Stimulation of DNA synthesis in mouse lymphoid cells by polyanions in vitro. I. Target cells and possible mode of action

Conjugation, characterization and toxicity of lipophosphoglycan-polyacrylic acid conjugate for vaccination against leishmaniasis

Research on the conjugates of synthetic polyelectrolytes with antigenic molecules, such as proteins, peptides, or carbohydrates, is an attractive area due to their highly immunogenic character in comparison to classical adjuvants. For example, polyacrylic acid (PAA) is a weak polyelectrolyte and has been used in several biomedical applications such as immunological studies, drug delivery, and enzyme immobilization. However, to our knowledge, there are no studies that document immune-stimulant properties of PAA in Leishmania infection. Therefore, we aimed to develop a potential vaccine candidate against leishmaniasis by covalently conjugating PAA with an immunologically vital molecule of lipophosphoglycan (LPG) found in Leishmania parasites. In the study, LPG and PAA were conjugated by a multi-step procedure, and final products were analyzed with GPC and MALDI-TOF MS techniques. In cytotoxicity experiments, LPG-PAA conjugates did not indicate toxic effects on L929 and J774 murine macrophage cells. We assume that LPG-PAA conjugate can be a potential vaccine candidate, and will be immunologically characterized in further studies to prove its potential.

Effects of Dextran Sulfate 500 on Cell-Mediated Resistance to Infection with Listeria monocytogenes in Mice

Injection of dextran sulfate 500 caused loss of antibacterial resistance. Mice became more susceptible to an infection with Listeria monocytogenes and were unable to develop antilisterial immunity after both active and passive immunization with passively administered spleen cells from Listeria-immune donors. Indirect evidence suggests that the phagocytic component of cell-mediated resistance to bacterial infection is the site of attack of dextran sulfate.

Bacterial lipopolysaccharide acts synergistically with selected macromolecular polyanions to induce MHC-nonrestricted cytotoxic cells

We examined whether bacterial lipopolysaccharide, at a dose range extending to less than 1.0 ng/ml, would work with cofactors to induce MHC-nonrestricted cytotoxic cells. To this end, normal mouse splenocytes were cultured for 5 days with LPS and potential cofactors, after which the cells were tested for cytotoxic activity in short-term 51Cr-release assays. We found that LPS can act synergistically with the macromolecular polyanions, dextran sulfate and polyinosinic acid. The effector cells induced by LPS and polyanions showed characteristics of activated NK cells in that they were (1) cytotoxic for widely differing sources of tumor cells, (2) not inhibited by an anti-T cell receptor antibody, and (3) not removed by depletion of CD4+ or CD8+ cells. LPS was active at picogram concentrations when dextran sulfate was included. Exposure of splenocytes to LPS was necessary during the early phase of the 5-day culture, but as little as 1 h of exposure was required, whereas exposure to the macromolecular polyanions during either the first or the last 2 days of a 5-day culture with LPS was effective. As expected with LPS activity, the cytotoxic cell response was prevented by polymyxin B or by the use of splenocytes from LPS non-responder C3H/HeJ mice. Screening of the S. minnesota R mutants and other partial LPS structures revealed that lipid A was closely associated with LPS activity in this assay system and that at least one partially detoxified structure, a deacylated LPS, could substitute for native LPS.

Synergistic effect on blastogenesis in murine spleen cells of lipopolysaccharide, lipid A, and acid-degraded polysaccharide from Fusobacterium nucleatum

Interchangeable combinations of Fusobacterium nucleatum Fev1 lipopolysaccharide (LPS) with its split products by acetic acid hydrolysis, i.e. lipid A (LA) and degraded polysaccharide (PS), amplified the blastogenic response in murine spleen cell cultures as measured by [3H]thymidine uptake. Athymic murine spleen cells precultured with LPS-Fev1 for 48 h (stage 1), washed twice and cultured together with fresh cells and either LA or PS for 72 h (stage 2) gave a synergistic response over that found in spleen cell cultures of thymic mice. Spleen cells pre-cultured with LA or PS and with fresh cells and LPS-Fev1 added to stage 2 cultures gave less significant amplification compared with precultures of LPS and either LA or PS together with fresh cells added to stage 2. Precultures with LA, PS or LPS-Fev1 and with pokeweed mitogen (PWM) and fresh cells added produced an additional increment of synergy which was most pronounced in spleen cell cultures of normal mice.

