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Biomedical subjects

D Bitter-Suermann

Publications and source records attributed to D Bitter-Suermann.

At least 109 records · Page 6Linked to original sources
PubMed1983

Induction of thromboxane release from macrophages by anaphylatoxic peptide C3a of complement and synthetic hexapeptide C3a 72-77.

Guinea pig peritoneal macrophages were examined for their response to homologous anaphylatoxic peptide C3a of complement. C3a caused the release of considerable amounts of thromboxane A2 from macrophages maintained in serum-free culture for up to 12 hr. Preincubation of C3a with the Fab portion of a monoclonal anti-C3a IgG abrogated its stimulatory capacity. C3a desarg was found to be rather ineffective in eliciting thromboxane release. Hexapeptide C3a 72-77, comprising the C-terminal amino acids of human C3a, proved also to stimulate the cyclooxygenation pathway of macrophage arachidonic acid metabolism, following the same routes of receptor-ligand interactions (rapid onset of activation, low dose, and cumulative desensitization) as proven for other anaphylatoxin-cell interactions. This novel effect of anaphylatoxins C3a and C3a 72-77 could contribute to inflammatory reactions in which macrophages play a role.

Animals↗
PubMed1982

Low zone desensitization: a stimulus-specific control mechanism of cell response. Investigations on anaphylatoxin-induced platelet secretion.

The biologic activity of the anaphylatoxic peptides C5a and C3a is regulated efficiently at the target-cell level by the phenomenon of desensitization. Desensitization of platelets is stimulus specific and can be induced by low concentrations of anaphylatoxins without any preceding secretory event. In contrast to activation to secretion, desensitization is Ca++ independent but much more time consuming, especially at lower temperatures where both processes differ markedly in reaction velocity. This low zone desensitization insures that secretion from platelets only occurs when high amounts of anaphylatoxins are rapidly generated in the vicinity of the target-cell. Consequently, stimulus-specific unresponsiveness of the target cells can be induced by slowly increasing the concentration of the respective stimuli in their vicinity. Cellular control seems to act as a first-line mechanism of regulation, whereas the role of fluid-phase control is considered as preventing longer persistence and systemic accumulation of active anaphylatoxins.

Anaphylatoxins↗
PubMed1982

Quantitative studies of the secretion of complement component C3 by resident, elicited and activated macrophages. Comparison with C2, C4 and lysosomal enzyme release.

To quantitate the secretion of complement component C3 by guinea pig peritoneal macrophages an enzyme-linked immunosorbent assay was developed. C3 secretion was studied in resident, elicited and activated macrophages and compared with release of hemolytically active C2 and C4, as well as the lysosomal enzyme beta-D-2-acetamido-2-deoxyglucosidase. Resident macrophages secreted about 6 ng C3/10(6) cells/h into culture supernatants over a period of 12 h. Corynebacterium parvum-activated cells were found to secrete 3 times that amount at nearly constant rates. There was a stepwise increase in secretion of functional C2 and C4 when comparing resident, elicited and activated macrophages; secretion was 2--4 times higher in activated than in resident cells.

Acetylglucosaminidase↗
PubMed1982

Biosynthesis of a structurally abnormal C2 complement protein by macrophages from C2-deficient guinea pigs.

In order to characterize a genetic deficiency of C2 in guinea pigs, production of C2 by peritoneal macrophage cultures derived from four normal, four heterozygous deficient, and four homozygous deficient animals was measured functionally and immunochemically after metabolic labeling with 35S-methionine. Macrophage monolayers from homozygous deficient animals failed to secrete hemolytically detectable C2 up to 74 hr in culture. A single cell hemolytic plaque assay also failed to demonstrate any functional C2 production by cells from homozygous deficient animals. No C2 protein was detected in media from three of the four homozygous deficient animals, but in one, apparent C2 fragments were present. In contrast, intracellular C2 protein was identified in all four homozygous deficient cell cultures. Its mobility on SDS-PAGE was slightly faster than normal. Much less abnormal intracellular C2 protein was recovered from homozygous deficient macrophage monolayers than intracellular C2 protein from normal macrophage monolayers. Monolayers from heterozygous animals produced functional and immunochemical C2 at approximately 30% of the normal rate. Normal rates of biosynthesis and secretion of two other MHC-linked class III antigens, C4 and factor B, were detected in macrophage cultures from homozygous and heterozygous deficient animals. These data suggest that a specific defect, i.e. a structural abnormality in C2 protein, underlies C2 deficiency in guinea pigs.

