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Biomedical subjects

A P Kaplan

Publications and source records attributed to A P Kaplan.

At least 19 recordsLinked to original sources
PubMed2005

Increased responsiveness of basophils of patients with chronic urticaria to sera but hypo-responsiveness to other stimuli.

BACKGROUND: Although it has been shown that basophils from patients with chronic ordinary urticaria (CU) are less responsive than normal basophils when stimulated with anti-IgE, very few studies have examined the response of those cells to alternative stimuli. OBJECTIVE: To compare releasability between basophils from healthy donors and patients with CU. METHODS: We examined the response of IL-3-treated basophils from healthy donors, atopic controls and CU patients to anti-IgE, monocyte chemoattractant protein-1 (MCP-1), bradykinin, C5a and to sera obtained from other urticaria patients and normal controls. We also compared the response of basophils from CU patients whose sera activate normal basophils (autoimmune CU) from those who do not (idiopathic CU). RESULTS: Basophils of CU patients release significantly less histamine than basophils of normal controls when stimulated with anti-IgE, and to a lesser degree with C5a. No differences were observed when basophils from patients were incubated with Bradykinin or MCP-1. However, when basophils of CU patients were incubated with sera from other CU patients or even normal sera, we found significantly higher histamine release compared with the response of basophils from normal donors. We could not distinguish responsiveness of basophils of patients with chronic autoimmune urticaria from patients with chronic idiopathic urticaria. CONCLUSION: Basophils of patients with chronic idiopathic urticaria and chronic autoimmune urticaria are hypo-responsive to anti-IgE and C5a, normally responsive to MCP-1 or bradykinin, and hyper-responsive to serum. The serum factor to which a response has not yet been identified; however, basophils of patients with chronic urticaria, in general, appear to have abnormal regulation of signaling pathways.

Antibodies, Anti-Idiotypic↗
PubMed2005

Effects of calcineurin inhibitors on an in vitro assay for chronic urticaria.

BACKGROUND: Chronic urticaria is a common skin disorder, which causes considerable morbidity. In approximately 40% of cases, patients have an autoimmune disorder in which functional antibodies cause degranulation of mast cells and basophils, and C5a complement augments this in varying amounts from patient to patient. Since the calcineurin inhibitor ciclosporin has been used in chronic autoimmune urticaria, we examined the effect of ciclosporin and other drugs on the release of histamine from basophils when stimulated by sera from patients with chronic autoimmune urticaria. METHODS: Leucocytes from healthy donors were isolated and incubated in varying concentrations of ciclosporin, ascomycin, methotrexate, diphenhydramine or hydroxyzine for 30 min prior to stimulation with serum from urticaria patients known to have functional immunoglobulin (Ig)G antibodies directed against the alpha subunit of the IgE receptor. Histamine release was then measured. RESULTS: Pre-incubating cells with ciclosporin and ascomycin produced dose-dependent inhibition of histamine release when cells were stimulated by sera of urticaria patients, by purified IgG from these sera, but not by C5a. Inhibition was not prevented by C5a receptor blocking antibodies. No inhibition was seen with methotrexate, diphenhydramine or hydroxyzine. CONCLUSIONS: This is the first demonstration of inhibition of histamine release by calcineurin inhibitors employing sera of patients with chronic autoimmune urticaria. These drugs may work by interfering with intracellular signalling in cells following cross-linking of the IgE receptor, but not following stimulation of the C5a receptor.

Basophils↗
PubMed2003

IL3 effect on basophils histamine release upon stimulation with chronic urticaria sera.

BACKGROUND: Chronic urticaria is thought to be an autoimmune disorder in 35-40% of patients because of the presence of an immunoglobulin G (IgG) antibody reactive with the IgE receptor. Patients possessing this antibody are identified by the ability of serum to degranulate donor basophils to release histamine. We questioned whether priming of basophils with interleukin 3 (IL3) would facilitate identification of patients and/or alter the percentage of patients who have a positive assay. METHODS: We incubated 37 chronic urticaria sera with basophils from donors with no urticaria with and without priming with IL3 and compared histamine release in each instance. We also preincubated basophils from a 'non-releaser' with IL3, used these cells to assay chronic urticaria sera, and assessed the contribution of complement. RESULTS: Interleukin 3 increases the amount of histamine release by the sera which is able to activate basophils, but it does not convert negative sera into positive releasers. Interleukin 3 is able to partially reverse 'non-releaser' basophils into cells that respond to chronic urticaria sera, and complement cannot account for the augmentation seen. CONCLUSIONS: Preincubating basophils with IL3 facilitates the identification of sera with anti-IgE receptor antibody but does not affect the percentage of sera designated as positive.

