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At least 109 records · Page 6Linked to original sources
PubMed1998

Stimulation of Human Platelet Cytotoxicity by Various Activators in the Absence of Antibodies: Release of Thromboxane A2 and Soluble Cytotoxic Factors. Purification and Partial Characterisation of 14 and 28 kDa Cytotoxic Proteins.

The cytolytic activity of human plasma free platelets treated with various stimulators (Ca-ionophore, PAF (platelet activating factor), PHA, and ricin) has been studied on human erythroid leukemia cell line (K562). The 14 kDa and 28 kDa platelet cytotoxic factors (PCF) have been purified from the supernatant obtained from platelets stimulated by 10(-7) M Ca-ionophore. The PCF-14 N-terminal sequence ((1)YAPQXQFGP(9)-) appeared to be homologous to the region 241-249 residues of the human C1s complement component. The PCF-28 N-terminal sequence (DVGLT-) did not display any homology to known human proteins. The PCF-14 and the PCF-28 have been detected both in the supernatants of platelets treated with various stimulators (10(-7) M Ca-ionophore A23187, or 10(-8) M PAF, or 10(-9) M PHA, or 10(-13) M ricin) and in the extracts of disrupted platelets treated by these stimulators. All of these stimulators enhanced the production of thromboxane A(2) by platelets, as evidenced from the accumulation of thromboxane B(2), a spontaneous hydrolysis product of thromboxane A(2). These results indicate that platelet cytotoxicity to the K562 cells and the release of PCF-14 and PCF-28 might be mediated by the stimulation of thromboxane A(2) synthesis, when platelets have been activated through the cycloxygenase pathway.

Journal Article↗
PubMed1990

Regulation of the hepatic synthesis of C1 inhibitor by the hepatocyte stimulating factors interleukin 6 and interferon gamma.

C1 inhibitor (C1INH), the major plasma inhibitor of activated C1, kallikrein, and activated Hageman factor, may be an important factor in limiting inflammatory injury mediated by the complement and contact systems. C1INH is thought to be synthesized primarily in the liver; however, the regulators of hepatic C1 inhibitor synthesis are completely unknown. In this report, we analyze the regulation of C1INH synthesis by hepatocyte stimulating factors in human hepatoma cell lines and primary hepatocytes. Interleukin-6 and interferon gamma increase C1INH production in both hepatoma cells and hepatocytes. These cytokines stimulate de novo synthesis of functional C1INH, acting at a pretranslational level as assessed by Northern blotting. The stimulatory effects of interleukin-6 and interferon gamma on C1INH synthesis are separate and are differentially modulated by interleukin-1. These results establish that hepatic C1INH synthesis is regulated by hepatocyte stimulating factors and reveal novel interactions between these factors.

Acute-Phase Proteins↗
PubMed1991

Amino acid residues 1101-1105 of the isotypic region of human C4B is important to the covalent binding activity of complement component C4.

The C4A and C4B isotypes of human C4 show certain functional differences that stem from their relative preference for transacylation to amino (-NH2) vs hydroxyl (-OH) nucleophiles, respectively, on complement-activating surfaces. Comparison of amino acid sequences of the alpha-chain fragment of C4, C4d, has shown C4A- and C4B-specific sequences at residues 1101-1106 are the only consistent structural difference between isotype, i.e., Pro, Cys, Pro, Val, Leu, Asp in C4A and Leu, Ser, Pro, Val Ile, His in C4B. These residues may be responsible either in part or entirely for properties associated with isotype. To examine the functional role of residues 1101-1106 in C4B-mediated hemolysis, whole serum or immunopurified human C4 with allotypes, A3B1, A3, B2B1, or B1 were preincubated in the presence or absence of an antipeptide mAb (BII-1) specific for amino acid residues 1101-1105 of C4B. Sensitized sheep E and C4-deficient guinea pig serum was then added and lysis measured by absorbance at 415 nm. Our results show lysis of antibody-sensitized sheep E is inhibited by antibody and C4B2B1, C4B1, or C4A3B1 but not antibody and C4A3. The interference of hemolysis by BII-1 could not be explained by inhibition of activation of C4B or inhibition of C3 or C5 convertase activity. Furthermore, results from uptake experiments show that BII-1 interferes with the covalent binding activity of C4B, indicating residues 1101-1105 play a role in the covalent binding reaction of C4B to the target E-antibody complex.

Amino Acid Sequence↗
PubMed1990

[A simplified method for the assessment of C1 esterase inhibitor function].

