Chapter 35: Immune System & Disease

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

Chapter 35: Immune System & Disease