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Biomedical subjects

V A Bokisch

Publications and source records attributed to V A Bokisch.

At least 19 recordsLinked to original sources
PubMed1977

Receptor-binding sites on C3 and C3b.

Human erythrocytes carry C3b receptors: Daudi lymphoid cells carry exclusively C3d receptors. With these two types of cells, it could be shown that isolated, uncleaved human C3 and soluble C3b possess two stable binding sites: SBS1-specific C3b receptors, and SBS2-specific for C3d receptors. Upon binding of freshly cleaved C3b (nascent C3b) via its labile binding site (generated on C3b through cleavage of C3) to the C3 acceptors on cell surfaces, the SBS2 becomes concealed. Kinetic experiments show that immediately after the action of fetal calf serum or partially purified C3b-inactivator on EAC1423b the SBS2 is accessible again. The reappearance of SBS2 does coincide with cleavage of surface-bound C3b into C3c and C3d but not with the release of C3c from the cell; C3c remains attached and is released only with delay. Concomitant with the cleavage event the number of SBS1 is reduced, stressing the importance of an unaltered steric configuration of the C3b structure for the expression of SBS1. An alternative explanation might be that the SBS1 is located at the site connecting C3c and C3d, so that it becomes altered upon dissection of the two fragments.

Binding Sites, Antibody↗
PubMed1975

Stimulation of murine B lymphocytes by isolated C3b.

Addition of isolated B3b to murine lymph node cell cultures induced increased DNA synthesis. The stimulation is dependent on the dose of C3b added and is potentiated by fetal calf serum present in the medium. Isolated C3 is less stimulatory than C3b; C3a and C3c had no effect on DNA synthesis in these cultures. 10-20% large immunoglobulin containing blastlike cells developed in lymph node cell cultures stimulated by 50 mug C3b in the presence of 3% fetal calf serum. The stimulation by C3b was observed in cultures of lymph node and spleen cells of several mouse strains including C3H/HeJ and congenitally thymus-deficient (nu/nu) mice. The results suggest that B lymphocytes are the main target of the stimulatory effect of C3b. Two mechanisms which may be involved in the stimulation of lymphocytes by C3b are discussed: (a) cross-linking of receptors on the cell surface or between cells, and (b) the binding of C3b to receptors of B lymphocytes and the formation of the complement enzyme C3bB. The results are compatible with the suggestion that activation of C3 is part of the events triggering the B lymphocytes.

Animals↗
PubMed1975

C1q deviation test for the detection of immune complexes, aggregates of IgG, and bacterial products in human serum.

This report describes a new, rapid, sensitive, and quantitative method for the detection of immune complexes, endotoxins, and other complement activating materials in patients sera utilizing the ability of these substances to react with isolated C1q. The procedure is based on the inhibition of radiolabeled C1q binding to sensitized sheep erythrocytes by C1q-reactive substances in pathological sera. The C1q deviation test may be performed on 50 mu1 of serum, using 1 mug of radiolabeled C1q per sample. The procedure may be completed in 1.5-2 h, it is capable of detecting 5 mug of aggregated human IgG per ml of serum, and its coefficient of variation is 4.2%. Application of the test to the study of 193 sera from 43 patients with Dengue hemorrhagic fever showed a positive correlation between degree of C1q deviation and severity of disease.

Antigen-Antibody Complex↗
PubMed1975

Complement changes and disseminated intravascular coagulation in Plasmodium falciparum malaria.

Complement activation as shown by increased clearance of radioactive C1q and reduction in serum-C3 level was found in fifteen (83%) of eighteen patients studied during Plasmodium falciparum infection. Six patients had haemostatic defects suggesting disseminated intravascular coagulation (D.I.C.), and five others had other clinical complications. A correlation was found between reduction of C3 and clinical complications as well as with the degree of anaemia and with thrombocytopenia. Moreover, the most severe thrombocytopenia and the most severe reduction of C3 levels were found in those patients with D.I.C. An immune reaction associated with complement activation in P. falciparum infection is believed to contribute to injury of red blood-cells and platelets and to promote the development of D.I.C. and other serious clinical complications.

Adolescent↗
PubMed1975

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.

Binding Sites↗
PubMed1975

Interaction of peptidoglycans with anti-IgGs and with complement.

This report describes the interaction of peptidoglycan (Streptococcus group A, Staphylococcus epidermidis and Micrococcus lysodeikticus) with 2 serum mediator systems, namely with the anti-IgG system and with complement. The observation that the majority of rabbits hyperimmunized with A-variant streptococcal vaccine produced anti-group carbohydrate antisera containing anti-IgGs and antibodies directed to peptidoglycan suggested that the production of these 2 latter antibodies was related. This view was supported by the finding of a monoclonal 7S anti-IgG with antibody specificity for the pentapeptide of peptidoglycan as evidenced by inhibition of the coprecipitation of 7S anti-IgG with antigen-antibody complexes by the pentapeptide. Inhibition of the anti-idiotype reaction by the pentapeptide provided further evidence for the antibody specificity of 7S anti-IgG for peptidoglycan. When added to normal human sera all peptidoglycan preparations inhibited the hemolytic activity of the sera. Consumption of C3 in C2 deficient serum and consumption of C2 in normal serum indicated the activation of both known complement pathways. Activation of the classical pathway of complement was more efficient since 50 mug of peptidoglycan consumed approximately 70% of C2 per ml normal serum whereas more than 2 mg of the same preparations was required to inactivate 17-24% of C3 in C2 deficient sera. Each of the different peptidoglycan preparations consumed similar amounts of complement in all 20 sera tested. This finding suggested that activation of the classical complement pathway by peptidoglycan was not mediated by anti-peptidoglycan antibodies present in only 20-40% of normal human sera.

