Lipoteichoic acid may affect the pathogenesis of bile duct damage in primary biliary cirrhosis

Aim: Intrahepatic bile ducts are the targets for inflammation in primary biliary cirrhosis (PBC), but their pathogenesis is not known. Gram-positive bacterial DNA was detected recently in gallbladder bile of PBC patients. In the present study, we assessed the possible pathological role of lipoteichoic acid (LTA), the Gram-positive bacterial cell wall component, in PBC.

Methods: Liver samples, obtained from 20 patients with PBC (stage 1–2 with CNSDC: stage 3–4 with loss of bile ducts = 10:10) and from 13 patients with chronic hepatitis due to hepatitis C virus (CH–C) with lymphocytic cholangitis, were subjected to immunohistochemical staining with polyclonal rabbit anti-LTA as the primary antibody. Serum reactivities to LTA were studied by ELISA. After 1 μg of purified LTA was placed in a 96-well microplate as an antigen, an antibody capture assay was carried out using serum samples from PBC (n = 20), CH–C (n = 13) and healthy subjects (n = 11).

Results: LTA was localized around the sites of chronic non-suppurative destructive cholangitis (CNSDC) in the portal area in stage 1–2 PBC but was not detected in the portal area in CH–C. In stage 3–4 PBC, LTA was localized around sites of ductular proliferation at the periphery of portal tracts. IgM class anti-LTA serum titers were significantly higher in PBC than in CH–C. IgA class anti-LTA serum titers were significantly higher in PBC than in healthy subjects.

Conclusions: In the PBC livers, the profile of immunoreactivity to LTA changed markedly as the disease progressed. Sera from PBC showed higher levels of anti-LTA titers than CH–C (IgM) or from healthy subjects (IgA). The LTA-mediated immune system might affect the initiation and/or progression of PBC.     

Characterisation of new monoclonal antibodies reacting with prions from both human and animal brain tissues

Post-mortem diagnosis of transmissible spongiform encephalopathies (prion diseases) is primarily based on the detection of a protease resistant, misfolded disease associated isoform (PrP(Sc)) of the prion protein (PrP(C)) on neuronal cells. These methods depend on antibodies directed against PrP(C) and capable of reacting with PrP(Sc)in situ (immunohistochemistry on nervous tissue sections) or with the unfolded form of the protein (western and paraffin embedded tissue (PET) blotting). Here, high-affinity monoclonal antibodies (mAbs 1.5D7, 1.6F4) were produced against synthetic PrP peptides in wild-type mice and used for western blotting and immunohistochemistry to detect several types of human prion-disease associated PrP(Sc), including sporadic Creutzfeldt-Jakob Disease (CJD) (subtypes MM1 and VV2), familial CJD and Gerstmann-Str?ussler-Scheinker (GSS) disease PrP(Sc) as well as PrP(Sc) of bovine spongiform encephalopathy (bovine brain), scrapie (ovine brain) and experimental scrapie in hamster and in mice. The antibodies were also used for PET-blotting in which PrP(Sc) blotted from brain tissue sections onto a nitrocellulose membrane is visualized with antibodies after protease and denaturant treatment allowing the detection of protease resistant PrP forms (PrP(RES)) in situ. Monoclonal antibodies 1.5D7 and 1.6F4 were raised against the reported epitope (PrP153-165) of the commercial antibody 6H4. While 1.5D7 and 1.6F4 were completely inhibitable by PrP153-165, 6H4 was not, indicating that the specificity of 6H4 is not defined completely by PrP153-165. The two antibodies performed similarly to 6H4 in western blotting with human samples, but showed less reactivity and enhanced background staining with animal samples in this method. In immunohistochemistry 1.5D7 and 1.6F4 performed better than 6H4 suggesting that the binding affinity of 1.5D7 and 1.6F4 with native (aggregated) PrP(Sc)in situ was higher than that of 6H4. On the other hand in PET-blotting, 6H4 reached the same level of reactivity as 1.5D7 and 1.6F4. This shows that 6H4 needs denatured PrP(RES) to reach maximal reactivity, confirming earlier results. As an exception, human PrP(RES) still reacted relatively poorly with 6H4 in PET-blotting, while 1.5D7 and 1.6F4 reacted well with PrP(RES) from most human CJD types. Taken together this implies that the binding epitope of 1.5D7 and 1.6F4 is accessible in the aggregates of undenatured PrP(Sc) (IHC) while the binding site of 6H4 is at least partly inaccessible. In techniques incorporating a denaturing and/or disaggregating step 6H4 showed good binding indicating increased accessibility of the binding site. An exception to this is human samples in PET-blotting suggesting that huPrP(RES) might not be as easily unfolded by denaturation as BSE and scrapie PrP(RES). Also of interest was the ability of 1.5D7 and 1.6F4 to discriminate between two allelic variants of PrP CJD(Sc) (VV vs. MM) in immunohistochemistry as opposed to the normally used antibody 3F4.     

