*The Immune System and Disease• pre 1600s - cause of disease not known

– Punishment from God, bad luck, bad air, witchcraft, curses etc….

• After 1600s, microscopy and germ theory of disease– Scientific basis for disease, doctors did not wear

gloves, no anesthesia, no sterile technique

• antibiotics - penicillin, 1940s. Revolutionized medicine

Pathogen = A biological unit that causes disease

• prion – protein – no DNA AND not alive!!• virus - non living, needs host cell to replicate• bacteria - single celled microbe• protozoa

– single celled eukaryote microbe

• parasite - multicellular

• Most microbes are NOT pathogens

Disease Terms

1. Infectious – Can be transmitted from person (or animal) to

person

Body fluids – example:

Vectors – example:

Ingestion – example:

Inhalation – example:

2. Epidemic– Contagious disease that spreads rapidly and

uncontrollably affected large numbers of people

3. Plague

epidemic that kills large numbers of people

~23% die of diarrhea (10 million children per year)- why/how?

Prions = (rare) spongiform encephalopathy disease

CJD in humans• Always fatal, no treatment• Most cases sporadic (arise

spontaneously) or inherited • Can be acquired from exposure to

infected brains

• Example: Kuru

Sponge-like brain

Outbreak in England 1980s

• Cows stagger, shake, fall down (“mad cow”)• Transmitted to ~18 humans via contaminated hamburger meat

• Caused by an infectious agent that is NOT alive and has no DNA !

How does a prion cause disease ?

• Normal prp protein undergoes a shape change

• Brain cells lyse spongy brain

• Don’t eat brains or meat from contaminated people or cows.

• Why hamburger?

VIRUSES• Antiviral drugs or wait it out

– consist of protein + genetic material

– infect cells and reproduce

–Smallpox virus (not in textbook)• pustules disfigure, blind, kill• eradicated in 1977

Other viruses

• Rhinovirus (50) colds

• Influenza -the flu (not in textbook)

• changes genetic makeup every year40 million deaths in 1920 in 4 months!>30,000 die in US each year!

• new vaccine needed every year because it changes so rapidly

• HIV - human immunodeficiency virusinfects T cells -> destroys immune system

May lead to AIDS and opportunistic infections

>60 million infected worldwide

Transmitted by:

Poliomyelitis virus• attacks the nervous system ->

paralysis• virus shed in feces (improved sanitation and hygiene

helps to prevent transmission but its easily transmissible!)

• 1916 New York, 27,000 infected, 9000 died

Bacteria

• single celled, prokaryotic

• May be killed by antibiotics– penicillin, tetracycline etc...– antibiotic resistance problem

• Lyme disease caused by B. burgdorferi bacteria

• Tick vector• Tick feeds on blood -> bacteria

migrate to mouthparts• Bulls-eye rash• treat early with antibiotics or

joint/nervous system problems

Look at the size of this tick!

Incidence of lyme disease …..

• Salmonella (not in textbook) (Daniel Salmon)

• From contaminated chicken, eggs• Must heat to 160 F to destroy, or wash off• Diarrhea, nausea, can be fatal in some

E. Coli Spinach Cases Rise to 173 (25 states)

• E. coli O157:H7 – pathogenic– Killed in 15 seconds at 160F

• E. Coli 0157:H7 lives in intestines of healthy cattle, can contaminate agriculture

73,000 cases of infection and 61 deaths occur in the United States each year

bloody diarrhea, and occasionally kidney failure. Treatment is not antibiotics!

.

• Consumers can prevent E. coli O157:H7 infection by – cook ground beef– avoid unpasteurized milk– wash hands before preparing or eating food– wash fruits and vegetables

ProtozoaMalaria - mosquito vector contains

protozoa (single-celled eukaryote)

– Periodic bursting of protozoa from red blood cells

– Fever, weakness, death

– 300 million infected, millions die each year

Parasites

Multicellular animals– hookworm, tapeworm,

pinworm, heartworm (dogs)– diarrhea, weakness, weight

loss

Roundworm infects millions of peopleUp to 12 inches in length

tapeworm

Note: you may not want to see next….

Loa loa Nematode worm transimitted

by Chrysops flies10 million in Western Africa

Elephantitislymphatic filariasisNematodes transmitted by

mosquitoes120 million in 80

countries

Head lice

Round worms (Ascaris)1.2 billion infected

Organs of the immune (lymphatic) system

spleen

Lymph nodesthymus

tonsils

Also, bone marrow

Many species of bacteria in human large intestines = gut flora

• 10 13 human cells and 1015 bacterial cells in gut, you excrete 100 billion of them per day

• A harmless strain of E. coli is one of the types

• Lymph nodes in groin, armpit, neck, intestines

• Tonsils

• Spleen

• Thymus

• Bone marrow

How do we fight disease? How can we ever win in this sea of pathogens?

• Non specific immunity– Skin, sweat, mucus, tears, stomach HCl, some

types of white blood cells, ear wax, pH….

Specific immunity

• Recognizing self from non-self– each foreign cell, protein, DNA has a unique

identity that can be recognized as foreign by the body’s immune system

– Self antigens• Mark your cells as “you”

– Foreign antigens• Are not yours …..

• Your immune system should be able to attack and destroy specific pathogens

white blood cells active in specific immunity• B cells (lymphocytes)

– Make antibodies

– Antibodies bind to foreign antigens (pathogens)

• T cells (lymphocytes)– coordinate immune response

– Kill infected cells

Vaccination/Immunization

• vaccine– Weakened or killed or piece of pathogen – Expose individual to vaccine and…..– B cells make antibodies to the vaccine (foreign

antigen)

antibody

• B cells have “memory”– When body is exposed to foreign antigen

(pathogen) years later, B cells rapidly produce large amounts of the correct antibody

• Enough B cells to recognize every foreign antigen in nature!

• Note: you can gain immunity by contracting disease itself

• Some vaccines require boosters (example: tetanus)

Vaccines

• Diphtheria, whooping cough, tetanus (DPT) - bacteria

• Chicken pox- virus

• Polio - virus

• Measles, mumps, rubella (MMR) -virus

• The flu (influenza) - virus

• Hib - bacteria

• Hepatitis B - virus

Quick Immunization Facts:

• 3 million children die every year from diseases that are entirely preventable.

• 30 million infants have no access to basic immunization each year.

• One child can be fully immunized for $17.

In the future…….• Malaria

• HIV

• Lyme disease

• Herpes

Available but not given to general population, why??

• Smallpox

• Anthrax