A chlorhexidine-releasing epoxy-based coating on titanium implants prevents Staphylococcus aureus experimental biomaterial-associated infection

Prevention of biomaterial-associated infections (BAI) remains a challenging problem, in particular due to the increased risk of resistance development with the current antibiotic-based strategies. Metallic orthopaedic devices, such as non-cemented implants, are often inserted under high mechanical stress. These non-cemented implants cannot be protected by e.g. antibioticreleasing bone cement or other antimicrobial approaches, such as the use of bioactive glass. Therefore, in order to avoid abrasion during implantation procedures, we developed an antimicrobial coating with great mechanical stability for orthopaedic implants, to prevent Staphylococcus aureus BAI. We incorporated 5 and 10 wt % chlorhexidine in a novel mechanically stable epoxy-based coating, designated CHX5 and CHX10, respectively. The coatings displayed potent bactericidal activity in vitro against S. aureus, with over 80 % of the release (19 µg/cm2 for CHX5 and 41 µg/cm2 for CHX10) occurring within the first 24 h. In mice, the CHX10 coating significantly reduced the number of CFU (colony forming units), both on the implants and in the peri-implant tissues, 1 d after S. aureus challenge. The CHX10-coated implants were well-tolerated by the animals, with no signs of toxicity observed by histological analysis. Moreover, the coating significantly reduced the frequency of culture-positive tissues 1 d, and of culture-positive implants 1 and 4 d after challenge. In summary, the chlorhexidine-releasing mechanically stable epoxy-based CHX10 coating prevented implant colonisation and S. aureus BAI in mice and has good prospects for clinical development.

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.

Intraplaque hemorrhage in cardiac allograft vasculopathy

Plaque hemorrhage, inflammation and microvessel density are key determinants of plaque vulnerability in native coronary atherosclerosis (ATS). This study investigates the role of intraplaque hemorrhage (IPH) and its relation with inflammation and microvessels in cardiac allograft vasculopathy (CAV) in posttransplanted patients. Seventy coronary plaques were obtained from 12 patients who died because of CAV. For each patient we collected both native heart and the allograft, at the time of transplantation and autopsy, respectively. Intralesion inflammation, microvessels and IPH were assessed semi-quantitatively. IPH was observed in 21/35 (60%) CAV lesions and in 8/35 (22.9%) native ATS plaques, with a strong association between fibrocellular lesions and IPH (p = 0.0142). Microvessels were detected in 26/35 (74.3%) of CAV lesions with perivascular leakage as sign of endothelial damage in 18/26 (69.2%). IPH was strongly associated with microvessels (p < 0.0001). Inflammation was present in 31/35 (88.6%) of CAV lesions. CAV IPH+ lesions were characterized by presence of both fresh and old hemorrhage in 12/21 (57.1%). IPH, associated with microvessel damage and inflammation, is an important feature of CAV. Fresh and old intralesion hemorrhage suggests ongoing remodeling processes promoting the lesion progression and vulnerability.

Could recombinant insulin compounds contribute to adenocarcinoma progression by stimulating local angiogenesis?

AIMS/HYPOTHESIS

Negative effects on the progression of adenocarcinomas by hyperinsulinaemia and the insulin analogue glargine (A21Gly,B31Arg,B32Arg human insulin) have recently been suggested. Most actions of this insulin analogue have hitherto been explained by direct stimulation of growth potential of neoplastic cells and by its IGF-1 related properties. However, insulin-stimulated angiogenesis could be an additional factor involved in tumour progression and clinical outcomes associated with cancer.

METHODS

Five types of human adenocarcinoma (breast, colon, pancreas, lung and kidney) were evaluated for the presence of insulin receptors (IRs) on angiogenic structures. In an in vitro angiogenesis assay, various commercially available insulin compounds were evaluated for their potential to increase capillary-like tube formation of human microvascular endothelial cells (hMVEC). Insulin compounds used were: human insulin, insulin lispro (B28Lys,B29Pro human insulin), insulin glargine and insulin detemir (B29Lys[e-tetradecanoyl],desB30 human insulin).

RESULTS

Insulin receptors were found to be strongly expressed on the endothelium of microvessels in all evaluated adenocarcinomas, in addition to variable expression on tumour cells. Low or no detectable expression of IRs was seen on microvessels in extratumoral stroma. Incubation with commercially available insulin compounds increased capillary-like tube formation of hMVEC in vitro.

CONCLUSIONS/INTERPRETATION

Our results suggest that all tested insulin compounds may stimulate tumour growth by enhancing local angiogenesis. Future studies need to confirm the association between insulin therapy in type 2 diabetes and tumour progression.

A focus on fixation

Three fixation issues related to immunostaining are discussed here: 1) Generally, a tissue block is fixed, then embedded and sectioned (pre-fixation). The type of fixative applied, crosslinking or coagulating, has an impact on selecting an epitope retrieval method. Individual antigens have a fixation-retrieval characteristic. 2) A long fixation time, especially with crosslinking fixatives, may compromise the result of immunostaining. This negative effect varies among different antigens and can be partially restored by applying a more sensitive/efficient detection system such as tyramide amplification. 3) Sections cut from a fresh frozen tissue block usually are acetone fixed(post-fixation). This was accepted as the "gold standard" for a long time. Post-fixation, however,may have serious consequences for preservation of small peptides leaking from the cut open cells,whereas this is not the case with pre-fixed intact cells. Consequently, the concept of an acetone post-fixed cryostat tissue section as "gold standard" no longer exists and a more appropriate use of the terms immunohistochemistry and immunocytochemistry therefore seems justified. For many antibodies, it is not known whether a formalin fixed, paraffin embedded tissue specimen is appropriate. Suggestions are made for creating a positive control cell block for testing such antibodies.

