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B J Longley

Publications and source records attributed to B J Longley.

At least 37 records · Page 2Linked to original sources
PubMed1998

Murine cutaneous mastocytosis and epidermal melanocytosis induced by keratinocyte expression of transgenic stem cell factor.

The growth and differentiation of mast cells and melanocytes require stem cell factor (SCF), the ligand for the kit receptor tyrosine kinase. SCF may exist as a membrane-bound or soluble molecule. Abnormalities of the SCF-kit signaling pathway, with increased local concentrations of soluble SCF, have been implicated in the pathogenesis of the human disease cutaneous mastocytosis, but have not yet been shown to play a causal role. To investigate both the potential of SCF to cause mastocytosis and its role in epidermal melanocyte homeostasis, we targeted the expression of SCF to epidermal keratinocytes in mice with two different transgenes controlled by the human keratin 14 promoter. The transgenes contained cDNAs that either produced SCF, which can exist in both membrane-bound and soluble forms, or SCF, which remains essentially membrane bound. Murine epidermal keratinocyte expression of membrane-bound/ soluble SCF reproduced the phenotype of human cutaneous mastocytosis, with dermal mast cell infiltrates and epidermal hyperpigmentation, and caused the maintenance of a population of melanocytes in the interadnexal epidermis, an area where melanocytes and melanin are found in human skin but where they are not typically found in murine skin. Expression of membrane-bound SCF alone resulted in epidermal melanocytosis and melanin production, but did not by itself cause mastocytosis. We conclude, first, that a phenotype matching that of human mastocytosis can be produced in mice by keratinocyte overproduction of soluble SCF, suggesting a potential cause of this disease. Second, we conclude that keratinocyte expression of membrane-bound SCF results in the postnatal maintenance of epidermal melanocytes in mice. Since the resulting animals have skin that more closely approximates human skin than do normal mice, their study may be more relevant to human melanocyte biology than the study of skin of normal mice.

Animals↗
PubMed1998

Tumor-specific peptides in cutaneous T-cell lymphoma: association with class I major histocompatibility complex and possible derivation from the clonotypic T-cell receptor.

We wished to identify and characterize tumor-associated class I peptides which could potentially serve as immunogens for an immunoprotective CD8 response in cutaneous T-cell lymphoma (CTCL). Candidate idiotypic peptides were identified from the third complementarity determining region (CDR3) of the clonotypic T-cell receptor (TCR) expressed on malignant T cells and native class I peptides were identified from CTCL cells. Idiotypic peptides were designed by sequencing of patients' CDR3 and identifying 9 amino acid peptides that could be accommodated in the peptide-binding motif of the class I alleles. Three candidate idiotypic peptides were synthesized and tested by measuring release of tumor necrosis factor-alpha (TNF-alpha) from autologous CD8 cells. Native peptides were acid-eluted from class I molecules on CTCL lymphocytes, fractionated, tested in the TNF-alpha assay and sequenced. Two unique idiotypic peptides were specifically recognized by autologous CD8 cells from CTCL patients. In addition, a native peptide eluted from class I molecules of CTCL tumor cells was identified, in the protein data base, as a novel molecule with partial sequence homology to the conserved portion of the patient's TCR. This homology was used to construct an extended native peptide sequence that was immunogenic for CD8 cells from both CTCL patients. Our results demonstrate that peptides derived from the TCR can be used as tumor-specific immunogens that are recognized by CD8 cells. Moreover, novel class I peptides isolated from the tumor cell also serve as immunogens. These peptides might form the basis of an anti-tumor vaccine for immunotherapy of CTCL.

Amino Acid Sequence↗
PubMed1998

c-kit mutation and osteopetrosis-like osteopathy in a patient with systemic mast cell disease.

We describe the case of a 69-year-old man with systemic mastocytosis and severe osteopetrosis who carries a somatic activating mutation in the c-kit proto-oncogene. The patient initially presented with urticaria pigmentosa, progressing to systemic mast cell disease with severe anemia due to bone marrow involvement, chronic diarrhea, and hepatosplenomegaly. Direct sequencing using amplimers from reverse transcriptase-polymerase chain reactions (RT-PCR) from skin mast cell-derived RNA revealed a point mutation in the c-kit proto-oncogene at position 2468, introducing a new recognition site for the restriction endonuclease HinfI. Treatment with interferon-alpha 2a, prednisone, and erythropoietin was initiated. Subsequently, clinical symptoms improved significantly and hemoglobin levels are now stable at 13 g/dl.