Periductal interleukin-17 production in association with biliary innate immunity contributes to the pathogenesis of cholangiopathy in primary biliary cirrhosis

An innate immune response to bacterial components is speculated to be involved in the pathogenesis of primary biliary cirrhosis (PBC). Recently, CD4-positive T helper type 17 (Th17) cells, characterized by the secretion of interleukin (IL)-17, have been implicated in the pathogenesis of autoimmune diseases. Human Th17 cells are generated from Th0 cells by IL-6 and IL-1β and maintained by IL-23. In this study, the role of IL-17 in PBC and its association with biliary innate immunity were examined. Using cultured human biliary epithelial cells (BECs), the expression of Th17-related cytokines and chemokines and changes therein on treatment with pathogen-associated molecular patterns (PAMPs) and IL-17 were examined. Immunohistochemistry for IL-17 and Th17-related cytokines was performed using tissue samples of human liver. Consequently, the expression of IL-6, IL-1β, IL-23p19 and IL-23/IL-12p40 mRNAs, and their up-regulation by PAMPs, were found in BECs. Moreover, BECs possessed IL-17-receptors and stimulation with IL-17 induced production of IL-6, IL-1β, IL-23p19 and chemokines. Several IL-17-positive cells had infiltrated damaged bile ducts and the expression of IL-6 and IL-1β was enhanced in the bile ducts of PBC patients. In conclusion, IL-17-positive cells are associated with the chronic inflammation of bile ducts in PBC which is associated causally with the biliary innate immune responses to PAMPs.     

Interleukin‐32 production associated with biliary innate immunity and proinflammatory cytokines contributes to the pathogenesis of cholangitis in biliary atresia

Biliary atresia (BA) is thought to be associated with infections by viruses such as Reoviridae and is characterized histologically by fibrosclerosing cholangitis with proinflammatory cytokine‐mediated inflammation. Interleukin (IL)‐32 affects the continuous inflammation by increasing the production of proinflammatory cytokines. In this study, the role of IL‐32 in the cholangitis of BA was examined. Immunohistochemistry for IL‐32 and caspase 1 was performed using 21 samples of extrahepatic bile ducts resected from BA patients. Moreover, using cultured human biliary epithelial cells (BECs), the expression of IL‐32 and its induction on stimulation with a Toll‐like receptor [(TLR)‐3 ligand (poly(I:C)] and proinflammatory cytokines was examined. BECs composing extrahepatic bile ducts showing cholangitis expressed IL‐32 in BA, but not in controls. Caspase 1 was expressed constantly on BECs of both BA and control subjects. Furthermore, poly(I:C) and proinflammatory cytokines [(IL‐1β, interferon (IFN)‐γ and tumour necrosis factor (TNF)‐α] induced IL‐32 expression strongly in cultured BECs, accompanying the constant expression of TLR‐3 and caspase 1. Our results imply that the expression of IL‐32 in BECs was found in the damaged bile ducts of BA and induced by biliary innate immunity via TLR‐3 and proinflammatory cytokines. These findings suggest that IL‐32 is involved initially in the pathogenic mechanisms of cholangitis in BA and also plays an important role in the amplification and continuance of periductal inflammatory reactions. It is therefore tempting to speculate that inhibitors of IL‐32 could be useful for attenuating cholangitis in BA.     