Adult↗
PubMed2003

Assessment of the role of heparan sulfate in high molecular weight kininogen binding to human umbilical vein endothelial cells.

The assembly and activation of the kinin forming system components on human umbilical vein endothelial cells (HUVEC) have been studied in great detail. Proteins such as gC1qR, cytokeratin-1 and u-PAR have been identified to be responsible for Zn2+-dependent binding of high molecular weight kininogen (HK) to HUVEC. Heparan sulfate has also been shown to have a major role in Zn2+-dependent binding of HK to the endothelial cell line, Ea.hy 926. In this study, we have analyzed the possible contribution of heparan sulfate to high molecular weight kininogen binding to HUVEC using multiple approaches. The presence of heparan sulfate on HUVEC was analyzed by staining with an antibody specific for heparan sulfate. Incubation of the cells with bacterial heparinases removed the heparan sulfate from the cell surface to the level seen with a control antibody, however, the Zn2+-dependent binding of HK was not affected. Further, blocking of heparan sulfate with a specific antibody to heparan sulfate even after digestion with heparinases did not reduce HK binding whereas antibodies to the proteins gC1qR and cytokeratin-1 consistently reduced the binding of HK to the endothelial cells. The binding intensities of FITC-labeled HK were similar in heparinase-treated and -untreated HUVEC. The rate of kallikrein formation by the assembly of factor XII, HK and PK were similar in both heparinase-treated and non-treated HUVEC. All of these data indicate that heparan sulfate does not contribute significantly to HK binding to HUVEC.

Antibodies↗
PubMed2001

Mechanisms of autoimmune activation of basophils in chronic urticaria.

BACKGROUND: Approximately 35% to 40% of patients with chronic urticaria possess a circulating antibody directed to the alpha subunit of the high-affinity type I IgE receptor (FcepsilonRI), which is detectable by using histamine release assays or immunoblotting. Prior reports suggest that purified IgG may not directly activate basophils but rather does so through complement activation. OBJECTIVE: We sought to further elucidate the mechanism by which this antibody causes basophil histamine release, including the role of complement, and to reassess the relationship of functional versus binding assays. METHODS: We incubated human basophils with patient serum, patient IgG, or patient IgG plus normal serum as a complement source and measured histamine release for each condition. IgG fractions were neutralized with cloned alpha subunit to determine whether histamine release decreased proportionately. We also screened sera from 260 patients to compare histamine release with immunoblotting results. RESULTS: We initially tested 35 sera from patients with chronic urticaria by using basophils from 2 atopic donors and one nonreleaser with rabbit anti-IgE. No histamine was released from the nonreleaser, yet all donors responded identically to monocyte chemotactic protein 1, indicating a requirement for IgE or the IgE receptor. Basophil histamine release was markedly augmented by complement if release by IgG alone was low. Incubation of purified IgG with an increasing concentration of cloned alpha subunit gradually reduced the histamine-releasing capability in patients with positive or negative immunoblot results. Of 260 patients tested, 43% had positive histamine release results, and 47% had positive immunoblot results, yet there was no correlation when individual patients were assessed. CONCLUSION: A subpopulation of patients with chronic urticaria possess IgG antibody directed to the alpha subunit of FcepsilonRI. This IgG activates basophils, which is dependent on or augmented by complement. Binding assays for the FcepsilonRI alpha subunit, such as immunoblotting, are not currently feasible as a screening method. A functional assay is required.

Autoantibodies↗
PubMed2001

Late asthmatic reactions provoked by intradermal injection of T-cell peptide epitopes are not associated with bronchial mucosal infiltration of eosinophils or T(H)2-type cells or with elevated concentrations of histamine or eicosanoids in bronchoalveolar fluid.

