Biomedical subjects

M J de Reuver

Publications and source records attributed to M J de Reuver.

8 recordsLinked to original sources

PubMed1989

Estimation of the avidity of antibodies in polyclonal antisera against Streptococcus pneumoniae type 3 by inhibition ELISA.

The reliability of the determination of antibody avidity in polyclonal sera by indirect sandwich ELISA was studied. Binding of IgM and IgG (sub)classes in unpurified serum to Streptococcus pneumoniae type 3 capsular polysaccharide, which was coated onto ELISA plates, was inhibited with different inhibitors. The inhibitor concn at which 50% inhibition of antibody binding to the ELISA coat was achieved, was used as a measure for antibody avidity. As this 50% inhibition value is dependent upon the dilution of the serum and thus upon the initial amount of free antibody, it is necessary to define (a narrow range of) final ELISA absorbance values to which the dilutions of non-inhibited sera have to be adjusted. The shapes of the serum dilution curves have a good correlation with the numerical 50% inhibition values of the antibody avidity. The inhibition ELISA is suitable to compare the avidity values of the different antibody isotypes, but two remarks should be made: (1) antibody heterogeneity should be considered to influence the results and prevent the accurate measurement of absolute numerical avidity values. Because in the ELISA system merely antibody "activity" is measured, comparison of the efficacy of vaccines by means of the 50% inhibition (avidity) value of various antibody (sub)classes can still be performed in a reliable way; (2) results of the determination of the 50% inhibition values of the different antibody (sub)classes showed them to be dependent on the molecular ratio between antibody (sub)class levels. More aspects of the determination should be taken into account, like shapes of simple dilution curves, influences of various inhibitor concns in the diluent and whole (extended) inhibition curves.

Animals↗

PubMed1988

Deletion analysis of the proteinase gene of Streptococcus cremoris Wg2.

The Streptococcus cremoris Wg2 proteinase gene, cloned in S. lactis, specified a proteinase which exhibited the same specificity toward casein as did the proteinase isolated from the original host. Although the cloned gene lacked the last 130 codons, the proteinase still specifically degraded beta-casein. Deletion of the C-terminal 343 amino acids from the proteinase did not influence this specificity. Cell-free transcription-translation studies of plasmids carrying deletion derivatives of the proteinase gene showed that the 100-kilodalton C-terminally truncated proteinase still exhibited proteolytic activity. Crossed immunoelectrophoresis revealed that proteins A and B identified in the proteolytic system of S. cremoris Wg2 are both encoded by the proteinase gene. A working model based on integration of available genetic, immunological, and biochemical data is presented to explain this result.

Amino Acid Sequence↗

PubMed1988

Serum amyloid P component induction by immunomodulators.

The capacity of immunoadjuvants to enhance serum amyloid P component (SAP) levels and to modulate the humoral immune response to sheep red blood cells in a number of different mouse strains was investigated. Although the synthetic adjuvants dimethyldioctadecylammonium bromide, dextran sulphate and bacterial-derived lipopolysaccharide did not enhance SAP levels in some of the mouse strains tested, these strains responded normally to the immunomodulating effects of the adjuvants. We conclude that increased SAP levels and modulation of immune responses are induced via at least partially different pathways. For these reasons, it is impossible to screen drugs for potential adjuvant activity by only measuring SAP levels in mice.

Adjuvants, Immunologic↗

PubMed1983

Impaired macrophage functions as a possible basis of immunomodification by microbial agents, tilorone and dimethyldioctadecylammonium bromide.

