A pathogen is any agent that causes disease. Robert Koch, a German doctor who studied anthrax, developed a method of determining the cause of a disease.
1. The pathogen must present in an animal that has the disease but not in animals that do not have the disease. 2. The pathogen must be isolated from the sick animal and grown in a laboratory. 3. When the pathogen is injected into a healthy animal, the animal must develop the disease. 4. The pathogen should be taken from the second animal and grown in a laboratory. It should be the same as the pathogen from the first animal.
First line of defense Mucous membranes are epithelial tissue that protect the interior surfaces of the body. Skin is a physical barrier. Mucous membranes secrete mucus, a sticky fluid that traps pathogens. Mucous membranes line the respiratory and digestive systems, the urethra, and the vagina. Sweat contains lysozyme, an enzyme that destroys some bacteria. The respiratory tract is lined with cells covered with beating cilia that sweep mucus and pathogens to the pharynx where they are swallowed and destroyed. Hair is also a part of the physical line of defenses.
Second line of defense
Any pathogen that gets past the skin or mucous membrane will stimulate the inflammatory response. Histamine increases blood flow and increases the permeability of capillaries. If blood vessels have been damaged, platelets begin blood clotting to stop additional pathogens from getting in the body. Phagocytes pass through the capillary walls and eat and destroy pathogens and foreign matter. The neutrophil is the most abundant type of phagocyte in the body. Another type is the macrophage. Natural killer cells are large white blood cells that attack infected cells, not pathogens by piercing the cell membrane of a infected cell. When the body begins to fight pathogens, the body temperature may rise. This slows down bacteria and speeds up macrophages.
47.2 Specific Defenses: The Immune System
The immune system are the cells and tissues that recognize and attack foreign substances in the body. The immune system includes bone marrow, thymus, lymph nodes, spleen, tonsils, and adenoids. The white blood cells of the immune system are called lymphocytes. Bone marrow makes billions of these every day. The thymus helps make a special type of lymphocyte. Lymph nodes contain lymphocytes. The spleen collects pathogens from the blood, and the lymphocytes in the spleen attack pathogens. The adenoids and tonsils are masses of lymph tissues in the nose and throat. There are 2 types of lymphocytes. B cells are made in the bone marrow and complete their development there. T cells are made in the bone marrow and complete development only after traveling to the thymus.
An antigen is any substance that the immune system can recognize and react with. When lymphocytes recognize an antigen, the bind to the antigen to start a specific attack, known as an immune response. Lymphocytes have unique receptor proteins that bond to the receptors on antigens and stop them.
The cell mediated and humoral responses occur at the same time and require helper T cells. When a macrophage engulfs a pathogen and bonds to a helper T with the matching receptor, it sends out a cytokine, interleukin-1, message activates more helper T cells, which then release another cytokine, interleukin-2, message.
Cell Mediated Immune Response Interleukin-2 speeds up T cell division. It stimulates the production of cytoxic T cells which recognize and destroy cells that have been infected by the pathogen. Cytoxic T cells can also kill cancer cells and attack parasites and foreign tissues. Suppressor T cells help shut down the immune response after the pathogen is gone.
Humoral Immune Response
This involves the action of B cells. The release of interleukin-2 stimulates B cells that have receptors that are complementary to the antigen to divide and change into plasma cells. Plasma cells are highly specialized cells that make defensive proteins called antibodies that are released into the blood. An antibody binds to a specific antigen or inactivates or destroys toxins. Antibodies are Y shaped and each identical arm has a receptor that can attach to a specific antigen. Antibodies bind to pathogens and inactivate them, sometimes deferring them to the nonspecific defenses.
Some memory cells remain in the body. They are lymphocytes that will recognize and attack an antigen during later infections. Because of memory cells, a person will get most disease only once. When exposed to a pathogen, memory cells divide rapidly and eliminate the pathogen. The first time the body encounters an antigen, it is called a primary immune response. The secondary immune response is faster, more powerful, and more effective.
Immunity is the ability to resist an infectious disease. One way for the body to gain imunity to a pathogen is to have the pathogen. A safer method is vaccination. A vaccine is a solution that contains a dead or weakened pathogen. Vaccines have been responsible for eradicating many of the worst diseases affecting humans. If the body attacks something that is not a pathogen, it is called an allergy. Allergies can also trigger asthma, a disease that makes the air passages tighten and make breathing difficult. Some disease cause the body to attack its own immune system. These disease are called autoimmune disease.
Passive immunity- Passive immunity is the means by which a person gains antibodies to a disease without actually having the disease. There are 4 forms of Passive immunity. The first is by getting a vaccine (explained above). Another method is through breast milk, which is rich in antibodies. Passive immunity can also be achieved through the placenta when antibodies are sifted out of the mothers blood. Gamma-globulin shots also provide passive immunity, these are just transfered blood of somebody who has had a disease and are used to boost the immune system for a short amount of time.
47.3 HIV and AIDS
HIV (Human immunodeficiency virus) bonds to receptor proteins and the virus replicates inside macrophages. After release from macrophages, HIV attaches to and enters helper T cells. Eventually, HIV kills enough T cells to cripple the immune system. Phase I
This is also called the asymptomatic stage, because there are almost no symptoms. Phase II
The body tries to make B cells, but T cells steadily drop. Swelling lymph nodes, fatigue, weight loss, fever, or diarrhea all develop and worsen. Phase III
AIDS is diagnosed and Opportunistic infections take advantage of the persons crippled immune system. AIDS is fatal. Few individuals live more than two years after being diagnosed. HIV is transmitted through the transfer of bodily fluid. HIV evolves rapidly, and becomes quickly resistant to drugs, so medicines and vaccines are hard to create to fight AIDS.