In situ immunological characterization of Langerhans cells with monoclonal antibodies: Comparison with other dendritic cells in skin and lymph nodes

Summary The antigenic properties of epidermal Langerhans cells (LC) were determined and compared with those of non-lymphoid dendritic dermal cells (DDC), interdigitating reticulum cells (IRC), dendritic reticulum cells (DRC), and histiocytic reticulum cells (HRC) by examination of serial and double immunoenzymatic and -fluorescence stained frozen sections of skin and lymph node biopsies.All of these cell types expressed leucocyte common antigen. LC, DDC, and IRC demonstrated similar antigenic phenotypes (HLA-DR⁺, Leu3⁺, OKT6^+/–, anti-C3 receptor^–, R4/23^–, Ig-complex^–, M02^–), whereas the antigenic properties on DRC (HLA-DR^–, Leu3^–, OKT6^–, anti-C3 receptor⁺, R4/23⁺, Ig-complex⁺, M02^–) and HRC (HLA-DR^+/–, Leu3^–, OKT6^–, anti-C3 receptor⁺ R4/23^–, Ig-complex⁺, MO2⁺) were markedly different.These data suggest that LC, DDC, and IRC are closely interrelated cell types, and support the concept that DRC and HRC are unique cell types which do not appear to be related to LC, DDC, or IRC. The lack of labelling of LC with monoclonal anti-C3b receptor antibody, and polyclonal antiserum recognizing C3b, C3bi, and C3d receptors strongly indicate that the EAC-rosetting of LC previously described is not due to the presence of C3 receptors on these cells. Alternatively, LC may express C3 receptor molecules different from those previously identified (C3b, C3bi, and C3d).     

Transdifferentiation into biliary ductular cells of hepatocytes transplanted into the spleen

AIMS: Transplantation of rat hepatocytes into the syngeneic rat spleen results in the appearance of cytokeratin (CK)7 and CK19 positive biliary cells that form ductules. We examined whether hepatocytes are the origin of these biliary ductular cells. METHODS: We transplanted rat dipeptidyl peptidase IV (DPPIV) positive hepatocytes into the liver of retrorsine-treated and partially hepatectomised DPPIV negative rats, which resulted in proliferation of DPPIV positive hepatocytes in the liver. Two months later, hepatocytes were prepared from chimaeric livers of these rats and transplanted into the spleen of DPPIV negative rats. Four weeks later, the expression of DPPIV in CK7 positive ductules in the spleen was examined by immunofluorescent double-staining. RESULTS: In the spleen of DPPIV negative rats transplanted with hepatocytes prepared from the chimaeric livers, DPPIV was found to be expressed in some CK7 positive biliary ductules where only a fraction of cells expressed DPPIV, whereas in the spleen of DPPIV negative rats transplanted with hepatocytes from livers of DPPIV positive rats, DPPIV was expressed in all CK7 positive biliary ductules. CONCLUSION: The present study indicates that hepatocytes transplanted into the spleen could transdifferentiate into biliary cells that aggregate to form ductular structures.     

Characterization of biliary intra-epithelial lymphocytes at different anatomical levels of intrahepatic bile ducts under normal and pathological conditions: numbers of CD4+CD28- intra-epithelial lymphocytes are increased in primary biliary cirrhosis

Distribution of intra-epithelial lymphocytes along intrahepatic biliary tree (bIEL), and their density and phenotype were examined in normal and diseased livers, particularly in primary biliary cirrhosis (PBC). Immunohistochemically, bIEL were examined in 28 normal livers, 13 cases of chronic viral hepatitis (CVH), 13 cases of PBC, five cases of primary sclerosing cholangitis (PSC), seven cases of extrahepatic biliary obstruction (EBO), and 16 hepatolithiatic livers. In normal livers, bIEL were relatively dense at large and septal bile ducts compared to interlobular ducts. Most of them were positive for CD3 and CD8, while a few were positive for CD4, CD20 and CD57. In CVH, PSC and EBO, neither distribution, phenotype nor density of bIEL differed from normal liver. In hepatolithiasis, numbers of CD8(+)bIEL were increased in stone-containing ducts. In PBC, numbers of CD4(+)CD28(-)bIEL, which are reportedly responsible for target tissue destruction in autoimmune diseases, were markedly increased in damaged interlobular ducts. In conclusion, CD3(+)CD8(+)bIEL may be involved in immune homeostasis of intrahepatic bile ducts in normal livers and in CVH, PSC and EBO. Altered distribution and phenotypes of bIEL in PBC and hepatolithiasis may reflect their participation in biliary lesions. Increased CD4(+)CD28(-)bIEL in damaged bile ducts of PBC may be related to immune-mediated biliary damage.     

