Search PubMed⌕ Search

Biomedical subjects

A C Chu

Publications and source records attributed to A C Chu.

At least 55 records · Page 3Linked to original sources
PubMed1995

Functional defect in cells involved in Langerhans cell histiocytosis.

The characteristic cell type involved in Langerhans cell histiocytosis, 'LCH cells', express most of the enzyme histochemical and immunocytochemical markers of normal epidermal Langerhans cells. It is not known, however, whether these LCH cells express the functional characteristics of normal epidermal Langerhans cells. We studied the alloantigen-presenting activity of LCH cells derived from lesional sites of three patients with the disease. Lesional cells expressing the CD1a molecule were enriched using either fluorescein-activated cell sorting or negative selection with indirect immunomagnetic beads, and functional activity was assessed using the 6-day primary allogeneic mixed-cell reaction. Compared to epidermal Langerhans cells from healthy controls, LCH cells showed minimal alloantigen-presenting activity on a per-cell basis. The diminished activity was not reversed by exogenous prostaglandin synthetase inhibitor or recombinant human IL-1 beta. This study confirms our previous report of a child, with fatal multisystem Langerhans cell histiocytosis suggesting that this disease represents a condition in which functionally defective cells of Langerhans cell phenotype accumulate and/or proliferate in various tissues. We postulate that the functional defect is a primary defect of these LCH cells that have acquired an as-yet-undetermined biological insult(s).

Adult↗
PubMed1995

Fluticasone propionate 0.05% cream in the treatment of atopic eczema: a multicentre study comparing once-daily treatment and once-daily vehicle cream application versus twice-daily treatment.

The aim of this study was to compare the efficacy and safety of once-daily with twice-daily application of a 0.05% cream formulation of fluticasone propionate in the treatment of atopic eczema in adults and children. Two hundred and seventy patients with moderate to severe atopic eczema were enrolled in the study, and randomized to receive either once-daily or twice-daily fluticasone propionate 0.05% cream for 4 weeks. Patients randomized to the once-daily group also received the vehicle cream to ensure that the study remained blinded. The clinical response of a preselected target area of affected skin was assessed by investigators at weekly intervals and compared with the baseline. Analysis of the investigators' overall assessment of the response of the target area for both the 'intent-to-treat' population and the per protocol population showed that 79-85% of patients were judged a clinical success. For both populations, there was no statistically significant difference between the response to once-daily and twice-daily active treatment (intent-to-treat; P = 0.35; 95% confidence interval for difference -14.2 to +5.0 percentage points: per protocol; P = 0.42; 95% confidence interval for difference -14.7 to +6.2 percentage points.) The improvement in the signs and symptoms was judged a success in 95-97% of patients. There was an equal reduction in severity scores for disease activity in both groups, and the speed of symptom relief was similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1994

Angioimmunoblastic lymphadenopathy with dysproteinemia and dermal T-cell lymphoma.

BACKGROUND: T-cell receptor (TCR)-gamma gene rearrangements provide a specific clonal marker for T-cell malignancies of both the alpha beta and gamma delta varieties. A polymerase chain reaction (PCR)-based method was used in this study for investigation of clonal TCR-gamma gene rearrangements in a patient with a classical presentation of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) that subsequently progressed into an indolent form of dermal T-cell lymphoma. METHODS: TCR gene rearrangements in patients with cutaneous T-cell lymphoma (CTCL) were examined using conventional Southern blot analysis and a newly developed PCR-based technique for clonal TCR gene rearrangements. The oligoprimers amplified rearranged V gamma and J gamma segments (including the N region) of the TCR-gamma gene, and PCR products were resolved using high resolution nondenaturing polyacrylamide gel electrophoresis. RESULTS: The authors' results demonstrated good correlation between the two techniques in 10 patients with CTCL (9 patients with C beta and 1 patient with delta 2 rearrangements) and 10 control subjects. The PCR-based technique allowed the authors to detect the presence of an identical T-cell clone in all skin nodules, but not in the original lymph node affected by AILD. CONCLUSIONS: This PCR-based method for detecting clonal TCR rearrangements is a highly sensitive and specific technique for detecting T-cell clones in fresh and paraffin embedded tissues. The presence of a T-cell clone in all skin nodules of this patient, but not in the original lymph node affected by AILD, confirms previous findings that in some cases of AILD, clonal T-cell expansion may not be detectable until a later stage of the disease.

