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K H Singer

Publications and source records attributed to K H Singer.

49 records · Page 3Linked to original sources
PubMed1983

Anti-cell surface pemphigus autoantibody stimulates plasminogen activator activity of human epidermal cells. A mechanism for the loss of epidermal cohesion and blister formation.

Binding of anti-cell surface pemphigus autoantibodies to cultured human epidermal cells stimulates synthesis and secretion of plasminogen activator (PA). Increases in PA activity were detected within 6 h of the addition of IgG and stimulation was dependent upon IgG concentration. Stimulation of PA activity was inhibited by cycloheximide, which indicates that synthesis of protein was necessary. Pharmacological doses of dexamethasone also prevented IgG-induced stimulation of PA. Electrophoretic profiles of PA secreted by cultured human epidermal cells in the presence or absence of pemphigus IgG were similar. The majority of the PA activity comigrated with the higher-molecular-weight species of human urokinase (approximately 55,000). Explants of normal human skin incubated with pemphigus vulgaris IgG displayed loss of epidermal cohesion similar to that observed in patient biopsies. The histologic changes were potentiated by the inclusion of human plasminogen. Loss of epidermal cohesion in normal skin explants incubated with pemphigus foliaceous IgG was dependent upon the addition of plasminogen and was inhibited by aprotinin or lima bean trypsin inhibitor, which indicated that plasmin is the active enzyme in producing acantholysis. These data support the hypothesis that stimulation of PA by the anti-cell surface autoantibodies of pemphigus results in a localized increase in plasmin, which through proteolysis produces the loss of epidermal cohesion characteristic of pemphigus.

Autoimmune Diseases↗
PubMed1983

Plasminogen activator in cultured human epidermal cells.

Primary cultures of human epidermal cells produce plasminogen activator (PA) as demonstrated by the ability of conditioned medium or cell lysates to hydrolyze fibrin in the presence of plasminogen, and to cleave [125I]plasminogen to characteristic fragments. The major molecular species of PA in human epidermal cells was inhibited by diisopropylfluorophosphate and comigrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with the high molecular weight band of human urokinase (Mr 55,000). Production of PA by human epidermal cells was inhibited by cycloheximide, stimulated by colchicine, and not affected by cytochalasin B or the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. Both cholera toxin and epidermal growth factor stimulated PA activity in human epidermal cells, and PA activity was maximal at concentrations that best support in vitro growth of human epidermal cells. Examination of individual cells indicated that at least 15% of cells within a culture produced detectable amounts of PA.

Cells, Cultured↗
PubMed1983

Molecular size of secreted and cell-associated plasminogen activators from cultured epidermal cells.

The molecular sizes of secreted and cell-associated plasminogen activators from four cultured cell types were determined using an SDS-PAGE technique in which plasminogen and casein were included during polymerization of the polyacrylamide gel. The major bands of plasminogen activators secreted by human neonatal epidermal cells, human adult epidermal cells and transformed human squamous cells migrated the same distance as the high molecular weight band of authentic urokinase, indicating that the apparent molecular weight of these plasminogen activators was approximately 55,000 daltons. Plasminogen activator extracted from normal adult human epidermis also migrated with this major band of plasminogen activator, and a minor higher molecular weight band was also detected. In contrast, plasminogen activators secreted by transformed mouse squamous cells migrated between the high molecular weight band (approximately 55K) and the low molecular weight band of urokinase (approximately 32K), indicating that plasminogen activators of mouse epidermal cells differ from those of human epidermal cells. The mobility of the major bands of plasminogen activators detected in cell lysates of the four cell types was identical to that of secreted plasminogen activators.

Adult↗
PubMed1983

Correlation of epidermal plasminogen activator activity with disease activity in psoriasis.

The specific activity of plasminogen activator was increased in clinically involved psoriatic epidermis compared with the uninvolved skin of the same eight patients. Alterations in plasminogen activator activity correlated with disease activity as measured by extent of body surface involved with psoriasis. Levels of plasminogen activator increased in uninvolved epidermis of psoriatic patients during retinoid therapy.

Adult↗
PubMed1982

Autodegradation of 125I-labeled human epidermal cell surface proteins.

