Bone decay and beyond: how can we approach it better.

Osseo-degeneration is a disorder related to several factors, that may lead to the disruption of several skeletal regions providing support, such as the femur head, the vertebrae and the alveolar bone. The functional condition can be restored by means of grafting procedures, using different materials: calcium powder, xenografts, ceramics and metals. Such procedures aim at reforming an adequate bone volume and strength, that is necessary to support loading forces. Bone regeneration requires that the basic biological principles of osteogenesis, osteoinduction, osteoconduction and biocompatibility are followed. The success of regenerative procedures may depend on the inner structural, mechanical and metabolic condition of the host's bone on which implants should be inserted, on the surgical technique, and on the biomaterial used. Among these, the aging process of the patient appears to be relevant. It can be associated with metabolic disease leading to systemic functional decay, which involves a gradual steady decline of hormonal, immune function and osteo-metabolic activity. The latter can affect the positive outcomes of bone reconstruction and implant therapy. This review will analyze the biological and physiological factors involved in the bone tissue break-down, such as the influences from gut microbiome unbalance and the consequent metabolic, endocrine, immune dysfunctions, the surgery procedures and the quality of the grafting material used. The decline of bone architecture and strength should be corrected by using an appropriate clinical regenerative approach, based on a bio-endocrine, metabolic and immunologic know-how. The final characteristics of the regenerated bone must be able to support the loading forces transmitted by the implants, independent of the body location, and should be individualized according to the different condition of each patient.

A newly discovered muscle: The tensor of the vastus intermedius.

The quadriceps femoris is traditionally described as a muscle group composed of the rectus femoris and the three vasti. However, clinical experience and investigations of anatomical specimens are not consistent with the textbook description. We have found a second tensor-like muscle between the vastus lateralis (VL) and the vastus intermedius (VI), hereafter named the tensor VI (TVI). The aim of this study was to clarify whether this intervening muscle was a variation of the VL or the VI, or a separate head of the extensor apparatus. Twenty-six cadaveric lower limbs were investigated. The architecture of the quadriceps femoris was examined with special attention to innervation and vascularization patterns. All muscle components were traced from origin to insertion and their affiliations were determined. A TVI was found in all dissections. It was supplied by independent muscular and vascular branches of the femoral nerve and lateral circumflex femoral artery. Further distally, the TVI combined with an aponeurosis merging separately into the quadriceps tendon and inserting on the medial aspect of the patella. Four morphological types of TVI were distinguished: Independent-type (11/26), VI-type (6/26), VL-type (5/26), and Common-type (4/26). This study demonstrated that the quadriceps femoris is architecturally different from previous descriptions: there is an additional muscle belly between the VI and VL, which cannot be clearly assigned to the former or the latter. Distal exposure shows that this muscle belly becomes its own aponeurosis, which continues distally as part of the quadriceps tendon.

Pharmacological blocking of the osteoclastic biocorrosion of surgical stainless steel in vitro.

In vitro studies suggest that human osteoclasts (OC) are able to corrode surgical stainless steel 316L (SS). The aim of this study was to investigate whether osteoclastic biocorrosion can be blocked pharmacologically. Human OCs were generated in vitro from peripheral blood monocytic cells (PBMCs) in the presence of OC differentiation cytokines. The osteoclastic viability, differentiation, and resorptive function (on both bone and SS) were assessed using standard colorimetric cell viability assay 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenil)-2H-tetrazolium, inner salt (MTS), fluorescence microscopy, tartrate-resistant acid phosphatase expression (flow cytometry), and scanning electron microscopy. OCs cultured on SS were exposed to nontoxic concentrations of bafilomycin A1, amiloride hydrochloride, or zoledronic acid. The extent of biocorrosion was quantified using atomic emission spectrometry (to measure the concentration of metal ions released into the supernatant) and scanning electron microscopy. PBMCs differentiated into mature and functional OC in the presence of all the drugs used. Osteoclastic resorption of SS was noted with differences in the resorption pattern for all drug treatments. Under the drug treatments, single areas of osteoclastic resorption were larger in size but less abundant when compared with positive controls. None of the drugs used were able to inhibit osteoclastic biocorrosion of SS.

[Metal ions: important co-players in aseptic loosening]. / Metallionen: Wichtige Mitspieler in der aseptischen Lockerung.