Animals↗
PubMed1974

Binding of soluble immune complexes to human lymphoblastoid cells. II. Use of Raji cells to detect circulating immune complexes in animal and human sera.

Cells from a human lymphoblastoid cell line (Raji), with B-cell characteristics, and having receptors for human IgG Fc, C3b, and C3d, were used in an immunofluorescence test as in vitro detectors of immune complexes in animal and human sera. By this test, as little as 200-300 ng aggregated human gamma globulin or immune complexes per ml serum could be detected. The receptors for IgG Fc on the Raji cells were shown to be inefficient in detecting aggregated human gamma globulin and binding of aggregates to these receptors was inhibited by physiologic concentrations of 7S human IgG. Enhancement of aggregated human gamma globulin binding and binding of immune complexes formed in vitro to Raji cells was observed when the receptors for complement on these cells were used. By using the receptors for complement on Raji cells, circulating immune complexes were detected in rabbits with acute serum sickness, in mice with acute lymphocytic choriomeningitis virus infection, and in humans with immune complex type glomerulonephritis. The Raji cell test may be useful in detecting complement fixing immune complexes in different disease states, in monitoring circulating complexes in patients with immune complex diseases and in identifying the antigen(s) responsible for the induction of pathogenic immune complexes in humans and animals.

Animals↗
PubMed1974

Receptor for the fourth component of complement on human B lymphocytes and cultured human lymphoblastoid cells.

This report describes receptors for C4b on human peripheral B lymphocytes. The simultaneous presence of C3b and C4b receptors on the same lymphocytes was demonstrated by the formation of mixed rosettes consisting of the lymphocytes, EAC14 and EAC1423. Furthermore, reduction of the number of EAC1423 rosette-forming lymphocytes in a lymphocyte population by albumin gradient centrifugation concomitantly reduced EAC14 rosette-forming lymphocytes. Binding of EAC14 intermediates to receptors on human lymphocytes and erythrocytes could be inhibited by equal amounts of soluble C3b or C4b, suggesting the presence of a single receptor for both ligands on those cells. In contrast, the results of the rosette assay with Raji cells, cultured human lymphoblastoid cells, EAC14 and EAC1423 suggested that the receptors for C4b and C3b are distinct entities, since Raji cells formed rosettes with EAC1423, but not with EAC14. Moreover, this report demonstrates a cooperation of erythrocyte-bound C4b and C3b in the binding of EAC1423 to B lymphocytes. In contrast to KAF-treated C3b, KAF-treated C4b did not bind to B lymphocytes, indicating that these cells lack a receptor for C4d.

Antigen-Antibody Complex↗
PubMed1974

Binding of soluble immune complexes to human lymphoblastoid cells. I. Characterization of receptors for IgG Fc and complement and description of the binding mechanism.

In the present work we studied the expression of membrane-bound Ig (MBIg) as well as receptors for IgG Fc and complement on nine human lymphoblastoid cell lines. When MBIg and receptors for IgG Fc were compared, four categories of cell lines could be distinguished: (a) cell lines having both MBIg and receptors for IgG Fc, (b) cell lines having MBIg but lacking receptors for IgG Fc, (c) cell lines lacking MBIg but having receptors for IgG Fc, and (d) cell lines lacking both MBIg and receptors for IgG Fc. Two types of receptors for complement could be detected on the cell lines studied, one for C3-C3b and one for C3d. When sensitized red cells carrying C3b or C3d were used for rosette tests, three categories of cell lines could be distinguished: (a) cell lines having receptors for C3b and C3d, (b) cell lines having receptors only for C3d and (c) cell lines lacking both receptors. However, when a more sensitive immunofluorescent method was used instead of the rosette technique, it was found that cell lines unable to form rosettes with EAC1423b(hu) were able to bind soluble C3 or C3b which indicated the presence of these receptors on the cell surface. Inhibition experiments showed that receptors for C3-C3b and receptors for C3d are distinct and that receptors for C3-C3b and C3d are different from receptors for IgG Fc. A cell line (Raji) without MBIg but with receptors for IgG Fc, C3-C3b, and C3d was selected for use in studying the binding mechanism of soluble immune complexes to cell surface membrane. Aggregated human gamma globulin was used in place of immune complexes. Immune complexes containing complement bind to Raji cells only via receptors for complement, namely receptors for C3-C3b and C3d. Binding of immune complexes containing complement to cells is much greater than that of complexes without complement. Immune complexes bound to cells via receptors for complement can be partially released from the cell surface by addition of normal human serum as well as isolated human C3 or C3b. We postulate that such release is due to competition of immune complex bound C3b and free C3 or C3b for the receptors on Raji cells.