Four microbial and two chemically defined immunomodulating agents namely viable BCG, killed Mycobacterium butyricum, killed Lactobacillus plantarum, zymosan, tilorone, and dimethyldioctadecylammonium bromide (DDA) were studied for their effects on macrophage functions in vitro and in vivo. All agents induced a dose-dependent mortality of macrophages as determined by trypan blue exclusion. DDA and especially tilorone were rather toxic for macrophages in vitro. All agents except tilorone and DDA inhibited phagocytosis of yeast cells and uptake of acridine orange in vitro at doses which killed up to about 30% of the macrophages. DDA and tilorone had no effect at similar doses. All agents but zymosan inhibited the spreading of macrophages. No interference with the fusion of lysosomes and yeast cell-containing phagosomes could be observed. The activity of the mononuclear phagocytic system (MPS) in vivo as measured by carbon clearance was stimulated by all substances within twenty-four hours. All agents but DDA and tilorone enhanced non-specific bacterial resistance. As demonstrated previously for DDA, tilorone could serve as adjuvant for induction of specific resistance to Listeria monocytogenes. The results are discussed in relation to other data on influencing of macrophage functions and on immunomodification. It is concluded that hampered antigen destruction by local macrophage suppression attended with MPS stimulation might be a basic mechanism for adjuvanticity exerted by these agents.

Adjuvants, Immunologic↗

PubMed1982

Delayed-type hypersensitivity in rabbits. Comparison of the adjuvants dimethyl dioctadecyl ammonium bromide and Freund's complete adjuvant.

Injection of rabbits with antigen mixed with the cationic surface-active lipid dimethyl dioctadecyl ammonium bromide (DDA) induced delayed-type hypersensitivity (DH), which could be measured as skin reactions and was confirmed by histology of the skin test sites. 1 week after injection of a conjugate of bovine serum albumine (BSA) with dinitrophenol (DNP30-BSAj) mixed with DDA, DH was detectable in most but not in all rabbits. Similar results were obtained using FCA as adjuvant. The animals treated with the latter adjuvant, however, produced a long-lasting DH (1-3 weeks) complicated by circulating anti-DNP antibodies (Arthus-type reactions). Skin testing with heterologous hapten-carrier complexes revealed that individual rabbits immunized with DNP30-BSA in DDA expressed DH with different reaction patterns, either to hapten, carrier or both. In conclusion, DDA is a useful adjuvant for the induction of a state of pure DH in rabbits. However, not all rabbits do respond, or respond similarly.

Adjuvants, Immunologic↗

PubMed1979

Regulation of the immune response by macrophages.

Regulation of the immune response by macrophages was studied with cellular resistance to Listeria monocytogenes as parameter. The use of agents which suppress macrophage activity during the induction-phase of immunity enabled the induction of protective immunity with killed listeria. Fractionation of the cell content of listeria yielded an RNA'se sensitive fraction which in a dose of 300 ng and in combination with the cationic surfactant dimethyl dioctadecyl ammonium bromide induced protective immunity against listeria.

Adjuvants, Immunologic↗

PubMed1976

Bacteriophage MS-2 in the immune response.

Several aspects of the immune response to bacteriophage MS-2 were studied. In thymectomized, irradiated and bone marrow-reconstituted (TXBM) mice, the response was normal when a high dose of antigen was used. With a 50-fold lower dose of MS-2, the response was impaired, indicating a T-cell involvement in antibody formation. More evidence for the (partial) T-cell dependence of MS-2 was obtained from experiments with anti-thymocyte serum or cyclophosphamide-treated mice. (3H)-thymidine incorporation experiments demonstrated that both B and T cells were active upon in vitro stimulation with MS-2. The dose of MS-2 which was able to induce a normal response in TXBM mice, proved to be optimal for both sensitization and elicitation of a DH. It is concluded that MS-2 is a thymus-dependent antigen which is only thymus independent in high doses.

Animals↗

PubMedDate not supplied

Influence on macrophage functions as a possible basis of immunomodification by polyanions.

The effects of the polyanions, carrageenan, dextran sulphate, polyanetholesulphonate and suramin, on macrophage functions and on the complement system were studied. The function of phagosomes and lysosomes in vitro was inhibited by all polyanions but carrageenan whereas phagocytosis in vitro was enhanced by small doses of all polyanions. Interaction with complement occurred already at very low doses polyanion. On intraperitoneal administration, the polyanions inhibited the mononuclear phagocytic system as measured with the carbon clearance test. In some instances this was followed within 72 h by a stimulation. While polyanion injections caused an increase in spleen weight, the effects on the liver weight diverged. Our results and data of other authors suggest that the immunomodifying properties of the polyanions studied can be explained partly by drug-macrophage interaction, partly by indirectly mediated modulation of macrophage function.

Adjuvants, Immunologic↗