Complement activation by hydroxyethylmethacrylate-ethylmethacrylate copolymers

Certain biomaterials, including nylon oxygenator and cellulosic dialysis membranes, are potent activators of human complement. In this study, the effect of polymers containing 2-hydroxyethyl methacrylate (HEMA) on the human complement system was investigated. Copolymers of HEMA with ethylmethacrylate (EMA) varying from 100 to 40% HEMA in the monomer made by radiation initiation were used to coat glass discs. These were equilibrated with human plasma in vitro and the degree of complement activation was quantitated by C3a radio immunoassay. Significant activation was caused by copolymers made from monomers containing 60% or greater HEMA. A direct relationship between the amount of activation and the percentage of HEMA was found. The degree of activation by poly HEMA, when corrected for surface area, was quite similar to that observed for dialysis and oxygenator membranes. Similar observations were made when solid casts of crosslinked HEMA/N-vinylpyrrolidone (NVP) copolymer gels were tested, but the magnitude of activation was much greater. The results are significant because complement activation may play an important role in the response to foreign surfaces, in both extravascular and intravascular settings. A new concept of molecular biocompatibility is proposed in which surfaces eliciting molecular transformations in any of the biological defense systems are deemed nonbiocompatible. By this criterion, the hydrogel poly-HEMA, which has so frequently been thought of as biocompatible, is considered to be a molecularly non-biocompatible material.

Activation/suppression of the immune response in vitro by antigen and dextran sulfate. I. Analysis by limiting dilution methods

Spleen cells of normal mice which were stimulated with either T-dependent or T-independent antigens and dextran sulfate (DxS) in microcultures at limiting dilution show at low cell densities an increased frequency of responding units (B cells) with both types of antigens. At higher cell densities, DxS induces a suppression of the immune response as assessed by a declining frequency of expressed B cells. When T cells were decreased in number, the stimulating effect of DxS on T-independent responses remained unaltered while the suppressive effect (dependent on cell density) was eliminated. It is suggested that DxS lowers the threshold of activation for regulatory T cells, i.e. of cells which under standard in vitro conditions remain unactivated, and which in the presence of DxS become activated. We conclude that the regulatory cells are rare and that they are not present in most low cell density cultures. The net effect is a potent activation in dilute cultures and lack of response in dense cultures.

Adjuvant actions of polyclonal lymphocyte activators. V. Proliferation of macrophage colony-forming cells in the draining lymph node

We investigated the action of various polyclonal lymphocyte activators (PLA) on the proliferation of macrophage colony-forming cells in vivo at the local site. As PLA, Klebsiella pneumoniae 03 lipopolysaccharide (K03 LPS), Escherichia coli 0111 lipopolysaccharide (E. coli LPS), dextran sulfate (DS), concanavalin A (Con A), phytohemaggulutinin (PHA), polyadenylic-polyuridylic acid (poly(A:U], polyinosinic-polycytidylic acid (poly(I:C], and pokeweed mitogen (PWM) were used. All PLA tested acted to proliferate macrophage colony-forming cells in the draining lymph node at a late stage after subcutaneous injection. The order of strength of this action of PLA was K03 LPS greater than E. coli LPS greater than Con A greater than DS greater than PHA, PWM, poly(I:C), and poly(A:U), which corresponded to the order of strength of their adjuvant action in initiating helper-T-cell response to subcutaneous injection of aggregate-free bovine gamma-globulin. The detailed relationship between the proliferation of macrophage colony-forming cells and the adjuvant action of PLA is discussed.