BACKGROUND: Isolated late asthmatic reactions can be provoked by intradermal challenge of allergen-derived T-cell peptide epitopes. OBJECTIVE: The purpose of this study was to determine whether the isolated LAR is associated with the local accumulation of inflammatory cells, the expression of T(H)2 cytokines, and the production of pharmacologic mediators. METHODS: A randomized, placebo-controlled, crossover study design was used. The investigation involved bronchial and skin biopsies and bronchoalveolar lavage (BAL) fluids from 8 cat-allergic subjects who developed significant late asthmatic reactions 6 hours after intradermal injection of Fel d 1 chain 1-derived peptides (FC1Ps). RESULTS: Immunostaining of bronchial biopsy specimens showed no changes in the numbers of eosinophils, neutrophils, basophils, mast cells, CD3(+), CD4(+) or CD8(+) T cells, CD25(+) cells or macrophages, or cells mRNA(+) for IL-4, IL-5, or IL-13 when the FC1P day was compared with the diluent control day. There were also no significant differences in eosinophil numbers, either in BAL fluids or in peripheral blood after FC1P challenge. Furthermore, there were no significant alterations in the concentrations of histamine, histamine-releasing factors, or eicosanoids (LTC(4)/D(4)/E(4), PGD(2), PGE(2), TXB(2), PGF(2alpha)) in BAL fluids. FC1Ps induced a significant (P <.05) elevation in CD8(+) cells in the skin and an unexpected decrease in IL-5 in BAL fluids (P =.043). CONCLUSION: Part of the asthma process might involve T cell-dependent airway narrowing with no requirement for IgE, mast cells, or infiltrating inflammatory cells.

Adult↗
PubMed2001

Chemokines, chemokine receptors and allergy.

Chemokines are a group of cytokines that are responsible for the influx of blood cells, including T and B lymphocytes, monocytes, neutrophils, eosinophils and basophils, in allergic and other inflammatory conditions. They function as G protein-coupled chemotactic factors which also activate the cells with which they interact. Certain chemokines function within the afferent arm of the immune system, in which antigen is processed and antibody formation initiated, and others are active within the effector pathways of cellular immunity and late-phase allergic reactions. Th2 lymphocytes, which are critical for allergy, employ the CC chemokine receptors CCR4 and CCR8 with the ligands thymus- and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC) and I-309, respectively. The chemokine receptor CCR3 and ligands monocyte chemoattractant protein (MCP)-3, MCP-4, regulated upon activation normal T cell expressed and secreted (RANTES) and eotaxins I and II are of particular relevance for the recruitment and activation of eosinophils. Th1 reactions depend upon interferon gamma-induced CXC chemokines interferon- inducible protein (IP)-10, interferon-inducible T cell-alpha chemoattractant (iTAC) and monokine induced by interferon-gamma (MiG), which bind to chemokine receptor CXCR3.

Antigen Presentation↗
PubMed2001

Activation of the kinin-forming cascade on the surface of endothelial cells.

Activation of the plasma kallikrein-kinin forming cascade takes place upon incubation with human umbilical vein endothelial cells. The mechanism by which initiation occurs is uncertain. Zinc-dependent binding of plasma proteins to gC1qR, cytokeratin 1, and perhaps u-PAR is requisite for activation to take place. We demonstrate here that during a 2 hour incubation time plasma deficient in either factor XII or high molecular weight kininogen (HK) fails to activate, as compared to normal plasma, but with more prolonged incubation, factor XII-deficient plasma gradually activates while HK-deficient plasma does not. Our data support both factor XII-dependent (rapid) and factor XII-independent (slow) mechanisms; the latter may require a cell-derived protease to activate prekallikrein and the presence of zinc ions and HK.

Antibodies, Blocking↗
PubMed2001

Factor XII-dependent contact activation on endothelial cells and binding proteins gC1qR and cytokeratin 1.