ACE mediates ventilator-induced lung injury in rats via angiotensin II but not bradykinin

Ventilator-induced lung injury is characterised by inflammation and apoptosis, but the underlying mechanisms are poorly understood. The present study proposed a role for angiotensin-converting enzyme (ACE) via angiotensin II (Ang II) and/or bradykinin in acute lung injury. The authors assessed whether ACE and, if so, Ang II and/or bradykinin are implicated in inflammation and apoptosis by mechanical ventilation. Rats were ventilated for 4 h with low- or high-pressure amplitudes in the absence or presence of the ACE inhibitor captopril. Nonventilated animals served as controls. ACE activity, Ang II and bradykinin levels, as well as inflammatory parameters (total protein, macrophage inflammatory protein-2 and interleukin-6) were determined. Apoptosis was assessed by the number of activated caspase-3 and TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick-end labelling)-positive cells. Bronchoalveolar lavage fluid ACE activity, levels of total protein, inflammatory parameters and the number of apoptotic cells were increased in the high-pressure amplitude group as compared with the control group. Blocking ACE activity by captopril attenuated inflammation and apoptosis in the latter group. Similar results were obtained by blocking Ang II receptors, but blocking bradykinin receptors did not attenuate the anti-inflammatory and anti-apoptotic effects of captopril. The current authors conclude that inflammation and apoptosis in ventilator-induced lung injury is, at least in part, due to angiotensin-converting enzyme-mediated angiotensin II production.

Colocalisation of intraplaque C reactive protein, complement, oxidised low density lipoprotein, and macrophages in stable and unstable angina and acute myocardial infarction

BACKGROUND

C reactive protein (CRP), an important serum marker of atherosclerotic vascular disease, has recently been reported to be active inside human atherosclerotic plaques.

AIMS

To investigate the simultaneous presence of macrophages, CRP, membrane attack complex C5b-9 (MAC), and oxidised low density lipoprotein (oxLDL) in atherectomy specimens from patients with different coronary syndromes.

METHODS

In total, 54 patients with stable angina (SA; n = 21), unstable angina (UA; n = 15), and myocardial infarction (MI; n = 18) underwent directional coronary atherectomy for coronary lesions. Cryostat sections of atherosclerotic plaques were immunohistochemically stained with monoclonal antibodies: anti-CD68 (macrophages), anti-5G4 (CRP), aE11 (MAC), and 12E7 (oxLDL). Immunopositive areas were evaluated in relation to fibrous and neointima tissues, atheroma, and media. Quantitative analysis was performed using image cytometry with systematic random sampling (percentage immunopositive/total tissue area).

RESULTS

Macrophages, CRP, MAC, and oxLDL were simultaneously present in a higher proportion of fibrous tissue and atheroma of atherectomy specimens from patients with UA and MI compared with SA (p<0.05). Quantitative analysis showed significantly higher mean percentages of macrophages in plaques from patients with MI (44%) than UA (30%; p<0.01) and SA (20%; p<0.001). Significantly higher mean percentages of CRP were also seen in MI (25%) and UA (25%) compared with SA (12%; p<0.05).

CONCLUSIONS

The presence of CRP, complement, and oxLDL in a high proportion of plaque tissue from patients with unstable coronary artery disease implies that these surrogate markers have important proinflammatory effects inside atherosclerotic plaques. This may increase vulnerability to plaque rupture and thrombosis, with subsequent clinical sequelae.

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.

Sudden unexpected death in young adults. Discrepancies between initiation of acute plaque complications and the onset of acute coronary death

AIMS

To study the time relationship between the onset of coronary thrombosis and sudden unexpected cardiac death in young adults.

METHODS AND RESULTS

Hearts of 11 young adults (< or = 35 years), who had died within 1h after onset of symptoms and presented with a coronary thrombotic occlusion were studied retrospectively for the type of underlying plaque complication and the time of onset of thrombus formation. In all cases tissue blocks were taken from the occluded artery and sectioned for microscopic evaluation. Of 11 culprit lesions 10 were mainly fibrocellular; only one was lipid-rich. Inflammatory cells were found in all plaques, albeit in highly variable amounts. Plaque erosion had occurred in nine; deep ruptures in two. Analysis of the plaque-related occluding thrombus revealed fresh thrombosis in three (both ruptured plaques and one erosion); the other eight, however, showed occlusion with different histological stages of organization of thrombus.

CONCLUSIONS

Despite strict inclusion criteria for sudden death in these young adults, the majority must have had plaque instability for some time, since thrombus formation had occurred at least days to weeks prior to the acute event.

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.

