Production and characterisation of polyclonal antisera against feline IgE

Cats, naturally or experimentally infected with Toxocara cati were immunised with dinitrophenylated ascaris antigen (DNP-Asc). All cats developed immediate skin reactivity to DNP coupled to bovine serum albumin (DNP–BSA) and the sera of the nine cats had a heat labile homocytotropic antibody detectable by homologous Prausnitz–Küstner (PK) tests. Reagin-rich fractions were prepared from these sera and used for the preparation of polyclonal antisera in rabbits. Resultant antisera were passed through a immunoabsorbent column of Sepharose 4B coupled to heated normal cat serum. An immunoabsorbent column prepared with the resultant antisera removed the PK reactivity from the cat sera, and the activity was recovered following acid elution. The antiserum failed to detect any recognised immunoglobulin in cat sera, but precipitated with a heat labile protein with γ-1 electrophoretic mobility in the sera of parasited cats. These findings support the contention that the antisera are specific for feline IgE.