic diseases, such as aneurysmas and dissections.

Leucocyte recruitment in rupture prone regions of lipid-rich plaques: a prominent role for neovascularization?

OBJECTIVE

Microvessels in atherosclerotic plaques provide an alternative pathway for the recruitment of leucocytes in the lesions. The present study was designed to investigate the potential role of these microvessels in creating vulnerable sites in atherosclerotic plaques.

METHODS

Thirty-four atherosclerotic plaques were obtained from 25 patients undergoing carotid endartherectomy (n = 16), femoral endartherectomy (n = 6) and aortic surgery (n = 12). Plaques were histologically classified as either lipid-rich (rupture prone, n = 21) or fibrous (stable, n = 13). Serial cryostat sections were immunohistochemically investigated using monoclonal antibodies against endothelial cells (ULEX-E and F-VIII), vascular endothelial growth factor (VEGF), endothelial adhesion molecules (ICAM-1, VCAM-1, E-Selectin, CD40) and inflammatory cells (macrophages (CD68) and T lymphocytes (CD3).

RESULTS

The microvessel density in lipid-rich plaques was significantly increased as compared to fibrous plaques. Most of these vessels were located in the shoulder-region of the plaque and at the base of the atheroma. Microvessels in lipid-rich plaques also expressed increased levels of ICAM-1, VCAM-1, E-Selectin and CD40. Moreover, inflammation was most abundantly present in the proximity of microvessels. VEGF was only observed on vessels and mononuclear cells in lipid-rich plaques, suggesting that this factor may play a role in microvessels formation.

CONCLUSIONS

Neovascularisation and expression of adhesion molecules by microvessels at sites of vulnerable lipid-rich plaques may sustain the influx of inflammatory cells and hence, could contribute to plaque destabilization.

Complete chromogen separation and analysis in double immunohistochemical stains using Photoshop-based image analysis

Simultaneous detection of two different antigens on paraffin-embedded and frozen tissues can be accomplished by double immunohistochemistry. However, many double chromogen systems suffer from signal overlap, precluding definite signal quantification. To separate and quantitatively analyze the different chromogens, we imported images into a Macintosh computer using a CCD camera attached to a diagnostic microscope and used Photoshop software for the recognition, selection, and separation of colors. We show here that Photoshop-based image analysis allows complete separation of chromogens not only on the basis of their RGB spectral characteristics, but also on the basis of information concerning saturation, hue, and luminosity intrinsic to the digitized images. We demonstrate that Photoshop-based image analysis provides superior results compared to color separation using bandpass filters. Quantification of the individual chromogens is then provided by Photoshop using the Histogram command, which supplies information on the luminosity (corresponding to gray levels of black-and-white images) and on the number of pixels as a measure of spatial distribution. (J Histochem Cytochem 47:119-125, 1999)

Recent activation of the plaque immune response in coronary lesions underlying acute coronary syndromes

OBJECTIVE

To discriminate between chronic inflammation and acute activation of the plaque immune response in culprit lesions of patients with acute coronary syndromes.

DESIGN

Retrospective study.

SETTING

Tertiary referral centre.

SUBJECTS

71 patients having coronary atherectomy were classified according to their ischaemic syndrome: stable angina (n = 23); stabilised unstable angina (n = 18); refractory unstable angina (n = 11); and acute myocardial infarction (n = 19).

MAIN OUTCOME MEASURES

Immunohistochemical measurement of interleukin 2 receptor (IL-2R) (CD25) positive cells expressed as a percentage of the total amount of (CD3 positive) T lymphocytes in frozen sections of atherectomy specimens.

RESULTS

The number of lesions containing IL-2R (CD25) positive T cells increased with severity of the ischaemic coronary syndrome (stable angina, 52%; stabilised unstable angina, 77.8%; refractory unstable angina, 90.9%; acute myocardial infarction, 89.4%). The percentage of activated T cells (CD25/CD3 ratios x100) increased in lesions associated with refractory unstable angina (7.8%) and acute myocardial infarction (18.5%), compared with those in lesions associated with either chronic stable angina (2.2%) or stabilised unstable angina (3.3%).