Although proteins of the kinin-forming pathway are bound along the surface of endothelial cells, the mechanism of activation of this proteolytic cascade is unclear. Endothelial cell surface proteins, gC1qR and cytokeratin 1, are capable of binding Factor XII and high molecular weight kininogen (HK) in a zinc-dependent reaction thus we considered the possibility that these proteins might catalyze initiation of the cascade. Incubation of Factor XII, prekallikrein, and HK with gC1qR or cytokeratin 1 leads to a zinc-dependent and Factor XII-dependent conversion of prekallikrein to kallikrein. We also demonstrate that normal plasma is capable of activating upon interaction with the cells whereas plasma deficient in Factor XII, prekallikrein and HK do not activate. Normal plasma activation was inhibitable by antibody to gC1qR and cytokeratin 1. Thus, gC1qR and cytokeratin 1, represent potential initiating surfaces for activation of the plasma kinin-forming cascade and may do so as a result of their expression along cell surfaces.

Carrier Proteins↗
PubMed2001

C1 inhibitor deficiency: hereditary and acquired forms.

C1 inhibitor deficiency can be hereditary or acquired. The hereditary disorder has two types, each of which is inherited as a dominant disorder, with genetic mechanisms leading either to low levels of normal C1 INH and little or no mutant problem as a result of mRNA or protein synthetic defects or degradative mechanisms (Type I) or with point mutations and synthesis of a functionless protein product with transinhibition of the normal allele (Type II). The acquired disorder with low C1q is due to C1 INH consumption associated with lymphoma or connective tissue disease (Type I) and/or autoimmune mechanisms (Type II). The swelling of all types is due to absence of inhibition of the plasma kinin forming cascade with liberation of bradykinin while complement activation, a critical marker of the disorder, is not responsible for the swelling. Treatment employs androgenic compounds, antifibrinolytic agents, or replacement therapy.

Angioedema↗
PubMed1999

Zinc-dependent activation of the plasma kinin-forming cascade by aggregated beta amyloid protein.

Beta Amyloid proteins (Abeta) of 38, 40, and 42 amino acids long were assessed for their ability to activate the plasma kinin-forming cascade in vitro. Incubation with a mixture of Factor XII (Hageman Factor), prekallikrein, and high-molecular-weight kininogen (HK) led to conversion of prekallikrein to kallikrein that was dependent on zinc ion. No activation occurred if Factor XII was omitted. There was rapid generation of bradykinin equal to the molar HK input indicating complete cleavage. Incubation of aggregated Abeta with diluted human plasma also led to prekallikrein activation and HK cleavage. Activation of the cascade by Abeta (1-38) was dependent upon its preincubation time in buffer, suggesting that aggregation of Abeta is required, and studies with Abeta (1-40) revealed time-dependent aggregation by microscopy and augmented zinc-dependent binding of both Factor XII and HK to aggregated Abeta. These data demonstrate that aggregated Abeta can bind and activate proenzymes of the plasma kinin-forming cascade in a zinc-dependent reaction to release bradykinin and is of sufficient potency to do so at physiologic concentrations of each protein and in the presence of naturally occurring protease inhibitors.

Amyloid beta-Peptides↗
PubMed1999

Cytokeratin 1 and gC1qR mediate high molecular weight kininogen binding to endothelial cells.

High molecular weight kininogen (HK) attaches to endothelial cells by separate sites on the heavy and light chains and requires 15-50 microM zinc. Previously identified binding proteins include gC1qR, cytokeratin 1, and the urokinase plasminogen activator receptor; however, their relative contributions to binding are not yet clarified. We have prepared affinity columns to which were coupled either cleaved HK or peptide LDCNAEVYVVPWEKKIYPTVNCQPLGM derived from heavy-chain domain 3. Endothelial cell membranes were solubilized and chromatographed in the presence or absence of zinc ion, the bound proteins were eluted, and active fractions were identified by dot blot using biotinylated HK, SDS/PAGE, and Western blot analysis. The peptide containing column eluate revealed but one band at 68 kDa if zinc ion was present which was identified as cytokeratin 1 by amino acid sequencing of an internal peptide. The HK affinity column revealed bands at 68 kDa (cytokeratin 1), 33 kDa (gC1qR), and 66 kDa (unidentified). HK or domain 3-derived peptide bound to the 68 kDa band; prekallikrein and Factor XII did not. HK or Factor XII bound to the 33-kDa band if zinc was present while no binding to the 66 kDa band was observed. Antibody to cytokeratin 1 inhibited HK binding to endothelial cells by 30%, antibody to gC1qR inhibited HK binding to endothelial cells by 72%, and a mixture of both inhibited binding by 86%. Our data suggest HK binding by interaction of the heavy-chain domain 3 with cytokeratin 1 and the light chain with gC1qR.