Adventitial infiltrates associated with advanced atherosclerotic plaques: structural organization suggests generation of local humoral immune responses

Advanced atherosclerotic lesions often contain adventitial lymphoid infiltrates, which occasionally contain nodular aggregates resembling lymphoid follicles. The structural organization suggests that local maturation of B cells may take place at these sites, as described for the mucosa-associated lymphoid tissue (MALT). This concept was evaluated by studying the micro-anatomy and cellular composition of adventitial infiltrates associated with advanced atherosclerosis of the aorta. Sections of 22 atherosclerotic aortas were stained immunohistochemically for cellular markers characteristic for lymphoid follicles, such as HECA-452-positive endothelial cells, CD20-positive B cells, CD21-positive follicular dendritic cells, and CD68-positive macrophages. Ki-67 was used as a proliferation marker. The TUNEL technique was used to study the presence of apoptotic cells. Specimens containing MALT served as comparison and positive controls. Seven of the 22 atherosclerotic aortas contained adventitial infiltrates resembling lymphoid follicles. The organized nodular centres were composed of CD45RA+ B cells, follicular dendritic cells (CD21+), a few T lymphocytes (CD3+) and 'tingible body' macrophages (CD68+). A large number of cells were Ki-67-positive; apoptotic bodies were numerous and phagocytosed by macrophages. The parafollicular area contained CD45RO-positive T cells and HECA-452-positive vessels. Vessels elsewhere were always HECA-452-negative. Specimens with MALT showed similar features. This study reveals a close resemblance between adventitial lymphoid infiltrates in advanced atherosclerotic aortic disease and MALT, suggesting local generation of a humoral immune response, likely to be initiated by antigens released during a process of long-standing tissue injury and inflammation as part of advanced atherosclerosis.

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.

The animal research kit (ARK) can be used in a multistep double staining method for human tissue specimens

The newly developed Animal Research Kit (ARK) offers a simple and economic way of biotinylating mouse primary antibodies for background-free immunostaining of mouse and rat tissue specimens. Biotinylation involves the use of a biotinylated goat anti-mouse immunoglobulin Fab fragment mixed with a mouse primary antibody and subsequent blocking with normal mouse immunoglobulin. Because a reliable immunoenzyme double staining procedure on human tissue specimens with two unlabeled mouse primary antibodies of identical subclass is almost impossible, we have tested the performance of ARK biotinylation of one primary antibody in a multistep indirect/direct staining protocol. The multistep double staining procedure involved the subsequent application of an unlabeled mouse monoclonal antibody (MAb) 1 detected with an enzyme-labeled EnVision reagent, normal mouse serum for blocking, followed by a biotinylated mouse MAb 2 and enzyme-labeled streptavidin. Alkaline phosphatase and peroxidase enzymatic activities were developed last. Double staining results obtained with an ARK biotinylated reagent were compared with a truly biotinylated reagent using N-hydroxy succinimide-biotin for conjugation. It appeared that both biotinylation procedures revealed identical double staining results. Although a limited number of antibody combinations have been tested, it is clear that this double staining procedure will be successful for many antibody pairs.

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.

Double staining of intracellular cytokine proteins and T-lymphocyte subsets. Evaluation of the method in blood and bronchoalveolar lavage fluid

An immunocytochemical staining method has been developed for simultaneous staining of both cell surface markers (CD4 and CD8) and intracellular cytokine proteins IFN-gamma, IL-4 and IL-5. Cell surface molecules were visualized with alkaline phosphatase, which was developed by Fast Blue BB. Intracellular cytokine proteins were detected by amino-ethyl carbazole. We applied this technique to T cells from T-cell lines and T-cell clones, peripheral blood mononuclear cells and broncho-alveolar lavage fluid cells. Cells were used either unstimulated or stimulated for 4 h with 1 ng/ml PMA and 1 microg/ml ionomycin, which proved to be an optimal stimulus taking cytokine staining, cell recovery and cell viability into account. We studied peripheral blood mononuclear cells from healthy subjects and found that without in vitro stimulation on average 0.4% of the cells were IFN-gamma positive cells. In unstimulated broncho-alveolar lavage fluid cells of the 2 allergic asthmatic subjects studied so far we found higher numbers of cytokine-positive cells (up to 22% of the lymphocytes being IL-4+ cells). By in vitro stimulation, the numbers of cytokine-positive peripheral blood mononuclear cells from the healthy subjects were increased to maximally 5% IFN-gamma+ cells. In stimulated lavage fluid cells from allergic asthmatic subjects maximally 34% of the lymphocytes became IFN-gamma+. We conclude that this method allows detection of intracellular cytokine proteins in both CD4+ and CD8+ T cells without the need for stimulating the cells in vitro. In vitro stimulation may change the cytokine profile detected.

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)

Distribution of inflammatory cells in atherosclerotic plaques relates to the direction of flow

BACKGROUND

The distribution of macrophages and smooth muscle cells (SMCs) within atherosclerotic plaques is highly variable. This is clinically relevant because these cell types have opposite effects on the stability of atherosclerotic plaques. The present study was designed to investigate whether local variations in arterial flow over the plaque surface could relate to differences in the distribution of SMCs and macrophages in plaques.

METHODS AND RESULTS

Thirty-three entire carotid plaques were collected at autopsy and marked at their proximal (in relation to the direction of the blood flow) ends, and the cell composition of upstream parts (where high flow and high shear prevail) was compared with that of downstream parts (low flow and low shear stress). Seventy percent of plaques showed more SMCs in their downstream part, and 67% of plaques contained more macrophages in the upstream part. Immunostained macrophage areas were larger in upstream parts (P=0. 011). Immunostained SMC areas were larger in downstream parts (P=0. 031). Rupture sites of 6 of 9 ruptured plaques were in the upstream part.

