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At least 127 records · Page 7Linked to original sources
PubMed1985

A synthetic nonapeptide corresponding to the NH2-terminal sequence of C3d-K causes leukocytosis in rabbits.

Numerous biologically active fragments have been described that are derived from the C3 molecule. Recently, a polypeptide (Mr 41,000) generated from the alpha chain of human iC3b by limited proteolysis with plasma kallikrein was shown to exhibit several biological functions. This C3-derived cleavage product, C3d-K, suppresses mitogen- and antigen-induced proliferation of human T-lymphocytes and induces leukocytosis in rabbits. We have identified and synthesized a portion of C3d-K that is associated with the leukocytosis phenomenon. A nonapeptide corresponding to the amino-terminal nine residues of C3d-K was synthesized using conventional Merrifield solid-phase peptide chemistry; the structure of this peptide is Thr-Leu-Asp-Pro-Glu-Arg-Leu-Gly-Arg (TLDPERLGR). At a final concentration of 4 X 10(-6) M, both the nonapeptide and the des-Arg octapeptide (TLDPERLG) were capable of inducing leukocytosis in rabbits. Additionally, both peptides enhance vascular permeability when injected in guinea pig skin. These activities are similar to those previously attributed to a C3 fragment identified as C3e by Ghebrehiwet and Müller-Eberhard (Ghebrehiwet, B., and Müller-Eberhard, H.J. (1979) J. Immunol. 123, 616-621). We conclude that the nonapeptide TLDPERLGR represents the active center of the C3-derived leukocytosis factors C3e and C3d-K. This active synthetic analogue of C3d-K should prove valuable in elucidating the mechanism of action for complement-dependent leukocyte mobilization in vivo.

Amino Acid Sequence↗
PubMed1985

Bronchoalveolar lavage in patients with the adult respiratory distress syndrome.

BAL in patients with ARDS provides material containing the soluble and cellular constituents of the alveolar compartment, and hence is a useful tool for the study of the pathogenesis of ARDS. The technique is imperfect as it is prone to problems of data acquisition and interpretation. However, it is lung-specific and may be used in serial studies of patients over the course of their disease. A large amount of evidence is rapidly being accumulated which documents the presence of effectors of inflammation in the BAL fluids of patients with ARDS. Confirmation of the importance of such mediators, pathways, or cellular constituents of BAL fluid in establishing the pathogenesis of ARDS ultimately depends upon proof of the efficacy of specific clinical interventions which both arrest the activity of the effector and predictably alter the course of the disease.

Capillary Permeability↗
PubMedDate not supplied

[Initial results of the clinical use of the immunostimulant bestatin (3-amino-2-hydroxy-4-phenylbutyryl leucine) in patients with chronic polyarthritis].

We tested the efficacy of the immunomodulator Bestatin, which has been successfully applied in Japan, in a preliminary open study in ten patients with classical or definite rheumatoid arthritis. Patients whose arthritis was characterized by a low humoral activity showed a partial remission of the disease after six months' application of increasing doses of 10-60 mg in 48 hours. We found a significant increase in superoxide release from peripheral monocytes. Humoral parameters of inflammation such as erythrocyte sedimentation rate, C3a complement fraction, prostaglandin E2, and thromboxane B2 decreased. Concerning the subpopulations of lymphocytes we found a slight increase of activated T-lymphocytes and a decrease of O-cells and B-cells. The T-helper/T-suppressor ratio remained unchanged. The rheumatoid factor and the antinuclear antibodies showed no alteration under the treatment. Two weeks after withdrawal of Bestatin the improvement of the clinical and humoral parameter of the inflammation in rheumatoid arthritis vanished. No serious side effects were seen. Our results contribute to a long-term controlled study of the immunomodulator Bestatin as basic drug in the treatment of rheumatoid arthritis.

Adjuvants, Immunologic↗
PubMed1981

Human C5a des Arg increases vascular permeability.

C5a were generated in human plasma by incubation with zymosan in the presence of a carboxypeptidase B inhibitor. The carboxypeptidase inhibitor was added to prevent cleavage of the carboxyl terminal arginine from C5a and enabled it to be purified on the basis of spasmogenic activity on the guinea-pig isolated ileum. When injected into rabbit skin, purified C5a induced marked plasma leakage over a 30-min period, but only if the substance was first mixed with a vasodilator substance such as prostaglandin (PG)E2. The responses to C5a + PGE2 did not appear to be related to anaphylatoxic, histamine-releasing activity because an antihistamine, mepyramine, had only a small effect on plasma leakage. Further, removal of the carboxyl terminal arginine by carboxypeptidase B abolished activity on the ileum but not in the skin. The observation that both human C5a and C5a des Arg were able to increase vascular permeability in vivo suggested a parallel with leukotactic activity in vitro. In support of this, no responses to C5a + PGE2 were obtained in rabbits depleted or circulating polymorphonuclear leukocytes. Thus, inflammatory edema resulting from extravascular complement activation may be dependent on 2 components: a leukocyte/endothelial cell interaction triggered by C5a, and the concomitant generation of a vasodilator, prostaglandin.

