The Immune System

1. By Ariana Elkins and Alyssa Perkins The Immune System

2. Infectious Diseases • Infectious diseases occur when microorganisms cause physiological changes that disrupt normal body functions. • Infectious diseases can be caused by viruses, bacteria, fungi, “protists”, and parasites. • Some diseases are spread through coughing, sneezing, physical contact, exchange of body fluids. Others are spread through contaminated water or food. In addition, other diseases are spread to humans from infected animals.

3. Non- Specific Defenses • Non specific defenses include the skin, tears, and other secretions, the inflammatory response, interferon's, and fever. • The most widespread nonspecific defense is the physical barrier called skin. • If the infection cuts through the skin, the second defense, called inflammatory response, begins. This is when histamines increase the flow of blood and fluids to the affected area. Fluid leaking from expanded blood vessels causes the area to swell. White blood cells move from blood vessels into infected tissues. Many of these white blood cells are phagocytes, which engulf and destroy bacteria.

4. Specific Defenses • The immunes system specific defenses distinguish between “self” and “other” and they inactivate or kill any foreign substance or cell that enters the body. • The specific immune responses has two main parts: humoral immunity and cell-mediated immunity. • Humoral immunity depends on the action of the antibodies that circulate in the blood and lymph. • Cell- mediated immunity is when the immune system defends the body against some viruses, fungi, and single-celled pathogens.

5. Fighting Infectious Diseases • Active immunity: Vaccination stimulates the immune system with an antigen. The immune system produces memory B cells and memory T cells that quicken and strengthen the body’s response to repeated infection. • Passive Immunity: Antibodies produced against a pathogen by other individuals or animals can be used to produce temporary immunity.

6. Influences against diseases • Public health measures help prevent disease by monitoring and regulating food and water supplies, promoting vaccination, and promoting behaviors that avoid infection. • Antibiotics can kill bacteria, and some antiviral medications can slow down viral activity. • Antibiotics have no effect on viruses, however, antiviral drugs have been developed to fight certain viral infections.

7. New and Re-Emerging Diseases • Two major reasons for the emergence of new diseases are the ongoing merging of human and animal habitats and the increase in exotic animal trade. • Misuses of medication has led to the re-emergence of diseases that many people thought were under control.

8. Immune System Disorders • A strong immune response to harmless antigens can produce allergies, asthma, and autoimmune disease. • When the immune system attacks the body’s own cells, it produces an autoimmune disease, such as type 1 diabetes.

9. HIV and Aids • In 1983, researchers identified the cause of AIDS-a virus they called human immunodeficiency virus (HIV). • The only no-risk behavior with respect to HIV transmissions is abstinence from sexual activity and intravenous drug use.

10. Vocabulary • Immune system: a system of biological structures and processes within an organism that protects against disease. • Pathogen: disease-causing agent • Antibody: protein that either attacks antigens directly or produces antigen-binding proteins. • Antibiotic: group of drugs used to block the growth of pathogens. • Vaccinations: injection of a weakened pathogen. • Vector: animal that transports a pathogen to a human.

11. Vocabulary continued • Histamine: chemical released by a mast cells that increases the flow of blood to the infected area. • Inflammatory response: nonspecific defense reaction to tissue damage. • Humoral immunity: immunity against antigens in body fluids. • Interferon: group of proteins that help cells resist viral infection.