47.1 Nonspecific Denfenses
A pathogen is any agent that causes disease. Robert Koch, a German doctor who studied anthrax, developed a method of determining the cause of a disease.1. The pathogen must present in an animal that has the disease but not in animals that do not have the disease.
2. The pathogen must be isolated from the sick animal and grown in a laboratory.
3. When the pathogen is injected into a healthy animal, the animal must develop the disease.
4. The pathogen should be taken from the second animal and grown in a laboratory. It should be the same as the pathogen from the first animal.
First line of defense
Mucous membranes are epithelial tissue that protect the interior surfaces of the body. Skin is a physical barrier. Mucous membranes secrete mucus, a sticky fluid that traps pathogens. Mucous membranes line the respiratory and digestive systems, the urethra, and the vagina. Sweat contains lysozyme, an enzyme that destroys some bacteria. The respiratory tract is lined with cells covered with beating cilia that sweep mucus and pathogens to the pharynx where they are swallowed and destroyed. Hair is also a part of the physical line of defenses.
Second line of defense
Any pathogen that gets past the skin or mucous membrane will stimulate the inflammatory response. Histamine increases blood flow and increases the permeability of capillaries. If blood vessels have been damaged, platelets begin blood clotting to stop additional pathogens from getting in the body. Phagocytes pass through the capillary walls and eat and destroy pathogens and foreign matter. The neutrophil is the most abundant type of phagocyte in the body. Another type is the macrophage. Natural killer cells are large white blood cells that attack infected cells, not pathogens by piercing the cell membrane of a infected cell. When the body begins to fight pathogens, the body temperature may rise. This slows down bacteria and speeds up macrophages.
47.2 Specific Defenses: The Immune System
The immune system are the cells and tissues that recognize and attack foreign substances in the body. The immune system includes bone marrow, thymus, lymph nodes, spleen, tonsils, and adenoids. The white blood cells of the immune system are called lymphocytes. Bone marrow makes billions of these every day. The thymus helps make a special type of lymphocyte. Lymph nodes contain lymphocytes. The spleen collects pathogens from the blood, and the lymphocytes in the spleen attack pathogens. The adenoids and tonsils are masses of lymph tissues in the nose and throat. There are 2 types of lymphocytes. B cells are made in the bone marrow and complete their development there. T cells are made in the bone marrow and complete development only after traveling to the thymus.An antigen is any substance that the immune system can recognize and react with. When lymphocytes recognize an antigen, the bind to the antigen to start a specific attack, known as an immune response. Lymphocytes have unique receptor proteins that bond to the receptors on antigens and stop them.
The cell mediated and humoral responses occur at the same time and require helper T cells. When a macrophage engulfs a pathogen and bonds to a helper T with the matching receptor, it sends out a cytokine, interleukin-1, message activates more helper T cells, which then release another cytokine, interleukin-2, message.
Cell Mediated Immune Response
Interleukin-2 speeds up T cell division. It stimulates the production of cytoxic T cells which recognize and destroy cells that have been infected by the pathogen. Cytoxic T cells can also kill cancer cells and attack parasites and foreign tissues. Suppressor T cells help shut down the immune response after the pathogen is gone.
Humoral Immune Response
This involves the action of B cells. The release of interleukin-2 stimulates B cells that have receptors that are complementary to the antigen to divide and change into plasma cells. Plasma cells are highly specialized cells that make defensive proteins called antibodies that are released into the blood. An antibody binds to a specific antigen or inactivates or destroys toxins. Antibodies are Y shaped and each identical arm has a receptor that can attach to a specific antigen. Antibodies bind to pathogens and inactivate them, sometimes deferring them to the nonspecific defenses.
Some memory cells remain in the body. They are lymphocytes that will recognize and attack an antigen during later infections. Because of memory cells, a person will get most disease only once. When exposed to a pathogen, memory cells divide rapidly and eliminate the pathogen. The first time the body encounters an antigen, it is called a primary immune response. The secondary immune response is faster, more powerful, and more effective.
Immunity is the ability to resist an infectious disease. One way for the body to gain imunity to a pathogen is to have the pathogen. A safer method is vaccination. A vaccine is a solution that contains a dead or weakened pathogen. Vaccines have been responsible for eradicating many of the worst diseases affecting humans. If the body attacks something that is not a pathogen, it is called an allergy. Allergies can also trigger asthma, a disease that makes the air passages tighten and make breathing difficult. Some disease cause the body to attack its own immune system. These disease are called autoimmune disease.
Passive immunity- Passive immunity is the means by which a person gains antibodies to a disease without actually having the disease. There are 4 forms of Passive immunity. The first is by getting a vaccine (explained above). Another method is through breast milk, which is rich in antibodies. Passive immunity can also be achieved through the placenta when antibodies are sifted out of the mothers blood. Gamma-globulin shots also provide passive immunity, these are just transfered blood of somebody who has had a disease and are used to boost the immune system for a short amount of time.
47.3 HIV and AIDS
HIV (Human immunodeficiency virus) bonds to receptor proteins and the virus replicates inside macrophages. After release from macrophages, HIV attaches to and enters helper T cells. Eventually, HIV kills enough T cells to cripple the immune system.Phase I
This is also called the asymptomatic stage, because there are almost no symptoms.
Phase II
The body tries to make B cells, but T cells steadily drop. Swelling lymph nodes, fatigue, weight loss, fever, or diarrhea all develop and worsen.
Phase III
AIDS is diagnosed and Opportunistic infections take advantage of the persons crippled immune system. AIDS is fatal. Few individuals live more than two years after being diagnosed. HIV is transmitted through the transfer of bodily fluid. HIV evolves rapidly, and becomes quickly resistant to drugs, so medicines and vaccines are hard to create to fight AIDS.