Page 935 - Veterinary Immunology, 10th Edition

example, both Teladorsagia circumcincta and Haemonchus contortus
VetBooks.ir produce chemoattractants for eosinophils, whereas the free-living

nematode Caenorhabditis elegans does not. This suggests that some
nematodes actively encourage eosinophil recruitment. Likewise,

when Trichinella spiralis survival was studied in mice lacking
eosinophils, it was found that the larvae in the muscles of these
mice died in much larger numbers than in wild-type mice.
Although the IgE-dependent eosinophil-mediated response is the

most significant mechanism of resistance to larval helminths, other
antibodies also play a protective role. The mechanisms involved
include antibody-mediated neutralization of larval proteases,
blocking of the anal and oral pores of larvae by immune-complexes,

and prevention of molting and inhibition of larval development by
antibodies directed against exsheathing antigens. Antibodies to the
enzyme glutathione-S-transferase protect sheep against Fasciola
hepatica. Antibodies against adult worms may stop egg production

or interfere with worm development (Fig. 28.8). Thus female
Ostertagia ostertagi fail to develop vulvar flaps when grown in
immune calves. Similarly, spicule morphology may be altered in
Cooperia males from immune hosts.

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