CONCLUSIONS

Significant differences in cell composition between upstream and downstream parts of plaques indicate a role for arterial flow in the distribution of different cell types. The low-flow/low-shear downstream areas of plaques contain significantly more SMCs, which could provide the background for slowly progressive growth at distal ends of plaques. The significantly high number of macrophages in the upstream areas suggests a relationship between high flow/high shear and plaque instability.

Mast cell infiltration in acute coronary syndromes: implications for plaque rupture

OBJECTIVES

To define the role of mast cells in plaque destabilization.

BACKGROUND

Inflammation is an essential feature of human coronary plaques. Macrophages and T lymphocytes are considered to contribute to destabilization of the plaques. The role of mast cells in this setting is less well studied. We therefore counted the mast cells in coronary atherectomy specimens from patients with chronic stable angina, unstable angina and severe unstable angina.

METHODS

Patients studied had chronic stable angina (group 1, n=11), "stabilized" unstable angina (group 2; Braunwald's class I and II, n=11) and "refractory" unstable angina (group 3; Braunwald's class III, n=7). Samples of culprit lesions (n=29) were obtained by directional atherectomy, snap-frozen and analyzed immunohistochemically. The numbers of mast cells and T lymphocytes per square millimeter squared were counted and the areas containing macrophages and smooth muscle cells were measured by computed planimetry.

RESULTS

We found that the numbers of mast cells and T lymphocytes increased from group 1 through groups 2 to 3. Specimens from group 3 also contained the largest numbers of tumor necrosis factor alpha (TNF-alpha)-positive mast cells and of matrix metalloproteinase (MMP)-9 (92 kD gelatinase)-positive macrophages.

CONCLUSIONS

Unstable coronary syndromes are associated with increased numbers of mast cells in culprit lesions. Activated mast cells secrete neutral proteases capable of degrading the extracellular matrix and TNF-alpha, capable of stimulating macrophages to synthesize MMP-9. Our observations suggest that mast cells, in addition to macrophages, contribute to matrix degradation and, hence, to progression of coronary syndromes.

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.

Costimulatory molecules in human atherosclerotic plaques: an indication of antigen specific T lymphocyte activation

Atherosclerotic plaques contain inflammation, composed largely of macrophages and lymphocytes. A proportion of lymphocytes shows signs of activation, but the question arises whether they are activated in an antigen specific way. The expression of costimulatory molecules-receptors that provide accessory signals during antigen-specific activation is a prerequisite for such a condition. This aspect of inflammation in atherosclerotic lesions has not been investigated. Human arterial segments with diffuse intimal thickening, fatty streaks and atherosclerotic plaques were studied with immuno-single and double staining methods. Macrophages and T lymphocytes were stained with CD68 and CD3, respectively, and pan-B cell markers CD19 and CD22 were also used. Costimulatory molecules B7-1 and B7-2, together with their common ligand CD28, and CD27 with its ligand CD70, were stained with specific monoclonal antibodies. The results show that most T lymphocytes were CD27 positive and that only a subpopulation of these (5-15%) was positive also for B7-1, CD28 and CD70. Macrophages expressed B7-1, B7-2, CD28 and CD70, while macrophages positive for CD28 and CD70 have not been reported yet. The expression of costimulatory molecules was most pronounced in the superficial layers at the fibrous cap, but decreased towards the lipid core. This study shows, therefore, that atherosclerotic plaques provide costimulatory signals generally accepted as a prerequisite for adequate T cell stimulation. In addition, this study reveals that only approximately 5-15% of the lymphocytes appears actively involved in the inflammatory reaction.

C-type natriuretic peptide in human coronary atherosclerotic lesions

BACKGROUND

C-type natriuretic peptide (CNP) belongs to the natriuretic peptide family and is considered to have regulatory effects on vascular tone and smooth muscle growth. Since these features play a role in atherogenesis, the presence of CNP at such sites was studied.

METHODS AND RESULTS

Thirty-three coronary artery segments were harvested at autopsy: 10 normal, with diffuse intimal thickening, and 23 atherosclerotic lesions. Samples were snap-frozen and processed for immunohistochemical staining. For the identification of CNP, a mouse monoclonal antibody (KY-CNP-1) was used. 1A4, EBM-11 (CD68), and von Willebrand factor antibodies were used to stain smooth muscle cells, macrophages, and endothelial cells, respectively. CNP is present in several cell types. Normal arterial segments show CNP-positive endothelial cells. Hypercellular atherosclerotic lesions show distinct CNP positivity of smooth muscle cells and macrophages but a decrease in positivity of endothelial cells. Advanced atherosclerotic lesions contain CNP-positive macrophages, but the smooth muscle cells within the fibrous cap and the surface endothelial cells are almost all CNP-negative.

CONCLUSIONS

These observations suggest that CNP has functional significance in atherogenesis.

Solar-simulated ultraviolet irradiation induces selective influx of CD4+ T lymphocytes in normal human skin

The proportion and composition of the human cutaneous CD3+ T lymphocyte population was determined in situ following a single exposure to physiological, erythema-inducing doses of simulated solar radiation, mainly consisting of UV radiation. Biopsies were taken 1, 2 and 7 days after local irradiation of normal volunteers with 1, 2 and 4 MED by a xenonarc lamp and immunohistochemistry was performed on cryostat sections. Ultraviolet radiation caused an initial decrease of intraepidermal CD3+ T-cell numbers or even could lead to T-cell depletion 24 and 48 h postirradiation, and this was followed by an infiltration of T cells in the epidermis as determined 1 week after UV exposure. The number of dermal CD3+ T cells was increased 24 h after irradiation, reached a maximum at 48 h and subsequently declined at day 7, though remained significantly higher than the unirradiated control. Double staining demonstrated that the CD3+ T cells, which immigrated into the (epi)dermis upon UV exposure, coexpressed CD4 but not CD8. Therefore the CD4/CD8 ratio in skin was markedly increased during the first week upon UV exposure. Our time course study shows that UV radiation affects the T-cell population within human skin by depleting the majority of epidermal T cells and initiating a selective influx of CD4+ T cells.

