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P C Aerts

Publications and source records attributed to P C Aerts.

15 recordsLinked to original sources
PubMed2003

Pneumococcal immune adherence to human erythrocytes.

BACKGROUND: Human red blood cells bind various C3b-coated microorganisms via their C3b/CR1 receptor, a phenomenon referred to as immune adherence. The aim of the present study was to measure pneumococcal adherence to human red blood cells by flow cytometry and to study kinetic aspects of this binding. MATERIAL AND METHODS: We quantified pneumococcal adherence to human erythrocytes by FACS analysis and tested the involvement of antibodies and complement activation in this process. RESULTS: Pneumococci are able to bind to human red blood cells in the presence of human serum. Coating with C3b/C4b appeared obligatory for pneumococcal adherence to red blood cells. The ligand on erythrocytes was confirmed to be complement receptor 1. Kinetic studies showed that innate (mannose-binding lectin) and specific immune factors (IgG antibodies) contributed to the binding of C3b-coated pneumococci to human erythrocytes. After initial binding, serum-derived factor I was found to induce bacterial detachment from the erythrocyte. CONCLUSIONS: Pneumococci are able to adhere to red blood cells. Both the classical and lectin complement pathways are important for optimal C3b-coating of pneumococci for immune adherence. Bound pneumococci are detached from red blood cells by factor I. These findings are in line with the hypothesis of immune adherence in which human erythrocytes are able to bind pneumococci and target the bacteria to the reticulo-endothelial system in the spleen.

Bacterial Adhesion↗
PubMed1999

Resistance to both complement activation and phagocytosis in type 3 pneumococci is mediated by the binding of complement regulatory protein factor H.

To study the role of surface-associated proteins in the virulence of Streptococcus pneumoniae, we used two serotype 3 strains, ATCC 6303 and WU2, and two PspA-negative mutants of WU2, an encapsulated one, JY1123 (Caps(+)/PspA(-)), and an unencapsulated one, DW3.8 (Caps(-)/PspA(-)). ATCC 6303 and WU2 were highly virulent in mice, while the virulence of JY1123 was slightly decreased (50% lethal doses [LD(50)s], 24, 6, and 147 CFU/mouse, respectively); DW3.8 was avirulent (LD(50), 2 x 10(8) CFU). In vitro, ATCC 6303, WU2, and JY1123 (Caps(+)/PspA(-)) strongly resisted complement activation and complement-dependent opsonophagocytosis, whereas DW3.8 (Caps(-)/PspA(-)) was easily phagocytized in fresh serum. Trypsin treatment of ATCC 6303, WU2, and JY1123 (Caps(+)/PspA(-)) resulted in enhanced complement activation and complement-dependent opsonophagocytosis. Trypsin had no deleterious effect on the polysaccharide capsule. In addition, trypsin pretreatment of ATCC 6303 strongly reduced virulence upon intraperitoneal challenge in mice. This indicated that surface proteins play a role in the resistance to complement activation and opsonophagocytosis and contribute to the virulence of type 3 pneumococci. In subsequent experiments, we could show that the modulation of complement activation was associated with surface components that bind complement regulator factor H; binding is trypsin sensitive and independent of prior complement activation. Immunoblotting of cell wall proteins of the virulent strain ATCC 6303 with anti-human factor H antibody revealed three factor H-binding proteins of 88, 150, and 196 kDa. Immunogold electron microscopy showed a close association of factor H-binding components with the outer surface of the cell wall. The role of these factor H-binding surface proteins in the virulence of pneumococci is interesting and warrants further investigation.

Animals↗
PubMed1992

Slp is an essential component of an EDTA-resistant activation pathway of mouse complement.