Adult↗
PubMed1994

Clonal proliferation of Langerhans cells in Langerhans cell histiocytosis.

X-chromosome-inactivation assays can be used to assess clonality. We used such an assay at the human androgen-receptor gene locus in three female patients with histologically proven Langerhans cell histiocytosis. All patients were heterozygous for this locus. Cells bearing the Langerhans cell phenotype were purified from involved tissue after fluorescence-activated cell sorting with monoclonal antibodies against the CD1a complex. After HhaI digestion of DNA, these CD1a positive cells demonstrated a non-random X-chromosome-inactivation pattern, whereas CD1a negative cells in the same tissue showed a random pattern. Our data suggest that Langerhans cell histiocytosis represents a clonal proliferation of cells bearing the Langerhans cell phenotype.

Antibodies, Monoclonal↗
PubMed1994

Relationship between the ability of sunscreens containing 2-ethylhexyl-4'-methoxycinnamate to protect against UVR-induced inflammation, depletion of epidermal Langerhans (Ia+) cells and suppression of alloactivating capacity of murine skin in vivo.

The UVB sunscreen 2-ethylhexyl-4'-methoxycinnamate was evaluated in hairless albino mouse skin for its ability to inhibit UVR-induced (i) oedema, (ii) epidermal Langerhans cell (Ia+) depletion and (iii) suppression of the alloactivating capacity of epidermal cells (mixed epidermal cell-lymphocyte reaction, MECLR). The sunscreen, prepared at 9% in ethanol or a cosmetic lotion, was applied prior to UVB/UVA irradiation. In some experiments there was a second application halfway through the irradiation. Single applications in both vehicles gave varying degrees of protection from oedema and Langerhans cell depletion but afforded no protection from suppression of MECLR. When the sunscreens were applied twice there was improved protection from oedema and Langerhans cell depletion and complete protection was afforded from suppression of MECLR. There was a clear linear relationship between Langerhans cell numbers and oedema with and without sunscreen application. The relationship between Langerhans cell numbers and MECLR was more complex. These data confirm published discrepancies between protection from oedema (a model for human erythema) and endpoints with immunological significance, but show that 2-ethylhexyl-4'-methoxycinnamate can afford complete immunoprotection, although protection is dependent on the application rate and vehicle.

Administration, Topical↗
PubMed1994

Successful in vivo immunolocalization of Langerhans cell histiocytosis with use of a monoclonal antibody, NA1/34.

The antibody NA1/34 is a murine monoclonal antibody directed against the CD1a surface antigen expressed on normal Langerhans cells, cortical thymocytes, and on lesional cells in Langerhans cell histiocytosis (LCH). Our hypothesis was that NA1/34 would localize sites of disease activity in patients with multisystem LCH. To test this hypothesis, indium 111-labeled NA1/34 was administered to five patients with multisystem LCH and serial gamma scans were obtained for up to 120 hours. Serial serum samples were obtained from one patient for analysis of anti-mouse Ig antibody and NA1/34 levels. Direct and indirect immunofluorescence staining for CD1a and NA1/34 were performed on a tissue biopsy specimen from one patient after administration of the antibody. The 1- and 4-hour scans showed distribution of antibody in the blood pool, but in later scans localization of the antibody was noted in areas of known disease activity in all five patients. Bony lesions, previously seen on skeletal radiographs, were especially well identified. Serum kinetics studies showed clearance of the antibody from the blood pool within 12 hours of administration. Direct binding of NA1/34 to lesional cells was demonstrated by direct immunofluorescence. The only adverse effect was urticaria in one patient. We conclude that NA1/34 localizes disease activity in vivo in bones of patients with LCH with minimal toxic effects. An evaluation of its role in determining disease extent ("staging") and in treatment is now needed.

