Differences in complement activation between complement-resistant and complement-sensitive Moraxella (Branhamella) catarrhalis strains occur at the level of membrane attack complex formation.

C M Verduin; M Jansze; C Hol; T E Mollnes; J Verhoef; H van Dijk

doi:10.1128/iai.62.2.589-595.1994

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PubMed · 8300216

Differences in complement activation between complement-resistant and complement-sensitive Moraxella (Branhamella) catarrhalis strains occur at the level of membrane attack complex formation.

C M Verduin·M Jansze·C Hol·T E Mollnes·J Verhoef·H van Dijk

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Abstract

The mechanism of resistance to human complement-mediated killing in Moraxella catarrhalis was studied by comparing different complement-sensitive and complement-resistant M. catarrhalis strains in a functional bystander hemolysis assay and an enzyme-linked immunosorbent assay (ELISA) for soluble terminal complement complexes. Complement-resistant stains appeared to activate complement to the same extent as, or even slightly better than, complement-sensitive strains. This indicates that complement-resistant strains do not inhibit classical or alternative pathway activation but interfere with complement at the level of membrane attack complex formation. A clear difference in dose-response curves for resistant and sensitive strains was observed both in the bystander hemolysis assay and in the ELISA. Complement-resistant strains showed optimum curves, whereas complement-sensitive strains gave almost linear curves. We conclude that resistant strains bind and/or inactivate one of the terminal complement components or intermediates involved in membrane attack complex formation. Trypsin, known to abolish complement resistance, changed the optimum dose-response curve of a resistant strain to a linear one, which strongly suggests that complement resistance is mediated by an M. catarrhalis-associated protein. This protein acts directly or through the binding of a terminal complement inhibitor present in serum.

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Bacterial Proteins Complement Activation Complement Membrane Attack Complex Cytotoxicity, Immunologic Humans In Vitro Techniques Kinetics Moraxella catarrhalis Species Specificity Comparative Study Journal Article

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C M Verduin, M Jansze, C Hol, T E Mollnes, J Verhoef, H van Dijk. 1994. Differences in complement activation between complement-resistant and complement-sensitive Moraxella (Branhamella) catarrhalis strains occur at the level of membrane attack complex formation.. https://doi.org/10.1128/iai.62.2.589-595.1994

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