Induction of proteolytic activity in serum by treatment with anionic detergents and organic solvents

Using casein plates as a sensitive assay for proteolytic activity, it was observed that sodium-dodecyl sulfate (SDS) and other anionic detergents induce caseinolysis when mixed with sera and plasma. Caseinolysis was dependent on the presence of plasminogen in the fluids and could be blocked by inhibitors of serine proteases and antibody to plasminogen. Similarly, organic solvents such as isopropanol induced caseinolysis after mixing with plasma, but not normal serum. Isopropanol dissociated complexes of alpha 1-antitrypsin or alpha 2-macroglobulin with trypsin preformed in vitro. As both SDS and organic solvents are widely used in biochemical investigations of biological fluids, attention should be paid to the possible induction of proteolysis.

Mitogenic effect of the mannans from Saccharomyces cerevisiae on mouse spleen lymphocytes

The DNA synthetic activities of mannans isolated from two Saccharomyces cerevisiae strains were examined in vitro using spleen cells obtained from normal or nude BALB/c strain mice. A highly branched mannan isolated from the S. cerevisiae wild type strain induced a greater increase in mitogenic activity than those displayed by the mannan of the S. cerevisiae X2180-1A-5 mutant strain which possessed fewer branching moieties. Acid-hydrolyzed wild type strain mannan with two-thirds of the molecular weight of the parent intact mannan showed weak mitogenicity. Increases in the DNA synthetic activities of nude and normal spleen cells were almost the same as that of wild type strain mannan, while nylon wool column-passed spleen cells obtained from both normal and nude mice did not show mitogenicity with this mannan. The results indicated that the mitogenic activity was responsible for the highly branched structure of the wild type strain mannan, and that this mannan is a B-cell mitogen.

Further studies of the polysaccharide of Klebsiella pneumoniae possessing strong adjuvanticity. III. Augmentation of the antibody response to subcutaneously injected sheep red blood cells by the adjuvant polysaccharide

The adjuvant action of the O3 antigen of Klebsiella (KO3) on the antibody response to sheep red blood cells (SRBC) was elucidated by injecting both KO3 and SRBC subcutaneously at the right inguinal region of SMA mice. We demonstrated that KO3 exhibits a novel ability to augment anti-SRBC plaque-forming cell responses in both the local lymph node and the spleen at a relatively late stage of immunization. Escherichia coli lipopolysaccharide, dextran sulfate and concanavalin A showed such an action only minimally. In parallel with the development of the adjuvant action, KO3 definitely activated B cells in the local lymph node polyclonally for either IgM or IgG synthesis, suggesting that the mechanism of the adjuvant action includes direct stimulation of B cells by KO3 at the late stage. Neither increase in trapping of lymphocytes in the local lymph node nor change in tissue distribution of antigen was shown to be primarily involved in the mechanism of the adjuvant action.

Suppression of B-memory cell function by polyclonal lymphocyte activators

When various polyclonal lymphocyte activators (PLA), such as the capsular polysaccharide of Klebsiella pneumoniae (CPS-K), E. coli lipopolysaccharide (LPS), concanavalin A (Con A), dextran sulfate (DS), phytohemagglutinin (PHA), and pokeweed mitogen (PWM) were injected into mice primed with sheep red blood cells (SRBC), anti-SRBC secondary plaque-forming cell (PFC) responses in vitro of their spleen cells to SRBC and to polyclonal B cell activatory (PBA) were more or less decreased. The decrease in the responsiveness was accompanied by the decrease in the number of SRBC-specific rosette-forming cells (RFC) of B-cell type (B memory cells). This resulted neither from emigration of RFC out of the spleen, nor from change of RFC to antibody-forming cells. Further, we revealed that the decreased responsiveness occurs exclusively in the B cell-rich fraction of the spleen cells from PLA-treated SRBC-primed mice, but not in their T cell-rich fraction. It is concluded therefore that PLA exhibited a common action to reduce selectively B-memory cell function by decreasing the number of B memory cells without differentiation to their end cells, although the strength of the action of various PLA varied.