AIM: The aims of this review were to discuss the different mechanisms of biocorrosion of orthopaedic metal implants in the human body, as well as the effects of the released metal ions on bone metabolism and the immune system in regard to their involvement in the pathophysiological mechanisms of aseptic loosening and metal hypersensitivity. Implant failure due to aseptic loosening is thought to occur in about 10-15% of cases. METHODS: A review of the literature (using PubMed with the search terms: biocorrosion, metal ions and bone metabolism) was performed. Additionally, we discuss our research results in the field of aseptic loosening. RESULTS: Despite a great effort in developing new implants, metal devices used in orthopaedic and trauma surgery remain prone to biocorrosion by several mechanisms including the direct corrosion by osteoclasts, leading to the production of significant amounts of wear particles and metal ions. In addition to the well documented increased osteolytic activity caused by large (in the nanometer range) wear particles, increasing evidence strongly suggests that the released metal ions contribute to the pathophysiological mechanism of aseptic loosening. Metal ions stimulate both the immune system and bone metabolism through a series of direct and indirect pathways leading to an increased osteolytic activity at the bone-implant interface. CONCLUSION: To date, revision surgery remains the only option for the treatment of a failed orthopaedic implant caused by aseptic loosening. A better understanding of the complex pathophysiological mechanisms (including the effects caused by the released metal ions) of aseptic loosening may have a significant potential in developing novel implants and therapies in order to reduce the incidence of this complication.

Apoptosis induction and reduced proliferation in human osteoblasts by rhBMP-2, -4 and -7.

BACKGROUND: The role of bone morphogenetic proteins (BMPs) in bone healing has been demonstrated in numerous in vivo animal models. BMP-2, -4 and -7 have also been shown to stimulate the differentiation of human and animal stem cells into osteoblasts in vitro. There are, however, contradictory reports of BMPs causing apoptosis and inhibition of proliferation of osteoblastic cells. Therefore, a more complete understanding of the effects of BMP-2, -4 and -7 on human osteoblasts is required. METHODS: Cells of the immortalised human fetal osteoblastic line hFOB 1.19 were exposed to recombinant human (rh) BMP-2, -4 and -7. In addition, primary human osteoblasts were exposed to rhBMP-7. Cell proliferation was measured using a colorimetric assay. Apoptotic cells were detected using the TUNEL assay. RESULTS: The hFOB cells exposed in a dose-dependent manner to rhBMP-2, -4 and -7 had significantly lower rates of proliferation than non-treated cells, (p<0.01 for rhBMP-2, -4 and -7). The proliferation results for rhBMP-7 were replicated using primary human osteoblasts. Additionally, rhBMP-2, -4 and -7 induced a significantly higher rate of apoptosis in the hFOB cells, with a temporal and dose-dependent pattern (p<0.05), irrespective of the presence of serum growth factors. CONCLUSIONS: Despite interest in the potential clinical application of BMPs to improve bone healing, further studies are necessary to determine their full biological function before they can be used confidently in humans.

[Heterotopic ossification - from the aetiology to the current management]. / Heterotope Ossifikation : Von der Atiologie zur aktuellen Therapie.

Heterotopic ossifications (HO) are defined as the abnormal formation of bone in soft tissues. It can be classified into acquired and congenital forms. The acquired form, of which the pathogenesis is not fully understood, is often diagnosed in patients with traumatic brain injury, spinal cord injury, musculo-skeletal trauma or injuries associated with burns. HO presents itself mostly asymptomatically, the symptoms of the initial stadium are often unspecific; however, severe forms can lead to severe disability. Imaging techniques, foremost bone szintigraphy, are mostly used for verification of the diagnosis. Local radiotherapy and nonsteroidal anti-inflammatory drugs are the classical therapeutic and prophylactic options. In advanced stages, surgical resection may be required.

Functional and structural characterization of two populations of human monocyte-derived dendritic cells.