From the result that the activated form of C1-s(C1-s) prolonged the kinetics of hemolysis via complement, this assay was applied to assess C1 esterase inhibitor (C1INH) function. In the kinetic assay, the complement hemolytic activity was evaluated by the time which required to cause 50% reduction of the initial turbidity of sensitized sheep erythrocytes, and was expressed as T1/2. (1) T1/2 of pooled normal human sera (p-NHS) showed dose-dependent prolongation by the addition of various amounts of C1-s. (2) Preincubation of various amounts of functionally pure C1INH with the constant amounts of C1-s inhibited dose-dependently the prolongation of T1/2 by C1-s. (3) The C1INH activity of NHS was 840 +/- 80 units/ml (n = 6) and that of the C1INH deficient serum was 80 units/ml, which were calculated from the standard curve established by the addition of various amounts of purified C1INH. This test requiring only C1-s and sensitized sheep erythrocytes is simple technically and high in sensitivity, and seems to be useful for the routine assay for C1INH function of human sera.

Animals↗
PubMed1977

An investigation of the complement system in patients with periodic disease (results from 29 cases).

The complement system was investigated in 29 patients suffering from authentic periodic disease. A statistically significant increase in C4, also in total complement and C3 could be demonstrated. It is possible that the increase in C4 was due to the macrophages which are always present in the infiltrates of periodic disease. This biological observation is of clear practical importance for the diagnosis of the condition both before and after colchicine therapy.

Complement C1 Inactivator Proteins↗
PubMed1978

Inhibition of the classical and alternative pathways by amino acids and their derivatives.

Effects of various aminoacids and their derivatives on the classical pathway and alternative pathway of the complement were studied. Leupeptin, acetyl-leucyl-leucyl-arginal, inhibited CH50 and Cl-esterase, but did not inhibit the alternative pathway. When aminoacids of carbon chains of the order of seven were used, arginine and lysine had stronger effects than trans-aminomethyl cyclohexane carboxylic acid (t-AMCHA), cis-aminomethyl cyclohexane carboxylic acid (cis-AMCHA) and epsilon aminocaproic acid (EACA). SH-compounds, cysteine, homocysteine and glutathione, had the strongest inhibitory effects among these aminoacids on both classical and alternative pathways. When effects on Cl esterase were compared, arginine, lysine, t-AMCHA, cis-AMCHA and EACA had weak inhibition while SH-compounds showed strong inhibition. Poly-L-lysine, which had extremely strong inhibition of CH50, had no inhibition of Cl esterase. The inhibitory effects of antifibrinolytic agents, EACA and t-AMCHA, were weak but when effects on early parts of the classical pathway, C(1,4,2)H50 were tested, some inhibitory activities were recognized. Thus inhibitory effects of these agents were due to their activities on the early parts of the classical pathway.

Amino Acids↗
PubMedDate not supplied

[Hereditary angioedema by defict of C1 esterase. Our experience in 8 cases].

Eight cases of hereditary angioedema, all of them with low values of C1-sterase inhibitor are analyzed. In 7 cases the C3 and C4 components of the complement were assessed; the results showed marked descent of C4. The 8 patients came from 4 different families; only 2 of them were males. Six patients presented digestive disorders, reporting colic pain, nausea and vomiting. In 1 of them the abdominal picture was the only evidence of the disease. In 5 patients the angioedema episodes occurred following traumatisms and in 3 because of emotional states. The duration of the attacks varied from several hours to six days. There was a familial history in all cases. Three of the patients had repeated episodes of pharyngolaryngeal angioedema, two of them requiring emergency tracheotomy because of suffocating crisis. Six patients were treated with Epsilon aminocaproic acid (16 to 20 gr daily) or with tranexamic acid (1 to 3 gr. daily). In 4 cases the results were excellent with either of these antifibrinolytic drugs. No side effects were observed in the tranexamic acid therapy whilst they were frequent in the treatment with Epsilon aminocaproic acid.

Adolescent↗
PubMed1985

[Current diagnostic possibilities in hereditary angioedema and acquired angioedema].

Amidolytic assays for the determination of C1 esterase inhibitor have been proposed some years ago; however, the substrates employed lacked sensitivity. The recent development of a C1 esterase-sensitive substrate (N-alpha-methoxycarbonyl-l-lysyl(epsilon-CBO)-glycyl-arginyl-4-nit roanilide) provides a method that can be routinely used. Any interferences with other plasma proteases could not be observed. Normal range was ascertained to be 1.48 +/- 0.23 kU/l; within-run precision revealed C.V.'s of 1.74% (for the normal range) and 7.3% (for the pathological range). This method can be considered most suitable for functional determination of C1 esterase inhibitor and is superior to the determination of antikallikrein activity. To point out to the diagnostic relevance of a functional C1 esterase inhibitor assay some examples are illustrated.

Angioedema↗