\nHomeostasis in an organism is constantly threatened. Failure to respond effectively can result in disease or death. Disease is a disturbance of homeostasis or steady state within an organism. Many organisms, such as viruses, bacteria, fungi, and parasites may cause disease. Disease also results from factors which are not living organisms.<\/p>\n
The immune response is the defensive reaction of the body to foreign substances or organisms. The immune system also protects against some cancer cells which may arise in the body.<\/p>\n
Some Causes of Disease<\/strong> Other factors may be involved which contribute to or cause the body to develop disease. Some of these factors include heredity, exposure to poisonous (toxic) substances, poor nutrition, organ failure or malfunction, and poor personal behavior and choices. Smoking, obesity, and over consumption of alcoholic beverages would be a few examples of poor personal choices which may have immediate or long term consequences for our health.<\/p>\n Immunity and Disease<\/strong> Many different kinds of white blood cells exist which are able to help the body fight foreign invaders in various ways. These various ways include:<\/p>\n Below are graphics of two different categories of white blood cells in action: Immune System Memory and Vaccinations<\/strong> Immune System Memory<\/strong> Allergies and Auto-immune Diseases<\/strong>
\nLiving organisms which cause disease are known as pathogens. Some viruses, bacteria, fungi, and parasites are examples of living things which are pathogens causing disease.<\/p>\n
\nImmunity describes the ability of an organism to resist foreign organisms or invaders which enter its body. The immune system is designed to protect against microscopic organisms (bacteria, viruses) and foreign substances which enter an organism from outside its body. The immune system also protects from many cancer cells which arise within our bodies. An antigen is any foreign substance which invades the body of an organism, while a pathogen is a living antigen (such as viruses or bacteria) which invade an organism.<\/p>\n\n
\nPhagocytic White Blood Cells in Action<\/strong>
\n![\"Immune](\"https:\/\/c8.staticflickr.com\/1\/306\/31674954615_4b7bbb6866_o.jpg\")
\nLymphocyte White Blood Cell Function<\/strong>
\n![\"Lymphocyte](\"https:\/\/c4.staticflickr.com\/1\/543\/31559509291_ebc1af07d9_o.jpg\")
\nIt is important to note that an antibody has a specific shape to destroy a specific antigen.<\/p>\n
\nWhen organisms are exposed to disease, they make specific antibodies which destroy that antigen during their first exposure to it. This first exposure to a disease and our making of antibodies in reaction to this to defend ourselves is sometimes called the primary immune response. Our immune system has a memory. This means that if we ever are exposed to that same particular disease antigen again, our immune system has a memory and will make antibodies so rapidly in response to another exposure that we will not get the disease. Our immune memory is sometimes called the secondary immune response.<\/p>\n
\n![\"Immune](\"https:\/\/c4.staticflickr.com\/1\/352\/30864946403_5fc87af9b4_o.jpg\")
\nVaccinations use dead or weakened microbes or parts of them to stimulate the primary immune response or first production of antibodies. Using dead or weakened microbes has the advantage of not making the organism sick as they would become if they caught and recovered from a disease. Because the vaccine has stimulated the immune system, the organism will now have a memory to subsequent exposures to that disease causing antigen.<\/p>\n
\nIn allergies, the body’s immune system produces chemicals in response to normally harmless substances which do not trouble other individuals. These chemicals make people with allergies feel sick. In auto-immune diseases, the body’s immune system for usually unknown reasons may attack and destroy some its own cells. Some kinds of arthritis and degenerative diseases result from auto-immune diseases.<\/p>\n