Slp (sex-limited protein) is a mouse serum protein encoded by a major histocompatibility complex class III gene. It is considered to be a product of a duplicated complement component C4 gene, but without functional activity. Originally it has been found expressed only in adult males with the S region of the H-2d or H-2s haplotype. In this report we present evidence that Slp is involved in a form of mouse complement activation that occurs after fractionation of serum by polyethylene glycol precipitation. This activation pathway is EDTA-resistant (i.e., independent of classical and alternative pathway activation), is regulated by C1 inhibitor, and leads to the generation of hemolytically active membrane attack complexes. A positive correlation between this EDTA-resistant mouse complement activity and reported Slp levels was found. Direct evidence for a functional role of Slp came from substitution experiments in which purified Slp induced hemolytic activity in polyethylene glycol-fractionated, Slp-deficient mouse serum. Selective depletion of other complement components suggested a role for C1s-, C2, and C5, but not C3, in the Slp-dependent complement activation. A model for this type of mouse complement activation is presented.

Aging↗
PubMed1992

C1-inhibitor prevents PEG fractionation-induced, EDTA-resistant activation of mouse complement.

Fractionation of mouse serum by precipitation with a critical amount of polyethylene glycol 6000 (PEG; 11% w/v) results in a classical and alternative pathway-independent activation of the terminal complement route. The activation can take place after the separation of an activating principle together with the terminal route components from a natural regulator. The isolation and identification of the regulatory component preventing this activation in serum, is subject of this paper. The regulator was purified by fractionated PEG-precipitation (15-25%), followed by heparin-Sepharose affinity, Mono Q anion-exchange, and Superose 12 gel filtration chromatography. The regulator appeared to be a single-chain protein with a Mr of 96 k. A protein with similar activity purified from human serum had a Mr of 104 k and was functionally and antigenically indistinguishable from C1-INH. The mouse 96 k protein inhibited C1-esterase activity indicating that this protein is indeed C1-INH. Mouse C1-INH regulates the PEG fractionation-induced bypass activation of complement, but does not interfere with the assembly or the lytic activity of membrane attack complexes. alpha 2-Macroglobulin appeared also to be capable of inhibiting the PEG-precipitation-induced activation process, but with lower efficiency.

Animals↗
PubMed1991

In vivo anti-complementary activities of the cobra venom factors from Naja naja and Naja haje.

The kinetics of complement (C) depletion and recovery of C levels upon injection of BALB/c mice with cobra venom factors (CVF), from N. naja (C3- and C5-depleting) and N. haje (selectively C3-depleting) were studied. The animals received i.p. or i.v. injections of either of the two preparations. CH50 and hemolytic C3 and C5 levels were followed as parameters of residual complement activity. N. naja CVF turned out to be as efficient in depleting total complement activity as N. haje CVF. Decreased CH50 values could largely be ascribed to C3 depletion. Complement consumption after N. naja CVF, however, lasted longer than after N. haje CVF administration. Estimated functional half-lives of N. naja and N. haje CVF were 11.5 and 4.5 h, respectively. Inhibition ELISAs showed that, after in vivo administration of either of the two CVF preparations, antigenic C3 and C5 kept circulating for days.

Animals↗
PubMed1991

C5 does not play a major role in the immune response of mice to SRBC in vivo.

The role of complement component C5 in the immune response of mice to sheep red blood cells (SRBC) was investigated. Congenic C5-sufficient and C5-deficient B10. D2 mice and genetically C5-deficient DBA/2 mice, as such or supplemented with C5-sufficient serum, were used as experimental animals. C5-substitution of the C5-deficient mice resulted in measurable C5 levels for days. The functional half-life of C5 in C5-deficient DBA/2 mice was about 21 h. No significant differences between the IgM-responses of C5-bearing and naive C5-deficient animals were observed. This suggests that C5 does not play a major role in the primary humoral immune response of mice in vivo, although C5 seems to do so in in vitro experiments, even with the same antigen. Antigen-induced C5-production by C5-deficient mice as one of the explanations of the in vitro/in vivo discrepancy could not be confirmed experimentally.

Animals↗
PubMed1990

Functional assay of C5-activating and nonactivating cobra venom factor preparations in the mouse system.

