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Biomedical subjects

K Resch

Publications and source records attributed to K Resch.

At least 163 records · Page 9Linked to original sources
PubMed1979

Cytotoxicity of human mononuclear cells against chicken and human red blood cells, induced by treatment of the effector cells with phospholipase C.

Human mononuclear cells from peripheral blood which were treated with phospholipase C (PLC), became cytotoxic against human or chicken red blood cells. PLC-induced cellular cytotoxicity against human red blood cells was further analyzed and compared to anti-D-mediated, antibody-dependent cellular cytotoxicity (ADCC), using the same target cells. ADCC, but not cytotoxicity of PLC-treated effector cells, was inhibited by free IgG. In addition, iodoacetate strongly enhanced PLC-induced cytotoxicity, but blocked ADCC completely. Addition of fetal calf serum or human AB serum impaired PLC-induced cytotoxicity. A similar inhibition was found by adding lecithin liposomes suggesting that the inhibitory effect of sera was also due to their phospholipid content. The data show that cytotoxicity of PLC-treated effector cells can be clearly distinguished from cellular cytotoxicity, occurring spontaneously or induced by target cell antibodies. We favor the notion that cytotoxicity of PLC-treated effector cells against human erythrocytes is due to the action of PLC, adsorbed to the effector cells.

Absorption↗
PubMed1978

Antibody dependent cellular cytotoxicity (ADCC) against human erythrocytes, mediated by blood group alloantibodies: a model for the role of antigen density in target cell lysis.

Antibody dependent cellular cytotoxicity (ADCC) of human mononuclear cells against human erythrocytes could be obtained with anti-A and anti-D sera. The degree of lysis varied considerably depending on the antigen system and on the experimental conditions. Anti-D mediated in contrast to anti-A mediated ADCC turned out to be very sensitive to conditions which interfere with target cell lysis: for most of the anti-D sera, removal of unbound IgG was found to be crucial to detect their ability to mediate ADCC. Pretreatment of the target cells with various enzymes dramatically improved specific lysis and left spontaneous release and spontaneous cytotoxicity essentially unaffected. In the case of neuraminidase treatment it could be shown that the effect was independent from the exposure of additional binding sites. When enzyme treatment and removal of excess IgG were applied in combination, as little as 10(4) antigenic determinants proved to be sufficient to induce specific lysis.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1977

Enhancement of the PGE1 response of macrophages by concanavalin A and colchicine.

The effect of concanavalin A (Con A) and colchicine on the prostaglandin E1 (PGE1)-mediated cyclic AMP generation in rat peritoneal macrophages have been studied. Although Con A and colchicine by themselves did not affect cyclic AMP levels, they greatly enhanced cyclic AMP production induced by PGE1. There was not only augmentation of cyclic AMP levels at maximally active concentrations of PGE1, but also an increased sensitivity to low (inactive) concentrations of PGE1. Except for lentil lectin, none of the other lectins affected PGE1 sensitivity whereas lumicolchicine was as effective as colchicine. In addition, both Con A and colchicine raised the sensitivity to isoproterenol and choleraenterotoxin. Although details of the mechanisms by which Con A or colchicine influenced the membrane-bound adenyl cyclase and PGE1 receptors remain unclear, these observations suggest that certain alterations of the cell membrane may render macrophages more susceptible to the regulating effects of prostaglandins.

Adenylyl Cyclases↗
PubMed1977

Induction of lymphocyte proliferation and membrane changes by lipopeptide derivatives of the lipoprotein from the outer membrane of Escherichia coli.

Lipoprotein from the outer membrane of E. coli, a potent novel mitogen, was digested by pronase treatment resulting in lipopeptide fragments containing 2-5 amino acids bound to diacylglyceryl-N-acylcysteinthioether. The lipopeptides were characterized by amino acid analysis and gas chromatography and were checked for mitogenicity. We found that all lipopeptide fragments were able to stimulate the uptake of 3H-uridine into RNA and 3H-thymidine into DNA in mouse spleen cells of several strains. The response of splenocytes of congenitally athymic mice was comparable to that of normal animals. A weak stimulation of DNA synthesis was also observed in thymocytes. The mitogenicity of the products was abolished by mild alkali hydrolysis which removes the ester-bound fatty acids. We conclude that the N-terminal lipopeptide region of lipoprotein is responsible for the mitogenic activity of the molecule. Lipopeptide as well as lipoprotein were found to cause early membrane changes in lymphocyte plasma membranes. After 4 hours we found an increased incorporation of 14C-oleate and 14C-acetate into lecithin. The membrane changes observed are similar to those brought about by mitogenic lectins, which suggests a similar mechanism for the induction of lymphocyte activation for both types of mitogens.

Amino Acids↗
PubMed1976

Phospholipid metabolism of stimulated lymphocytes. Comparison of the activation of acyl-CoA:lysolecithin acyltransferase with the binding of concanavalin A to thymocytes.

Calf thymocytes were isolated and incubated with concanavalin A. The effect of the mitogen on the enzyme activity of membrane-bound lysolecithin acyltransferase (acyl-CoA:1-acylglycero-3-phosphorylcholine-O-acyltransferase, EC 2.3.1.23) was determined as also the binding of 125I-labelled concanavalin A to intact cells and isolated membranes. The lysolecithin acyltransferase was found to be activated three times in microsomal membranes. The activation occurred directly after binding of concanavalin A and was temperature independent, since similar activities were found in cells treated with concanavalin A at 0 and 37 degrees C. The acyltransferase activation using increasing concentrations of concanavalin A revealed a different behaviour, as compared to the binding of concanavalin A. While the binding of concanavalin A to intact cells expressed a normal hyperbolic saturation function the activation process of the acyltransferase described a sigmoidal relationship. Correspondingly, the interaction coefficients for both functions were different (Sips coefficient for binding = 1.0 and Hill coefficient of the enzyme activation = 1.8). These results indicate that the acyltransferase activation is due to a cooperative interaction between the ligand-receptor complex and the enzyme.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1976

Initial stages of differentiation of thymocytes in the plasma membrane.

There is some evidence in the plasma membrane after binding of molecules triggering differentiation processes that different membrane areas exist possessing different functions. We have tried to isolate these different membrane areas, using a type of affinity chromatography on Con A-Sepharose. Our results from binding sites, affinity constant and fatty acid composition seem to reinforce the evidence that heterogeneous plasma membrane areas exist having different functions in the proliferation and differentiation process of thymocytes after triggering with Con A.

Acyltransferases↗