Effect of Concanavalin A on the Functional Activity of Hemolytic Antibody

Concanavalin A (Con A), either in solution or insolubilized by covalent binding to Sepharose 4B, can inhibit the ability of fluid phase 19S, but not 7S, anti-Forssman antibody to sensitize sheep red cells (E) toward lysis by excess guinea pig complement. The efficiency of 19S antibody is unaffected when E are treated with Con A before sensitization or when antibody sensitized cells (EA) are exposed to the lectin before complement is added. Although whole complement activity is retained on a column of Con A-Sepharose, cell bound lectin did not act as a complement fixing antibody. Consistent with this result, there was no difference in the amount of C1 fixed by E and E-Con A, or by EA and EA-Con A.     

Effect of Concanavalin A on the Functional Activity of Hemolytic Antibody

Concanavalin A (Con A), either in solution or insolubilized by covalent binding to Sepharose 4B, can inhibit the ability of fluid phase 19S, but not 7S, anti-Forssman antibody to sensitize sheep red cells (E) toward lysis by excess guinea pig complement. The efficiency of 19S antibody is unaffected when E are treated with Con A before sensitization or when antibody sensitized cells (EA) are exposed to the lectin before complement is added. Although whole complement activity is retained on a column of Con A-Sepharose, cell bound lectin did not act as a complement fixing antibody. Consistent with this result, there was no difference in the amount of C1 fixed by E and E-Con A, or by EA and EA-Con A.     

Hemolytic assay of complement and its components from Syrian hamster (Mesocricetus auratus) and Mongolian gerbil (Mariones unguiculatus).

Syrian hamster sera may be assayed for hemolytic complement (C) activity by standard procedures with sensitized sheep erythrocytes as used for human sera, but mongolian gerbil sera had higher complement titers when tested with sensitized guinea pig erythrocytes as target cells. The optimal conditions for in vitro testing of hamster C were pH 7.3, ionic strength 0.15, and presence of 1 micrometer of Mg2+ and 0.3 micrometer Ca2+. For gerbil C the optimum pH was 8, ionic strength 0.074, and the same concentration of Mg2+ and Ca2+ as for hamster. Incubation at 37 degrees C for 60 minutes yielded optimal results. Complement components in the serum of both species could be tested with commercially prepared intermediates of sheep erythrocytes pretreated with guinea pig C1 and human C4 respectively, using purified human C2 through 9 and standard methods applied for testing human C components. Both species have all nine components of the complement system.     

Evidence for mannose-mediated adherence of Candida albicans to human buccal cells in vitro.

Various lectins and sugars were used to study the possible role of saccharide-containing moieties on the surface of Candida albicans and human buccal cells in the adherence of this yeast to mucosal surfaces. The lectins possessed affinities for several different sugar moieties and were used to pretreat C. albicans or buccal cells before mixing and incubating in the adherence assay. It was found that concanavalin A, a lectin that recognizes mannose and glucose, inhibited adherence of the pretreated yeasts to buccal cells and also inhibited adherence of pretreated buccal cells to nonpretreated yeast cells. Adherence was restored by preincubating the concanavalin A with a mannose derivative, but preincubation of concanavalin A with other sugars did not produce this effect. Lectins that do not recognize mannose had no effect on adherence. The presence of alpha-D-methyl mannopyranoside in the incubation medium during the assay inhibited adherence, whereas other sugars did not. Germinated yeasts adhered to buccal cells more effectively than nongerminated cells and were more susceptible to adherence inhibition by concanavalin A than were nongerminated yeasts. Thus, mannose-containing moieties on the surface of C. albicans and buccal cells could mediate the adherence of this yeast to human epithelium.     