Complement (C3) conversion by rat intestinal glycoprotein and its degradation products

Several fragments obtained from alkaline borohydride degradation of a rat intestinal glycoprotein fraction have been tested for anti-complementary activity. Oligosaccharide alditols with a molecular weight of less than about 1 X 10(3) daltons showed no activity, whereas reduced oligosaccharides in the molecular weight range of about 1 X 10(3) to 3 X 10(3) daltons exerted a minor conversion of C3 by the alternative pathway. The low molecular weight fragments tested did not influence C3 conversion induced by the intact intestinal glycoprotein fraction. Of the fragments, a peptide fraction, with an 'average' molecular weight of 2 X 10(3) daltons, and peptide-containing glycoconjugates exerted activation by C3 by both the classical and alternative pathways. Classical pathway activation by the intestinal glycoproteins depended on antibody, whereas alternative pathway activation did not. Alternative pathway activation appeared to require Factor B in that the intestinal glycoproteins induced no C3 conversion in serum heated to 50 degrees C for 20 min. The rat intestinal glycoproteins had no protease activity on casein and no stimulating effect on human lymphocytes in vitro. Branching of oligosaccharide chains was not indicated by the methylation analyses carried out.

Effects of cadmium on the immune system of mice

Chronic oral exposure of mice to Cd++ inhibits cell-mediated immunity of delayed type hypersensitivity induced by sheep red blood cells (SRBC). No effect was detected on humoral immune response to SRBC. Spleen cells derived from mice exposed to Cd++ showed in vitro enhanced response to T and B cell mitogens. These results demonstrate that Cd++ exposure alters the immune system of mice.

Specific binding of poly(I)-poly(C) to the membrane of murine B lymphocyte subsets

Indirect immunofluorescence revealed that 13% of BALB/c and 33% of CBA spleen cells of B type carry specific binding sites at their surface for double-stranded poly(I).poly(C). Pretreatment of BALB/c spleen cells with anti-mouse immunoglobulin serum increased the number of B cells capable of binding poly(I).poly(C) indicating the existence of a second B lymphocyte subpopulation carrying masked poly(I).poly(C)-binding sites. Pretreatment of the cells with mitogenic doses of either lipopolysaccharide (LPS) or single-stranded polynucleotides, e.g. poly(I) or double-stranded poly(A).poly(U), failed to affect binding of poly(I).poly(C) to the cells. Poly(I).poly(C) converts small poly(I).poly(C)-binding lymphocytes into lymphoblasts carrying poly(I).poly(C)-binding sites. Lymphoblasts derived from LPS-stimulated cells do not carry poly(I).poly(C)-binding sites. Thymocytes or splenic T cells failed to bind poly(I).poly(C). As measured by thymidine uptake, CBA mice containing a higher percentage of poly(I).poly(C)-binding cells, are high responder mice to poly(I).poly(C), compared with low responder BALB/c mice.

Synergistical effects of ficoll and phytohemagglutinin on human lymphocytes

The influence of increasing concentration of the highly polymerized dectran Ficoll on cultured peripheral human blood lymphocytes stimulated or not stimulated by PHA was studied. The incorporation of 14C-thymidine into acid-insoluble material of unstimulated lymphocytes has not been influenced in the presence of increasing concentrations of Ficoll either pretreated with chelating resin or not pretreated. Ficoll not pretreated with chelating resin potentiates the PHA-induced stimulation by the factor 4.3 at 0.1 mg Ficoll/ml culture medium, and by the factor 3.2 at 1.0 mg/ml when PHA stimulated HPBL were used. Ficoll after pretreatment with chelating resin does not influence the DNA-synthesis at 0.1 mg Ficoll/ml medium, but causes a drop of the incorporation of 14C-thymidine by the factor 2.0 at 1.0 mg/ml. Using 10.0 mg per ml, both Ficoll preparation cause a decrease of the DNA-synthesis by the factor 2.5--3.0--probably a cytotoxic effect. The results obtained with emission spectrographic analysis and conductivity measurements show, that Ficoll after treatment with chelating resin contains about 10 times more ions (Mg, Ca, Na, Si) and has a 3.2-fold higher conductivity then Ficoll without pretreatment. It is possible that phenomena like electrochemical changes on the surface of the lymphocytes and osmotic alterations in the culture medium are responsible for these effects.

