Characterization of a rabbit homocytotropic antibody responsible for passive cutaneous anaphylactic reactions with a short (4-hour) latent period.

Abstract

Adult New Zealand rabbits were immunized intraperitoneally with 1·0 <i>μ</i>gof ovalbumin (EA) in alumina gel or subcutaneously with 1.5 <i>μ</i>g of bovine <i>γ</i>-globulin (BGG) and alumina. Immunizations were repeated at 30 and 60 days and every 2 months thereafter. The rabbit sera were examined for homocytotropic antibody by a 72-hour passive cutaneous anaphylactic (PCA) reaction in rabbit skin. Seven of 20 rabbits immunized with EA and 3 of 9 given BGG developed titers of 1:20 or greater; 2 in each group had titers in excess of 1:200. Rabbit sera with 72-hour PCA titers greater than 1:200 also caused vascular permeability of rabbit skin after a 4-hour latent period. The 4-hour anaphylactic antibody had physical-chemical characteristics similar to the 72-hour PCA antibody. It eluted from DE-52 cellulose with 0.10 m saline, was excluded from Sephadex G-200 between the first and second peak, and appeared in a sucrose density gradient slightly in advance of the bulk of the IgG. Absorption with monospecific antisera to rabbit IgE eliminated both the 4- and 72-hour PCA reactions, but there was little effect from an antibody to rabbit IgG. These findings suggest that the same antibody was responsible for the 4- and 72-hour anaphylactic reactions and that it is rabbit IgE.