<p>Immunoglobulin E (IgE) occurs exclusively in mammals and is one of five immunoglobulin (Ig) classes found in man. Unlike other isotypes, IgE is best known for its pathological effects, whereas its physiological role remains somewhat elusive. </p><p>To trace the emergence of IgE and other post-switch isotypes we have studied Ig expression in two monotreme species, the duck-billed platypus (<i>Ornithorhynchus anatinus</i>) and the short-beaked echidna (<i>Tachyglossus aculeatus</i>), leading to the cloning of IgE, two IgG isotypes in platypus and echidna IgE. The presence of IgE and the conservation of the overall structure in all extant mammalian lineages indicates an early appearance in mammalian evolution and a selective advantage of structural maintenance. Furthermore, both of the two highly divergent platypus γ-chains have three constant domains. Hence, the major evolutionary changes that gave rise to the IgE and IgG isotypes of present day mammals occurred before the separation of monotremes from the marsupial and placental lineages, estimated to have occurred 150-170 million years ago.</p><p>As the central mediator in atopic allergy, IgE is a prime target in the development of preventive treatments. This thesis describes an active immunization strategy that has the potential to reduce IgE to a clinically significant extent. The active vaccine component is a chimeric IgE molecule, Cε2-Cε3-Cε4. The receptor-binding target domain, Cε3, is derived from the recipient species, whereas the flanking domains, acting both as structural support and to break T-cell tolerance, are derived from an evolutionarily distant mammal. Vaccination of ovalbumin-sensitized rats resulted in a substantial reduction in total IgE in three out of four strains, accompanied by a significant reduction in skin-reactivity upon allergen challenge. No cross-linking activity was observed and the response to vaccination was reversible with time. The apparent safety and efficacy of the vaccine suggest that active immunization against IgE has the potential to become a therapeutic method for humans. </p><p>Furthermore, the cloning and expression of the pig (<i>Sus scrufa</i>) ε-chain will facilitate the development of sensitive and specific assays for pig IgE, thus increasing the possibilities of using the pig model in future studies of IgE-mediated reactions.</p>

Immunoglobulin E (IgE) occurs exclusively in mammals and is one of five immunoglobulin (Ig) classes found in man. Unlike other isotypes, IgE is best known for its pathological effects, whereas its physiological role remains somewhat elusive. To trace the emergence of IgE and other post-switch isotypes we have studied Ig expression in two monotreme species, the duck-billed platypus (Ornithorhynchus anatinus) and the short-beaked echidna (Tachyglossus aculeatus), leading to the cloning of IgE, two IgG isotypes in platypus and echidna IgE. The presence of IgE and the conservation of the overall structure in all extant mammalian lineages indicates an early appearance in mammalian evolution and a selective advantage of structural maintenance. Furthermore, both of the two highly divergent platypus γ-chains have three constant domains. Hence, the major evolutionary changes that gave rise to the IgE and IgG isotypes of present day mammals occurred before the separation of monotremes from the marsupial and placental lineages, estimated to have occurred 150-170 million years ago. As the central mediator in atopic allergy, IgE is a prime target in the development of preventive treatments. This thesis describes an active immunization strategy that has the potential to reduce IgE to a clinically significant extent. The active vaccine component is a chimeric IgE molecule, Cε2-Cε3-Cε4. The receptor-binding target domain, Cε3, is derived from the recipient species, whereas the flanking domains, acting both as structural support and to break T-cell tolerance, are derived from an evolutionarily distant mammal. Vaccination of ovalbumin-sensitized rats resulted in a substantial reduction in total IgE in three out of four strains, accompanied by a significant reduction in skin-reactivity upon allergen challenge. No cross-linking activity was observed and the response to vaccination was reversible with time. The apparent safety and efficacy of the vaccine suggest that active immunization against IgE has the potential to become a therapeutic method for humans. Furthermore, the cloning and expression of the pig (Sus scrufa) ε-chain will facilitate the development of sensitive and specific assays for pig IgE, thus increasing the possibilities of using the pig model in future studies of IgE-mediated reactions.

<p>Immunoglobulin E (IgE) is an important mediator in atopic allergies. This thesis describes the development of a therapeutic vaccine against IgE and its effects in rats and dogs. The development of an assay to determine IgE levels in dogs, and the finding of a chromosome region in rats that affects IgE levels are also reported. </p><p>The vaccine is a chimeric molecule consisting of the constant domains Cε2, Cε3 and Cε4 from IgE. The target domain of the vaccine is the Cε3 domain in the recipient species, which is the domain directly involved in receptor binding, while the flanking regions, Cε2 and Cε4, are from a distantly related mammal. In rats, the vaccine induced an immune response against circulating IgE, which decreased IgE levels by 90% and substantially reduced their allergic symptoms. Further, the effects of adjuvants in rats and dogs were evaluated, and when co-administered with the vaccine certain adjuvants were shown to increase the immune response against IgE. Mineral-oils were the most potent adjuvants in inducing a response against IgE, but metabolizable oils spiked with immunostimulatory substances were also efficient. </p><p>It was also shown that the therapeutic vaccine could induce a decrease in IgE levels in adult dogs, even though their initial levels were exceptionally high compared with humans. The IgE levels in 76 dogs ranged between 1 and 41 μg/ml while humans normally have around 150 ng/ml. However, the high IgE levels did not correlate to any specific breed, nor did they distinguish between dogs that were diagnosed as healthy and those suffering from atopic eczema, autoimmunity or skin parasites. </p><p>Regulation of total IgE levels probably involves many genes. In the final phase of the study, one candidate locus known to be involved in arthritis susceptibility in rats was investigated, and was found also to affect IgE levels.</p>

Immunoglobulin E (IgE) is an important mediator in atopic allergies. This thesis describes the development of a therapeutic vaccine against IgE and its effects in rats and dogs. The development of an assay to determine IgE levels in dogs, and the finding of a chromosome region in rats that affects IgE levels are also reported. The vaccine is a chimeric molecule consisting of the constant domains Cε2, Cε3 and Cε4 from IgE. The target domain of the vaccine is the Cε3 domain in the recipient species, which is the domain directly involved in receptor binding, while the flanking regions, Cε2 and Cε4, are from a distantly related mammal. In rats, the vaccine induced an immune response against circulating IgE, which decreased IgE levels by 90% and substantially reduced their allergic symptoms. Further, the effects of adjuvants in rats and dogs were evaluated, and when co-administered with the vaccine certain adjuvants were shown to increase the immune response against IgE. Mineral-oils were the most potent adjuvants in inducing a response against IgE, but metabolizable oils spiked with immunostimulatory substances were also efficient. It was also shown that the therapeutic vaccine could induce a decrease in IgE levels in adult dogs, even though their initial levels were exceptionally high compared with humans. The IgE levels in 76 dogs ranged between 1 and 41 μg/ml while humans normally have around 150 ng/ml. However, the high IgE levels did not correlate to any specific breed, nor did they distinguish between dogs that were diagnosed as healthy and those suffering from atopic eczema, autoimmunity or skin parasites. Regulation of total IgE levels probably involves many genes. In the final phase of the study, one candidate locus known to be involved in arthritis susceptibility in rats was investigated, and was found also to affect IgE levels.