BACKGROUND: The characterization of human monocyte-derived dendritic cells (HM-DC) subsets have been a very difficult and elusive task because of the lack of appropriate reagents. We, therefore utilized several diverse approaches to evaluate two populations of HM-DC including flow cytometry, ultra-structural evaluation by electron microscopy, and functional assays. In addition, we studied the kinetics of the expression of antigens on HM-DC at diverse intervals of time and identify surface markers and functional differences of these two HM-DC subsets. RESULTS: This study identified that a phenotype of HM-DC as defined by CD11c+, CD86+, and CD40+ could be separated in the presence or absence of TGF-beta1 into two different subsets of DC: (i) HM-DC without Birbeck granuli (Mo-DC) and (ii) HM-DC with Birbeck granuli (Mo-LC). Furthermore, the functional studies showed that the HM-DC treated with TGF-beta1 (Mo-LC) exhibited the presence of Birbeck granuli and could actively divide. In addition, after undergoing more than four cell divisions, these cells split into at least two additional subsets of Mo-LC: (iia) Mo-LC with high forward scatter (FSC) and (iib) Mo-LC with normal FSC. In contrast, the Mo-DC cultured in absence of TGF-beta1 did not exhibit Birbeck granuli, showed reduced ability to divide, and kept the normal FSC when analyzed. CONCLUSIONS: This study enabled us to determine in HM-DC: (i) the existence of antigenic and functional differences between various subpopulations of Mo-DC and Mo-LC; (ii) the existence of differences in the kinetics of antigens expression among the subsets of Mo-DC and Mo-LC; (iii) the existence of specific markers for each of the subpopulations of HM-DC.

Drenaje transrectal de abscesoperianastomótico en resección anterior baja porcáncer de recto. Un método de rescate en casosseleccionados / Transrectal drainage of perianastomotic abscess after low anterior resection for rectal carcinoma. A rescue method in selected patients

Las fístulas anastomóticas tras resección anterior baja mediante técnica de doble grapado en cáncer de recto pueden abocar al fracaso de la técnica con colostomía definitiva. Presentamos una pauta terapéutica de rescate en tres pacientes mediante drenaje transanastomótico del absceso retrorrectal, nutrición parenteral y antibioterapia (AU)

Carcinoembryonic antigen (CEA) presentation and specific T cell-priming by human dendritic cells transfected with CEA-mRNA.

The feasibility of dendritic cells (DC) for cancer immunotherapy after transfection by electroporation with mRNA encoding the human carcinoembryonic antigen (CEA) was investigated. Both, total RNA from the CEA(+) colon cancer cell line SW480 and mRNA transcribed in vitro from cDNA3.1-plasmids (pcDNA3.1+/-HisC) with a CEA-insert (ivt-CEA-mRNA, ivt-CEA/HisC-mRNA) were used. Labelled ivt-CEA-mRNA was detectable in DC by light and electron microscopy and by fluorescence-activated cell-sorting (FACS) even 15 min after electroporation. Four hours after transfection with ivt-CEA/HisC-mRNA, we detected specific expression of CEA and the histidine-tag by immunofluorescence microscopy and by FACS. CEA-specific T lymphocytes were successfully primed by transfected DC and were able to lyse CEA-expressing target cells, even from the CEA-expressing human colon adenocarcinoma cell line SW480. Thus, DC transfected by electroporation with CEA-mRNA are valuable tools for the immunotherapy of CEA(+) tumour entities.

Flow cytometric assessment of the reactivity of a panel of monoclonal antibodies (mAb) against two populations of human dendritic cells (DC).

BACKGROUND: The identification of antigens on human DC has been a very difficult and elusive task because of the lack of appropriate reagents. Therefore, we evaluated by flow cytometry a panel of mAb that recognize antigens on human DC, aiming to determine the kinetics of DC antigen expression at 7, 14, 21 and 28 days in (i) Dermal DC like cells (Mo-DC) and (ii) Langerhans cell like DC (Mo-LC). In addition we aimed to identify markers for DC subpopulations. RESULTS: It was found at day 7, that mAb BG6, HP-F1, BU10, RFD-1, CMRF-44 recognized <20% of Mo-DC. In contrast, 7H5, ZM3.8, CDlb/c, 55K-2, MMR1.16, MMR190.BB3 and L25 reacted with >50% of Mo-DC. Moreover, 7H5, ZM3.8, CMRF-56, CDlb/c, 55K-2, MMR1.16, MMR190.BB3 and L25 showed increased MFI reactivity against Mo-DC. mAb BG6, BU10 and CMRF-44 recognized <20% Mo-LC while RFD-1 reacted with 21% of Mo-LC. In contrast, HP-F1 showed 87% of Mo-LC positive. Also, 7H5, ZM3.8, RFD-7, MR15-2, CDlb/c, 55K-2, MMR1.16, MMR190.BB3 and L25 reacted with >50% of Mo-LC. The increase in % of positive cells was paralleled by MFI increases. At day 14, fourteen mAb recognized >50% of the Mo-DC, while five recognized 20-50% of Mo-DC. BG6 reacted with 7% of the Mo-DC. Nineteen mAb recognized >48% of Mo-LC while BG6 had negative reactivity. At day 21 and 28, all mAb reacted with >20% of Mo-DC and yielded a significant MFI with Mo-DC. Also nineteen mAb yielded significant MFI with Mo-LC while RFD-7 did not. CONCLUSIONS: The immunophenotyping assays demonstrated differences between the two DC populations as well as variations in the reactivity of the mAb at diverse time points, suggesting the existence of subpopulations within the Mo-DC and Mo-LC.

