Feline reaginic antibody has been shown to be present in the serum of some cats with allergic skin
disease or parasitic infections. However few studies have attempted to characterise feline IgE and the
production of antisera specific for feline IgE has yet to be reported. The involvement of this isotype in feline
allergic diseases is thus unclearThe first aim of these studies was to purify and characterise feline IgE to produce specific
polyclonal antisera and investigate anitigen-specific IgE responses in cats. Cats naturally or experimentally
infected with T. 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 Prausnitz-Kiistner (PK) tests. Reagin-rich fractions
were prepared from these sera by a variety of techniques and used for the preparation of antisera in rabbits.
Resultant antisera were passed through an immunoabsorbent column of heated normal cat serum. An
immunoabsorbent column prepared with the putative anti-IgE serum removed PK reactivity from the cat
sera, and the reactivity was recovered following acid elution. The antiserum failed to detect any recognised
immunoglobulin in cat sera but precipitated with a heat labile protein with y-1 electrophoretic mobility in
the sera of parasitised cats. These findings support the contention that the antiserum is specific for feline IgE.Ten normal cats were immunised with Dermatophagoides farinae (DF) antigen and intradermal skin
tests (IDSTs) were performed weekly. Sera from the latter were also assessed for DF-specific IgE by ELISA
and PK tests. Detectable DF-specific IgE was induced in all of the 10 cats, however levels were found not to
be correlated with the development of positive IDSTs nor with the levels of IgE as assessed by PK tests.Sera from 10 cats with symptoms consistent with atopy, from 15 normal household cats and from 11
laboratory maintained cats were assessed for allergen-specific IgE and IgG to DF by ELISA. Although DFspecific IgE was detectable in all the atopic cats, there was no significant difference between the levels in
this group and in the clinically normal household cats. However levels in both these groups were
significantly higher than those in the laboratory maintained cats.The influence of vaccination and endoparasitism on the IgE response to a food antigen was assessed
in 34 cats. Seventeen kittens experimentally infected with T. cati and 17 parasite-free kittens were dosed
with human serum albumin (HSA) daily for 3 weeks. Seven cats from both groups were given two injections
of a live attenuated viral vaccine. The group of parasitised cats had significantly higher levels of HSAspecific IgE, IgG and IgA than did the group of parasite-free cats. Vaccinated cats had also higher levels
than non vaccinated cats but only in the group of parasite-free cats. None of the cats developed clinical signs
of food allergy.The findings from these studies are strongly suggestive of the existence of a heterogeneity of IgE in
cats, and imply that endoparasitism and vaccination have an immunomodulatory role on the antigen specific
antibody response
