Complement components of a haemolytically deficient strain of rabbits

Abstract

A strain of complement (C′) deficient rabbits was studied. No C′₆ haemolytic activity was found in the sera of these rabbits. Both haemolytic and leucocidal activities were stored upon adding purified C′₆ isolated from either normal rabbits or normal guinea-pigs. The mixture of deficient serum with sensitized sheep cells resulted in the generation of active C′₅ sites, SAbC′_1,4,2,3,5, since lysis occurred after the addition of highly purified C′₆, C′₇, C′₈ and C′₉ to the washed cells. These rabbits possess a heat labile substance which is considerably heavier than C′₆. This C′₆ inactivator reacts specifically with the intermediate complex, EAbC′_1,4,2,3,5,6. The product of the reaction appears to be incapable of combining with the next component in the haemolytic sequence, C′₇. The inactivator is not depleted from the fluid phase during interaction with cells possessing active C′₆ sites.

The elution characteristics from DEAE- and CM-cellulose and the sedimentation constants C′₆ and of the inactivator, as well as of certain other rabbit C′ components, were determined. C′₆ inactivator was also found in normal rabbit serum. A mechanism to explain the variability in results of homotransplant rejection in C′₆ deficient rabbits is offered.