Abnormalities of intrahepatic bile ducts in extrahepatic biliary atresia

The infantile cholangiopathies are a group of conditions associated with neonatal jaundice, which include extrahepatic biliary atresia, paucity of intra-hepatic bile ducts and disorders associated with persistence of fetal biliary structures, the so-called ductal plate malformations. Although previously regarded as distinct entities, it has recently been suggested that they may represent parts of a disease spectrum in which the principal process is one of bile duct destruction, the morphological manifestations in individual cases being influenced by the stage of intra-uterine development at which such injury occurs and by the site within the biliary system at which there is maximum damage. To further examine this concept, we have studied liver biopsy specimens from 37 neonates with extrahepatic biliary atresia, with particular reference to abnormalities of the intrahepatic bile ducts. Paucity of intrahepatic ducts, defined as a bile duct: portal tract ratio of less than 0.9, was identified in six cases (16.2%). In eight cases (21.6%) we found concentric tubular ductal structures similar to those observed in ductal plate malformations. In one case, both abnormalities could be demonstrated. Our findings support the concept that there is overlap between the various types of infantile cholangiopathy.     

Production of human monoclonal IgG antibodies reacting with cytomegalovirus (CMV)

A human monoclonal antibody (MoAb) reacting with cytomegalovirus (CMV) has been produced using somatic cell hybridization between Epstein-Barr virus (EBV) infected B lymphocytes and a human-mouse heteromyeloma cell line (SHM-D33). The hybrids were selected in HAT medium containing 5 × 10⁻⁷ ouabain. The median level of Ig production was 5 (0.1−20) μg/10⁶ cells/day. One selected hybridoma (IB-8E9H5) has been maintained in continuous culture for more than 30 months with a stable IgG2, λ production. Molecular hybridization using EBV-specific probes demonstrate that our hybrids have lost the IR-1 EBV sequence during fusion. Unexpectedly, these blotting experiments revealed the presence of multiple EBNA-1 sequences dispersed among the genomic DNA of the SHM-D33 cell line. Screening for anti-CMV specificity was performed by ELISA and confirmed by immunofluorescence staining. Thus far, three CMV reference strains and 14 local strains are stained by the MoAb as early as 3 h after CMV infection of human fibroblasts, apparently through the recognition of a nuclear viral antigen of 67 kDa. In conclusion, this technique permits (a) the removal of the EBV genome contained in the lymphoblastoid parental cell line and (b) the production of human anti-CMV MoAb with potential applications in the prevention of life threatening CMV infections.     

T-Lymphocyte subpopulations in Crohn's disease: Definition by monoclonal antibodies

Summary Thirty-two patients with Crohn's disease (CD) and 32 age- and sex-matched controls were studied for T lymphocytes and T-lymphocyte subpopulations in the peripheral blood, using monoclonal antibodies defining the helper/inducer and the suppressor/cytotoxic compartment. T cells were reduced in patients with CD (P<0.05), and this reduction was more pronounced in patients with active discase (P<0.01). This T-cell deficiency involves helper and suppressor cells proportionally. The proportion of helper and suppressor cells in CD was independent of disease activity and therapy. We conclude that the T-cell deficiency in CD is a secondary event, and that there is no derangement in the immunoregulatory ratio (helper to suppressor cells) in CD which might have served as an explanation for a possible autoimmune mechanism in the pathogenesis of this disease.     

Anti-bombesin monoclonal antibodies modulate fetal mouse lung growth and maturation in utero and in organ cultures

Fetal pulmonary neuroendocrine cells (PNECs) contain abundant gastrin-releasing peptide (GRP, mammalian bombesin-like peptide [BLP]). Previously, addition of bombesin resulted in increased fetal lung growth and maturation in utero and in organ cultures. A monoclonal antibody (mAb) to bombesin (2A11) blocked baseline automaturation of lung organ cultures in serum-free medium. In the present study, we analyze lung development following daily in utero administration of 2A11 from gestational days 15–18. Fetal lung treated with 2A11 and then harvested on day 18 demonstrated a dose-dependent decrease in surfactant phospholipid synthesis compared to controls treated with MOPC, an unreactive mAb. However, 2A11-treated fetal lung harvested on day 17 showed paradoxical increases in ³H-choline incorporation into saturated phosphatidylcholine, ³H-thymidine incorporation into DNA, and relative numbers of differentiated type II pneumocytes. In serum-containing day 17 lung organ cultures, 2A11 stimulated choline and thymidine incorporation. Since epidermal growth factor (EGF) is the only agent besides bombesin known to stimulate both fetal lung growth and maturation, we added EGF to serum-free cultures and reconstituted the stimulatory effects. A murine EGF receptor mAb (ERA) blocked 2A11-induced lung growth and maturation in serum-containing cultures, and this effect was overcome by adding EGF. In vivo, ERA also blocked stimulatory effects of 2A11 in fetal lung on day 17. These observations suggest that EGF receptor up-regulation may maintain lung growth and maturation if BLP levels are diminished on day 17. Nonetheless, BLPs appear to be involved in lung maturation on day 18, supporting a role for PNECs in normal lung development. © 1993 Wiley-Liss, Inc.     