Animals↗
PubMed1982

C3a induced activation and stimulus specific reversible desensitization of guinea pig platelets.

C3a and its C-terminal hexapeptide lead to a dose dependent release of biogenic amines and nucleotides stored in platelet's granules. The release reaction can be measured by tritiated serotonin or by ATP, indicated by an ATP specific bioluminescence assay. We tested the capability of C3a to induce aggregation of washed platelets. The recently described phenomenon of low dose, stimulus specific desensitization of platelets to the anaphylatoxic peptides C3a and C5a could be shown by measuring the release reaction as well as the aggregation. Further we could demonstrate the reversibility of the stimulus specific desensitization within 2 to 3 hours. The desensitization was proven to be temperature dependent. The recovery of function was independent of newly synthetized protein and is discussed as the result of receptor-recycling.

Anaphylatoxins↗
PubMed1981

Activation of the alternative pathway of complement: efficient fluid-phase amplification by blockade of the regulatory complement protein beta1H through sulfated polyanions.

Current concepts of activation of the alternative pathway of complement (APC) focus on the central role of an amplification mechanism triggered by C3b which is covalently bound to the surfact of activating substances. Using sulfated polyanions as model substances, an efficient fluid-phase activation of complement is demonstrated in contrast to solid-phase activation. It is shown that particulate high-molecular weight sulfated polyanions are capable of reversible binding the guinea pig and human regulatory protein beta1H. This fixation leads to an extensive activation of C3 and factor B because the regulatory function of beta1H is blocked in the fluid-phase C3b-dependent amplification system of the APC. Addition of beta1H-depleted C4-deficient guinea pig serum reconstitutes the physiological control mechanisms of the APC. Guinea pig beta1H, purified to homogeneity, is described as a 160000 dalton protein of a single-chain structure. In addition, highly specific and sensitive test systems for beta1H are described.

Absorption↗
PubMed1981

Comparative study on biological activities of various anaphylatoxins (C4a, C3a, C5a). Investigations on their ability to induce platelet secretion.

Several anaphylatoxic substances (human C3a, guinea pig C3a, human C4a, guinea pig C5a, and a synthetic C3a-related hexapeptide) were compared with regard to their ability to induce secretion of [3H] serotonin from guinea pig platelets. Functional identity of the C3a preparations, C4a, and the hexapeptide was demonstrated by the phenomenon of crossed desensitization. Whereas C3a of human and guinea pig origin proved to be qualitatively and quantitatively identical, C4a expressed only 3% of the activity of the C3 fragments on a molar basis. Investigations with goat anti-guinea pig C3a demonstrate that human and guinea pig C3a possess one antigenic determinant in common; however, this determinant is not the C-terminal amino acid sequence. Addition of the anaphylatoxins with low doses of thrombin led to a potentiation of [3H] serotonin release from the platelets. Under these conditions C3a concentrations of 1.5 X 10(-10) mumol/liter (65 pg of C3a) could be detected. Thus the platelet system represents the most sensitive in vitro assay known for evaluation of biological activity of the C3a anaphylatoxins.

Anaphylatoxins↗
PubMed1981

Synthetic C3a analogs as specific inhibitors of C3a activity.

Various C3a-related C-terminal synthetic oligopeptides were investigated for their ability to induce a release of serotonin from guinea pig platelets. The results confirm earlier findings that expression of biological C3a activity requires the four to five C-terminal amino acids of the C3a primary structure and underlines the essential role of the C-terminal arginine. Besides their ability to induce a specific release reaction, these peptides--after short incubation with the platelets--lead to a specific desensitization of the cells for C3a or C3a-related stimuli. Expression of this inhibitory activity required concentrations of the peptides more than 100-fold lower than those that were necessary to induce secretion. The possibility of using C3a analogs as specific inhibitors for C3a offers a valuable tool for in vivo studies of biological C3a activity.