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.

Expression of platelet derived growth factor B chain and beta receptor in human coronary arteries after percutaneous transluminal coronary angioplasty: an immunohistochemical study

OBJECTIVE

To evaluate whether expression of platelet derived growth factor B (PDGF-B) protein is associated with expression of its receptor protein in human coronary arteries after angioplasty and to identify cells involved.

BACKGROUND

PDGF is considered an important growth factor in the repair process of the vessel wall after angioplasty. In situ hybridisation has revealed expression of PDGF-A and -B chain messenger ribonucleic acid (mRNA) in human coronary arteries at sites of postangioplasty injury.

METHODS

Target and non-target sites of eight coronary arteries were studied immunohistochemically for PDGF-B and PDGF-beta receptor proteins in relation to macrophages, T lymphocytes, smooth muscle cells, and HLA-DR positive cells.

RESULTS

The PDGF-B and PDGF-beta receptor proteins were expressed in areas with distinct repair, containing alpha actin negative spindle cells, macrophages and, at later stages, alpha actin positive smooth muscle cells as well. When the neointima was composed mainly of alpha actin smooth muscle cells, PDGF-B expression was rare and PDGF-beta receptor expression was negative.

CONCLUSIONS

There is expression of PDGF-B and PDGF-beta receptor proteins at sites of postangioplasty repair in human coronary arteries. The associated cells are mainly macrophages and alpha actin negative spindle cells; the latter may be dedifferentiated smooth muscle cells. A link between PDGF expression and the postangioplasty time interval suggests a relation with cell differentiation as part of the maturation of the repair tissue. Mutual expression of both the growth factor and its receptor protein strongly suggests that in humans a PDGF mediated repair process occurs, with involvement of smooth muscle cells and macrophages.

Fibrous and lipid-rich atherosclerotic plaques are part of interchangeable morphologies related to inflammation: a concept

BACKGROUND

The morphology of advanced atherosclerotic plaques varies from solid fibrous lesions, considered essentially stable, to lipid-rich lesions with large atheromas prone to rupture. The latter situation is often associated with large amounts of foam cells. An in-situ inflammatory process influenced by activated T cells and macrophages can be demonstrated in atherosclerotic plaques; however, the relationship between the inflammation and clinically relevant morphological types has not yet been investigated. A study of plaque morphology, focusing on the relationship between inflammatory cells, smooth muscle cells, and the collagen matrix, on the one hand, and the 'classic' plaque morphologies (fibrous versus lipid-rich), on the other, may shed light on this concept.

MATERIALS AND METHODS

Immunocytochemical techniques were used in combination with connective tissue stains to study the topographic distribution of smooth muscle cells, collagen, and inflammatory cells in different morphologic types of advanced atherosclerotic plaques in aortic and carotid arteries obtained at autopsy.

RESULTS

Lesions with an inconspicuous lipid core were defined as fibrous (n = 7). They contained a dense collagen matrix and the dominant cell type was the smooth muscle cell; lymphocytes and macrophages were sparse. Lesions with a large lipid core were defined as lipid-rich (n = 13). They contained a thin fibrous cap with a loosely arranged matrix dominated by macrophages and T cells. Most lesions (n = 21), however, had a morphology that ranged between fibrous and lipid-rich. The cellular components consisted either of mixed smooth muscle and inflammatory cells or of local distinct zones of inflammatory cells within a fibrous cap otherwise dominated by smooth muscle cells and collagen. Thus, zones of severe inflammation were invariably associated with dissolution of the connective tissue matrix and abundant human leukocyte antigen-DR expression on inflammatory cells and the remaining smooth muscle cells.

CONCLUSION

Our observations support the concept that inflammatory mechanisms modulate plaque morphology, by promoting either synthesis or lysis of the fibrous cap. Our hypothesis is that fibrous and atheromatous lesions are essentially interchangeable.

The neonatal heart has a relatively high content of total collagen and type I collagen, a condition that may explain the less compliant state

OBJECTIVES

This study evaluated the extent of the collagen network in neonatal heart muscle and whether the type I/type III collagen ratio is the same as in the adult heart.

BACKGROUND

The functional integrity and the stress-strain relation of heart muscle depends largely on the extracellular collagen matrix. The question therefore arises whether the altered compliance of the neonatal heart could relate to the developmental state of collagen and, in particular, the distribution of types I and III collagen. Type I collagen mainly provides rigidity and type III collagen elasticity.

METHODS

Specimens from the left lateral wall of the left ventricle of human hearts (immature to full term, n = 23; 3 weeks to 12 years, n = 17) were used to determine the total collagen amount, using the hydroxyproline assay. Similar left ventricular specimens of human hearts (fetal to mature, n = 20; 2 months to 1.5 years, n = 6) were fixed in formalin, paraffin embedded and stained with Sirius red F3BA for total collagen. The ratio of total collagen to total protein was quantified spectrophotometrically. Frozen sections of left ventricular myocardium (immature to mature, n = 17; 4 months to 12 years, n = 10) were stained with antibodies raised against types I and III collagen. Antibody titration was done on human leiomyoma tissue with a known type I/type III collagen ratio. The endomysial collagen types were quantified using a spectrophotometer and expressed as a ratio. Adult human myocardium (n = 10) was used as reference.