Inhibition of the classical and alternative pathways of human and guinea pig complement by pyran copolymer

The ability of pyran copolymer to interact with the classical and alternative pathways of complement was assessed in human and C4-deficient guinea pig serum. Pyran induced a dose-dependent inhibition of hemolytic activity in both serum systems. Immuno-electrophoretic analysis of pyran-treated human serum revealed that C3 was not cleaved. Factor B was altered into a more anionic mobility which was not similar to biologically cleaved Ba or Bb fragments. Pyran-treated serum was unable to lyse antibody-coated erythrocytes (EA or EA coated with C1 and C4 and EA coated with C1, C4 and C2. Pretreatment of serum with ethylenediaminetetraacetic acid did not prevent inhibition of hemolytic activity by pyran. Cobra venom factor did not cleave C3 in the presence of pyran. These data indicate that pyran does not activate complement by standard mechanisms but does inhibit one or more of its components.     

Lectin-binding affinities of the epithelium in the respiratory tract. A light microscopical study of ciliated epithelium in rat, guinea pig, and hamster

Complex carbohydrate components of surface coat and secretory granules were investigated in the laryngo-tracheo-bronchial epithelium of 3 laboratory animals (rat, guinea pig, and Syrian hamster). 2 groups of epithelial cells were distinguished in the light microscope: ciliated cells and non-ciliated cells. The latter mainly represent secretory cells and are subdivided into serous and mucous secretory cells. Apical glycocalix: In the rat, ciliated cells possess a significant number of Con A, RCA I, and WGA receptors, and a smaller number of UEA I binding sites. In hamsters and in guinea pigs additional binding sites for HPA could be demonstrated. The apical glycocalix of the non-ciliated cells in the rat evince marked staining with RCA I, WGA, and HPA, and less intensive binding of UEA I. In guinea pigs and in hamsters, the presence of additional Con A receptors was noted. Basolateral glycocalix: The basolateral surface coat of ciliated and non-ciliated cells shows identical lectin binding affinities. In the rat, the basolateral glycocalix binds RCA I; in the guinea pig, in addition, positive staining with UEA I and HPA is observed; in the hamster, the basolateral surface coat is outlined by RCA I and HPA receptors. Secretory products: Secretory granules of mucous cells in the rat react with Con A, UEA I and HPA lectins. In guinea pigs, these substances also bind RCA I and WGA lectins. Mucous granules in the secretory cells of the hamster are positive for Con A, RCA I, and HPA lectins. Granules of non-ciliated serous cells of rats bind Con A, UEA I, and HPA lectins. In the guinea pig, this reaction is weaker for UEA I lectin but comparable for Con A and HPA binding. A positive reaction with RCA I lectin only is found in the serous secretory granules of the hamster.     

Complement activation by female protein, the hamster homologue of human C-reactive protein

The capacity of Syrian hamster female protein (FP), a phosphorylcholine (PC)-binding pentraxin, to activate complement was tested in an in vitro system consisting of PC-coupled sheep red blood cells and guinea pig serum as the complement (C) source. FP was demonstrated to fix complement as reflected by hemolysis. Such hemolysis was eliminated by heat treatment (56 degrees C, 30 min) of guinea pig serum and inhibited by PC chloride but not dinitrophenyl lysine. The inability of C4-deficient guinea pig serum to provide lytic activity indicated that lysis proceeded through the classical hemolytic pathway.     

Effects of zinc chloride on guinea pig complement component activity in vitro: concentration-dependent inhibition and enhancement

We have studied the in vitro effects of zinc chloride on the hemolytic activity of each component of the guinea pig classical complement pathway over a wide range (25 to 500 muM) of zinc concentrations. At high concentrations (>200 muM) the activity of all components was strongly inhibited by this metal. Concentrations of 500 muM inhibited C1 and C5 by 80 and 65%, respectively, whereas all other components were inhibited by more than 94%. Zinc chloride at 25 muM produced more varied effects, with C2, C3, and C6 inhibited by 36, 35, and 55%. C7 and C8 were inhibited by approximately 25%, whereas C1, C4, and C9 were not appreciably affected. The activity of the fifth component, on the other hand, was strongly enhanced by the presence of zinc. Concentrations of 25, 50, and 100 muM zinc chloride produced increases of 92, 44, and 18%, respectively, in C5 titers when present during the activation-binding step of this component. Further studies indicated that the activities of cell-bound complement components were unaffected by zinc treatment after activation and/or binding to the sheep erythrocyte surface had occurred. In addition, zinc did not appear to inhibit by causing irreversible denaturation of either total complement proteins or its various components. Rather, it appears that zinc must be present as a reactant during the activation and/or binding step of each component for inhibition or enhancement to occur.     

