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PubMedDate not supplied

The biological role of the complement system and the clinical importance of complement measurements.

Properties of serum proteins belonging to the complement system, two pathways of the complement activation (classical and alternative pathway) as well as the physiological role of the complement system are discussed. Complement has essential importance in some physiological processes: In the induction of the humoral immune response, in the elimination of immune complexes and in the protection against bacterial and viral infections. After a short discussion of the genetics of the complement system, the principle and possibilities of clinical applications of the complement measurements are described. Finally, different approaches to the therapeutic manipulation of the complement system are discussed.

Angioedema↗
PubMed1979

Activation of the classical complement pathway by nephritic factor bound to the alternative pathway C3/C5 convertase.

Nephritic Factor (NF), the potent alternative pathway activator, which is occasionally found in association with certain types of nephritis has recently been identified as an IgG class autoantibody specific for the C3 convertase (C3bB) of the alternative pathway. In these studies we have examined the possibility that the cell-bound NF-stabilized C3 convertase (EC3 bBNF) binds and activates the first component of the classical pathway of complement. EC3bBNF bound C1q, and the extent of binding was dependent upon the number of NF molecules bound per cell and decreased parallel to the dissociation and release of NF from the cells. Interaction of C1 with bound NF resulted in its activation as shown by the proteolytic conversion of proenzyme C1s to its activated form C1s. As was the case with C1q binding, C1 activation was dependent on the number of NF molecules bound per cell. Thus the NF-stabilized C3 convertase binds and activates C1.

Binding Sites↗
PubMedDate not supplied

[Nucleotide sequence of two exons of the human T-lymphocyte CD4 receptor gene].

Genome DNA encoding the N-part of human CD4 gene located in the 15 kilobase (kb) Sau3a restriction fragment was cloned and nucleotide sequence of a part (3430 b.p.) of this fragment determined. Exons 2 and 3, intron 2, and partially introns 2 and 3 of this gene were located in the sequenced fragment. Six Alu repeats and open reading frames (ORFs) coding for proteins very close to C5 and C3 components of the complement were detected in this fragment.

Amino Acid Sequence↗
PubMed1977

Conversion of C5 precipitin line in the serum treated with activating substances of complement system.

The hemolytic activity of C5 in the serum treated with zymosan, immune precipitate, or C1s was measured, and the C5 precipitin line on immunoelectrophoresis and the protein concentration of C5 in these serum specimens were also analyzed. A marked decrease in the hemolytic activity of C5 and a complete conversion of C5 precipitin line from beta- to alpha-globulin region were observed in teh serum treated with more than 1 mg/ml of zymosan. The elongation of C5 precipitin line from beta- to alpha-globulin region and the decrease in C5 hemolytic activity were observed in the serum treated with the immune precipitate. But neither change in C5 precipitin line, nor a decrease in hemolytic activity of C5 was observed in C1s treated serum. C5 protein concentrations in these serum preparations were essentially the same as those of control. From these results, it was concluded that the immunoelectrophoretic change of C5 precipitin line might express the grade of the decrease in C5 hemolytic activity in the serum treated with the activating substances of the complement system.

Antigen-Antibody Complex↗
PubMed1999

Complement inhibition with an anti-C5 monoclonal antibody prevents hyperacute rejection in a xenograft heart transplantation model.

BACKGROUND: The present study was undertaken to determine whether anti-complement 5 (C5) monoclonal antibodies (mAb) prevent hyperacute rejection (HAR) in a rat-to-presensitized mouse heart transplantation model and whether these mAb, combined with cyclosporine (CsA) and cyclophosphamide (CyP), can achieve long-term graft survival. METHODS: BALB/c mice were presensitized with 2x10(7) splenocytes from Lewis rats 14 days before grafting. Heart grafts from Lewis rats were heterotopically transplanted into BALB/c mice. Presensitized mice were treated with either anti-C5 mAb or a combination of anti-C5 mAb, CsA, and CyP. Controls included: presensitized mice with no treatment, presensitized mice treated with either CsA + CyP or IgG, and nonpresensitized mice with either no treatment or with CsA + CyP treatment. RESULTS: Although typical features of HAR were evident in the presensitized grafts, the mAb completely inhibited complement activation and successfully prevented HAR. Despite complement inactivation, the graft was rejected on postoperative day 6 with acute vascular rejection (AVR) also known as delayed xenograft rejection (DXR). Notably, this type of rejection cannot be effectively overcome by CsA and CyP. CONCLUSIONS: We conclude that (1) anti-C5 mAb prevents HAR, (2) AVR/DXR still occurs when HAR is prevented by complement inactivation, and (3) AVR/DXR cannot be overcome by conventional immunosuppression. These data suggest that anti-C5 mAb may be valuable for preventing HAR in future clinical xenotransplantation and that additional interventions may be required to address AVR/DXR.

Acute Disease↗
PubMed1990

Evidence for participation of the macrophage in Shiga-like toxin II-induced lethality in mice.

Seven strains of inbred mice were compared for their susceptibility to the lethal effects of Shiga-like toxin II (SLT II). A/J mice, which are unable to produce the C5 component of complement, did not differ from C5 normal mice in susceptibility to SLT II. CBA/NJ mice (hemizygous for X-linked immunodeficiency) did not differ from the B-cell sufficient CBA/J strain. C3H/HeJ mice, defective in macrophage response to lipopolysaccharide (Lpsd), showed a consistently and significantly longer mean time to death than did the normally responsive C3H/HeN strain. C57BL/10ScN mice, which also carry the Lpsd allele, showed a similar but smaller difference in mean time to death compared with the C57BL/10SnJ strain. Production of tumor necrosis factor could be induced in vitro by SLT II treatment of C3H/HeN, but not C3H/HeJ macrophages. These results imply that antibody and complement production do not modulate SLT II lethality in mice, but that the macrophage may contribute to SLT II-induced injury.

Alleles↗