RESULTS

The study showed that the total amount of collagen increases with age. However, the ratio of total collagen to total protein and the ratio of type I to type III collagen were very high in hearts of the very young. During development, a gradual decrease occurred, with the total collagen/total protein ratio reaching normal levels at approximately 5 months after birth and the type I/type III collagen ratio stabilizing at a much later age.

CONCLUSIONS

These findings suggest that the relative high content of collagen, related to the myocytes, and the high ratio of type I to type III collagen provide the substrate for a rigid, less compliant heart in neonates.

Quantification in immunohistochemistry: the measurement of the ratios of collagen types I and II

Quantitative techniques in immunohistochemistry are needed, but they are rarely applied because of doubtful reproducibility. We have developed a method for the detection of collagen types I and III in situ. The method applied was a two-step immuno-alkaline phosphatase technique with visualization of the end-product with Fast Red. The staining intensity was measured with a microdensitometer and the results expressed as ratios. The method yielded results that were unaffected by variations in tissue section thickness but which were proportionally related to time and antigen concentrations. Leiomyoma tissue, with a ratio of collagen types I and III of approximately 1.0, was used to establish the appropriate dilutions of the antibodies, thus assuring identical optical densities. By having the leiomyoma tissue sections incubated together with the heart tissue specimens, leiomyoma tissue was also helpful in correcting deviations from the 1.0 ratio. Accurate measurements of collagen type I/III ratios in normal human heart specimens were obtained with the present quantitative immunohistochemical technique.

Double epi-illumination microscopy with separate visualization of two antigens: a combination of epi-polarization for immunogold-silver staining and epi-fluorescence for alkaline phosphatase staining

We present a method for an epi-illumination immunohistochemical double staining approach. The method combines the use of an immuno-alkaline phosphatase technique and the immunogold-silver technique, visualized with epifluorescence and epi-polarization illumination, respectively. Out of six tested alkaline phosphatase activity-revealing methods, only the reaction product obtained with the Becton Dickinson CAS Red kit showed an intense red fluorescence with a rhodamine filter set and no signal with epi-polarization illumination. The silver precipitate did not exhibit any signal with the rhodamine filter set. This allows separate observation and photographic recording of two antigens in one tissue section, an objective that cannot be achieved with conventional immunoenzyme double staining methods. The double epi-illumination approach presented is compatible with different immunoenzyme double staining protocols.

Reappraisal of in situ immunophenotypic analysis of psoriasis skin: interaction of activated HLA-DR+ immunocompetent cells and endothelial cells is a major feature of psoriatic lesions

Psoriasis is an inflammatory skin disease of unknown aetiology. Many observations indicate that T cells play an important role in the pathogenesis of the disease. Upregulation of MHC class-II molecules on immunocompetent cells, endothelial cells and keratinocytes on lesional psoriatic skin has been regarded as a hallmark of the disease. However, there is some controversy in the literature regarding the cell types expressing class-II molecules and there is limited information about the presence of immune cells other than T cells and antigen presenting cells in the cellular infiltrates of psoriatic skin. We therefore reinvestigated the subject using immunocytochemical single and multiple staining techniques. In agreement with earlier reports, our studies showed that the cellular infiltrates in lesional skin consist largely of HLA-DR+/IL-2R+ T cells, HLA-DR+/CD1a+ Langerhans cells, and HLA-DR+/CD68+ macrophages. We found increased HLA-DR expression mostly on immuno-competent cells and endothelial cells, but no prominent HLA-DR expression on keratinocytes in lesional psoriatic skin. Upregulation of HLA-DR on endothelial cells and in mononuclear infiltrates was also evident in the non-lesional skin of psoriatic patients as compared with normal controls. B cells and natural killer cells were also found in the cellular infiltrates in lesional psoriatic skin. In spite of the presence of a large amount of activated T cells in the epidermis, we found that HLA-DR expression on keratinocytes was not a major feature of psoriatic skin.

Site of intimal rupture or erosion of thrombosed coronary atherosclerotic plaques is characterized by an inflammatory process irrespective of the dominant plaque morphology

BACKGROUND

The study was designed to verify the concept of plaques "at risk" and whether inflammation could play a role in plaque rupture and thrombosis.

METHODS AND RESULTS

In 20 patients who had died of acute myocardial infarction, the thrombosed coronary artery was identified and the site of plaque rupture was traced in serial sections. The cellular characteristics of the fibrous cap at the immediate site of rupture were analyzed and compared with the adjacent cap tissue by use of monoclonal antibodies reactive with macrophages, T lymphocytes, and smooth muscle cells. A deep intimal rupture, extending into the lipid core, was encountered in 12 plaques, whereas 8 had superficial erosions only. Ten atherosclerotic plaques had a distinctly attenuated fibrous cap covering a large atheroma, 7 showed a thick fibrocellular cap overlying a lipid pool, and 3 showed a fibrocellular lesion without a clear lipid core. Macrophages, and to a lesser extent T lymphocytes, were the dominant cells at the immediate site of either rupture or superficial erosion in each instance. These sites, moreover, were always characterized by abundant expression of HLA-DR antigens on both inflammatory cells and adjacent smooth muscle cells, suggesting an active inflammatory reaction. In terms of overall cellular composition of the ruptured plaques, the dominant cell types were macrophages and T cells in 11, smooth muscle cells in 3, and mixtures of both in 6.