Adult↗
PubMed1994

Morphological and quantitative analyses of normal epidermal Langerhans cells using confocal scanning laser microscopy.

Confocal scanning laser microscopy (CSLM), when used in conjunction with computerized image processing systems, provides a powerful tool for morphological and quantitative analyses of biological tissues. In this study, normal human epidermal sheets were stained by an indirect immunofluorescence method using anti-CD1a monoclonal antibody. Positively stained epidermal Langerhans cells (LCs) were visualized using the Bio-Rad MRC-600 Confocal Imaging System. Images obtained from the confocal microscope were volumetrically rendered and quantitatively analysed using ANALYZE (Version 4.0) running on a Sun SPARC 2 Workstation. Normal epidermal LCs were shown to be large disc-like structures with five to nine long dendritic processes per cell, orientated with their flat surfaces parallel to the skin surface. LCs form a monolayer network of cells distributed evenly throughout the suprabasal layers of the epidermis, with no direct physical contact between dendritic processes. Mean LC density was estimated to be 582 per mm2 (95% confidence intervals, CI = 233-940), and mean cell volume was 612 microns3 (95% CI = 257-1020). LCs in sun-exposed sites were significantly lower in mean cell density, but larger in mean cell volume, than in covered sites. Mean surface area projected by LCs was estimated to be 26.8% (95% CI = 18.9-34.2), and this value did not show significant regional or individual variation. Our data support the notion that epidermal LCs are organized in such a way as to maximize their surface area for efficient trapping of antigens, and a reduction in LC density per unit area in sun-exposed sites is compensated for by an increase in the mean cell volume.

Cell Count↗
PubMed1994

Langerhans' cell expression of the selectin ligand, sialyl Lewis x.

Cellular adhesion molecules play a central role in leucocyte migration through peripheral blood and tissues. A crucial stage in these events in selectin-mediated adhesion involving E-selectin expressed on activated endothelium interacting with a range of carbohydrate ligands expressed by specific subpopulations of leucocytes. As such mechanisms may be relevant to bone marrow-derived dendritic epidermal Langerhans' cell (LC) migration, expression of these carbohydrate ligands was assessed immunocytochemically in whole skin biopsies and in epidermal cell suspensions obtained from adult humans. Double-labelling experiments revealed that sialyl Lewis x, recognized by the monoclonal antibody CSLEX1, was expressed on epidermal LC (n = 9). Furthermore, expression was enhanced at 24 hr following epicutaneous application of antigen and in the inflammatory disorder psoriasis (n = 10). E-selectin was concomitantly strongly expressed on dermal endothelium in psoriasis and allergic contact dermatitis. Intradermal injection of the T-cell-derived cytokine interferon-gamma (IFN-gamma) led to increased LC expression of sialyl Lewis x. In epidermal cell suspensions, in contrast to keratinocytes, CD1a+ cells expressed sialyl Lewis x, intensity of which was enhanced after 4 days in culture. CSLEX1 staining could be abolished and CD15 (non-sialated Lewis x) expression induced by saponification and treatment with neuraminidase. Expression of other selectin ligands was also examined. While the cutaneous lymphocyte antigen defined by the monoclonal antibody HECA-452 reacted with a small minority of LC, sialyl Lewis a and sulphatide were not expressed under any experimental conditions. These studies indicate that E-selectin-sialyl Lewis x interactions are potentially important in LC migration, both into and out of skin.

Adult↗
PubMed1994

Fractographic analysis of failed porous and surface-coated cobalt-chromium alloy total joint replacements.