The Hemolytic Equivalence of Human, Guinea Pig and Canine Complement Proteins

The ability of functionally pure human, guinea pig and canine complement proteins to fulfill the hemolytic function of a substituted analanous component in an otherwise totally homogeneous complement sequence was investigated by means of conventional hemolytic assays. A striking feature was the observation that for hemolysis to occur, differing requirements for enzyme-substrate homology were exhibited by each of the three species of C3 and C5 convertases (C3 and C5 CVA). The results suggest that different strategies of molecular interaction evolved in complement systems of different species.     

Effect of surface modifiers on an ectoenzyme: granulocyte 5''-nucleotidase.

Several agents that react with plasma membranes, namely the native lectins concanavalin A, Ricinus communis agglutinin, and wheat germ agglutinin, the modified lectin succinyl concanavalin A, and sodium meta-periodate, inhibited the ecto-5'-nucleotidase of intact guinea pig granulocytes. Stimulation of the enzyme was not observed at any lectin concentration. Inhibition by native lectins could be blocked or reversed by appropriate competing hapten sugars. In the case of concanavalin A, reversal could be achieved at 37 degrees C, but not at 5 degrees C. When lectins were used in combination with each other, the effects were found to be largely independent. However, when concanavalin A and R. communis agglutinin were applied together, complications arose because the former lectin binds to the latter as well as to the cell surface. To avoid some of the complexities inherent in studying intact cell 5'-nucleotidase and to gain additional information about the system, two broken cell enzyme preparations were also examined. The enzyme of plasma membrane-enriched fractions was inhibited by all five agents mentioned above. 5'-Nucleotidase solubilized in sodium deoxycholate was inhibited by the four lectins but stimulated by periodate. The effects of the surface modifiers on kinetic data for all three enzyme preparations are consistent with the hypothesis that direct interactions with the enzyme molecule give rise to changes in Vmax; interactions at membrane sites other than 5'-nucleotidase itself could cause increases in apparent Km values. Effects of interactions of ectoenzymes with plant lectins may serve as models for phenomena that result from cell-cell interactions or from interactions of animal cells with lectin-like components of the cellular environment.     

Physicochemical characterization of the fifth (C5), sixth (C6), seventh (C7), eighth (C8) and ninth (C9) component of guinea pig complement

A physicochemical characterization of the purified guinea pig complement components C5 to C9 is given. For this purpose the sedimentation rate, the diffusion coefficient, the molecular weight and the isoelectric point were determined and compared with the values already known for the guinea pig and human complement system. For the determination of the physicochemical parameters gel filtration on Sephadex G-200, ultracentrifugation applying a sucrose density gradient and thin-layer isoelectric focusing were used. By comparing the values of the human and guinea pig complement a remarkable similarity is shown.     