CONCLUSIONS

The underlying atherosclerotic plaque morphology in complicated coronary artery lesions causing acute myocardial infarction is heterogeneous with respect to both plaque architecture and cellular composition. However, the immediate site of plaque rupture or erosion is always marked by an inflammatory process. This suggests that inflammation plays a role in destabilizing the fibrous cap tissue and, thus, in enhancing the risk of coronary thrombosis.

Practical suggestions for successful immunoenzyme double-staining experiments

Many methodologies exist to perform an immunoenzyme double staining. Hence, the practical problem arises as to which of these methods is optimal for one's own experimental design. A process of selection is described which is derived from our own practical experience. First, a general strategy is outlined for the handling of tissue sections to be used for multiple staining methods. Secondly, the selection of an appropriate immunoenzyme double-staining concept is made using a flow chart. Thereafter we give criteria for the definitive selection of an immunoenzyme double-staining protocol based on the characteristics of the tissue or cell type under study. Particular attention is given to the selection of appropriate detection systems, applying enzymes or gold particles, and good contrasting colour combinations. The problems of visualizing co-localization using immunoenzyme double staining are dealt with, and suggestions are made to adapt the method, if necessary, in order to optimize it.

Atherosclerotic lesions in humans. In situ immunophenotypic analysis suggesting an immune mediated response

The immunophenotypical features of the cellular infiltrates in different types of human atherosclerotic lesions, including diffuse intimal thickening as a potential but controversial precursor lesion, have been examined using monoclonal antibodies. Special emphasis is put on monocytes/macrophages, lymphocytes, and their possible interactions. Immuno-double staining techniques have been employed to study these aspects. T lymphocytes and macrophages were detected in diffuse intimal thickening, fatty streaks, and atheromatous plaques. In some lesions a predominance of suppressor/cytotoxic lymphocytes was found, whereas in other lesions mixtures of T suppressor/cytotoxic cells and T helper/inducer cells were found in ratios varying from 1:1 to 4:1. A substantial number of T cells and macrophages was considered to be immunoactivated because of the expression of HLA-DR and, to a lesser extent, of I12 receptor molecules. The activation was particularly evident at sites of close cell-to-cell contact between monocytes/macrophages and lymphocytes. These observations suggest that a specific in situ immune mediated hypersensitivity reaction is associated with the development of atherosclerosis.

Use of commercially available monoclonal antibodies for immunoenzyme double staining

An immunoenzyme double-staining method for the simultaneous detection of two cellular epitopes, using commercially available mouse monoclonal antibodies, is described. The method employs a combination of the suppression of endogenous biotin and two successive indirect techniques with a blocking step in between. The first indirect method involves an unlabelled monoclonal antibody followed by an alkaline phosphatase-conjugated goat anti-mouse immunoglobulin. After a blocking step with normal mouse serum, the second indirect method is applied using a biotinylated monoclonal antibody followed by the visualization of this antibody by avidin-biotinylated peroxidase complex (ABC) or rabbit anti-biotin and peroxidase-conjugated swine anti-rabbit immunoglobulin in successive steps. Using these methods in combination with the introduction of dioctyl sodium sulphosuccinate and tetramethylbenzidine as chromogens for peroxidase activity, two cellular epitopes could be distinguished clearly in tissue sections by the green- and violet-stained peroxidase and alkaline phosphatase activities, respectively. The expression of two epitopes on the same cellular constituent is outlined by the coappearance of both enzyme activities as a bluish-purple colour. This method allows for the simultaneous identification, localization and enumeration of two cellular epitopes. These can serve as parameters for a number of pathological processes.

Ultrastructural localization of steroid sulphatase in cultured human fibroblasts by immunocytochemistry: a comparative study with lysosomal enzymes and the mannose 6-phosphate receptor

Immunocytochemistry was used to study the subcellular localization of steroid sulphatase in cultured human fibroblasts. Ultra-thin cryosections were incubated with antibodies raised against steroid sulphatase purified from human placenta and immune complexes were visualized with gold probes as electron dense markers. Steroid sulphatase was found in rough endoplasmic reticulum, Golgi cisternae and in the trans-Golgi reticulum, where it co-distributes with lysosomal enzymes and the mannose 6-phosphate receptor. The enzyme was not detected in lysosomes. Steroid sulphatase was also found at the plasma membrane and in the endocytic pathway (i.e. coated pits, endosomes and multivesicular endosomes). These may be the sites where sulphated oestrogen precursors are hydrolysed. Also here, it co-localizes with lysosomal enzymes and the mannose 6-phosphate receptor. It is concluded that microsomal steroid sulphatase and lysosomal enzymes share several cellular compartments.

