The Immune System

Germ Theory Germ theory proposes that microorganisms cause diseases (not spirits, as once believed). Proposed by Louis Pasteur Led to rapid advances in understanding disease Supported by Koch’s postulates. Disease-causing agents, or particles, are called pathogens.

There are different types of pathogens Bacteria are single-celled organisms: Cause illness by destroying cells, release toxic chemicals Ex: Food poisoning, MRSA Viruses are genetic material surrounded by a protein coat: Force host cells to make more viruses, small Ex: Flu, Cold, HIV Fungi can be multicellular or single-celled: Take nutrients from host cells by piercing healthy cells Occur in warm and damp places Ex: Athlete’s foot Protozoa are single-celled organisms. Use host cells to complete their life cycles Take nutrients from host cell Ex: Malaria Review: Parasite

Different pathogens cause common infectious diseases

Pathogens can enter the body in different ways Pathogens can be transferred by indirect or direct contact. Indirect contact does not require touching an infected individual. Touching an infected surface Breathing in infected air Vectors :Carry a pathogen and transmit into healthy cells Ex: Insects (ticks, mosquitoes, fleas), food

Direct contact requires touching an infected individual. Includes: Kissing Sexual intercourse Hand shaking tick

Many body systems protect you from pathogens The immune system is the body system that fights off infection and pathogens. Many other tissues and systems help the immune system. Skin is the (first) physical barrier to infection. Mucous membranes trap pathogens entering the body. The circulatory system transports immune cells.

Cells and proteins fight the body’s infections White blood cells attack infections inside the body. Phagocytes engulf and destroy pathogens. T cells destroy infected cells. B cells produce antibodies, which deactivate the pathogen.

3 types of proteins fight off invading pathogens Complement proteins weaken pathogen membranes. Antibodies make pathogens ineffective. Interferons prevent viruses from infecting healthy cells. antibody pathogens

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Immunity prevents a person from getting sick from a pathogen In all types of immunity, pathogens are destroyed before you get sick. Passive immunity occurs without an immune response. Mother’s milk Genetics Active immunity occurs after a specific immune response. Having chicken pox Acquired Immunity occurs after given a vaccine. Flu shot

Artificial methods are used to control pathogens Antibiotics and antiseptics cause pathogens to burst Antiseptics kill pathogens outside of the body Do not target specific pathogens Ex: Vinegar, Soap, Rubbing Alcohol, Purel Antibiotics kill pathogens inside the body. Target one specific bacterium or fungus NOT effective against viruses

Antibiotic Resistance Overuse and misuse of antibiotics can cause medicines to become ineffective. Some bacteria in a population have genes that make them immune to antibiotics. These bacteria spread the gene, making the antibiotics useless. A bacterium carries genes for antibiotic resistance on a plasmid. A copy of the plasmid is transferred through conjugation. Resistance is quickly spread through many bacteria.

Vaccines artificially produce acquired immunity Vaccines control pathogens and disease Injected with antibodies that have been exposed to the pathogen. Gives instant but short- term protection. Given mild or dead version of the pathogen. Your body makes the antigens itself for long-term protection. Memory B cells stay for a long time, ready for another attack from the same organism.

How a vaccination provides immunity Antigens in a vaccine trigger an immune response, and memory B cells are made. 1 memory B cells Stimulates a specific immune response Causes memory cells to be produced A memory B cell is stimulated when the real pathogen binds to it. 2 Allows immune system to respond quickly to infection The B cell quickly activates and makes antibodies that fight the pathogens before you get sick. 3 Has a fast response, a person will not get sick