1. The Immune System and Disease

2. Diseases
Disease = any change, other than injury, that disrupts the normal functions of the body
Diseases can be inherited (ex. Hemophilia)
Diseases can be caused by materials in the environment (ex. Cigarette smoke)
Diseases can be produced by agents (ex. Bacteria, viruses, fungi) = pathogens
Pathogens = “sickness-makers”
Diseases caused by pathogens = infectious diseases, because they enter, or infect, the body

3. Agents of Disease
The human body provides great conditions for pathogenic growth
You have many different microorganisms living in your body that are actually harmless or beneficial
However, some microorganisms are dangerous
Some bacteria break down body tissues and others release toxins (poisons)
Some protists, fungi, and worms are parasites that live inside you and use up your nutrients or destroy blood/nerve cells
Viruses are nonliving pathogens that use a host cell to make copies of the virus and destroy other cells

4. Spreading Infectious Diseases
Infectious diseases are spread
From person to person: coughing, sneezing, or physical contact
Common cold, mumps, measles, influenza, STDs (AIDS), meningitis, athlete’s foot
Contaminated water and/or food
Cholera, dysentery, E.coli infection, salmonellosis
Vectors: infected animals (ticks/mosquitoes)
Lyme disease, malaria, West Nile virus, rabies

5. Figure 40–3 Pathogens and Disease
Section 40-1
Pathogen Types
Disease
Agent That Causes Disease
Method of Transmission
Common cold
Rhinovirus
Two types (A, B), plus subtypes
Varicella
Paramyxovirus
Mycobacterium tuberculosis
Neisseria meningitidis
Vibrio cholerae
Clostridium tetani
Trypanosoma
Plasmodium
Entamoeba histolytica
Schistosoma
Taenia saginata
Imperfect fungi
Airborne; direct contact with infected person
Airborne; droplet infection; direct contact with infected person
Droplets in air; direct contact with secretions of infected person
Droplets in air; contaminated milk and dairy products
Direct contact with a carrier
Contaminated drinking water
Contaminated wound; usually puncture wound
Spread by tsetse fly
Spread by Anopheles mosquitoes
Freshwater streams and rice paddies
Contaminated meat
Contact with infected person
Exchange of hats, combs, or athletic head gear with infected person
Viruses
Influenza
Chicken pox
Measles
Bacteria
Tuberculosis
Meningitis
Cholera
Tetanus
Protists
African sleeping sickness
Malaria
Amoebic dysentery
Worms
Schistosomiasis
Beef tapeworm
Fungi
Athlete’s foot
Ringworm

6. Fighting Infectious Diseases
Drugs have been developed to use against pathogens
Antibiotics = chemicals that kill bacteria without harming the cells of humans or animals
Penicillin = interferes with the synthesis of cells walls by Eubacteria (breaks down peptidoglycan in their cell walls)
Streptomycin = interferes with bacterial growth by blocking protein synthesis in ribosomes
Antivirals = inhibit the ability of viruses to invade cells or multiply inside cells

7. The Immune System
A series of defenses that guard against diseases = body’s protection
Nonspecific defenses = “walls” of the immune system keeping everything out
Specific defenses = “security guards” identifying and inhibiting pathogens

8. Nonspecific Defenses Skin = most important nonspecific defense
Physical barrier
Acidic environment on surface kills bacteria
Mucus, sweat, tears and saliva
Traps pathogens and removes them from the body by cilia or destroys them using the enzyme lysozyme, which breaks down cell walls
Inflammatory response = reaction to tissue damage caused by injury or infection
Blood vessels around wound expand, white blood cells enter infected tissue and phagocytes (special WBCs) engulf and destroy bacteria, tissue becomes swollen and painful, body temperature ingrowth and increase circulation and activity of WBCs
Interferon = proteins that “interfere” with the virus
creases (fever) to slow pathogen Proteins released by virus-infected cells to help other cells resist viral infection by inhibiting viral protein synthesis, blocking viral replication