CONCLUSIONS

An increase in the percentage of IL-2R positive T lymphocytes in culprit lesions of patients with acute coronary syndromes indicates recent activation and amplification of the immune response within plaques. This may result in a burst of inflammatory products with tissue degrading and vasoactive properties and, hence, could initiate or accelerate the onset of an acute coronary event.

Multiple labeling in electron microscopy: its application in cardiovascular research

The heart is a muscular pump kept together by a network of extracellular matrix components. An increase in collagens, as in chronic congestive heart failure (CHF), is thought to have a negative effect on cardiac compliance and, thus, on the clinical condition. Conventional electron microscopy allows for the study of cellular and extracellular components and scanning electron microscopy (SEM) can put these structures in three-dimensional perspective. However, in order to study extracellular matrix components in relation to cells, immunoelectron microscopy is superior. We have used this technique in our studies on heart failure. Heart specimens were fixed in 4% paraformaldehyde and 0.1% glutaraldehyde in sodium cacodylate buffer, dehydrated by the method of progressive lowering of temperature and embedded in LR Gold plastic. Immunolabeling could be achieved with different sized gold-conjugated secondary antibodies or protein-A gold conjugates. Depending on the objective, ultra small gold (USG) conjugates or a regular probe size can be used. Labeling efficiency could be increased by bridging antibodies. The double and triple staining procedures were based on single staining methods using one- and two-face labeling. The choice of antibodies and gold conjugates depended on the objectives. Immunoelectron microscopy, using multiple labeling, allowed a detailed study of the organization of the extracellular matrix and its relationship with cardiac myocytes. This may prove to be a useful tool for the study of chronic heart failure.

Heterogeneity in morphological characteristics of coronary arteries and aortae in various models of hypertension

OBJECTIVE

Hypertension is associated with important structural and functional changes in vascular smooth muscle. The question arises whether different vascular beds and different models of hypertension react similarly or in a heterogeneous manner to the hypertensive state.

METHODS

We quantitatively investigated the morphology of the coronary arteries and thoracic aortae taken from 4, 30 and 52-week-old spontaneously hypersensitive rats (SHR) and Wistar Kyoto rats (WKY), respectively, and from hypertensive rats with aortic stenosis (ASR).

RESULTS

In coronary arteries taken from the SHR the media area was slightly increased compared with those obtained from the age-matched WKY. Increasing age caused a significant increase in media area of the SHR vessels, but not in WKY tissues. No differences were found in the media area values of the coronary arteries obtained from the ASR compared with those obtained from SHAM (operated control rats) rats. The media area of the aortae taken from SHR was increased when compared with those from the age-matched WKY rats. In addition, the media area of the aortae from the surgically induced aortic stenosis rats (ASR) when compared with tissues from SHAM rats was significantly increased.

CONCLUSIONS

Different animal models of hypertension appear to develop largely heterogeneous profiles of vascular hypertrophy, with different morphometric characteristics.

Remodeling after myocardial infarction in humans is not associated with interstitial fibrosis of noninfarcted myocardium

OBJECTIVES

This study was specifically designed to evaluate whether noninfarcted hypertrophic myocardium in patients with end-stage heart failure after myocardial infarction (MI) is associated with an increase in interstitial fibrous tissue.

BACKGROUND

Postinfarction remodeling consists of complex alterations that involve both infarcted and noninfarcted myocardium. The question arises whether ventricular dysfunction is due to physical events, such as inadequate myocardial hypertrophy to compensate for increased tangential wall stress, or is caused by the development of progressive interstitial fibrosis in noninfarcted myocardium.

