Chapter 35: Immune System & Disease Ms. Luaces Honors Biology

Pathogens

35.1 Infectious Disease Pasteur & Koch came up with the germ theory of disease: infectious diseases occur when microorganisms cause physiological changes that disrupt normal body function Can be caused by viruses, bacteria, fungi, protists and parasites Except for parasites, all others known as pathogens

35.1 Infectious Disease Koch’s Postulates: 1. Pathogen must always be found in sick body but not healthy body 2. Pathogen can be isolated & grown in lab 3. If pathogen infects healthy host, should produce sickness 4. Pathogen can be isolated from new host & looks identical

35.1 Infectious Disease What’s the different between a symbiont and pathogen? Symbionts are either harmless or beneficial Pathogens destroy host cells, release poisons, block blood flow, and take up hosts nutrients

35.1 Infectious Disease Diseases spread through coughing, sneezing, physical contact, exchange of body fluids, contaminated water/food/animals

35.1 Infectious Disease Natural selection favors pathogens with adaptations that help them spread from host to host Coughing, sneezing, body-to-body contact, sexual activity, drug usage, poor sanitation Best way to avoid infection is to constantly wash your hands!

35.1 Infectious Disease Those pathogens that thrive in both human and animal hosts are known as zoonosis West Nile virus, Mad cow disease, Lyme disease, Ebola Carriers of the disease who don’t get sick are known as vectors

Let’s Practice! Pg. 475 – 476 Q & A Work with a buddy – one sheet of paper for both of you!

35.2Nonspecific Defenses Include skin, tears and other secretions, inflammatory response, interferon's and fever First line of defense: skin, which is the most widespread defense

35.2Nonspecific Defenses Pathogens can enter through the mouth, nose or eyes which are protected by saliva, mucus and tears Contains lysozyme which breaks down bacterial cell walls Stomach secretions (acid) also protect

35.2Nonspecific Defenses Second line of defense includes inflammatory response, interferon's, and fever

35.2Nonspecific Defenses Inflammatory response causes areas to become red and painful because of histamines (release by mast cells to increase flow of blood and fluids to the area) White blood cells (phagocytes) will then engulf and destroy bacteria

35.2Nonspecific Defenses Interferon's inhibit synthesis of viral proteins Aka “interfere” with viral growth, slowing down the production of new viruses

35.2Nonspecific Defenses Fever increases body temperature to slow down or stop the growth of some pathogens Sometimes also speeds up several parts of the immune response

35.2 Specific Defenses Specific defenses distinguish between “self” and “other” and inactivate / kill any foreign substance or cell that enters the body Nonspecific = general threat Specific = particular pathogen

35.2 Specific Defenses Recognizes specific chemical markers on own cells – own secret password If the marker is not recognized, will attack and remember it for later as “non-self” so that it can kill it quickly if it enters the body again: immune response

35.2 Specific Defenses Antigens are any foreign substances that can stimulate an immune response Found on the outer surface (the “flag”) Immune responds by increasing # of cells to attack or produce proteins called antibodies

35.2 Specific Defenses Antibodies tag antigens for destruction by immune cells (the “alert!!”) The shape of each antibody allows it to bind to only one antigen – very specific

35.2 Specific Defenses Main working cells of the immune system are B lymphocyte cells: grow and mature in red bone marrow; have antibodies on them; attack in body fluids T lymphocyte cells: grow in red bone marrow but mature in thymus; have to be presented with antigen to attack

35.3 Fighting Infectious Disease Vaccination: injecting a weakened form of a pathogen, or of a similar but less dangerous pathogen, to produce immunity Jenner

35.3 Fighting Infectious Disease Vaccination stimulates the immune system with an antigen. The immune system produces memory B cells and T cells that quicken and strengthen the body’s response to repeated infection

35.3 Fighting Infectious Disease 2 types of immunity: Active: natural / deliberate exposure to antigen Passive: antibodies are produced by other individual or animal and passed through pregnancy, breast milk, or injection (only gives TEMPORARY immunity)

35.3 Fighting Infectious Disease 1900 – 30% deaths related to infectious diseases 2005 - <5% deaths “ “ How? Public health has prevented disease by monitoring & regulating food and water, providing vaccinations, and promoting healthy behaviors

35.3 Fighting Infectious Disease Antibiotics can kill bacteria (but CANNOT kill viruses) and some antiviral medications can slow down viral activity Alexander Fleming – discovered first antibiotic, penicillin

35.3 Fighting Infectious Disease We had mostly wiped out polio in the U.S. & eliminated smallpox globally, but now it’s back! Why? Human / animal interaction Misuse of medications leads to resistance by pathogens