Abstract: Since the initial characterization of IgE by Ishizaka et al. (1966), IgE was described in several mammalian species. In horses, a single gene encoding the IgE heavy chain constant region (IGHE gene) exists per haploid genome and several allelic variants of the equine IGHE gene were found. IgE occurs in its soluble form in equine serum and physiological concentrations of total IgE are around 1000-fold higher in normal horse than in normal human serum. Maternal IgE is enriched in the colostrum and transferred to the neonatal foal after birth. Foals do not produce detectable concentrations of endogenous IgE for several months after birth. IgE is also found on the surface of a small percentage of equine peripheral blood cells including basophils, and subpopulations of B-cells and monocytes, and on mast cells in various tissues such as the skin, and the submucosa of the airways and intestine. Both, the high- and low-affinity IgE receptor genes are identified in the horse suggesting binding of soluble IgE from the circulation to these receptors. Horses naturally develop type I hypersensitivities. IgE-mediated mechanisms were implicated in the pathogenesis of several allergic diseases in horses since almost 30 years. The findings were mainly based on the induction of immediate skin reactions after intradermal testing with allergen extracts. With the development of the first monoclonal antibodies to equine IgE within the past years, more insights into the pathogenesis of allergic diseases could be obtained. Today, various techniques are available to detect soluble IgE and the sensitization of mast cell or basophils with IgE in horses. An IgE-mediated allergic etiology is confirmed for skin hypersensitivity. The causing role of IgE in other diseases such as recurrent airway obstruction (RAO) still remains controversial. More recent studies did not confirm an IgE-mediated pathogenesis of RAO. This suggested that the disease is a chronic inflammatory condition with some indication for an involvement of delayed-type hypersensitivity mechanisms. In summary, our knowledge about the role of IgE during the immune response of the horse improved tremendously during the past decade. New IgE-specific tools and technologies are likely to uncover additional aspects of IgE-mediated mechanisms in equine health and disease.
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The study discusses the role of the immunoglobulin E (IgE) antibody in horses, including its presence in normal conditions, its production and distribution, and its potential contribution to various health conditions including allergies and recurrent airway obstruction.
Characteristics and Behavior of IgE in Horses
The research revealed that in horses, there exists a single gene that codes for the IgE heavy chain constant region, known as the IGHE gene. Readily identifiable in human and many mammalian immunology, this has extended the understanding of equine immunology.
Interestingly, the study suggests that the concentrations of the IgE antibody are around 1000 times higher in healthy horses compared to a healthy human’s serum, implying a significant role for IgE in equine health.
A fascinating discovery is that maternal IgE is enriched in colostrum (first milk after birth) and is transferred to the newborn foal. However, foals cannot produce their own antibodies for several months post-birth.
IgE antibodies surface at a smaller percentage of equine peripheral blood cells such as basophils, subpopulations of B-cells, and monocytes. They are also present on mast cells in various tissues such as the skin, the submucosa of the airways, and the intestine.
The Role of IgE in Equine Hypersensitive Reactions
The research indicates that horses naturally develop a type I hypersensitivity which is often related to allergies. IgE-mediated mechanisms were implicated in the pathogenesis of several allergic diseases in horses. The findings were evidenced mainly based on immediate skin reactions after intradermal testing with allergen extracts.
Tools to detect soluble IgE and the sensitization of mast cells or basophils with IgE in horses are now more advanced. This allows for continued research into the role of IgE during the immune response of horses.
IgE’s Correlation with Recurrent Airway Obstruction (RAO)
There has been controversy concerning the role of IgE in diseases such as the recurrent airway obstruction (RAO). Some studies had suggested an IgE-mediated pathogenesis of RAO, but the recent study fails to confirm this.
The inconsistency suggests that RAO is a chronic inflammatory condition with some evidence for an involvement of delayed-type hypersensitivity mechanisms instead of an IgE-mediated etiology.
Summary and Future Direction
The research shows how our understanding of IgE in the immune response of horses has advanced over the past decade and how new IgE-specific tools and technologies will continue to reveal further IgE-mediated mechanisms in equine health and disease.
Cite This Article
APA
Wagner B.
(2009).
IgE in horses: occurrence in health and disease.
Vet Immunol Immunopathol, 132(1), 21-30.
https://doi.org/10.1016/j.vetimm.2009.09.011
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