METHODS

Fifteen hearts were obtained as cardiac explants (n = 13) or at autopsy (n = 2) from patients with end-stage coronary artery disease. Sixteen normal hearts served as reference hearts. Samples were taken from the left ventricular (LV) wall that contained the infarcted area, the border area and noninfarcted myocardium remote from scar areas. Collagen was quantified biochemically and microdensitophotometrically. Collagen type I and III ratios were analyzed by using the cyanogen bromide method and immunohistochemical staining, followed by microdensitophotometric quantification.

RESULTS

In noninfarcted myocardium remote from the scar areas, total collagen levels and collagen type I/III ratios did not differ statistically from those in reference hearts. These observations contrasted with high total collagen content and high collagen type I/III ratios in scar and border areas.

CONCLUSIONS

Remodeling of LV myocardium after MI in patients with end-stage heart failure is not necessarily associated with interstitial fibrosis in noninfarcted hypertrophic myocardium remote from scar areas. This finding raises questions regarding therapeutic interventions designed to prevent or retard the development of interstitial fibrosis.

Clinically stable angina pectoris is not necessarily associated with histologically stable atherosclerotic plaques

OBJECTIVE

To investigate the extent of plaque inflammation in culprit lesions of patients with chronic stable angina.

DESIGN

Retrospective study.

SETTING

Amsterdam reference centre.

SUBJECTS

89 consecutive patients who underwent directional coronary atherectomy, 58 of whom met the following inclusion criteria: chronic stable angina (Canadian Cardiovascular Society classification 1-3 (group 1, n = 28)); unstable angina (Braunwald class II (group 2, n = 18)); unstable angina (Braunwald class III (group 3, n = 12)).

INTERVENTIONS

Directional atherectomy in patients with angina pectoris.

MAIN OUTCOME MEASURES

Tissue areas of culprit lesions occupied by inflammatory cells and smooth muscle cells related to clinically defined ischaemic syndrome.

RESULTS

Areas (% of total surface area (mean (SEM)) rich in smooth muscle cells were larger in patients with chronic stable angina (group 1, 51.2 (20.9)) than in those with unstable angina (group 2, 42.1 (20.5); group 3, 29.5 (19.4)) (1 v 2 and 2 v 3, NS; 1 v 3, P < 0.004). Macrophage rich areas were significantly smaller in patients with stable angina (group 1, 21.8 (11.9)) than in those with unstable angina (group 2, 31.5 (14.6); group 3, 46.4 (16.7)) (1 v 2, P < 0.02; 2 v 3, P < 0.02; 1 v 3, P < 0.001). Mean numbers of T cells per mm2 were as follows: group 1, 17 (9.4); group 2, 25 (15.9); group 3, 41 (30.6) (1 v 2, P 0.04; 2 v 3, P 0.07; 1 v 3, P < 0.001). Areas with HLA-DR positive cells showed the same pattern as macrophages and T cells and were smaller in stable (29.9 (12.4)) than in unstable angina (group 2, 40.4 (17.6); group 3, 52.4 (12.0)) (1 v 2, P < 0.02; 2 v 3, P < 0.05; 1 v 3, P < 0.001).

CONCLUSION

The inverse relation between the extent of inflammatory activity in plaque tissues of culprit lesions and the clinical stability of the ischaemic syndrome supports the concept that reduction of inflammation favours plaque stabilisation. At the same time, the considerable overlap between groups indicates that patients with clinically stable angina do not all have histologically stable plaques.

Dilated cardiomyopathy is associated with an increase in the type I/type III collagen ratio: a quantitative assessment

OBJECTIVES

The aim of this study was to quantify total collagen and the type I/type III collagen ratio and their localization in hearts with dilated cardiomyopathy.

BACKGROUND

Patients with dilated cardiomyopathy have an increase in intramyocardial fibrillar collagen. Types I and III are the main constituents and have different physical properties that may affect cardiac compliance.