Intralipid-based short-term total parenteral nutrition does not impair small intestinal mucosa-related cellular immune reactivity in the healthy rat.

BACKGROUND: The lipid component of total parenteral nutrition (TPN) has reportedly been associated with trophic effects on the intestinal mucosa and suppressive effects on the immune system. METHODS: We have challenged these hypotheses using a 7-day TPN rodent model comparing the effects of isocaloric, isonitrogenous lipid-based (TPN-lipid, 50% of calories as long-chain triacylglycerol) and carbohydrate-based TPN (TPN-CH, 100% of calories as carbohydrates) on mucosal morphology and immune function. Enterally fed animals were included to establish a baseline for immunologic read-outs. The study was performed in healthy, metabolically stable animals to avoid interference by septic or trauma-related stress factors. RESULTS: Both TPN regimens resulted in a significantly smaller weight gain (TPN-lipid, 29.8 +/- 4.0 g; TPN-CH, 30.3 +/- 4.4 g) compared with enterally fed reference animals (49.2 +/- 3.2 g; p = .007), with no difference in nitrogen balance between the TPN groups. Mucosal sucrase activity was significantly lower in both TPN groups (TPN-lipid, 8.8 +/- 1.0 x 10(-7) katal per gram (kat/g) of protein; CH: 11.9 +/- 1.6 x 10(-7) kat/g of protein) compared with enteral feeding (17.4 +/- 0.9 x 10(-7) kat/g of protein; ANOVA: p = .0007). Morphometric analysis of the small intestine revealed no differences between the two TPN groups although a significantly depressed villus height in the TPN-lipid group could be observed in comparison to enterally fed reference rats (TPN-lipid, 0.47 +/- 0.02; TPN-CH, 0.50 +/- 0.01; enteral, 0.56 +/- 0.02 mm; ANOVA: p = .0298). Light and electron microscopy revealed a normal surface architecture in all three groups of rats. Cellular immune reactivity was evaluated using a novel specific immunization protocol: animals were immunized against OVA 4 weeks before TPN. OVA-induced lymphoproliferative responses and phenotypic data from draining popliteal and mesenteric lymph nodes were evaluated after the different regimens. Results did not differ among the three groups. CONCLUSIONS: In healthy rodents, short-term lipid-based and carbohydrate-based TPN regimens lead to limited mucosal atrophy with preserved surface architecture compared with enteral feeding. However, peripheral and mesenteric cellular immune responsiveness after both TPN regimens remained comparable to enterally fed reference animals. Therefore, mesenteric and systemic cellular immune reactivity does not appear to be impaired by lipid-based or carbohydrate-based TPN.

Human skin Langerhans cells are targets of dengue virus infection.

Dengue virus (DV), an arthropod-borne flavivirus, causes a febrile illness for which there is no antiviral treatment and no vaccine. Macrophages are important in dengue pathogenesis; however, the initial target cell for DV infection remains unknown. As DV is introduced into human skin by mosquitoes of the genus Aedes, we undertook experiments to determine whether human dendritic cells (DCs) were permissive for the growth of DV. Initial experiments demonstrated that blood-derived DCs were 10-fold more permissive for DV infection than were monocytes or macrophages. We confirmed this with human skin DCs (Langerhans cells and dermal/interstitial DCs). Using cadaveric human skin explants, we exposed skin DCs to DV ex vivo. Of the human leukocyte antigen DR-positive DCs that migrated from the skin, emigrants from both dermis and epidermis, 60-80% expressed DV antigens. These observations were supported by histologic findings from the skin rash of a human subject who received an attenuated tetravalent dengue vaccine. Immunohistochemistry of the skin showed CD1a-positive DCs double-labeled with an antibody against DV envelope glycoprotein. These data demonstrate that human skin DCs are permissive for DV infection, and provide a potential mechanism for the transmission of DV into human skin.