Development and characterization of a hemolytic assay for mouse C4

The previously described one-step hemolytic assay for the fourth component of complement (C4) that employs C4-deficient (C4D) guinea pig serum was modified to allow assessment of mouse C4. Of a number of variables evaluated including the class and quantity of sensitizing antibody, concentration of C4D serum and metals, ionic strength of the buffer, and the duration and temperature of incubation, substitution of IgG anti-sheep red blood cell antibodies for the standard IgM hemolysin and the use of C4D serum at relatively high concentrations (1 : 20) were necessary to obtain an accurate, reproducible and sensitive hemolytic assay. The sensitivity of the assay could be increased approximately 2-fold by the addition of human C2 and approximately 30% by employing ⁵¹Cr-labeled sheep red blood cells. The former probably helped to overcome a partial incompatibility between mouse C4 and guinea pig C2 and the latter permitted the use of 10-fold fewer erythrocytes in the assay system. Employing this assay, C4 activity was determined in H2-congenics and recombinants and the effect of age, sex, and methods of procuring and preserving mouse serum and plasma evaluated. In most strains, males had a 10–30% higher level of C4 hemolytic activity than females, and young (<6 weeks) and older (>20 weeks) mice had lower activity compared to mice between 6 and 12 weeks. Procuring samples in 5 mM EDTA (final concentration) and subsequent storage at ?70°C permitted long-term preservation without loss of hemolytic activity. Allowing mouse blood to clot at 4, 22 or 37°C, even for brief periods, was associated with complement activation and depletion of C4 functional activity. C4 assays of H2-congenics and infromative recombinants conclusively demonstrated that this hemolytic activity mapped to the S region of the H-2 complex.     

A radial hemolysis method in agarose for the functional assay of properdin

A simple one-step radial hemolytic assay for properdin has been devised. In this assay, the test material is introduced into a well in an agarose plate containing optimal concentrations of normal human serum immunochemically depleted of properdin (RP), EGTA, magnesium ions and unsensitized guinea pig erythrocytes. Following radial diffusion, the area of the hemolytic zones resulting from the activation of the alternative complement pathway and bystander lysis of guinea pig erythrocytes was directly proportional to the concentration of properdin in the test material. The assay is specific reproducible and sensitive and the correlation with the radioimmunoassay for properdin is very good. The assay has been used to measure properdin activity in animal sera.     

Polyclonal activation of guinea pig spleen lymphocytes

The incorporation of 3H-thymidine in newly formed DNA was studied in guinea pig spleen cells stimulated by phytohemagglutinin (PHA) and/or concanavalin A (Con A). In spleen cells stimulated by PHA, two peaks of thymidine uptake were observed for two different doses of lectin whatever the number of cultured cells. Furthermore, thymidine uptake is proportional to the number of the cultured cells. During Con A-induced mitogenesis, two peaks were also observed but only when using a great concentration of cells. Maximal thymidine incorporation depended on both the cell number and the concentration of Con A. When cells were stimulated by both PHA and Con A, thymidine uptake was strongly depressed as compared to the one observed using PHA or Con A alone. On the other hand, supernatants from unstimulated spleen cells had opposite effects on blastogenesis induced by Con A or by PHA; they depressed PHA-induced blastogenesis while enhancing the one induced by Con A. These results suggest that, in guinea pigs, both PHA and Con A induce thymidine incorporation in at least two lymphocyte populations through different mechanisms. This heterogeneity of lectin-induced T cell mitogenesis has to be taken in account when studying the mechanisms by which the immunomodulators are active at the T cell level.     

The inhibition capacity of concanavalin a on monomeric and polymeric hemolytic antibodies

The ability of concanavalin A (Con A) to inhibit the complement consumption by sheep erythrocytes coated with IgG, (IgG₂-SpA₁)₂ complex and IgM anti-Forssman antibodies was studied. The (IgG₂-SpA₁)₂ anti-Forssman antibody complex showed an increased hemolytic activity compared to uncomplexed IgG antibody. Con A in the presence of the (IgG₂-SpA₁)₂ complex or the IgM antibody exhibited a high inhibitory capacity. An inhibitory capacity of Con A on IgG antibody hemolytic activity was also proved but at a Con A: IgG antibody concn ratio about 10 times higher than that for the Con A-IgM antibody system. A time dependence of Con A inhibitory capacity was determined, thus explaining the variable behaviour of the IgG antibody in the inhibition experiments. Radioactivity experiments demonstrated that only half of the Con A interacted with the (IgG₂-SpA₁)₂ complex compared to the amount of Con A which interacted with IgG uncomplexed antibody.     

