Investigation of the Specificity of Substances in Some Human Sera Which Are Inhibitory in Certain Viral and Rickettsial Complement-Fixing Antigen-Antibody Systems

Abstract

In the first paper of this series, we reported our discovery of substances in certain human sera which inhibit complement fixation in the antigenantibody systems of lymphogranuloma venereum, psittacosis, mumps, Q fever, and lymphocytic choriomeningitis (Schmidt and Harding, 1956). Previous investigators have found that certain avian and mammalian species, or sometimes single individuals of a particular species, respond to antigenic stimuli by producing substances in their serum which are not complement-fixing antibodies, but inhibit complement fixation. These are specific for a given antigen-antibody system and are considered to be a type of antibody. Goodner and Horsfall (1936) investigated the inhibitory activity of horse antipneumococcus type III sera in an antigen-antibody system consisting of the pneumococcus type III polysaccharide and rabbit antipneunococcus type III serum. They further demonstrated that the specificity of the inhibitory activity of the horse heterologous immune serum would not prevent the fixation of complement by rabbit immune serum and homologous antigen. The indirect complement fixation technique was employed by Downie and MacDonald (1950) for their study of the antigenic relationships of the viruses of variola, alastrim, vaccinia, cowpox, and mouse pox. Karrer et al. (1950a) tested the specificity of anti-ornithosis inhibitory substances in the sera of chickens, ducks, and turkeys by infecting these birds with the virus and following the inhibitory titers during the course of the disease. These