Amino Acid Sequence↗
PubMed1981

Platelet-serotonin release by C3a and C5a: two independent pathways of activation.

C3a and C5a were investigated for their ability to induce secretion of serotonin from platelets in a homologous guinea pig system. Platelets respond to either anaphylatoxin with a dose-dependent release that does not exceed a plateau at the 70% level. On a molar basis. C5a is about 50-fold more active than the C3 fragment. The C5a effects in the platelet system can be clearly distinguished from the activity of C3a and vice versa by a phenomenon of specific desensitization of the platelets to either stimulus. Our observations lead to the postulation of distinct receptors for C3a and C5a on guinea pig platelets as well as 2 independent pathways of platelet activation, which both lead to a specific release.

Animals↗
PubMed1981

Linkage of total deficiency of the second component (C2) of the complement system and of genetic C2-polymorphism to the major histocompatibility complex of the guinea pig.

In the guinea pig six common phenotypes for hemolytically active C2 were detected. They resulted from three allotypic variants: a basic C2B and two more acidic variants C2A and C2A1. (The gene frequency for C2B in the outbred population was 0.36, 0.33 for C2A, and 0.31 for C2A1.) These variants were inherited as autosomal codominant traits. A strong linkage-disequilibrium between C2 and C4 allotypes was observed consisting of the pairs C2A1-C4F. C2A-C4S, whereas C2B was associated with either C4S or C4S1. To investigate the linkage of C2 to the MHC a family of strain 2 X strain OM3 was studied: the C2B allotype segregated with the strain haplotype of OM3 whereas C2A1 does the same with the strain 2 haplotype. During the C2-typing, an animal totally deficient in hemolytic C2 activity was discovered. Its C1, C4, C3, C5, factors B, D, and H were normal. Breeding yielded finally homozygous and heterozygous-deficient individuals. The latter ones exhibited 50 to 60% of the hemolytic activity of normal guinea pigs. Combined typing data of C4, C2 and GPLA showed that the deficient gene behaved like a rare, silent allele of C2, which is GPLA-linked and inherited like the normal C2-variants. An antiserum against C2 was raised in C2-deficient animals, which reacted with normal guinea pig serum but not with serum from C2-deficient animals. No cross-reactivity with human or mouse serum could be detected.

Alleles↗
PubMed1979

Killing of tumor cells in vitro by macrophages from mice treated with synthetic dehydrodipeptides.

Treatment of NMRI mice i.p. with dehydrodipeptides [acetyldehydro-3-(2-thienyl)alanyltyrosine (SI); acetyldehydro-3-(2-furyl)alanyltyrosine (SII)] rendered macrophages cytolytic for several tumor cells in vitro. Normal peritoneal mouse macrophages from untreated mice not given injections of the peptides or from control mice given injections of phosphate-buffered saline were not cytotoxic. Moreover, supernatants from these in vivo-activated mouse peritoneal macrophages significantly increased the release of the cytoplasmic enzyme lactate dehydrogenase from freshly added target cells, showing that these cells had been killed. The macrophage activation to lyse tumor cells was sharply dose dependent and appeared about 48 hr after injection of the peptides. Although dehydrodipeptide SI was active in vivo at concentrations as low as 500 microgram/mouse, the same substance lacked activity in vitro at all concentrations tested up to 800 microgram/ml. Dehydrodipeptides activate macrophages through a T-cell-independent process to lyse tumor target cells. Macrophages from athymic nude (nu/nu) mice were less cytotoxic, but they still were stimulated; and the culture supernatants could kill about 50% of the tumor cells used. There are indications for a relative specific structure-activity relationship of dehydrodipeptides for inducing cytotoxic macrophages.

Animals↗