Fractographic analyses were performed on retrieved porous and surface-coated cobalt-chromium alloy prostheses which were revised because of metallurgical fracture. Two femoral neck fractures and one fractured post of a femoral component of a total knee replacements were retrieved and analyzed via light, stereo and scanning electron microscopy (SEM). In all cases, fatigue was the mechanism of failure. The life time of these prostheses was 3-5 years. The porous coating; microstructural features, including large grains, carbides, porosity, inclusions and defects; design and manufacturing defects were all likely causative factors in these fatigue failures. In light of these and other reported fractures, further study of fatigue mechanisms and improvement of design and manufacturing processes are warranted.

Adult↗
PubMed1993

T-Lymphocytes bearing the gamma delta T-cell receptor in cutaneous lesions of Langerhans' cell histiocytosis.

The aim of this study was to investigate the regional importance of gamma delta T cells in cutaneous lesions of Langerhans' cell histiocytosis. Six cases of Langerhans' cell histiocytosis were investigated by immunohistochemical techniques (alkaline phosphatase-antialkaline phosphatase complex and indirect immunoperoxidase). Increase of gamma delta T cells was observed in 3 cases of Langerhans' cell histiocytosis. In these cases up to 30% of CD3+ cells stained with an anti-TCR gamma delta monoclonal antibodies and in two of them gamma delta T cells showed a marked epidermotropism. In the specimens of the remaining three cases gamma delta T cells were found in an overall percentage of 5% of CD3+ cells, but in two cases a significant increase of epidermal gamma delta T cells was observed. The finding of numerous gamma delta T cells in Langerhans' cell histiocytosis is provocative and supports the suggestion of a functional relationship between gamma delta T cells and LCH cells.

Antibodies, Monoclonal↗
PubMed1993

Gamma delta T lymphocytes in oriental cutaneous leishmaniasis: occurrence and variable delta gene expression.

It has been suggested that T lymphocytes expressing gamma delta T-cell receptors could play an important role in defence against some intracellular infectious pathogens. The present study was undertaken to characterize the occurrence and variable delta gene expression of T lymphocytes expressing the gamma delta T-cell receptor in oriental cutaneous leishmaniasis. Eleven cases of oriental cutaneous leishmaniasis were investigated by immunohistological analysis using an alkaline phosphatase-anti-alkaline phosphatase (APAAP) technique. In three cases, we observed an increased percentage of gamma delta T cells (about 20% of CD3+ cells). In these cases gamma delta T cells generally expressed the V delta 2 segment, and only rarely the V delta 1 gene product. V delta 2+ cells were predominantly localized in the dermis, and were virtually absent in the epidermal compartment. The rare gamma delta T cells observed in the epidermis were almost exclusively V delta 1+. This study demonstrates that an increase of gamma delta T cells may be found in oriental cutaneous leishmaniasis, although it is not a constant feature of the disease. The finding of a preferential expansion of the V delta 2 subset suggests that this subpopulation of gamma delta T cells might be selectively involved in the recognition of Leishmania antigens. The distinct compartmentalization of gamma delta T-cell subpopulations indicates that these subsets may recognize distinct sets of antigens.

Antigens, Protozoan↗
PubMed1993

Molecular analysis of the gamma delta T-cell receptor repertoire in normal human skin and in Oriental cutaneous leishmaniasis.

The extent of diversity of the gamma delta T-cell receptor (TCR) in normal human skin and Oriental Cutaneous Leishmaniasis (OCL) was examined by molecular analysis of the variable (V) delta gene segment, junctional (J) delta gene segment and junctional regions. To examine the expression of TCR delta genes, segments of gamma delta T lymphocytes, DNA isolated from normal human skin and from OCL were subjected to enzymatic gene amplification by the polymerase chain reaction (PCR) method using TCR V delta- and J delta-specific oligonucleotides as primers. PCR amplification using these primers indicated that the V delta 2 gene segment was predominantly used by gamma delta T lymphocytes in both normal human skin and OCL. To determine the extent of junctional diversity in the delta gene of gamma delta T cells in normal human skin and OCL, we sequenced the nucleic acid sequences corresponding to the V delta 2/J delta 1 junctional regions. Sequence analysis of junctional regions demonstrated broad junctional diversity in normal skin but only limited diversity in OCL. Our findings support the hypothesis that skin gamma delta T lymphocytes may derive from a fetal subset of gamma delta T lymphocytes that leaves the thymus early and colonizes the periphery. The limited junctional diversity demonstrated in OCL lesions indicates that gamma delta T cells can undergo oligoclonal expansion following recognition of a specific ligand and supports the idea that junctional regions are important in the recognition of antigenic determinant.