The polyclonal B cell activator dextran-sulphate induces formation of colony stimulating activity

The effect of dextran-sulphate (DS), a polyclonal activator known to stimulate immature murine B-cells, was assayed in a culture system allowing the growth of myeloid cells. It was known that DS induced the production of a myeloid colony stimulating factor (CSF) by cells from both spleen and bone marrow. Nylonwool purified mouse spleen cells, enriched for T cells, showed a dimished CSF production in response to DS, while CSF production in response to Con A was increased. Furthermore, DS induced CSF in both spleen and bone marrow cells from nude mice. Removal of macrophages did not affect CSF production. The CSF induced was non-dialysable and no small molecular weight or lipoprotein inhibitors could be demonstrated. The results suggest that DS activates cells other than T cells or macrophages (possibly B cells or null cells) to produce a myeloid stem cell stimulating substance. These results indicate that interactions between lymphoid and myeloid cells can take place during differentiation.

Quantitative contributions of IgG, IgM and C3 to erythrophagocytosis and rosette formation by peritoneal macrophages, and anti-opsonin activity of dextran sulfate 500

In vitro phagocytosis by guinea pig peritoneal macrophages of immune complexes (EA) was shown to be dependent on IgG antibody in a dose-dependent fashion. C3b enhanced phagocytosis of EA at limited IgG antibody concentrations only. When IgM antibody was used for sensitization of sheep red blood cells (SRBC), phagocytosis and rosette formation did not occur in the absence of bound C3. The polyanion, dextran sulfate 500 (DS), was shown to depress both rosette formation and phagocytosis of EAIgG, C1423 and EAIgMC1423, as well as immune adherence of human group 0 erythrocytes and hemolytic activity of C3. This effect of DS was seen only when it was actually present in the incubation medium.

Cooperative binding of concanavalin A to thymocytes at 4 degrees C and micro-redistribution of concanavalin A receptors

The mode of binding of 125I-labelled concanavalin A and succinyl-concanavalin A to rat thymocytes at 4 degrees C was investigated. Simultaneously, the free binding sites of the cell-bound lectin molecules were quantified by horseradish peroxidase binding. Concanavalin A showed cooperative binding while succinyl-concanavalin A did not. The number of molecules of concanavalin A bound to the cell surface when it was saturated was twice the number of molecules of succinyl-concanavalin A. We interpret these results as showing that the binding of native concanavalin A to thymocytes at 4 degrees C brings about a cooperative modification of the membrane which leads to appearance of new receptors. Divalent succinyl-concanavalin A has no such effect. Horseradish peroxidase binding to cell-bound lectin was shown to be related to the immobilization of membrane receptors; the more they are immobilized, the more receptor-associated lectin can bind horseradish peroxidase. This allowed us to establish that post-binding events, which we called micro-redistribution, occurred at 4 degrees C when either concanavalin A or succinyl-concanavalin A binds to cells. A cooperative restriction of the micromobility of cell receptors is produced by increasing concentrations of concanavalin A. Succinyl-concanavalin A does not restrict cell receptor mobility at any concentration tested. The results are discussed in terms of cell stimulation and cell agglutination.

