Cytotoxicity of human and baboon mononuclear phagocytes against schistosomula in vitro: induction by immune complexes containing IgE and Schistosoma mansoni antigens.
Normal human blood monocytes, pre-incubated at 37 degrees C with sera from patients infected with Schistosoma mansoni, strongly adhered to S. mansoni schistosomula in vitro, whereas no significant adherence was induced by sera from uninfected individuals. Comparable adherence occurred with normal baboon blood monocytes or peritoneal macrophages when these cells were incubated with sera from S. mansoni-infected baboons. Adherence of macrophages to schistosomula was associated with damage to the larvae, as estimated by a 51Cr release technique. Neither adherence nor cytotoxicity was induced by pre-incubation of the schistosomula, instead of the monocytes, with immune serum. The relevant factor in immune serum was heat-labile, but was not a complement component. Absorption and ultracentrifugation experiments showed that immune complexes, containing S. mansoni-specific IgE antibody and soluble parasite antigens, produced monocyte or macrophage adherence and cytotoxicity. Similar observations have been reported previously in the rat model. Since the production of large amounts of IgE is a predominant feature of schistosome infections in man and experimental animals, it is possible that this new mode of mononuclear phagocyte activation could act as an immune effector mechanism against S. mansoni. (+info)
Reaction of an activated complex of guinea-pig complement components, C56, with unsensitized erythrocytes and with erythrocytes carrying C3b molecule.
During the interaction of guinea-pig complement intermediate cells, EAC423, with guinea-pig C5 and C6, an activated complex of C5 and C6, C56, was demonstrated in the fluid phase of the reaction mixture. C56 also was eluted from EAC42356 which had been generated by the interaction of EAC423 with C5 and C6. Both preparations of C56 showed quite similar characteristics and were not distinguished from one another. Both were capable of reacting with unsensitized erythrocytes (E) in the presence of C7 to form EC567. Further, they were able to react with EAC43 in the absence of C7 to form EAC43568 but did react with EAC43 pretreated with C3b inactivator, dithiothreitol or N-bromosuccinimide. These results indicate that guinea-pig C56 generated on EAC423 has a tendency to dissociate into the fluid phase. Nevertheless, the dissociated C56 can bind again to intact C3b molecule on the cells. The ability of cell-bound C3b to combine with C56 may lead to localization of C56 to the cell membrane carrying C3b, resulting in acceleration of attachment of C567 to the membrane. This assumption could be supported by the finding that the replacement of E by EAC43 increased the susceptibility of the cells to lytic action of complement induced by cobra venom factor. Thus, a new function of cell-bound C3b as localizing C56 to the membrane of sensitized cells was indicated. (+info)
The effect of cholesterol oleate treatment of mice on the rosette forming cell response against sheep erythrocytes.
Mice injected with a single dose of 60 mg cholesterol oleate emulsion showed substantial blockade of the monoclear phagocyte system measured by the rate of vascular clearance of radio-labelled sheep erythrocytes. The labelled rythrocytes, in lipid treated mice, localized mainly in the spleen, contrasting with control mice in which localization was mainly in the liver. Treatment with this lipid, 24 hr before the intravenous of two different doses of sheep erythrocytes, resulted in significant depression of the rosette forming cell response in the spleen, whereas the responses in the lymph nodes of both control and lipid treated mice were at a low level and not significantly different. Intravenously administered cholesterol oleate emulsion is known to localize mainly in the Kupffer cells and in splenic red pulp macrophages. Cultured macrophages treated with this lipid show inhibition of antigen-binding and depressed phagocytosis of heterologous erythrocytes. The lipid does not affect lymphocytes. These findings are in keeping with the hypothesis that macrophages play a direct role in the induction of an immune response against a particulate antigen. (+info)
Third component of complement (C3): structural properties in relation to functions.
The third component of complement (C3) fulfills a pivotal role in the functions of the complement system. We have investigated the topological relationships among its polypeptide chains, physiologic fragments, enzyme attack regions, and functional sites. C3 consists of two chains (alpha and beta) which are linked by disulfide bonds and noncovalent forces and which have molecular weights of, respectively, 120,000 and 75,000. C3 is activated by action of C3 convertase on the alpha-chain. With hydrolysis of one polypeptide bonds, C3a, the 9000 dalton activation peptide is dislocated from the NH2-terminal portion of the alpha-chain. A previously concealed binding region is thereby transiently revealed in the C3b-fragment (181,000 dalton) which displays affinity for apparently nonspecific acceptors present on biological membranes. Binding of nascent C3b membranes occurs through the C3d portion of the fragment because subsequent action of the C3b-inactivator or trypsin on bound C3b causes release of C3c, but not of C3d. Bound C3b and C3d possess stable sites that are capable of binding to specific receptors present on a limited variety of cells. We propose that all known physiologically occurring fragments of C3 arise by enzymatic cleavage of the alpha-chain: C3a, C3b, C3c, and C3d. Whereas C3a (alpha1) and C3e (alpha2) consist of a single chain and C3b consists of two chains (alpha' and beta), C3c is composed of the entire beta-chain and multiple fragments of the alpha-chain, each of which is linked by disulfide bonds to the beta-chain. (+info)
Localization of the IgG effector site for monocyte receptors.
