Inhibition of anaphylactic histamine release by Forssman antiserum. I. Characteristics of the reaction and inhibitor.

Forssman antiserum produced in rabbits immunized with sheep erythrocyte stromata was found to contain an IgG antibody which inhibited both passive anaphylactic sensitization of guinea-pig lung and also histamine-releasing activity of soluble immune complexes. This Forssman antibody did not itself cause histamine release or depletion of lung histamine stores. The IgM haemolysin component of the Forssman antiserum was not associated with inhibitory activity. The inhibition by the IgG Forssman antibody differed from that of normal rabbit gammaglobulin both in its irreversible character and in being absorbed by sheep erythrocytes. The inhibitory antibody had no effect on the histamine-releasing activity of compound 48/80, anaphylatoxin or reversed anaphylaxis. It was concluded that IgG Forssman antibody probably blocks the tissue receptor(s) for anaphylactic antibody in guinea-pig lung.