METHODS

Nineteen hearts with dilated cardiomyopathy were studied (17 cardiac explants, 2 hearts obtained at autopsy) and compared with reference hearts. Total collagen was determined by hydroxyproline analysis. Collagen types I and III were analyzed using the cyanogen bromide method and immunohistochemical analysis followed by microdensitophotometric quantification. Localization of collagen types I and III was established at the light and electron microscopic levels. Immunoelectron microscopy provided information regarding their localization.

RESULTS

Total collagen and the collagen type I/type III ratio were increased in hearts with dilated cardiomyopathy (p < 0.05). Electron microscopy showed a diffuse increase in collagen fibrils in the endomysium; the perimysium showed an inhomogeneous increase. Collagen fibrils were thicker, and fibrous long-spacing collagen occurred in the endomysium. Immunoelectron microscopic findings confirmed an increase in type I collagen.

CONCLUSIONS

Hearts with dilated cardiomyopathy have a statistically significant increase in the collagen type I/type III ratio. The changes occur in the endomysium and perimysium, although with differences in distribution. These changes in intramyocardial collagen may be clinically relevant because they may affect cardiac rigidity and, therefore, eventually may render the heart less compliant. Further studies are needed to evaluate at what point in the course of the disease these changes appear.

Long-spacing collagen and proteoglycans in pathologic tissues

The presence of proteoglycans in fibrous long-spacing collagen (FLSC) was assessed in various pathologic tissues using the highly selective proteoglycan stains cuprolinic blue and polyethyleneimine. Two types of FLSC could be distinguished: one that contained proteoglycans and one that did not. The conditions in which these types occurred suggested a completely different physiologic significance. Also, their morphologies were different: The FLSC containing proteoglycans constituted compact, often fusiform structures long known in diagnostic electron microscopy as Luse bodies. In accordance with the literature, this compact type of FLSC was found especially in schwannomas and other neurogenic tumors. Enzymatic digestion experiments indicated that the proteoglycan present was dermatan sulfate proteoglycan. The average periodicities measured ranged from 101 to 147 nm. The type of FLSC lacking proteoglycans, on the other hand, formed dispersed aggregates. This dispersed FLSC had periodicities ranging from 79 to 103 nm (ie, just below those of the compact type). It was found only under circumstances in which there was high collagen breakdown and/or turnover. That dispersed FLSC is a marker for collagen degradation was further supported by its presence inside fibroblasts engaged in collagen phagocytosis.(ABSTRACT TRUNCATED AT 250 WORDS)

The mycobacterial secreted antigen 85 complex possesses epitopes that are differentially expressed in human leprosy lesions and Mycobacterium leprae-infected armadillo tissues

The granulomatous skin lesions in leprosy are thought to be initiated by the immune response to certain antigens of the causative agent, Mycobacterium leprae. The antigen 85 complex is one of the major targets in the immune response to M. leprae infection. In the present study, a panel of previously characterized monoclonal antibodies (MAbs) (3A8, Rb2, A4g4, A2h11, Pe12, and A3c12) reacting with different epitopes of the 85 complex proteins of Mycobacterium tuberculosis and M. leprae was employed in a comparative immunohistological analysis to demonstrate the in situ expression of 85 complex antigenic epitopes in leprosy lesions across the clinical spectrum and in M. leprae-infected armadillo liver tissues. These MAbs showed a heterogeneous staining pattern in a given leprosy lesion. In highly bacilliferous borderline and lepromatous leprosy lesions, MAbs Rb2, A4g4, A2h11, and Pe12 stained clear rod-shaped M. leprae bacilli within macrophages, and the degree of staining correlated with the bacillary index of the lesion. On the other hand, MAbs 3A8 and A3c12 staining was mostly seen as a diffuse staining pattern within interstitial spaces and on the membranes of the infiltrated cells but not the bacilli. In paucibacillary borderline and tuberculoid leprosy lesions, only 3A8, Rb2, and A3c12 showed distinct staining in association with infiltrates in the granuloma. None of these MAbs showed any detectable reaction with control nonleprosy skin lesions, while MAb A3c12 positively stained the granulomas of both leprosy and control specimens. In situ reactivity of these MAbs with M. leprae-infected armadillo liver tissues also showed a heterogeneous staining pattern. Interestingly, a clear difference in expression of these epitopes was observed between armadillo tissues and human leprosy lesions. By immunogold ultracytochemistry, we further showed the differential localization of these MAb-reactive epitopes on the cell surface, in the cytosol, and at the vicinity of M. leprae within Kupffer cells of armadillo liver tissues. Our results indicate that these antigenic epitopes of the antigen 85 complex are differentially expressed in leprosy lesions and infected armadillo tissues and that they could be target determinants in the immunopathological responses during M. leprae infection.