Aged↗
PubMed1998

Genital variant of folliculosebaceous cystic hamartoma.

BACKGROUND: Clinically, folliculosebaceous cystic hamartomas (FSCH) present as skin-colored papulonodules of the face, especially the nose. This is in contrast to sebaceous trichofolliculomas which often present as depressed ostia containing terminal or vellus hairs. OBSERVATION: A 34-year-old female had a skin-colored multinodular plaque of the labia majora that demonstrated the histologic findings of an FSCH. These included an irregularly shaped central cystic structure surrounded by multiple sebaceous lobules as well as a fibrous stroma. The epithelial-lined cyst contained no hair shafts. CONCLUSION: A single case report of a scrotal lesion with a similar clinical appearance and histologic findings has previously been described as a genital variant of sebaceous trichofolliculoma. However, the report predated the initial description of FSCH. In our opinion, both cases represent examples of the genital variant of FSCH.

Adult↗
PubMed1997

Chymase cleavage of stem cell factor yields a bioactive, soluble product.

Stem cell factor (SCF) is produced by stromal cells as a membrane-bound molecule, which may be proteolytically cleaved at a site close to the membrane to produce a soluble bioactive form. The proteases producing this cleavage are unknown. In this study, we demonstrate that human mast cell chymase, a chymotrypsin-like protease, cleaves SCF at a novel site. Cleavage is at the peptide bond between Phe-158 and Met-159, which are encoded by exon 6 of the SCF gene. This cleavage results in a soluble bioactive product that is 7 amino acids shorter at the C terminus than previously identified soluble SCF. This research shows the identification of a physiologically relevant enzyme that specifically cleaves SCF. Because mast cells express the KIT protein, the receptor for SCF, and respond to SCF by proliferation and degranulation, this observation identifies a possible feedback loop in which chymase released from mast cell secretory granules may solubilize SCF bound to the membrane of surrounding stromal cells. The liberated soluble SCF may in turn stimulate mast cell proliferation and differentiated functions; this loop could contribute to abnormal accumulations of mast cells in the skin and hyperpigmentation at sites of chronic cutaneous inflammation.

Binding Sites↗
PubMed1997

Role of CD4+ T cells in pathogenesis associated with Leishmania amazonensis infection.

Most inbred strains of mice are susceptible to Leishmania amazonensis infection. We have examined the mechanism(s) underlying this generalized susceptibility using mice deficient in T cell development or in the expression of either MHC class I or class II. In contrast to wild-type C57BL/6 (B6) mice that uniformly developed large ulcerating lesions, mice lacking functional CD4+ T cells (due to targeted disruption of genes for either MHC class II trans-activator or I-A beta) showed no signs of lesion development for up to 12 to 14 wk postinfection and contained significantly lower numbers of parasites in lesions. Similarly, both B6 nude and RAG2 -/- mice failed to develop lesions. However, RAG2 -/- mice reconstituted with naive wild-type CD4+ T cells and beta2m -/- mice did develop lesions. Lesions of MHC class II -/- mice contained minimal numbers of CD8+ T cells, a marked reduction of monocytes/macrophages, and evident extracellular parasites. The inability to mount an inflammatory response in MHC class II -/- mice correlated with the failure to produce lymphokines that lead to the recruitment of monocytes/granulocytes. These results demonstrate that CD4+ T cells are the primary lymphocyte subset that mediates cellular infiltration, lesion pathology, and therefore, susceptibility to L. amazonensis infection. The disease-promoting CD4+ T cells in L. amazonensis-infected mice have the characteristics of Th1 cells. The striking differences in the course of infection between MHC class II -/- mice infected with L. amazonensis and Leishmania major suggest that these parasites may have adapted different strategies regarding the CD4-dependent immune response.

Animals↗
PubMed1997

Human skin/SCID mouse chimeras as an in vivo model for human cutaneous mast cell hyperplasia.