Soluble C5b-9 complex of guinea pig complement: Demonstration of its heterogeneity and the mechanism of its C9 hemolytic activity as transfer of reversibly bound C9 molecules from the complex

Doubly radiolabeled soluble complex of the late acting components (SC5b-9) was formed by activating guinea pig complement (C)2 serum mixed with C5 and C9 each labeled with either ¹²⁵I or ¹³¹I with zymosan. It was isolated by sequential gel filtrations and sucrose density gradient centrifugation. Fractions of the complex obtained by centrifugation were heterogeneous in size, composition and hemolytic activity as C9. The heavier fractions contained four to six molecules of C9 per C5b molecule. The lighter fractions contained two to three C9 molecules to one C5b molecule and had stronger C9 hemolytic activity. On recentrifugation on the same sucrose density gradient, the factions moved to the same positions as on the first centrifugation.Guinea pig SC5b-9 complex bound to the surface of EA, EAC-3, EAC-5, EAC-6, EAC-7 and EAC-8 in similar amounts. Therefore, combination of the complex with these intermediate cells seems to be nonspecific. EAC-7 cells bound to the complex could be lysed by addition of C8.Lighter, hemolytically more active complex purified by recentrifugation was stable when incubated alone in buffer. But when it was incubated with free C9, it released radiolabeled C9, the amount released increasing with increase in the amount of free C9 added to a maximum of 10 to 15% of the C9 in the complex. A minute part of the complex was converted to heavier complex by incorporation of additional C9, but most of the complex did not change in size. Therefore, it did not seem to be an uncompleted complex to be saturated with more C9. The C9 molecules released from the complex were in an active form and could be reincorporatd into SC5b-9 when they were treated with zymosan in fresh guinea pig serum.It is concluded that the C9 hemolytic activity of guinea pig SC5b-9 is exerted by transfer of reversibly bound C9 molecules in the complex to C5b-8 sites on EAC-8 cells, not by the action of the complex in toto.     

C3 Cleaved by Membrane Proteases Binds to C3b Acceptors Expressed on Concanavalin A-Stimulated Human Lymphocytes and Enhances Antibody-Dependent Cellular Cytotoxicity

On activation of cells membrane-associated proteases--including serine esterases known to cleave the third component of complement (C3)--become expressed. In this paper it is shown that as a consequence of this enzyme activity isolated native human C3 added to concanavalin A (Con A)-activated human lymphocytes is cleaved on the surface of the blast cells. This enables the immediate fixation of nascent C3b (C3bx) through its short-lived metastable binding site to C3b acceptors (C3bA's) newly expressed on Con A-stimulated cells. Acceptor-bound C3b is detected by the immune adherence rosette formation of the C3-treated Con A blasts with the C3b receptor (C3bR)-bearing O, Rh+ erythrocytes (32 +/- 4%). The cleavage of C3 and the covalent fixation of C3b are shown to be inhibited by phenylmethylsulphonyl fluoride and methylamine, respectively. As a functional consequence of the covalent fixation of C3b to the mitogen-activated lymphocytes it is demonstrated that the antibody-dependent cellular cytotoxicity (ADCC) of these cells against O, Rh+ erythrocytes sensitized with anti-D IgG is significantly enhanced. The C3 specificity of the process and the role of C3bR's of the target cells are proved. It is postulated that effector cell-bound C3b amplifies ADCC by improving effector cell-target cell contact.     

Activation of the alternative complement pathway by Trichomonas vaginalis.