9. Specific Defenses Pathogen: any disease causing agent
Antigen = a substance that triggers the immune response (organic molecules on the surface of pathogens)
Antigens are chemicals present on the surface of viruses, bacteria, pollen grains etc.
Antibody = protein that helps destroy pathogens by binding to antigen and attracting phagocytes to engulf and destroy them

11. Humoral Immunity
Immunity against pathogens in the body fluids (blood/lymph)
Immunity produced by lymphocytes (type of WBC)
B lymphocytes (B cells) produce antibodies to mark pathogens and prevent future infections

12. The Immune System

13. Cell-mediated Immunity
Immunity that relies on lymphocytes (cells)
Killer T cells (cytotoxic T cells) can attack infected cells and destroy their cell membranes
Killer T cells are what make organ transplants difficult, because they see the new organ as foreign and begin to attack it = rejection.

14. Permanent Immunity
People that survived infectious diseases, never developed the same disease again
Memory B and T cells remain capable of producing specific antibodies to that pathogen, ensuring the disease never gets a chance to develop again

15. Active Immunity
An immediate active immune response against the pathogen in a vaccine
Vaccination = injection of a weakened or mild form of a pathogen to produce immunity
Prevents serious human diseases by stimulating the immune system to create plasma cells capable of producing the specific antibodies for another possible infection
Active Immunity lasts long term (permanent)

16. Passive Immunity
Antibodies produced by other animals for a pathogen are injected into the bloodstream
The antibodies will produce passive immunity against a pathogen as long as they remain in circulation (several weeks)
Antibodies from the mother are passed to the fetus through the placenta or to the infant in the mother’s milk = maternal immunity
The antibodies will produce passive immunity against most infectious diseases for the first few months of life or longer if breast-fed

17. Immune System Disorders
Although the immune system defends the body from potential pathogens, sometimes disorders occur
The immune system may overreact to an antigen, producing discomfort or disease
The cellular nature of the immune response is a potential weak point

18. Allergies
Overreaction of the immune system
Allergies occur when antigens from allergens (pollen, dust, dust mites) bind to mast cells (type of immune cell common in nasal passages)
Activated mast cells release chemicals = histamines, which increase the flow of blood and fluids to the surrounding area (sneezing, runny eyes/nose, etc)
Antihistamines = drugs used to reduce allergy symptoms by counteracting the effects of histamines
Asthma = allergic reaction where smooth muscle contractions reduce the size of air passageways in the lungs making breathing difficult

19. Autoimmune Disease
The immune system has the ability to distinguish “self” from “nonself”
The immune system makes a mistake and attacks the body’s own cells (“it attacks itself”)
Juvenile-onset diabetes (immune system attacks insulin-producing cells in pancreas)
Myasthenia gravis (attacks neuromuscular junctions)
Multiple Sclerosis (destruction of myelin sheath – attacks nervous system)
Lupus (attacks cells and tissues resulting in inflammation and tissue damage: heart, joints, skin, lungs, blood vessels, liver, kidneys and nervous system)

20. AIDS
Acquired Immune Deficiency Syndrome (AIDS) = when cells of the immune system are weakened by infection
Caused by HIV (human immunodeficiency virus) and spread by contact with body fluids (drug needles, unprotected sexual intercourse, breast milk, blood during birth, blood transfusions)
HIV attaches and destroys most helper T cells, so body is more susceptible to infections
People DO NOT die from HIV/AIDS, they die from the infections they get because the HIV virus has left their immune system unable to respond to the infections

21. Cancer
Cancer is caused by defects in the genes that regulate cell growth and division
Inherited genes
Viruses: interfere with cell cycle (mitosis)
Ex. Human papilloma virus (HPV: an STD) can lead to cervical cancer or genital warts (non cancerous)
Radiation: causes mutations in DNA
Ex. X-rays, nuclear radiation, sunlight (UV Rays)
Chemicals: cause mutations in DNA
Carcinogens = chemicals that cause cancer
Ex. Chloroform and benzene (industrial solvents used in production of drugs, plastics and synthetic rubber, small component in gasoline), cigarette smoke

22. Blood Antigens and Antibodies