Human skin xenografted to mice with severe combined immunodeficiency syndrome (SCID) was evaluated to determine the integrity and fate of human dermal mast cells. There was an approximately 3-fold increase in number of dermal mast cells by 3 mo after engraftment (p < 0.05). These cells were responsive to conventional mast cell secretagogues and were confirmed to be of human origin by ultrastructural characterization of granule substructure and by reactivity for the human mast cell proteinase, chymase. CD1a+ Langerhans cells, also bone marrow-derived cells, failed to show evidence of concomitant hyperplasia, and increased mast cell number was not associated with alterations in number of dermal vascular profiles identified immunohistochemically for human CD31. RT-PCR analysis demonstrated human but not murine stem cell factor (SCF; also termed mast cell growth factor, c-kit ligand) mRNA in xenografts. Epidermal reactivity for stem cell factor protein shifted from a cytoplasmic pattern to an intercellular pattern by 3 mo after engraftment, suggesting a secretory phenotype, as previously documented for human cutaneous mastocytosis. The majority (>90%) of mast cells demonstrated membrane reactivity for human SCF at the time points of peak hyperplasia. These data establish SCID mouse recipients of human skin xenografts as a potential in vivo model for cutaneous mast cell hyperplasia.

Animals↗
PubMed1997

Chronically KIT-stimulated clonally-derived human mast cells show heterogeneity in different tissue microenvironments.

Human mast cell precursors arise in the bone marrow and circulate to different tissue microenvironments, where they develop distinct phenotypes that may be characterized by differential expression of the serine protease, chymase. The growth and development of mast cells is stimulated by mast cell growth factor, which is also known as kit ligand because its obligate receptor is KIT, the protein product of the c-KIT proto-oncogene. The in vivo influence of the KIT-kit ligand axis on the phenotype of human mast cells has not been determined. We used immunohistochemistry to detect in situ expression of tryptase and chymase by mast cells of a patient with urticaria pigmentosa and aggressive systemic mastocytosis, whose pathologic mast cells are clonally derived and chronically stimulated by KIT because they all contain the same point mutation causing constitutive activation of KIT. Mast cells in both spleen and skin expressed tryptase, but only in the skin did a majority of mast cells express chymase. We conclude that chronic stimulation of the KIT-kit ligand axis does not irrevocably commit mast cells to a chymase-positive or chymase-negative phenotype. These findings suggest that factors other than kit ligand predominate in determining mast cell phenotype.

Chymases↗
PubMed1996

Disruption of CD40-CD40 ligand interactions results in an enhanced susceptibility to Leishmania amazonensis infection.

To study the role of CD40 ligand (CD40L) in the host immune responses against intracellular pathogens, we infected CD40L knockout (CD40L-/-) mice with Leishmania amazonensis. Although wild-type mice were susceptible to infection and developed progressive ulcerative lesions, tissue parasite burdens in CD40L-/- mice were significantly higher. This heightened susceptibility to infection was associated with an impaired T cell and macrophage activation and altered inflammatory response, as reflected by low levels of IFN gamma, lymphotoxin-tumor necrosis factor (LT-TNF), and nitric oxide (NO) production. Furthermore, CD40L-/- mice failed to generate a protective immune response after immunization. These results indicate an essential role of cognate CD40-CD40L interactions in the generation of cellular immune responses against an intracellular parasite.

Animals↗
PubMed1996

Somatic c-KIT activating mutation in urticaria pigmentosa and aggressive mastocytosis: establishment of clonality in a human mast cell neoplasm.

Mastocytosis is characterized by accumulations of mast cells in various organs (1). Most cases are indolent and confined to the skin, where discrete mast cell infiltrates are associated increased epidermal melanin, a clinical picture known as urticaria pigmentosa (UP). Other forms of mastocytosis combine UP with aggressive involvement of other organs or with haemotologic abnormalities (1-4). It is not known whether all forms of mastocytosis are true neoplasms or whether some might represent reactive hyperplasias (5-7). The c-KIT proto-oncogene encodes a type III receptor tyrosine kinase (KIT) that is critical to the development and survival of mast cells and melanocytes (8-11). The ligand for KIT (KL) can stimulate mast cell development, proliferation, and mediator release (9,12-17), as well as melanocyte proliferation and pigment production (18-20). To determine the role of c-KIT in the pathogenesis of mastocytosis, we examined tissue and cells isolated from a patient with UP and aggressive systemic mastocytosis with massive splenic involvement. We found a mutation that results in constitutive activation and expression of c-KIT in mast cells of both skin and spleen. This is the first in situ demonstration of an activation c-KIT mutation in neoplastic cells. It also demonstrates the clonal and neoplastic nature of this form of mastocytes.

Adult↗
PubMed1995

Papilloma formation in human foreskin xenografts after inoculation of human papillomavirus type 16 DNA.

