The human body is continually exposed to disease producing organisms, called pathogens, and other harmful substances in the environment. The immune system is the body's defense against these harmful invaders. The body's ability to counteract the effects of pathogens and other harmful agents is called resistance and it is dependent on a variety of defense mechanisms.
The immune system is made up of billions of special cells called white blood cells, lymphocytes, unique proteins called antibodies, chemicals that mediate immune response, and special organs that replenish and integrate the whole immune process. All of these defense mechanism must act together and are designed to react rapidly to provide protection against disease-producing organisms and their toxins. There are two aspects of the immune system's response to disease: innate and acquired. Natural, or innate, immunity is present from birth and is the first line of defense against the vast majority of infectious agents. Innate immunity involves barriers that keep harmful material from entering the body. The skin provides an impenetrable barrier. The eyes use fluids, such as tears, and the presence of enzymes, such as lysozyme, that destroy bacteria. The respiratory system utilizes cilia, mucus, and coughing to get rid of foreign materials. If infection-causing organisms gets past these defenses, the body produces fever, inflammation, and other reactions designed to conquer the unwelcome invader. Inflammation causes an increase in the local blood supply so that large numbers of white blood cells can be brought to the area to fight the infection. Some of these white blood cells are phagocytes and macrophages that literally eat the invading microorganism. In most cases of minor infection, these cells solve the problem. If the pathogen succeeds in passing this barrier, a more complex process, involving other cells of the immune system, is necessary. When a virus enters the body an immune response begins automatically. A scavenger macrophage will eat the virus and display the viral antigen on its surface. Anything that can trigger an immune response is called an antigen. An antigen can be a germ such as a virus, or even a part of a virus. Other white blood cells in your body called 'helper T-cells' will see the viral antigen and produce toxins that will destroy it. The helper T- cells then send chemical messages that activate lymphocytes called B-cells which make antibodies that recognize the viral antigen. These cells ' remember' the specific disease organism and divide into many more cells. The resulting 'clone' of identical cells starts producing very large numbers of antibodies that bind to all the organisms of that disease and destroy them. This process is called acquired immunity. It is a learning process of the immune system that develops either through exposure to microorganisms. It is estimated that the body has more than 100 million different kinds of antibodies, each one custom-built to identify a particular pathogen. If the body is exposed a second time, no symptoms occur because the organism is destroyed quickly - the bofy is immune to that particular pathogen. Research The Immune System
Abbreviations
Medicine
Research The Immune System