Lipoproteins from Borrelia burgdorferi applied in liposomes and presented by dendritic cells induce CD8(+) T-lymphocytes in vitro.

Borrelia burgdorferi (Bb) is the tick-borne etiologic agent of Lyme borreliosis, which has many aspects of autoimmune diseases. Bb is unable to recycle synthesized membrane lipids and lipoproteins. Consequently, a large amount of liposome-like vesicle (Bb-blebs) is shed from the outer bacterial membrane. The influence of Bb-blebs on the cellular immune response is not yet known. As a Bb-blebs model, we established standardized Bb-liposomes, produced from freshly extracted lipids and lipoproteins of live Bb. Bb-liposomes were incorporated via nonendocytotic mechanisms by different human cell types, namely dendritic cells (DC), lymphocytes, and fibroblasts, as visualized by immunofluorescence and transmission electron microscopy. Bb-liposomes were localized in the cytosol and in the nucleus of the cells. With this in mind, we generated in vitro Bb-specific T-cells from nonadherant peripheral blood mononuclear cells by use of Bb-liposomes loaded autologous DC. More than 95% of those T-cells were CD8(+) and they killed autologous Bb-liposome-loaded T-cell blasts. These results suggest that Bb-blebs may be responsible for the autoimmune-like appearance of Lyme disease.

The lipid component of lipoproteins from Borrelia burgdorferi: structural analysis, antigenicity, and presentation via human dendritic cells.

The spirochaetal bacteria Borrelia burgdorferi (Bb) is the tick-borne causative agent of lyme disease. The major membrane immunogens of Bb are outer surface proteins. The lipid component of these lipoproteins is relevant for the immunogenicity of Bb-lipoproteins. To characterize the antigenic properties, the native lipid component of lipoproteins was isolated and the detailed molecular structure was analyzed. The molecular structure of the lipoprotein-lipid component turned out to be S(propane-2',-3'diol)-3-thio-2-aminopropanic acid (S-glyceryl-cysteine) with one ester-linked fatty acid, one acetyl group, and one N-terminal amide-bound fatty acid. Fatty acid analysis of the lipid component indicated a heterogeneous composition comprising C16:0, C18:0, C18:1, C18:2, and C 20:0. The antigenicity was tested with in vitro bioassays using human blood-derived dendritic cells (DCs) as antigen-presenting cells and autologous Bb-specific T-cells. We found that human DCs present the lipid component of Bb-lipoproteins via MHC class II inducing an antigen-specific T-cell immune response in vitro.

Shwachman-Diamond syndrome: early bone marrow transplantation in a high risk patient and new clues to pathogenesis.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterised by exocrine pancreas insufficiency, metaphyseal dysostosis and bone marrow dysfunction. Recurrent severe bacterial infections and susceptibility to leukaemia are the major causes of morbidity and mortality occurring preferentially in patients with pancytopenia and features of myelodysplasia. Here we report a patient with SDS leading to recurrent bacterial infections and a deteriorating condition since early infancy. Extensive investigations disclosed severe pancytopenia, myelodysplasia and a clonal cytogenetic abnormality, inv(14)(q11q32), as risk factors of leukaemic transformation. He therefore underwent allogeneic geno-identical bone marrow transplantation which resulted in correction of all haematological and immunological abnormalities within an 18-month follow up period. Conclusion Bone marrow transplantation may be considered early as a valuable treatment option especially in high risk Schwachman-Diamond syndrome patients anticipating malignant transformation, life-threatening severe infections or further organ damage.

Potential strategies utilised by papillomavirus to evade host immunity.