A mouse model of high-risk human papillomavirus infection was developed in which human papillomavirus (HPV) type 16 DNA was inoculated into human foreskin grafted to the skin of severe combined immunodeficient (scid) mice. Grafted skin contained human epidermis and dermis and, like normal human skin, expressed involucrin in differentiating keratinocytes. HPV type 16 DNA, attached to gold particles, was delivered directly into human epidermal cells and induced exophytic papilloma with histologic features of papillomavirus infection, including koilocytosis and expression of papillomavirus capsid antigen. This model should be useful for determining in vivo the functions of viral genes and for developing strategies to prevent and treat HPV-associated disease. It may also be of value in developing animal models of other human skin diseases.

Animals↗
PubMed1994

Restoration of differentiation and suppression of tumorigenicity in somatic cell hybrids of human squamous carcinoma cells and keratinocytes.

Somatic cell hybrid cell lines derived from the fusion of human squamous carcinoma cells (FaDu-Hyg) with human keratinocytes were used to examine the relationships between cell differentiation and tumorigenicity. Treatment of the parental keratinocytes or the two hybrid cell lines with the combination of calcium and fetal bovine serum increased the expression of the envelope precursor, involucrin, 4- to 8-fold, whereas it remained unchanged in FaDu-Hyg cells. Similarly, calcium- and serum-treated keratinocytes and the two hybrid cell lines displayed a 7- to 13-fold increase of the activity of membrane-associated type I transglutaminase, whereas transglutaminase activity in FaDu-Hyg cells did not change appreciably. FaDu-Hyg cells were tumorigenic in vivo, but tumorigenicity was suppressed in both hybrid cell lines. Analysis of additional tumor cell lines indicated that the expression of transglutaminase I and involucrin are under separate genetic control and that loss of transglutaminase activity can result either from a lack of protein or from a defect in the activation step. Thus, keratinization of squamous epithelial cells appears to be controlled by several different recessive genes, which cosegregate with but are probably only partly identical with the genes that suppress tumor formation in vivo.

Animals↗
PubMed1993

Altered metabolism of mast-cell growth factor (c-kit ligand) in cutaneous mastocytosis.

BACKGROUND AND METHODS: The lesions of cutaneous mastocytosis are characterized by dermal infiltrates of mast cells and may appear hyperpigmented because of the presence of increased levels of epidermal melanin. Mast-cell growth factor, the ligand for the product of the c-kit proto-oncogene, stimulates the proliferation of mast cells and increases the production of melanin by melanocytes. We therefore looked for the expression of the mast-cell growth factor gene in the skin of patients with cutaneous mastocytosis using immunohistochemical techniques and the polymerase chain reaction. RESULTS: In the skin of normal subjects and those with unrelated diseases, immunoreactive mast-cell growth factor was associated with keratinocytes and scattered dermal cells, a pattern consistent with cell-bound mast-cell growth factor. In skin samples containing lesions and in clinically normal skin from patients with mastocytosis, however, mast-cell growth factor was also found free in the dermis and in the extracellular spaces between keratinocytes, suggesting the presence of a soluble form of this protein. Messenger RNA (mRNA) that can encode soluble mast-cell growth factor was present in the skin of patients as well as in that of normal control subjects. No sequence abnormalities were detected in mRNA for mast-cell growth factor from one patient. CONCLUSIONS: The altered distribution of mast-cell growth factor in the skin of patients with cutaneous mastocytosis is consistent with abnormal production of the soluble form of this factor. This abnormality is probably due to increased proteolytic processing, since it was not explained by differences in the splicing or sequence of mast-cell growth factor mRNA in the patients. Soluble mast-cell growth factor may cause the characteristic accumulation of mast cells and the hyperpigmentation of skin found in cutaneous mastocytosis. These findings suggest that some forms of mastocytosis represent reactive hyperplasia rather than mast-cell neoplasia.

Adult↗
PubMed1992

Primary cutaneous B-cell lymphoma. Diagnosis, treatment, and prognosis.

BACKGROUND: An elderly woman with B-cell lymphoma confined to the skin of the lower extremity was treated with combination chemotherapy and radiation therapy. She relapsed with new skin lesions outside the original radiation port that responded to additional radiation therapy and remains in remission 12 months after her last treatment. OBJECTIVE: This article investigates the diagnosis, treatment, and prognosis of primary cutaneous B-cell lymphoma. METHODS: The relevant literature was researched through computer data bases and bibliographies. RESULTS: Patients who present with localized lesions of primary cutaneous B-cell lymphoma have a favorable prognosis regardless of the type of therapy, although relapses may occur in the absence of systemic disease. CONCLUSION: We advocate the use of local therapies as initial treatment in patients with localized primary cutaneous B-cell lymphoma.

Aged↗