Identification and characterization of epitopes shared between the mycobacterial 65-kilodalton heat shock protein and the actively secreted antigen 85 complex: their in situ expression on the cell wall surface of Mycobacterium leprae

Both mycobacterial hsp65 and the actively secreted antigen 85 complex of 30-kDa region proteins are considered to be major immune targets in mycobacterial diseases. In this study, by using a novel series of monoclonal antibodies (MAbs) directed to these antigens, we identified and partially characterized three unique epitopes (Rb2, Pe12, and A2h11) that are shared between mycobacterial hsp65 and the individual components of the antigen 85 complex. Dot blot assays with native purified proteins revealed that all three MAbs are strongly bound to hsp65 and antigens 85A (MPT44) and 85B (MPT59), while a weak reaction or no reaction was found with antigen 85C (MPT45). Immunoblotting showed that MAb Rb2 reacted strongly with both hsp65 and the antigen 85 complex proteins, whereas MAbs Pe12 and A2h11 reacted strongly with the former but weakly with the latter. Moreover, these MAbs did not react with other closely related MPT51 and MPT64 secreted proteins. Further characterization of these epitopes was performed by using recombinant fusion and truncated proteins of Mycobacterium bovis BCG hsp65 (MbaA) and the M. leprae 30- and 31-kDa antigen 85 complex fusion proteins. In hsp65, Rb2-Pe12- and A2h11-reactive epitopes were found to reside in the C-terminal region of amino acid residues 479 to 540 and 303 to 424, respectively. In the M. leprae 30- and 31-kDa antigen 85 complex, all three epitopes were located in an N-terminal region of amino acid residues 55 to 266, one of the known fibronectin-binding sites of the M. leprae antigen 85 complex. Comparison of these MAb-reactive amino acid sequence regions between mycobacterial hsp65 and the components of the antigen 85 complex revealed that these regions show certain amino acid sequence identities. Furthermore, by immunoperoxidase and immunogold ultracytochemistry, we demonstrated that Rb2-, Pe12-, and A2h11-reactive epitopes are expressed both on the cell wall surface and in the cytosol of M. leprae bacilli within the lesions of lepromatous leprosy patients and in M. leprae-infected armadillo liver tissue.

Cytopathology of malignant mesothelioma. Reappraisal of the diagnostic value of collagen cores

The identification of malignant mesothelial cells in cytological smears prepared from serous effusions is still hampered by the lack of features specific for mesothelial differentiation. We examined the diagnostic value of collagen cores within clusters of tumour cells in cytological smears prepared from effusions from 43 patients with malignant mesothelioma and of 62 cases of metastatic adenocarcinoma. In Giemsa-stained smears collagen cores were detected in 51% of the cases of malignant mesothelioma and in none of the smears with metastatic adenocarcinoma. Using the Azan stain, collagen cores were detected in 64% of the malignant mesotheliomas and 4% of the adenocarcinomas. Immunoelectron microscopy demonstrated that the collagen cores are largely composed of collagen type III fibrils and some elastin embedded in a homogenous extracellular matrix. It can be concluded that the presence of collagen cores within clusters of tumour cells is highly suggestive of mesothelial differentiation and a common finding in malignant mesothelioma.