The co-evolution of papillomaviruses (PV) and their mammalian hosts has produced mechanisms by which PV might avoid specific and non-specific host immune responses. Low level expression of PV proteins in infected basal epithelial cells, together with an absence of inflammation and of virus-induced cell lysis, restricts the opportunity for effective PV protein presentation to immunocytes by dendritic cells. Additionally, PV early proteins, by a range of mechanisms, may restrict the efficacy of antigen presentation by these cells. Should an immune response be induced to PV antigens, resting keratinocytes (KC) appear resistant to interferon-gamma-enhanced mechanisms of cytotoxic T-lymphocyte (CTL)-mediated lysis, and expression of PV antigens by resting KC can tolerise PV-specific CTL. Thus, KC, in the absence of inflammation, may represent an immunologically privileged site for PV infection. Together, these mechanisms play a part in allowing persistence of PV-induced proliferative skin lesions for months to years, even in immunocompetent hosts.

[Emphysematous cholecystitis. Diagnosis, clinical course, and treatment]. / Colecistitis enfisematosa. Diagnóstico, evolución y tratamiento.

Emphysematous cholecystitis is the most severe acute cholecystitis with infection by gas-producing organism. The morbidity and mortality rate are 15%. We present a retrospective study of emphysematous cholecystitis seen in our department during three years (1992-1994). Inclusion criteria were made on the basis of a characteristic history, physical examination and radiology findings. Eight patients were studied. All were men, medium age 75 years (range: 45-88). None of them was diabetic. Clinical history was typical for the disease. Radiological examinations included abdominal X-ray (none of them was demonstrative), abdominal ultrasound (carry out in five patients and diagnosis in two) and computerised tomography scanning was necessary in the others three patients. Surgery was required since complication occurred in two patients. The mean duration until surgery was 5.21 day. Only three patients had any postoperative complication and nobody death. We concluded that the treatment of choice is cholecystectomia, except for high risk patient in whom puncheon and drainage is required.

Human dermal dendritic cells process and present soluble protein antigens.

Recently, a novel type of dendritic antigen-presenting cell has been identified in the dermis of normal human and mouse skin. These dermal dendritic cells (DDC) occur in higher numbers than epidermal Langerhans cells, represent a distinct differentiation pathway of dendritic cells, and are as potent as Langerhans cells in the activation of superantigen specific T cells. As yet, nothing is known about their capacity to take up, process, and present soluble protein antigens. We used the model of tetanus toxoid (TT) driven T cell proliferation to address these questions. To test for active internalization of TT protein, gold labeled TT was incubated with Langerhans cells and DDC and could be traced to multivesicular endo-lysosomal compartments. DDC internalize TT through a receptor-mediated, clathrin-independent pathway, whereas Langerhans cells predominantly use macropinocytosis. To verify that DDC process TT by the exogenous pathway of antigen presentation, we pulsed DDC with TT protein or TT peptide after preincubation with chloroquine. Preincubation with chloroquine diminished the capacity of DDC to induce TT protein specific T cell proliferation (70-80%), but was not effective to suppress TT peptide induced T cell responses. DDC were as potent as Langerhans cells and 5-10 x more potent than plastic adherent monocytes in the presentation of TT to autologous resting T cells. Furthermore, as few as 50 DDC (stimulator:responder ratio of 1:1000) were able to induce a significant TT specific T cell proliferation. Because a subpopulation of DDC expresses low levels of CD1a, a phenotypic marker of Langerhans cells, sorting of CD1a positive and negative DDC was performed. On a per cell basis, CD1a positive and negative DDC were equally potent at mediating TT specific T cell proliferation. Thus, DDC are able to internalize, process, and present soluble protein antigens such as TT and may therefore play an important role in the regulation of skin immune responses.

Characterisation of two human dendritic cell-lines that express CD1a, take-up, process and present soluble antigens and induce MLR.

Dendritic cells (DC) are bone marrow derived cells present in diverse tissues and organs including the skin, mucosae and blood. DC have a capital role in the afferent pathway of the immune response because of its role in up-take, processing and presenting antigens to immune cells. Human DC are usually identified by the expression of surface CD1a and HLA-DR. Despite the significant recent developments for in vitro generation of DC derived from blood by using cytokines like GM-CSF and IL-4, the studies on DC and specially on human Langerhans cells (LC) have been hampered by the laborious isolation procedure and the small yield of cells obtained by the various methods of isolation used so far. Therefore, a priority has been a search for monoclonal dendritic cell-lines with LC characteristics in order to facilitate the research in this area. The present study reports on the generation of two stable, self-replicant, adherent, dendritic, CD1a+, HLA-DR , CD45RO , CD23/FcERII+ cell-lines that up-take and process soluble antigens but also inducing MLR and antigen-dependent T-cell response.