This paper deals with a new, functional assay of cobra venom factor (CVF) preparations with or without C5-activating property. Existing methods lack sensitivity and use diluted human complement as target of inactivation. An adapted assay using diluted mouse serum as complement source was hampered by underestimation of C3 depletion by bystander lysis and an overvaluation of C5 consumption resulting from C3 inactivation in the reagent used. These disadvantages prompted us to develop the new assay which is based on the incubation of CVF preparations with undiluted mouse serum. After incubation, residual total C activity, as well as functional C3 and C5 are estimated by titration. The procedure permits the assessment of CVF activities with minimal interference from undesired processes. The conditions in the new assay approach the in vivo situation in mice by the use of undiluted serum from the same animal species.

Animals↗
PubMed1990

Trial and error in producing ankylosing-spondylitis-selective antisera according to Andrew Geczy.

Geczy found that rabbit sera raised against Klebsiella strain K43 cross-reacted with the cells from HLA-B27 positive patients with ankylosing spondylitis (AS). Other laboratories failed to reproduce these results. After a series of unsuccessful attempts, however, we managed to prepare one selective antiserum, using E. coli, isolated from a Dutch Bechterew patient, in offspring of rabbits Geczy sent us. Ever since we obtained irreproducible results only. This paper reports about the many attempts we have made to produce a discriminating antiserum for use in a combined vital stain and dye-exclusion assay.

Animals↗
PubMed1988

Rabbit antisera to enterobacteriaceae isolated from HLA-B27 positive patients with ankylosing spondylitis (AS) are lytic for the mononuclear cells of AS patients.

Vaccines prepared from Gram-negative bacteria isolated from the stools of HLA-B27 positive AS patients were used to immunize rabbits. Three of the sera obtained were lytic in vitro for the mononuclear cells of HLA-B27 positive AS patients. One of these sera discriminated between AS patients and healthy HLA-B27 positive individuals. Cytolysis was determined in an automated, non-radioactive assay based on the release of carboxyfluorescein diacetate and the incorporation of propidium iodide.

Animals↗
PubMed1987

A one-step isolation procedure for phospholipase A2-free cobra venom factor by fast protein liquid chromatography.

A very rapid and efficient procedure for isolation of cobra venom factor (CoF) from Naja naja venom is presented. The method is based on Mono Q anion exchange chromatography on a system for fast protein liquid chromatography (FPLC). CoF was eluted by a buffer of pH 7.4 at 280 mM salt. A purification of 33.7 X was reached with a yield of at least 27%. Contamination with phospholipase was under the detection limit of a sensitive radiometric assay (less than 25 ppm), while the starting material contained 5%. The preparation displays high C-depleting activity in vivo.

Animals↗
PubMed1987

House dust extracts contain potent immunological adjuvants.

A crude aqueous extract of house dust and two house dust subfractions were tested for adjuvant activity in a sensitivity assay performed in mice. Evidence is presented that house dust contains at least two potent immunological adjuvants. One of these, present in both subfractions, was probably endotoxin and acted in a complement-independent way. The immunostimulatory effect of the other adjuvant was abrogated by prior complement depletion of the animals. This apparently complement-dependent adjuvant needs further identification.

Adjuvants, Immunologic↗
PubMed1986

House dust allergen activates the classical complement pathway in mouse serum.

A house dust fraction was tested for complement activation in mouse serum using a microtitre complement fixation assay. It was observed that the preparation was a potent activator of the classical, but not of the alternative pathway suggesting an analogy with the complement activation in human serum. The activation showed similarity with that by classical complement activators such as aggregated IgG, DNA, lipopolysaccharide (LPS), but some discrepancy with mite allergen was observed. The contamination of the preparation with LPS was negligible and could not account for the anticomplementary effect. The role of DNA fragments in the activation of mouse complement by the house dust fraction is discussed. Our results suggest that the mouse is suited to study the role of complement activation by house dust constituents in the induction of the IgE response.

Allergens↗