A peptide consisting of 10 amino acids derived from the CH3 region of human IgG was shown to bind to monocytes and to inhibit rosette formation of antibody-coated erythrocytes with human monocytes. Two myeloma proteins of the IgG1 and IgG3 subclass, both with known deletions in the CH2 region of the gamma chain, showed unimpaired ability to bind to monocytes. These experiments suggest that the isolated peptide represents the primary site of attachment of IgG to monocytes. (+info)
Anticomplementary activity of tuberculin: relationship to platelet aggregation and lytic response.
Experiments were performed to examine the interaction of tuberculin with platelets and complement. Hemolytic complement titrations show that tuberculin consumes complement in human, rabbit, and guinea pig serum. Evidence in support of classical pathway activation was provided by observation of C1 consumption and failure to detect significant conversion of alternative pathway factor B to B by immunoelectrophoresis. Platelets in plasma from guinea pigs deficient in the fourth component of complement were not affected by tuberculin. However, studies on platelet aggregation in plasma chelated with ethyleneglycolbis(beta-aminoethyl ether)-N,N-tetraacetic acid indicated that tuberculin may initiate sluggish activation of the alternative pathway. That the reaction between tuberculin and platelets is a lytic one was evidenced by observing the release of the cytoplasmic enzyme lactic dehydrogenase and efflux of rubidium-86. Studies with C6-deficient rabbits indicated that platelet release of exogenously supplied tritiated serotonin is caused by platelet lysis. (+info)
Serial observations on terminal deoxynucleotidyl transferase activity and lymphoblast surface markers in acute lymphoblastic leukemia.
Terminal deoxynucleotidyl transferase activity and cell surface markers were measured in peripheral lymphoid cells from 27 children with acute lymphoblastic leukemia in various phases of their disease. Lymphoblasts from untreated patients had smooth surface ultrastructure but heterogeneous surface receptors. Greater than 60% of lymphoblasts from 4 to 7 untreated patients formed rosettes with sheep red blood cells. Transferase activity was variable, ranging from 8 to 210 units/10(8) blasts, but it was consistently elevated at diagnosis and in relapse. Transferase levels did not correlate with the presence of lymphoblast surface receptors. During induction therapy transferase activity decreased rapidly, but it remained elevated in peripheral lymphoid cells even when blasts were not detectable in peripheral blood smears. Patients in remission had normal surface receptors and undetectable or minimally elevated levels of transferase. Terminal transferase activity may be a sensitive biochemical marker for a primitive cell population and may be important in the evaluation of therapeutic effectiveness in acute lymphoblastic leukemia. (+info)
Further characterization of the circulating cell in chronic lymphocytic leukemia.
Peripheral lymphocytes from normal individuals and from patients with chronic lymphocytic leukemia (CLL) were cultured in vitro for 1-7 days. The growth response to phytohemagglutinin (PHA) was quantitated by the incorporation of tritiated uridine into RNA nucleotide during a 2-hr pulse with the radioisotope. While the maximum response in PHA-stimulated normal cultures appeared at 2-3 days, CLL cultures required 5-7 days to develop their maximal response, which was 50%-60% of the normal magnitude. Dilution of the number of normally reactive lymphocytes by culturing them with totally unreactive, mitomycin-treated cells produced a normal 72-hr maximal response, no matter what proportion of unreactive cells was included in the PHA-stimulated cultures. In addition, the response of peripheral lymphocytes from patients with myeloblastic leukemia, where large numbers of unreactive myeloblasts diluted the normal small lymphocytes, a depressed reaction occurred at the anticipated 2-3 days. Nylon fiber-adherent lymphocytes consisting of 85% immunoglobulin (Ig)-bearing cells responded minimally to PHA, but showed no evidence of a delay. When isolated from CLL patients, both fiber-adherent cells (Ig-bearing) as well as non-fiber-adherent (sheep erythrocyterosetting) cells responded to PHA in a delayed fashion. Similarly, a case of CLL, in which 93.5% of the circulating lymphocytes bore sheep red blood cell receptors, showed its peak response to PHA at 7 days. Therefore, using surface marker criteria considered characteristic of normal T cells and B cells, the delayed response to PHA on the part of CLL lymphocytes was independent of thymic or nonthymic origin. (+info)