Amino Acid Sequence↗
PubMed1993

Multisystem Langerhans' cell histiocytosis with pancreatic involvement.

Langerhans' cell histiocytosis, a rare disorder of unknown cause affecting both children and adults, can affect many different organs and present to a wide range of medical specialties. An infant with fatal multisystem Langerhans' cell histiocytosis in whom the pancreas and the intestine were extensively affected is reported. The direct pancreatic involvement by this disease has not previously been described.

Histiocytosis, Langerhans-Cell↗
PubMed1992

Langerhans' cell histiocytosis and the nervous system.

We report two cases of Langerhans' cell histiocytosis with unusual central nervous system (CNS) involvement. The first patient had behavioural disturbances, memory loss and diabetes insipidus. His response to a range of treatments was poor. The second patient presented with seizures and headaches suggestive of raised intracranial pressure. Etoposide (VP16) chemotherapy led to a dramatic clinical and radiological improvement. The various CNS manifestations of Langerhans' cell histiocytosis and their management are discussed.

Adult↗
PubMed1992

Treatment of adult Langerhans cell histiocytosis with etoposide.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a reactive disease in which abnormal Langerhans cells accumulate in various body sites and cause damage to affected organs. Adults often do not respond to conventional therapy with local or systemic steroids. OBJECTIVE: Our purpose was to investigate intravenous etoposide as monotherapy in the treatment of adult patients with severe or resistant LCH. METHODS: In an open study, three adult patients with LCH (one with single-system skin disease and two with multisystem disease) were treated with etoposide, 100 mg/m2/day, for 3 days. This was repeated every 3 or 4 weeks for three or four cycles. RESULTS: All patients achieved clinical remission that persisted during a 12- to 14-month follow-up. No serious side effects were noted. CONCLUSION: We recommend the use of etoposide monotherapy in severe or restricted LCH in adults.

Adult↗
PubMed1992

A multicentre, parallel-group comparison of calcipotriol ointment and short-contact dithranol therapy in chronic plaque psoriasis.

Short-contact treatment with dithranol (anthralin) is a widely used treatment for chronic plaque psoriasis. Although effective, it causes staining and irritation, and is therefore inconvenient. Calcipotriol is a recently developed vitamin D analogue which is effective and easy to use. To evaluate the relative efficacy, safety and acceptability of these treatments a multicentre, open, randomized, parallel-group comparison was performed. Four hundred and seventy-eight patients with chronic plaque psoriasis were randomized to use one of the two treatments for 8 weeks. One group applied calcipotriol ointment (50 micrograms/g) twice daily. The other used a single application for 30 min each day of Dithrocream in the highest concentration tolerated. Severity of psoriasis was assessed by modified PASI score at baseline, and after 2, 4, and 8 weeks of treatment. A five-point scale was used by subjects and by investigators as an additional assessment of overall response, and a similar scale was used by subjects to grade acceptability. Total serum calcium was monitored at baseline and after 2 and 8 weeks on treatment. The mean PASI score fell from 9.1 to 4.7 after 8 weeks on dithranol (P < 0.001), and from 9.4 to 3.4 on calcipotriol (P < 0.001). The difference between the two treatments was significant in favour of calcipotriol at 2 weeks (P < 0.001), and remained so at subsequent assessments. At 8 weeks the difference between mean improvements in scores for the two groups was 1.6 (95% confidence interval 0.5-2.7). Efficacy grading by subjects and investigators, and acceptability grading by subjects, were all significantly better for calcipotriol.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