Anemia↗
PubMed1974

Receptor for soluble C3 and C3b on human lymphoblastoid (RAJI) cells. Properties and biologocal significance.

This study describes the presence of a receptor for fluid phase human C3 and C3b on Raji cell membranes. The binding of C3 and C3b was demonstrated indirectly by a fluoresceinated anti-C3 serum and directly by using radioiodinated proteins. No other complement proteins or serum factors were needed to mediate binding of C3 and C3b to the receptor. The possibility of enzymatic cleavage of C3 before or after its attachment on the cell membrane was ruled out by the demonstration of antigenically intact C3 on Raji cells. Inhibition and dissociation of Raji cell-EAC1423 rosettes by C3 and C3b indicated that both of these proteins bind to the same receptor site or closely associated receptor sites on Raji cells. C3b-bearing Raji cells were immune adherence negative, indicating that C3b binding to the receptor is brought about through the immune adherence region of the molecule and not the C3d portion. The C3 receptor on Raji cell membranes is uniformly distributed and can move on the membrane plane. Approximately 4 x 10(5) molecules of C3 or C3b bind per Raji cell. The receptor had a higher affinity for C3 than C3b, as was shown by uptake experiments and inhibition of Raji cell-EAC1423 rosette formation. Apart from the described receptor for C3 and C3b another specific receptor for C3b inactivator-cleaved C3b (C3d) bound to red cells was shown to be present on Raji cells. Raji cells cultured in medium containing fresh normal human serum and cobra venom factor were lysed. Similar results were obtained when C3b-bearing Raji cells were cultured in medium with fresh normal human serum. The lytic effect could be abolished by inactivating serum C3 proactivator (C3PA) and required C6. It was concluded that C3b bound to the Raji cell membrane activates the complement system through the alternate pathway and results in membrane damage and cytolysis. It is postulated that cell destruction by this mechanism may play an important role in vivo in controlling cell growth.

Animals↗
PubMed1973

Homogenous rabbit 7S anti-IgG with antibody specificity for peptidoglycan.

The relationship between 7S anti-IgG and antibodies to streptococcal cell wall peptidoglycan was examined for four streptococcal Group C antisera. Homogeneous 7S anti-IgG components in these sera were isolated by means of an IgG immunoadsorbent column. For two of the four antisera, the anti-peptidoglycan activity of the 7S anti-IgG had specificity for the pentapeptide, L-Ala-D-Glu-gamma-L-Lys-D-Ala-D-Ala, the antigenic determinant of peptidoglycan, as well as for the Fc of IgG. Detailed studies on the 7S anti-IgG from one of the antisera revealed that the pentapeptide inhibited the coprecipitation reaction of 7S anti-IgG R3387 with antigen-antibody complexes and the precipitin reaction between 7S anti-IgG R3387 and its anti-idiotype serum.

Animals↗
PubMed1973

Detection of idiotypic cross-reactions among streptococcal antisera from related rabbits.

Idiotypic cross-reactions among antibodies to Group C streptococcal carbohydrate were studied using idiotypic antisera prepared in allotypically matched rabbits. Antibodies with idiotypic cross-specificity to one proband antibody were detected in 58% of the antisera from related rabbits, while approximately 1% of nonrelated rabbits produced antibody with this specificity. The cross-specificity was related to the group a (V(H)) allotype of 133 rabbits tested with only one exception. Studies utilizing antisera against a second proband antibody failed to detect antibodies with idiotypic cross-reactivity among the same group of related rabbits. This result emphasizes the variation in expression of idiotypic determinants of antibodies. It was further shown that the presence of anti-IgG's in the streptococcal antisera interfere with the detection of idiotypic cross-reactions. These anti-IgG's masked the presence of antibodies with idiotypic cross-specificity when inhibition of precipitation tests were used for their detection.

Animals↗
PubMed1973

Isolation and immunochemical characterization of rabbit 7S anti-IgG with restricted heterogeneity.

7S anti-IgGs were isolated from four rabbit antistreptococcal antisera by the use of immunoabsorbent columns. The isolated proteins were of restricted molecular heterogeneity; they formed a monodisperse band on microzone electrophoresis and had a limited number of light chain bands when analyzed on urea polyacrylamide gel. The binding site of the 7S anti-IgGs was detected in the F(ab')(2) portion of the molecule. The binding site has antibody specificity for the Fc portion of IgG. For one 7S anti-IgG the combining site on the Fc portion could further be defined. A pepsin fragment of Fc, described as Pep-III', was a potent inhibitor of the coprecipitation of 7S anti-IgG with antigen-antibody complexes. An idiotypic cross-reaction was detected between the 7S and 19S anti-IgGs isolated from the same rabbit with anti-idiotype sera prepared in guinea pigs. This idiotypic specificity was not detected in the 7S anti-IgGs of 20 other rabbits.

Animals↗