The mechanism underlying the lysis of Trichomonas vaginalis by normal human or guinea pig serum was investigated. The involvement of the complement system was demonstrated by the failure of human serum deficient in C3 or C8 to mediate parasite killing and by the ablation of lytic activity observed when fresh sera were heated at 56 degrees C or treated with ethylenediaminetetraacetate. Fixation of human C3 on the parasite surface was demonstrated by indirect immunofluorescence. The involvement of the alternative complement pathway was demonstrated (i) by the inability of properdin-depleted human serum to lyse T. vaginalis and (ii) by the normal killing observed with guinea pig serum lacking C4 and with normal human or guinea pig serum treated with ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid and Mg2+ to selectively inhibit the classical pathway.     

Binding of lectins to Streptococcus mutans cells and type-specific polysaccharides, and effect on adherence.

The lectin concanavalin A (Con A) agglutinated the cells of 13 of 15 strains of the seven serotypes of Streptococcus mutans in an 18-h incubation period. Strains of types a, d, f, and g agglutinated within 2 h. Strains of a, d, and f were also agglutinated in 2 h by the castor bean lectin RCA. S. sanguis, S. salivarius, S. bovis, Actinomyces viscosus, A. naeslundii, and Lactobacillus plantarum were agglutinated within 2 h. The S. mutans type f polysaccharide was precipitated by Con A. The a, b, c, d, and e polysaccharides were not precipitated. Glucan from d and e strains of S. mutans and dextran T2000 were also precipitated by Con A. D-glucose inhibited the agglutination of type f cells by Con A and the agglutination of type d cells by D-galactose. The quantity of [acetyl-3H]Con A bound was not proportional to the degree of agglutination. Cells grown in sucrose medium bound more Con A than those grown in glucose medium. After treatment with dextranase, the sucrose-grown cells bound two- to fourfold more Con A. The binding of Con A to the type-specific polysaccharide or to teichoic acid could not be determined by the use of specific antibody due to the binding of Con A to the antibody globulin on the cell surface. Con A bound to S. mutans cells did not inhibit the activity of cell-bound glucosyltransferase, glucan synthesis, and in vitro adherence. Bound Con A also did not inhibit the ability of heat-treated cells to bind glucosyltransferase, synthesize glucan, and produce in vitro adherence.     

Human platelets after their contact with influenza virus activate the complement system in autologous serum

Guinea pig erythrocytes that have been exposed to influenza virus activate the alternative pathway through virus-induced desialation of the cells. Neuraminidase treatment of rabbit platelets enhance their clearancein vivo. Washed human platelets were labeled with⁵¹Cr exposed to Influenza virus, and resuspended in autologous serum that had been dialyzed against Veronal-buffered saline containing Ca⁺⁺ and Mg⁺⁺ (VBS⁺⁺), VBS containing 8 mM EGTA and 2 mM Mg⁺⁺ (VBS-MgEGTA) or VBS containing 20 mM EDTA (VBS-EDTA) for 60 min at 37°C. Three per cent⁵¹Cr release and no complement consumption were observed in VBS-EDTA serum. In contrast, 6%⁵¹Cr release with 37 and 54% decrease in C3 and B hemolytic activities respectively occurred in VBS-MgEGTA serum and 14%⁵¹Cr release with 50% decrease in C2 hemolytic activity occurred in VBS⁺⁺ serum. These results suggest that influenza virus may alter the platelet surface in such a way that both complement pathways might be recruited and the cells be lyzed in autologous serum.The human complement system is activated by a number of viruses and virus-infected cells through antibody-dependent and independent mechanisms. Guinea pig erythrocytes that have been treated with influenza virus are lyzed in human serum through activation of the classical and of the alternative pathways: activation of the alternative pathway is dependent on an acquired resistance of the cell-bound C3 amplification convertase to control mechanisms that are directly related to desialation of the cells by viral neuraminidase [1]. Since,in vivo, clearance of desialated platelets is enhanced in animal models and since human platelets do not express the C3b receptor-associated inhibitory activity of the complement system, we investigated whether human platelets, after contact with influenza virus, acquire the ability to activate complement in autologous serum.