[A mechanism of human complement activation by immunostimulators from the bacterial cell wall]

Effects on the human complement system of the cell wall preparations: lipopolysaccharides and polysaccharides of E. coli, Salmonella typhi (pyrogenal, salmosan), Bact. prodigiosum (prodigiosan) and peptidoglycan of Lactobacillus bulgaricus (blastolysin) have been studied. Lipopolysaccharide of E. coli, pyrogenal and salmosan were found to bind efficiently the first complement factor C1q. The constants for inhibition of the C1q binding to antibodies by the mentioned preparations were determined, and their ability to initiate the classical pathway of complement activation (consumption of C4, C2 and C3 factors) was assayed. These preparations only slightly affect the alternative pathway. Prodigiosan, not influencing the classical pathway, initiates the alternative one. Its binding constant with the activated Bb factor was determined. This constant reflects the Bb association with C3b and is (2,4 +/- 0,1) x 10(7) mole-1 l. Blastolysin is effective both in the C1q binding and initiation of the alternative pathway of complement activation. Immunostimulating activity of the bacterial cell wall preparations seems to involve activation of the complement system and the release of the fragments from the complement factors which are mediators of the immune response.