1. Immune System and Disease Chapter 35

2. Nonspecific Defenses  The human body faces against many dangerous enemies  Harmful bacteria, viruses, fungi, and protists  Pathogens:  Disease causing agents

3. First line of Nonspecific Defense  Body’s surface defenses are nonspecific  Skin is an impenetrable barrier to invading pathogens Oil and sweat inhibit the growth of pathogens. Sweat has an enzyme called lysozyme that digests bacterial walls and kills the bacteria.  Body’s internal surface uses  Mucous Membranes  Layers of epithelial tissue that produce a sticky, viscous fluid  Lines nasal passages, lungs, respiratory passages, and reproductive tract

4. Second Line of Nonspecific Defense  Injury or local infection like a cut can cause and  Inflammatory Response:  Series of events that suppress infection and speed recovery  Histamine:  Causes local blood vessels to dilate, increasing blood flow to the area.  Temperature Response  Fever  Temperature rises to fight against invading pathogens  Higher temperatures are harmful to many bacterial pathogens  Over 103° can destroy body’s cellular processes (destroy enzymes  Over 105° can be fatal  Destroys cells

5. Second Line of Nonspecific Defense Cont.  Proteins  Complement System:  20 different proteins which circulate in the blood and become active when they encounter pathogens  Interferon:  A protein released by cells infected with viruses  Cause nearby cells to produce an enzyme that prevents viruses from making proteins and RNA.  White Blood Cells  Neutrophils:  WBC that engulfs and destroys pathogens  Macrophages:  Ingest and kill pathogens they encounter  Natural Killer cells:  Large WBC that attacks cells infected with pathogens

6. Cells Involved  The third line of defenses is specific  4 Main kinds of WBC’s that participate in the immune response  Macrophages  Cytotoxic T cells:  Attack and kill infected cells  B cells:  Label invaders for later destruction by macrophages  Helper T cells:  Activate both T and B cells

7. Recognizing Invaders  An infected body cell will display antigens of an invader on its surface  Antigen: Substance that triggers an immune response.

8. Immune Response Parts  B cell response is a passive defense that aids in the removal of pathogens.  T cell response is an active cell-mediated defense that involves the destruction of pathogens by cytotoxic T cells.

9. Steps of an Immune Response  When a virus infects a cell, the cell displays viral antigens on its surface.  Macrophages engulf and destroy viruses and also display viral antigens.  Helper T cells bind to antigens on the macrophages and they (macro) release interleukins.  Interleukins make Helper T cells activate Cytotoxic T and B cells.

10. Steps Continued plasma  B cells divide and turn into plasma cells antibodies  Plasma cells make antibodies that bind to viral parts and to infected cells and mark them for death.  Macrophages  Macrophages engulf and destroy the “marked” viral parts and infected cells.  Cytotoxic  Cytotoxic T cells also destroy infected cells that are marked. memory  Some B cells become memory cells that will immediately destroy the virus if it tries to invade the body again.

11. Disease Transmission and Prevention  Diseases are transmitted in 5 different ways  Person to person contact  Air  Food  Water  Animal bites

12. Detecting Disease  German physician Robert Koch established a procedure for diagnosing causes of infection  Koch’s Postulates:  Guide for identifying specific pathogens  4-step procedure  1. The bacteria must be present in every case of the disease.  2. The bacteria must be isolated from the host with the disease and grown in pure culture.  3. The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host.  4. The bacteria must be recoverable from the experimentally infected host.

13. Resistance to Disease  Immunity:  Resistance to a particular disease  Vaccination:  Medical procedure used to produce immunity  Vaccine:  A solution that contains a dead or modified pathogen that can no longer cause disease  Antigen Shifting:  Subsequent exposure to a virus causes the body to make new antibodies.

14. Disorders of the Immune System  In some people, the immune system can not distinguish between the body’s antigens and foreign antigens.  Autoimmune disease:  The body launches an immune response against its own cells, attacking body cells as if they were pathogens.  Examples:  Graves Disease  Multiple Sclerosis  Type 1 Diabetes

15. HIV and AIDS  HIV, the virus that causes AIDS, infects helper-T cells  HIV: Human immunodeficiency virus  AIDS: Acquired immunodeficiency syndrome  HIV is contracted through sexual contact, blood transfusions, and contaminated needles (drug users, tattoos, piercing)  HIV infects cells by using proteins on its surface attach to the host cell (helper-T cells)  The HIV virus infects only a few cells at time, so it takes a long time to show symptoms.