"COMPLETE RIDER" YOUR #1 HORSE DESTINATION

Republished with permission from U Davis Equine Immunology White blood cells (macrophages) from the equine lung in culture. These cells are the immune system's first line of defense. Researchers set up controlled conditions in a laboratory setting to investigate the immune response. Researchers added interleukin-4 (IL-4), a protein produced by T lymphocytes during an immune response. The cells are reacting and changing the way they look. At the end of the reaction, the cells produced a new receptor (CD-23), a protein that is frequently seen in people with allergic reactions. Researchers are now ready to investigate this process in the horse's body to further define the horse's immune response. Over the last decade, there have been two main areas of advancement in immunology: 1) the development of markers for cells of the immune system (monoclonal antibodies) and 2) the cloning of genes involved in immune system function. Thanks to the generous support of many individuals and organizations such as the Harriet Pfleger Foundation, the Bernice Barbour Foundation, Inc., and the Southern California Equine Foundation, researchers now have many more tools available at their disposal to unlock the secrets of the immune system. Vaccines - UC Davis researchers have identified differences between adult horses and foals in their response to vaccination. Researchers determined that foals do not respond with the same measurable antibody response as some adults. Researchers also found that the maternal antibodies that are passed to the nursing foal interfere with antibodies from vaccinations given to foals. This information has changed the vaccination recommendations for foals (Wilson, Mihalyi). Researchers have also investigated novel vaccine formulations for equine viral arteritis (EVA) (MacLachlan, Balasuriya, Hedges), and "Pigeon Fever" or Corynebacterium pseudotuberculosis (Spier). These studies have yielded important information regarding the future manufacture of effective vaccines for these diseases. Antibodies - IgE is the specific antibody that is responsible for allergy in any animal. Human IgE was discovered in 1966. UC Davis researchers have cloned the gene that codes for equine IgE and synthesized a portion of this molecule in bacteria. This is the first step towards developing a test for equine IgE (Gershwin, Watson). Cytokines - Cytokines are the molecules which the immune system's cells use to communicate amongst themselves. These molecules deliver specialized messages to help orchestrate the type, strength and length of an immune response to a given disease agent. UC Davis researchers have developed a very sensitive test called TaqMan PCR for a number of equine cytokines. It is now possible to measure a dozen different equine cytokines in blood, cells or tissues sampled during the course of a disease. Researchers are currently looking at cytokine responses in a number of diseases. Their goal is to define the specific type of immune response the animal is mounting. In the future, this information will be valuable for both vaccine development and new therapies (Madigan, Leutenegger). Lymphocytes - Lymphocytes are the cells that coordinate the type of immune response an animal will mount. In the last 20 years, research has shown that all lymphocytes are not created equal. There are B cells which are responsible for antibody production, T cells which provide motivation for B cells to respond (helper), T cells which kill virus infected cells (cytotoxic), and T cells which are preprogrammed to kill anything they find that is not part of the body (natural killers). UC Davis researchers have worked hard to produce markers for these different subsets so that the numbers and types of lymphocytes present during a horse's immune response can be described. CD3 and CD5 are T lymphocyte markers. CD3 is a very important marker because it positively identifies T lymphocytes, the cells that play a central role in regulating, focusing and affecting the proper immune response (Blanchard, Stott). Researchers now know that foals have many more B cells than adult horses. This information may help researchers tailor the way vaccines are designed for young animals (Stott, Blanchard, Moore). T cell Receptor genes - There is a complex series of genes involved in the development of a specific immune response. T cell receptor genes are one set of these complex genes and UC Davis researchers have cloned the majority of these genes (Schrenzel, Ferrick). Tumor immunity - UC Davis researchers are investigating the equine immune response to certain types of tumors. These studies may provide essential information to develop specialized vaccines for equine tumors like sarcoids and melanomas (Theon, Carr, McEntee). Allergic disease - UC Davis researchers have cloned and expressed one of the receptors for IgE in the horse (CD23). This receptor is normally found on lymphocytes and can be found on other cell types in allergic individuals. In these studies, researchers discovered that cells from equine lungs treated with a cytokine important for allergy (IL-4) increase the expression of this receptor on their surface a thousand-fold. This receptor shows promise both as a diagnostic tool and a potential avenue for therapy. In a related study, UC Davis researchers are currently investigating the receptor for IL-4 and its importance in the equine allergic response (Watson, Stott). Ongoing research at UC Davis is aimed at improving the accuracy of allergy testing in the horse (Gershwin). Respiratory disease - Many kinds of respiratory diseases commonly limit the use of horses for performance and/or pleasure; therefore, researchers are investigating how the immune system reacts with respiratory disease. When the lung is diseased or inflammed, cells of the immune system travel there to "help out." The beta-2 integrins or leukointegrins are surface proteins that the white blood cells use to travel to the site of inflammation. Researchers have characterized equine markers for a number of these proteins and are now using them in the clinical laboratory (Affolter, Moore). An investigation of equine chronic obstructive pulmonary disease (COPD) revealed that horses have high numbers of T lymphocytes in their lungs, both in and around the airways. It is very likely that these cells play a role in the regulation of COPD and future studies may help researchers further understand this process (Watson, Wilson, Wilson). Wildlife birth control - UC Davis researchers have utilized the body's immune system to develop natural birth control for wild horses and other wildlife in need of population control. By injecting a single vaccine using a dart, the egg actually sets up antibodies around itself, thus preventing the sperm from fertilizing the egg. The animals still cycle normally and maintain their natural behavior, they just become infertile for a one-year period. When the effects wear off, the animal can become pregnant again (Liu). "Our understanding of how the body's defense system works, and developing the means to strengthen and control those processes, will form an integral part of all therapeutic strategies in the coming years." -- Dr. Gregory L. Ferraro   The Horse Report is Copyrighted © 2001 by the Regents of the University of California. Use of this material for re-publication is allowed only by permission of the Center for Equine Health. Contact CEH (cehwebmaster@ucdavis.edu) for availability of printed materials.   immune system Immunization Schedule for Horses|West NileVirus|ColicBasics|Lameness?|Tapeworms | Mare Reproduction Loss|Foal Vaccination for Equine Influenza

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