A reagin-like antibody in horse serum: 1. Occurrence and some biological properties.

The demonstration of a reagin-like antibody against Culicoides pulicaris extract in the serum of horses and ponies affected with recurrent seasonal dermatitis (sweet itch) is reported. This antibody can confer Prauznitz-Küstner (P-K) sensitivity on homologous skin for up to 5 days and, like human IgE, is thermolabile and susceptible to 2-mercaptoethanol reduction. It is eluted on diethylaminoethyl dextran-52 anion exchange chromatography independently of IgG, IgG(T) and IgM, and its elution characteristics indicate similarity in net molecular charge to human IgE. The P-K response observed in horse skin is biphasic, and is morphologically similar to the late cutaneous anaphylactic response in man. Both phases of the P-K response are dependent upon the reagin-like antibody, although other serum factors appear involved in the delayed phase of the response.