Characterization of dextran-sulfate-sensitive cells

The cell type participating in the mitotic response to the polyclonal B-cell activator (PBA) dextran-sulfate (DS) was investigated. Cells from murine fetal liver, adult bone marrow, and spleen were studied; only a limited number of all cells present in each organ responded to DS. Morphological studies of the activated cells showed the major population of activated cells in spleen to have the appearance of lymphoblasts. In bone marrow, several classes of hematopoietic cells were mitotically active, including mononuclear cells (lymphoblasts and monocytes), megakaryocytes, and myeloblasts. In these cultures, however, it was not possible to differentiate between DS-activated and spontaneously proliferating cells. Bone marrow and, to some extent, spleen cell cultures activated with DS contained a relative increase in numbers of phagocytic cells, whereas stimulation of spleen cells with lipopolysaccharide did not result in an increased phagocytosis. However, adherent cells were not necessary for activation of DNA synthesis by DS in spleen, and this cell type did not contribute to a measurable degree to the DNA synthetical response. DS cannot be regarded as a general stem cell mitogen for bone marrow cells since it failed to promote colony growth of hematopoietic cells in an in vitro system. However, supernatants from DS-activated spleen and bone marrow cell cultures did stimulate colony growth of murine bone marrow cells, indicating that stem cells of nonlymphoid origin might be indirectly activated by DS. In conclusion, the major cell population activated by DS in spleen is lymphocytes. In bone marrow, other cell types seem to participate in the response as well, but the activation mechanism may be indirect and not primarily the result of DS interaction with these cells.

Heterogeneity of B cells: direct evidence of selective triggering of distinct subpopulations by polyclonal activators

This investigation was undertaken to assess directly the previous postulate that distinct subsets of B cells in the adult mouse spleen are selectivity triggered by different polyclonal B-cell activators (PBA). Several strains of mice and lipopolysaccharide (LPS), purified protein derivative of tuberculin (PPD), and dextran sulphate (DS) were used in this study. Two experimental approaches were used: stimulation after addition of two PBAs simultaneously to cell cultures and eliminating the responding population to one PBA, by a hot pulse of radioactive thymidine, on a later response to another PBA. The results of these experiments indicated that DS stimulated a cell population completely different from that stimulated by the LPS- and PPD-sensitive cells. When LPS and PPD stimulations were compared, it was found that the cells responding to these PBAs were largely distinct, although some cells were sensitive to both these PBAs. The extension of the overlaps in these subsets (the number of cells that could be activated by either PBA) was found to vary from one strain to another. These experiments gave direct evidence of the existence of subsets that can be activated by different PBAs. The present results also provided indications of the functional performance of distinct subsets of B cells on activation.

Responsiveness of lymphoid precursors to polyclonal B-cell activators

We have shown previously that in the differentiation of fetal liver cells to mature B cells in irradiated hosts, these cells sequentially gain responsiveness to the polyclonal B-cell activators dextran-sulphate (DxS), lipopolysaccharide (LPS), and purified protein derivative from tuberculin (PPD), in that order. In this paper we show that both fetal liver cells and adult bone marrow cells responded with proliferation to DxS, but not to LPS OR PPD. However, neither fetal liver nor bone marrow cells gave rise to detectable numbers of high-rate antibody-secreting cells on short-term stimulation by polyclonal B-cell activators. The lack of LPS and and PPD responses of fetal liver and bone marrow cells could not be ascribed to the presence of inhibitory cells, and the DxS-induced response in these cell populations was not dependent on adherent cells. However, LPS could inhibit the DxS response of fetal liver cells, possibly indicating that DxS-responsive cells are precursors to B cells. Direct evidence was provided that DxS activated B-cell precursors in bone marrow. Thus, this cell population became responsive to LPS after DxS prestimulation, as measured by DNA synthesis. Bone marrow cells, sequentially stimulated with DxS and LPS, contained increased numbers of cells with surface immunoglobulin, although no significant increase in numbers of antibody-secreting cells was obtained. These data indicate that DxS had the capacity to increase the rate of differentiation of B-cell precursors. Finally, we show that the sequential appearance of responsiveness in B-cell differentiation to polyclonal B-cell activators is not due to lack of accessory cells during early stages in maturation.