Monoclonal antibodies to the human mammary gland

Summary Mouse monoclonal antibodies have been raised to the human milk fat globule membrane. The distribution of the antigens detected by four of the antibodies has been examined in formalin-fixed, paraffin-embedded human tissues by light microscopic immunocytochemistry. The four antibodies stain lactating breast and normal resting breast. Two exclusively stain the luminal membranes of breast epithelial cells. A third antibody stains in addition the lateral membranes of duct epithelial cells. The fourth antibody stains both epithelial and myoepithelial cells. None of the antibodies is breast specific, nor do they stain every epithelial cell within the breast. Instead, each antibody reveals a complex and heterogeneous distribution of staining throughout the normal tissues. Within the breast, the staining by a given antibody is usually segmental and conforms to secretory units and their associated ducts. Similarly heterogeneous patterns of staining are also observed in the extramammary normal tissues. Despite the apparent morphological identity between breast epithelial cells when examined by conventional light microscopy, the hitherto unrecognised functional heterogeneity, which has been revealed by the monoclonal antibodies could have importance in understanding the biology of the normal breast and the pathology of breast cancer.     

Cytotoxic mechanisms of immunotherapy: Harnessing complement in the action of anti-tumor monoclonal antibodies

Several mAbs that have been approved for the treatment of cancer make use of complement-dependent cytotoxicity (CDC) to eliminate tumor cells. Comprehensive investigations, based on in vitro studies, mouse models and analyses of patient blood samples after mAb treatment have provided key insights into the details of individual steps in the CDC reaction. Based on the lessons learned from these studies, new and innovative approaches are now being developed to increase the clinical efficacy of next generation mAbs with respect to CDC. These improvements include engineering changes in the mAbs to enhance their ability to activate complement. In addition, mAb dosing paradigms are being developed that take into account the capacity as well as the limitations of the complement system to eliminate a substantial burden of mAb-opsonized cells. Over the next few years it is likely these approaches will lead to mAbs that are far more effective in the treatment of cancer.     

Use of monoclonal antibodies in formol-paraffin sections

Summary Thirteen monoclonal antibodies (the VI-series) reactive with B- and T-lymphocytes, monocytes, granulocytes and erythrocytes were tested in sections fixed with formalin, formalin-sublimate or formalin-acetic acid. After fixation and embedding, most of the antigens were not detectable. However, VIE-G 4, a monoclonal antibody selective for glycophorin A, produced a strong reaction with erythroid cells in formalin fixed sections. The binding of the monoclonal antibodies VIM-D 5, VIM-2 and VIM-13 to myeloid, myelomonocytic and monocytic cells became either more intense or was inhibited by preincubation of the sections with pronase, trypsin, papain or neuraminidase. Following enzyme digestion, the monocyte-specific antibody VIM-13 reacted selectively with some of the germinal centre cells.     

Frequent cellular senescence in small bile ducts in primary biliary cirrhosis: a possible role in bile duct loss

The pathogenesis of progressive bile duct loss in primary biliary cirrhosis remains unclear. In this study, the involvement of cellular senescence of biliary epithelial cells was examined in liver tissue samples from patients with primary biliary cirrhosis (n = 33), and compared with control diseased and normal livers (n = 83). In addition, cellular senescence was induced by oxidative stress in cultured mouse biliary epithelial cells. Biliary epithelial cells in small bile ducts in primary biliary cirrhosis, especially those in patients presenting with chronic non-suppurative cholangitis, frequently expressed senescence-associated beta-galactosidase, and senescence-associated p16(INK4) and p21(WAF1/CIP). In contrast, senescence-associated markers were rarely expressed in small bile ducts in control livers. The infiltration of myeloperoxidase-positive inflammatory cells into biliary epithelial cell layers was closely associated with the cellular senescence of biliary epithelial cells in early-stage PBC. Cellular senescence of cultured mouse biliary epithelial cells was induced by treatment with H2O2 via the p38MAPK-dependent pathway and nitric oxide-augmented H2O2-induced cellular senescence. Oxidative stress- and nitric oxide-mediated cellular senescence may be involved in bile duct lesions, which are followed by progressive bile duct loss in primary biliary cirrhosis.     

