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Part of the Cε3–Cε4 region of the ovine immunoglobulin E (IgE) gene (nucleotides 1111–1575) was amplified by PCR. The recombinant protein (recIgE1-2) was expressed in E. coli and both monoclonal and polyclonal antibodies were produced. These antibodies recognized recIgE1-2 and native IgE on Western blots and in ELISA. The polyclonal serum showed cross-reactivity with other sheep immunoglobulin classes. The monoclonal antibody was specific for ovine IgE and goat IgE. Infection of sheep with the abomasal nematode Haemonchus contortus resulted in elevated IgE levels in serum 2–4 weeks after infection, as measured by sandwich ELISA using the rabbit polyclonal as capture antibody and the monoclonal antibody against ovine IgE as second antibody. A negative correlation between worm counts and total serum IgE levels at the end of the experiment was found in repeatedly infected sheep. Significant increased levels of excretory–secretory antigens specific IgE levels were found after H. contortus infection. In contrast, no significant changes in 3rd-stage larvae (L3) antigen-specific IgE titre in sera could be detected after infection.