"COMPLETE RIDER" YOUR #1 HORSE DESTINATION

Republished with permission from U Davis The Immune System = The National Defense "Battle of Chancellorsville, VA" May 3,1863. Currier and Ives lithograph. By Dr. Johanna Watson The immune system -- you cannot see it on a radiograph or an ultrasound -- you cannot point to it like your heart or your stomach…without it you would die. Well, you could say that about many organs. You cannot live without a heart, a liver, a pancreas or a brain. Yet, each of these organs, and others, require the immune system to protect them from attackers - diseases. Think of the body as the nation and the immune system as the national defense. The immune system is a fascinating network of cells and cell "depots." This network not only protects the body from invaders like bacteria, viruses and parasites, but it also travels long distances, communicates specifics regarding the enemy invader and coordinates special forces to return to the front line. The immune system also keeps detailed records about all previous invaders for many years, allowing a very rapid response in case the same "enemy" invades the body a second time. The first defenses, the innate immune system, include cells called macrophages and neutrophils. The immune system sends information via macrophages to T and B lymphocytes which are cells of the immune system that focus the response on the specific type of invader (bacteria, protozoa, virus). The T lymphocytes coordinate waves of T and B lymphocytes that are highly specific for the particular invader/pathogen. When the battle is over, memory T and B lymphocytes remain containing all the information necessary to re-mount an effective response the next time the invader happens to gain access to the body. This specific response is called the adaptive immune response. There really is no other system that compares. Imagine that in order to evade a disease, you needed to change the color of your eyes. That would require changing the genes that code for eye color in every cell in your iris. Sound impossible? Well, that is all in a day's work for the immune system. For each new disease agent or pathogen encountered, the immune system (T and B lymphocytes) rearranges its genes to accomplish a highly specific defense against the disease. The English word immunity has its roots in the Latin term immunis, meaning exempt. People at least had a vague concept of immunity all the way back to 430 B.C. Thucydides, the historian of the Peloponnesian war, wrote that only those who had recovered from the plague could nurse the sick because they would not contract the disease a second time. However, the science of immunology has only developed in the last 200 years. In the 15th century, the Chinese and Turks developed crude forms of vaccination. At the close of the 18th century, the English physician Edward Jenner improved upon these concepts by vaccinating people against smallpox using material from cows with cowpox. It took scientists another 100 years to completely understand vaccination and apply it to other diseases. In the 1880s, Louis Pasteur demonstrated that it was possible to "weaken" a pathogen and administer the weaker strain as a vaccine. He called this weaker strain a vaccine (from the Latin vacca, cow) in honor of Jenner's work with cowpox. The discovery of vaccinating individuals to protect against disease marked the beginnings of immunology. In the last 70 years, scientists discovered most of what we know about the immune system. In the 1930s, researchers discovered antibodies and in the 1950s, they determined that lymphocytes were the cells that govern the immune response. In the 1920's, scientists conducted early allergy studies, but IgE, the antibody responsible for allergic reactions, was not discovered until 1966. Immunology as a science has grown exponentially in the last 30 years and there are many new tools available to study immune responses to different diseases in mice and humans. However, many of these tools are not available for the horse. In this century, the challenge for immunology researchers is to improve the science of vaccination and to develop immunotherapeutic drugs to assist the body with a weak or inappropriate response. The challenge for those in equine immunology is to develop enough tools to do the same for the horse. Due to differences in their genes, people and animals respond differently to the same disease causing pathogen. Once scientists can identify the genes responsible for these differences, then they can design therapies to help individuals with a "sub-standard" response to a given disease. Studying the immune system is paramount in our fight against infectious and communicable diseases of all species. Over the last 200 years, there were two major advances in medicine that helped in the fight against infectious diseases: antibiotics and vaccines. Unfortunately, bacteria have developed resistance to many antibiotics, and now they threaten to leave us behind in the race for new, effective antibiotics. Viruses continue to evolve, producing new strains of known organisms, and producing new, emerging diseases. It is extremely important that the researchers understand how the immune system works against various types of diseases so they can devise the best vaccine strategies and develop new therapeutics to help strengthen the immune system's national defense when it is faced with a new enemy/pathogen. Next week the immune system and the horse. 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