SP-40,40 is an inhibitor of C5b-6-initiated haemolysis

Brendan F. Murphy, Jocelyn R. Saunders, Moira K. O'bryan, Louis Kirszbaum, Ian D. Walker, Anthony J.F. D'apice

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This study examines the function of SP-40,40, a newly identified component of the SC5b-9 complement complex, In the regulation of the terminal complement pathway. Purified SP-40,40 was shown to inhibit, in a dose-dependent manner, C5b-6-initiated haemolysls. Apparently additive inhibition was also demonstrated in conjunction with complement S-protein, although SP-40,40 appears to be the more potent inhibitor on an equimolar basis. The data suggest that SP-40,40, like S-protein, probably combines with the nascent C5b7 complex, forming a cytolytically inactive SC5b7-SP-40,40 complex. Preparations of S-protein, purified by an established technique, were shown to be contaminated with SP-40,40. Preparations of affinitypurified SP-40,40 were also shown to contain S-protein, suggesting that these proteins may be partially complexed in plasma.

Original languageEnglish
Pages (from-to)551-554
Number of pages4
JournalInternational Immunology
Issue number5
Publication statusPublished - 1 Nov 1989
Externally publishedYes


  • C5b-9
  • Clusterin
  • Complement
  • S-protein
  • SGP-2

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