Active cutaneous anaphylaxis in the guinea-pig. Immunological and inflammatory reactions.

Active cutaneous anaphylaxis was studied in guinea-pigs sensitized by inhalation of egg albumen powder and producing high titre IgGγ1 and low titre IgE homocytotropic antibodies. On cutaneous antigen challenge an immediate increase in venular permeability occurred which declined rapidly over the next hour, normal permeability being restored by 2 hours. This was followed by a biphasic tissue eosinophilia with peaks at 3–6 hours and 14–16 hours. Tissue neutrophilia was also maximal at 14–16 hours with a preceding `shoulder' between 6 and 12 hours. Injection of antigen into non-sensitized animals produced only the early peak of leucocytosis. Fluorescent protein tracing demonstrated that little antigen persisted in lesions older than 7 hours. Neutrophil phagocytosis of antigen was maximal between 1 and 3 hours; eosinophil phagocytosis of antigen was not observed. IgGγ1 and IgGγ2 were localized to granulocytes during the 3–6 hour peak of leucocytosis, but not in older lesions. IgGγ1 was detected in eosinophils, but which granulocytes contained IgGγ2 antibodies remained uncertain. Binding of IgGγ1 antibodies to mast cells was not observed and C3 was not detected in any lesion. It is concluded that antigen induced the first peak of tissue leucocytosis; possible mediators of the second leucocytic peak include eosinophil chemotactic factor of anaphylaxis, mast cell products and leucoegresin.