Anaphylatoxins↗
PubMed1984

Pathophysiologic mechanisms of allergic and pseudo-allergic reactions to foods, food additives and drugs.

Allergic or pseudo-allergic reactions elicited by per os intake of foods, food additives or drugs may be based on one or several of the following immunopathologic mechanisms: 1) specific IgE bound to mast cells and/or basophils; 2) antigen-IgE soluble complexes hitting various target cells; 3) antigen-IgG complexes generating anaphylatoxins; 4) generation of anaphylatoxins by alternate pathway complement activation; 5) release of mast cell mediators by other direct triggering mechanisms (e.g., basic peptides, peptones); 6) effects on other target cells such as neutrophils and platelets; 7) reactions mediated by specific effector lymphocytes. While allergic reactions in a classical sense involve a sensitization process leading to the formation of specific immunologic agents such as antibodies or specific T lymphocytes, pseudo-allergic reactions appear to involve the same inflammatory mediators which are formed and/or released through different mechanisms and without the necessity for specific sensitization. The complexity of the phenomena possibly involved continues to create great difficulties in the objective diagnosis of food allergy.

Anaphylatoxins↗
PubMed1986

[A new case of bronchospasm under extracorporeal circulation].

A case of bronchospasm occurring after the termination of cardiopulmonary bypass is reported. The complement fractions C3a, C4a and C5a were measured before and right after CPB. Complement activation is not specific to CPB but may occur in any thoracotomy. The statistically significant increase in complement C3a without any pulmonary symptomatology has been reported by several authors. Complement activation cannot therefore be considered as the explanation of this bronchospasm.

Bronchial Spasm↗
PubMed1976

Cytolytic effects of the complement cleavage product, C3a.

Purified C3a, a cleavage product of the third component of complement,was incubated with various cell types of human and mouse origin. All the tumour cell types tested were lysed by low concentrations of C3a, whereas normal human lymphocytes were relatively resistant. No lysis was produced by C3 or C3b. The possible role of C3a in immunity against tumours is discussed.

Animals↗
PubMed1978

Macrophage secretion and the complement cleavage product C3a in the pathogenesis of infections by mycoplasmas and L-forms of bacteria and in immunity to these organisms.

Mouse peritoneal macrophages in culture exposed to Mycoplasma pulmonis show marked biochemical changes. This micro-organism induces the release of hydrolytic enzymes from macrophages. The release is time- and dose-dependent and is not associated with loss of the cytoplasmic enzyme lactate dehydrogenase or any other sign of cell death. Secretory products of macrophages may play a role in the pathogenesis of chronic inflammatory responses elicited by mycoplasma infections. One of the products of activated macrophages is the complement cleavage product C3a. Purified C3a was incubated with M. hominis, M. pulmonis, Proteus mirabilis and an L-phase variant of this organism. All mycoplasmas and the L-phase variant were lysed by low concentrations of C3a, whereas the bacterial form of Pr. mirabilis was resistant.

Animals↗
PubMed1975

Human anaphylatoxin (C3a) from the third component of complement. Primary structure.

C3a anaphylatoxin is derived from the third component (C3) of the blood complement system. Selective proteolysis of C3 by activated proenzymes indigenous to blood generates the C3a fragment. Human C3a was isolated from inulin-activated serum containing 6-aminohexanoic acid, according to recently published procedures (Hugli, T. E., Vallota, E., and Müller-Eberhard, H. J. (1975) J. Biol. Chem. 250, 1472-1498). The human C3a fragment is a highly cationic molecule exhibiting an approximate molecular weight of 9000 and composed of 77 amino acid residues. It consists of a single polypeptide chain containing 8% cysteine and lacks both tryptophan and carbohydrate. A tentative primary structure for the human C3a molecule, deduced from overlapping peptides obtained after cyanogen bromide cleavage, tryptic and chymotryptic digestion, is: See article. Two cystelhylcysteine sequences were established at positions 22, 23 and 56, 57 in human C3a. The 6 half-cystine residues in C3a are all interconnected through three disulfide linkages intersecting in a disulfide knot. The functionally amino acid residues distributed among 14 residues at the COOH-terminal end of C3a. This unusually cationic COOH-terminal region of C3a is presumed to play an important role in the interaction of this protein molecule with cellular receptors. A comparison between the linear sequence of human C3a and the NH2-terminal sequences of light and heavy chains of human immunoglobulin indicates that limited identity exists.

Amino Acid Sequence↗