Opsonic requirements for hepatic clearance of pneumococci

An in situ isolated, perfused rat liver system was used to evaluate various opsonins for hepatic trapping and killing of encapsulated, virulent, type 3 pneumococci. Pneumococci were rapidly trapped in the liver in the presence of all potential opsonins including Hanks balanced salt solution with added colloid. However, with some of the potential opsonins the organisms remained viable and could be recovered from the liver. With others there was killing of pneumococci. The combination of rat antibody and complement was effective as an opsonin and produced about the same degree of killing as the same human components. When tested separately killing was not promoted by rat complement, human complement, or human antibody. However, when ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-Mg2+ was added to block the classical pathway and preserve the alternative pathway there was significant pneumococcal killing which may have been complement mediated or due to an adverse effect of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-Mg2+ on the organisms. Fibronectin and C-reactive protein reduced the number of surviving microorganisms, although the change was not significant. Immunoglobulin G (IgG)-IgM, IgG, or IgM with complement, and antibody + the classical complement pathway, significantly reduced survival of the organisms. The best killing occurred with antibody plus complement plus fibronectin, which reduced mean survival to 24% during the 1-h perfusion.