Triton X-100 extracts of cultured human epidermal cells exhibited proteolytic activity as measured by the hydrolysis of [3H]-casein at neutral pH. The majority of endogenous proteolytic activity was inhibited by parahydroxy mercuribenzoate and by mersalyl acid, indicating the enzyme(s) was a thiol class proteinase(s). Crude Triton X-100 extracts were prepared from epidermal cells following labeling of proteins with 125I. Autodegradation of labeled proteins at 37 degrees C was detected as early as 1 hr and reached a plateau level by 4 hr. Degradation was inhibited by thiol class proteinase inhibitors. Among the detergent-solubilized radiolabeled proteins a polypeptide chain of Mr 155,000 was particularly sensitive to degradation by endogenous thiol proteinase(s).

Cells, Cultured↗
PubMed1982

Antibody-induced release of cellular proteinases: loss of adhesion of human melanoma cells after binding of anti-melanoma antibody.

Incubation of monolayer cultures of human melanoma cells with monkey anti-human melanoma IgG resulted in loss of cellular adhesion. Release of melanoma cells from the culture dish was not the result of cytotoxicity. Antibody-induced cell detachment was partially inhibited by the addition of diisopropylfluorophosphate (DFP), and detachment was completely inhibited by the addition of lima bean trypsin inhibitor. Thiol and carboxyl proteinase inhibitors did not block antibody-induced cellular detachment. An IgG dose-dependent increase in DFP-inhibitable caseinolytic activity was demonstrated in the culture medium of melanoma cells incubated with anti-melanoma IgG, but not in those incubated with normal monkey IgG. Medium collected from antibody-treated cell cultures and incubated with protein A-Sepharose to remove IgG caused detachment of melanoma cells in fresh cultures. Preincubation of this conditioned medium from antibody-treated cell cultures with DFP abolished the medium's ability to mediate loss of cellular adhesion. These data suggest that incubation of melanoma cells with immune IgG results in release of a serine proteinase that mediates cellular detachment.

Animals↗
PubMed1981

Antibody-induced proteinase activation: a proposed mechanism for pemphigus.

The current state of understanding of pemphigus includes the following: 1. Pemphigus is an autoimmune disease. In all variants a circulating autoantibody is found which binds to epidermal cells. In vivo antibody may be found deposited in the epidermis of patients. 2. The autoantibody levels generally correlate with disease activity indicating a relationship between antibody and clinical disease. 3. Although complement components are found in lesional skin, complement does not appear to be necessary for dissolution of the epidermal cement substance. 4. The treatment of pemphigus with corticosteroids has drastically reduced mortality rates. 5. Three different groups have presented results in two different experimental systems which indicate that subsequent to binding of pemphigus antibody to epidermal cells a proteinase is activated. This proteinase(s) degrades the intercellular cement substance of epidermis which results in loss of cellular adhesion and acantholysis. There are numerous questions still remaining. What is the nature of the proteinase(s) and the surface protein(s) it cleaves? Does the binding of pemphigus antibody to the cell surface induce enzyme synthesis, specific enzyme activation, or generalized lysosomal secretion? The answers to these questions will have broad biologic relevance since they may elucidate the role of anticell surface antibodies in disease states.

Acantholysis↗
PubMed1980

Proteinase activation: a mechanism for cellular dyshesion in pemphigus.

An in vitro model system using cultured newborn epidermal cells was employed to investigate the binding of pemphigus autoantibody and subsequent loss of adhesion between epidermal cells. Pemphigus antibodies bound to both mouse and human cultured epidermal cells. Incubation of cultured newborn mouse epidermal cells with pemphigus antibody followed by gentle agitation induced loss of adhesion between the epidermal cells and the plastic culture dish. Release of viable epidermal cells from the dish was inhibited by the proteinase inhibitors, soybean trypsin inhibitor and alpha 2-macroglobulin. These observations suggest that pemphigus antibody induces viable epidermal cells to activate cellular proteinases which then degrade the glycocalyx and cause cellular dyshesion and acantholysis.

Acantholysis↗
PubMed1978

Interaction of cytotoxic T lymphocytes with target cells. I. Specific inhibition by detergent-solubilized, partially purified mouse histocompatibility antigens.

H-2 antigens from EL4 (H-2b) and RLmale 1 (H-2d) leukemias were solubilized with deoxycholate and partially purified based on their adherence to a Lens culinaris hemagglutinin column. In double reciprocal experiments we have shown that these preparations specifically inhibit conjugate formation between target cells and alloimmune peritoneal lymphocytes, a preparation rich in cytotoxic T lymphocytes.

Animals↗