Immunochemical identification of mouse IgE.

Immunochemical identification of a distinct immunoglobulin class associated with mouse reaginic antibody and designated IgE has been performed. An antiserum against mouse reaginic antibody was prepared in rats by immunization with homologous peritoneal mast cells sensitized with mouse reaginic antibody. This antiserum, after adequate absorption, recognized only one component existing in mouse serum or fractions of serum containing reaginic antibody. This component was not any of the already known γ, γ, IgA or IgM immunoglobulins; its immunoglobulin nature was indicated by its antigen-binding capacity in radioimmunodiffusion analysis. Fractionation experiments (zone electrophoresis, gel filtration on Sephadex G-200) showed that there was a strict association between reaginic anaphylactic activity and IgE immunoglobulin. Molecular weight of IgE was found to be about 200,000. In biological tests, anti-IgE neutralized anaphylactic activity attributed to reaginic antibody, but not that attributed to γ-antibody. Anti-IgE degranulates normal and sensitized mouse peritoneal mast cells, and rat peritoneal mast cells after they have been sensitized by mouse reaginic antibody.