An immunoenzyme triple-staining method using both polyclonal and monoclonal antibodies from the same species. Application of combined direct, indirect, and avidin-biotin complex (ABC) technique

For immunohistological analysis, simultaneous detection of multiple cellular epitopes, as compared to single staining of serial sections, is sometimes needed. Therefore, immunoenzyme triple-staining protocols were tested with polyclonal and monoclonal antibodies on tissue sections and cytospin preparations. Various immunoconjugates were used in different combinations of methods, of which not all proved to be suitable. Of the tested protocols, one yielded superior results for both monoclonal and polyclonal antibodies, with optimal preservation of their original avidity. The method consists of a combination of indirect, direct, and avidin-biotin complex technique. The three antigens can be distinguished clearly and selectively by the reaction products of the enzyme activities of beta-galactosidase (green), alkaline phosphatase (blue), and horseradish peroxidase (red).

The skin immune system (SIS): distribution and immunophenotype of lymphocyte subpopulations in normal human skin

The complexity of immune response-associated cells present in normal human skin was recently redefined as the skin immune system (SIS). In the present study, the exact immunophenotypes of lymphocyte subpopulations with their localizations in normal human skin were determined quantitatively. B cells were not found to be present in normal human skin. Lymphocytes were always of T-cell type, and 90% of these T cells were clustered in 1-3 rows around postcapillary venules of the papillary vascular plexus or adjacent to cutaneous appendages. In such perivascular localizations, they were found to differ from their circulating counterparts in three ways. First, skin perivascular cells were found to be approximately evenly distributed over CD4+ inducer and CD8+ suppressor-cytotoxic T-cell subsets (mean CD4/CD8 ratio: papillary layer 0.96, reticular layer 0.99). Second, within the category of CD4+ inducer T cells, most were phenotyped as CD4+, 4B4+ helper inducer T lymphocytes, whereas CD4+, 2H4+ suppressor inducer T lymphocytes were found to be relatively rare (less than 5%). Third, the majority of skin perivascular T cells were activated as they expressed HLA-DR and interleukin 2 receptors. Intraepidermal, directly subepidermal, and other ("free") lymphocytes were mostly of the CD8+ suppressor-cytotoxic T-cell subset but accounted for less than 10% of the total number of lymphocytes. Intraepidermally localized T cells accounted for less than 2% of the total number of lymphocytes present in normal skin. Our results indicate that preferential perivascular localization of activated T lymphocytes is the characteristic of normal human skin. This might be a reflection of continuous antigen recognition upon endothelial cell presentation and/or continuous T cell-mediated endothelial cell activation thereby inducing enhanced antigen clearing by the skin's endothelium.

Human placental steroid sulphatase--purification and monospecific antibody production in rabbits

Human steroid sulphatase was purified 43-fold from placental microsomes using a four step procedure: solubilization with Miranol H2M, Bio-Gel A 1.5 m chromatography, column chromatofocusing and Sephadex G-75 chromatography. The purified enzyme that appeared electrophoretically homogeneous was used to immunize rabbits. Protein blotting demonstrated that the resulting antiserum mainly reacted with a polypeptide of 63 000 dalton, which is about the size of placental steroid sulphatase. The antiserum was freed from minor impurities by absorbing it to Sepharose 4B with immobilized antigens prepared from a steroid sulphatase deficient placenta.

The nature of placental steroid sulphatase deficiency in man

Human placental steroid sulphatase was partially purified from microsome suspensions of control and steroid sulphatase deficient placentae. After polyacrylamidegel electrophoresis, staining for protein and enzymatic activity revealed that steroid sulphatase from control placenta migrates at Rf = 0.44. In steroid sulphatase deficient microsomes no protein band and only a very faint sulphatase activity band could be detected at Rf = 0.44. Immunoelectrophoresis employing antisera raised against both steroid sulphatase preparations, only gave a protein precipitation line with sulphatase activity when using control placenta microsomes and the antiserum against steroid sulphatase from control placenta. All other placental microsomes-antisera combinations appeared to be negative. Our results strongly suggest that the nature of X-linked steroid sulphatase deficiency is a decreased amount of steroid sulphatase protein.

Biochemical investigation to the reliability of the histochemical demonstration of microsomal arylsulphatase activity in cryostat sections

Polyacrylamide gel-electrophoresis was performed with an extract from cultivated skin fibroblasts. Arylsulphatase activity is measured and visualised using the biochemical substrate dehydroepiandrosterone sulphate and the histochemical substrate 6-bromo-2-naphthyl sulphate respectively. The histochemical substrate was hydrolysed at Rf = 0.49 and 0.58 while the biochemical substrate was hydrolysed only at 0.49. We conclude that two different microsomal arylsulphatases exist: a sulphatase able to hydrolyse steroid sulphatases (Rf = 0.49) and one unable to hydrolyse steroid sulphatases (RF = 0.58). In consequence if is recommended to carry out an electrophoresis experiment after the histochemical investigation, in order to discriminate between these two types of sulphatase.

Combined histochemical and biochemical investigation to the reliability of the demonstration of arylsulphatase activity in cryostat sections

The reliability of the enzyme histochemical technique, for the demonstration of arylsulphatase activity, using 6-bromo-2-naphthylsulphate as a substrate, is biochemically tested by using partly purified lysosome and microsome preparations from fresh human placenta tissue. Microsomes from frozen placenta with an arylsulphatase deficiency and lysosomes from rat liver, are also investigated. For the biochemical test methods, 6-bromo-2-naphthylsulphate and p-nitrocatecholsulphate are used as substrates. Under similar reaction conditions, varying the pH of the incubation medium and adding inhibitors or activators, the histochemical and biochemical reactions are compared. The results of this study show that the enzyme histochemical technique--except for some limitations--is suitable for the demonstration of microsomal arylsulphatase in cryostat sections.