The Immune System Biology Chapter 41

Pathogen-disease causing agent (various types of bacteria, viruses, fungi, protists) Body uses both specific and nonspecific defense mechanisms to prevent infection and destroy pathogens

Nonspecific defenses Do not target a specific pathogen Skin and mucous membranes (line digestive system, lungs, nasal passages)

Nonspecific defenses 2. Inflammatory response-suppress infection and speed recovery. Injured cells release Histamine which increases blood flow to area bringing more white blood cells (WBC’s). Also causes swelling and redness in the infected area

Temperature response/Fever; Nonspecific defenses Temperature response/Fever; many bacteria do not grow well in higher temps; however, too high a fever can result in destruction of important enzymes

Nonspecific defenses 4. Proteins: Complement system- proteins that circulate in the blood and when they encounter a pathogen they form a structure that ruptures the cell membrane of the pathogen. Interferon- protein released by cells infected with a virus, causes nearby cells to produce an enzyme that prevents viruses from making proteins and RNA.

5. WBC’s- most important counterattacks carried out by 3 kinds of WBC’s - Neutrophils-most abundant type, engulf and destroy pathogens - Macrophages-ingest and kill pathogens, concentrated especially in spleen and lungs

- Natural killer cells-destroy an infected cell by puncturing the cell membrane causing water to rush into the cell and burst. One of the best defenses against cancer, can detect and kill cancer cells before a tumor develops

Specific Immune Responses Cytotoxic T cells-attack and kill infected cells B cells- label invaders for later destruction by macrophages Helper T cells- activate both cytotoxic T cells and B cells cytotoxic T-cell tumour cell

Two distinct processes work together in the immune response B cell response which is a passive, humoral defense that aids in the removal of pathogens T cell response, an active, cell-mediated defense that involves the destruction of pathogens by cytotoxic T cells

Interactions Between Responses

Antigen: Proteins or other components on the cell surface of the pathogen. WBCs have receptor proteins that bind to specific antigens. Antibody: Y-shaped molecule produced by plasma cells upon exposure to specific antigen

Immune Responses Immune responses

Disease Transmission Person-to person contact (contagious/communicable) Air Food Water Animal Bites

Koch’s Postulates: 4 step procedure for identifying specific pathogens Pathogen must be found in an animal with the disease, not a healthy animal Pathogen is isolated and cultured Pathogen is injected into healthy animal; animal must develop the disease Pathogen taken from second infected animal is cultured and it must be the same as the original pathogen

Resistance to a disease is called immunity Vaccination is a medical procedure used to produce immunity. Edward Jenner developed a vaccine against smallpox. A small amount of dead or modified pathogen is injected into the body to produce an immune response without symptoms of the infection. Your body develops antibodies and memory cells against the pathogen (measles, polio, tetanus, diphtheria, etc).

Some pathogens have the ability to mutate over time Some pathogens have the ability to mutate over time. The viruses produce new antigens that your body does not recognize (antigen shifting). That is why you can get the flu, even if you have had a vaccination or already had it before.

Disorders of the Immune System Autoimmune disease-body attacks its own cells (multiple sclerosis, rheumatoid arthritis, Graves’ disease, Type I Diabetes). AIDS is caused by HIV (human immunodeficiency virus). HIV invades helper T cells causing them to produce more virus and then die. HIV is transmitted through HIV-infected WBC’s in body fluids and can be exchanged through sexual contact and/or sharing of needles

3. Allergic Reactions An allergy is the body’s overreaction to a normally harmless antigen. Most allergic reactions cause cells to produce histamines, which cause swelling, redness, increased mucus production, runny nose, itchy eyes and congestion Most allergy medicines contain antihistamines, which prevent the action of the histamine. Severe allergic reactions, like asthma and bee stings, can be life threatening.