Amino Acid Sequence↗
PubMed1999

A double-blind, placebo-controlled trial of fexofenadine HCl in the treatment of chronic idiopathic urticaria.

BACKGROUND: Symptoms of chronic idiopathic urticaria (CIU) include relentless itching and painful wheals, which can be physically and psychologically debilitating. Half of all patients with urticaria have angioedema, which is often disfiguring. OBJECTIVE: To evaluate the safety and efficacy of fexofenadine HCl for the treatment of CIU symptoms. METHODS: In this 4-week, multicenter, placebo-controlled study, 439 patients with moderate to severe pruritus and urticaria received 1 of 4 oral doses of fexofenadine HCl (20, 60, 120, or 240 mg twice a day) or placebo. Patients reflectively assessed (over the previous 12 hours) the severity of pruritus, the number of wheals, and the interference with sleep (7 AM) and normal activities (7 PM) due to urticaria. Efficacy measures included a change from baseline of daily mean pruritus score (MPS), daily mean number of wheals (MNW) score, daily mean total symptom score (MTSS) (ie, the sum of the wheal and pruritus scores), and mean interference with sleep and daily activities due to urticaria. RESULTS: All 4 doses of fexofenadine were statistically superior to placebo (P </=.0238) for MPS, MNW score, and MTSS. Patients receiving fexofenadine HCl also experienced significantly less interference with sleep and daily activities than patients receiving placebo (P </=.0001). Efficacy results were similar in the 60-, 120-, and 240-mg groups and were quantitatively better than those in the 20-mg group. Adverse events were mild and occurred with similar incidence in all treatment groups. CONCLUSIONS: Fexofenadine HCl is well tolerated and is statistically superior to placebo in reducing signs and symptoms of CIU and in ameliorating interference with sleep and daily activities due to urticaria. Doses of 60 mg twice a day or greater are most effective.

Adolescent↗
PubMed1999

Complement dependence of histamine release in chronic urticaria.

BACKGROUND: IgG autoantibodies directed to the alpha-subunit of the IgE receptor have been identified in 30% to 45% of patients with chronic urticaria. However, the exact mechanism by which histamine secretion is initiated is uncertain. OBJECTIVE: Histamine release from cutaneous mast cells may occur by cross-linking the IgE receptor or by activation of complement. Our goal is to distinguish these 2 possibilities. METHODS: We incubated human cutaneous mast cells with patient sera, decomplemented sera, or purified patient IgG. The IgG was also added to pooled normal serum or to sera deficient in either C2 or C5, and its ability to activate mast cells was assessed. Mast cells were incubated with human IgE myeloma to saturate alpha-subunits to determine the effect on histamine release. RESULTS: Patient sera released histamine (18.26% +/- 4.39%), but purified IgG from patients (5.5% +/- 4.3%) did not. Addition of the patient IgG to normal sera rendered the sera positive for histamine-releasing activity (18.4% +/- 4.3%), whereas control IgG or patient IgG added to C2- or C5-deficient sera did not release histamine. Histamine release with decomplemented patient sera was also diminished (8.34% +/- 4.3%). Preincubation of mast cells with a C5-blocking peptide decreased histamine release but was not statistically significant; there was a significant decrease after preincubating mast cells with IgE myeloma. CONCLUSION: The degranulation of mast cells by IgG autoantibodies in patients with chronic urticaria requires binding to the IgE receptor and activation of the classical complement cascade. Saturation of the IgE receptor with IgE inhibits such degranulation, presumably by preventing binding of the requisite IgG.

Cell Degranulation↗