Isolation of IgE from normal mouse serum.

Mouse IgE was isolated from reaginic ascitic fluid and an antiserum to it was produced in rabbits. An immunoadsorbent, prepared with this antiserum, was used to isolate IgE from normal mouse serum. Mouse serum proteins, isolated by (NH4)2SO4 (40--60%) precipitation, were applied to the anti-IgE immunoadsorbent and eluted with 3 M KI or 3.5 M NaSCN. In addition to containing IgE, the eluate contained other immunoglobulins which were subsequently removed with specific immunoadsorbents to IgG1, IgG2a, IgG2b, IgA and IgM. Further purification was achieved by gel filtration on Bio Gel A 0.5 m, ion exchange chromatography on DEAE cellulose, and Pevikon block electrophoresis. Since non-immunoglobulin components were demonstrated by immunoelectrophoresis, IgE was isolated from this pool with an anti-Fab immunoadsorbent and eluted with 3.5 M NaSCN. Based on recovery of 987 micrograms IgE from 855 ml NMS, IgE concentration was estimated at 1.15 microgram/ml. Analysis of purified IgE by immunoelectrophoresis and immunoprecipitation in gel detected a single component, partially identical to isoelectric focused rat IgE myelomas IR162 and IR331 Antiserum to it could completely abolish 48 h but not 2 h passive cutaneous anaphylaxis (PCA) reactions. Normal IgE, when used as a diluent, could inhibit 48 h PCA reaction of reaginic antibody suggesting that it binds to mouse skin in a way similar to reagin. This demonstrates that IgE can be isolated from normal mouse serum. The availability of this source of mouse IgE should facilitate further use of this animal model in studies of allergic reactions.