新型的抗线粒体抗体M2亚型IgG和IgA抗体的检测方法在原发性胆汁性肝硬化诊断中的价值

目的: 评价以新型天然M2抗原和BPO融合蛋白M2-3E(BPO)为靶抗原的 ELISA法(抗-M2-3E ELISA)检测抗线粒体抗体M2亚型(AMA-M2)IgG和IgA抗体在原发性胆汁化肝硬化(PBC)诊断中的敏感性、特异性。 方法: 分别用间接免疫荧光法(IFL)、以丙酮酸脱氢酶复合体(PDC)为靶抗原的ELISA法(抗- PDC ELISA)、抗-M2-3E ELISA法检测107例PBC、31例自身免疫肝炎(AIH)、10例原发性硬化性胆管炎(PSC)、17例丙型病毒性肝炎(HCV)、29例乙型病毒性肝炎(HBV)患者和26例健康体检者。 结果: (1)107例PBC患者用IFL、抗-PDC ELISA和抗-M2-3E ELISA 3种方法检测AMA-M2 IgG的检出率分别为:87/107(81.3%)、78/107(72.9%)、97/107(90.6%)。特异性分别为98.1%、97.2%、98.3%。抗-M2-3E ELISA法AMA-M2 IgG的检出率(90.6%)显著高于IFL法(81.3%)和抗-PDC ELISA法(72.9%)(均P<0.01)。用抗-M2-3E ELISA法检测AMA-M2 IgA的检出率为59/107(55.1%),特异性为97.2%。而总体AMA-M2 IgG和/或IgA的检出率99/107(92.5%),特异性为95.2%。(2)IFL 和 抗-M2-3E ELISA的重叠度为85%,抗-M2-3E ELISA可以在超过一半的IFL阴性的患者中检出AMA-M2 IgG和/或IgA。 结论: 抗-M2-3E ELISA法具有比IFL和抗-PDC ELISA法更高的敏感性、特异性。但是,AMA-M2 IgG和IgA都不可以单独用于诊断PBC的标记。     

Increased heterogeneity of serum thyroglobulin in thyroid cancer patients as determined by monoclonal antibodies

Summary We investigated the immunological heterogeneity of plasma Tg in thyroid cancer patients using monoclonal antibodies in an immunoradiometric assay and a conventional RIA system with a polyclonal rabbit antibody. The results were compared with measurements of plasma Tg in patients with nonmalignant disease. We can demonstrate an increased immunological heterogeneity in tumor patients compared with patients with non-malignant thyroid diseases. In one case the Tg value measured by a monoclonal test system exceeded the value obtained by a polyclonal RIA system in the same sample by a factor of 25. It has to be further investigated whether this increase in heterogeneity is of diagnostic value in the follow-up of thyroid cancer patients.Abbreviations IRMA 11, IRMA 13 Immunoradiometric assay using mabTg 11 or mabTg 13 - mabTg monoclonal antithyroglobulin antibodies - Tg Thyroglobulin     

Identification of macrophages and smooth muscle cells with monoclonal antibodies in the human atherosclerotic plaque

Summary Sections of human atherosclerotic plaques, obtained from 21 autopsy cases with various degrees of atherosclerosis, were stained with the indirect immunoperoxidase technique using specific monoclonal antibodies against macrophages and smooth muscle cells. Distinctive results were found in differing stages: Single blood monocytes were observed in diffuse intimal thickening and the foam cells seen in fatty streaks were mostly identified as mature tissue macrophages, while only very few blood monocytes were present. The spindle cells observed in fibroelastic plaques showed positive reactions to antibodies against desmin, which points to their derivation from smooth muscle cells, whereas only a few macrophage-derived foam cells were seen in these lesions. In the complicated lesions the majority of foam cells were macrophage-derived, but there was also a small number of foam cells positive to antibodies against desmin, suggesting a smooth muscle cell derivation. - Our results confirm that in human atherosclerotic plaques the majority of the foam cells are obviously macrophage-derived, which emphasizes the important role of macrophages in the morphogenesis of these lesions.Supported by Landesamt für Forschung Nordrhein-Westfalen