The Immune SystemThe Immune System

and Diseaseand Disease

chapter 40chapter 40

Sections 1 and 2Sections 1 and 2

Disease (Disease (disdis--ease)ease)

•• Any change, other than injury, that Any change, other than injury, that

disrupts normal body functionsdisrupts normal body functions

•• Can be caused by agents or Can be caused by agents or

pathogenspathogens, environmentally, or are , environmentally, or are

inheritedinherited

What are some examples of pathogens?

PathogensPathogens

•• VirusesViruses

•• BacteriaBacteria

•• ProtistsProtists

•• WormsWorms

•• FungiFungi

Diseases SpreadDiseases Spread

•• Physical contactPhysical contact

–– Direct contact with bodily fluidsDirect contact with bodily fluids

–– Indirect through air or touching Indirect through air or touching

contaminated objectscontaminated objects

•• Contaminated Food and WaterContaminated Food and Water

•• Infected AnimalsInfected Animals

––VectorsVectors: animals that carry : animals that carry

pathogenspathogens

Immune SystemImmune System

•• Functions to fight infections through Functions to fight infections through

the production of cells that the production of cells that

inactivate foreign substances or cells inactivate foreign substances or cells

= = immunityimmunity

•• Body fights infection:Body fights infection:

1.1. Nonspecific DefenseNonspecific Defense

2.2. Specific DefenseSpecific Defense

Nonspecific DefenseNonspecific Defense

•• First line of DefenseFirst line of Defense::

–– Keep pathogens out of bodyKeep pathogens out of body

–– Skin, mucus, sweat, tearsSkin, mucus, sweat, tears

•• Second line of DefenseSecond line of Defense::

–– Inflammatory responseInflammatory response

••White blood cells producedWhite blood cells produced

••FeverFever

••InterferonInterferon –– resist viral infection, resist viral infection,

secreted by infected cells to protect secreted by infected cells to protect

other cells from infectionother cells from infection

SkinWound

Bacteria enter the wound

Phagocytes move into the area and engulf the bacteria

and cell debris

Capillary

The Inflammatory ResponseThe Inflammatory Response

Animation

Specific DefenseSpecific Defense

•• Immune response:Immune response:

–– Pathogen, or Pathogen, or antigenantigen, gets past , gets past nonspecific defensenonspecific defense

––LymphocytesLymphocytes recognize specific recognize specific antigens:antigens:

••B cells B cells -- humoralhumoral immunityimmunity

••T cells T cells -- cellcell--mediated immunitymediated immunity

––MacrophagesMacrophages: WBC consume : WBC consume infected cellsinfected cells

HumoralHumoral ImmunityImmunity

•• Antibody mediated immunityAntibody mediated immunity

1.1. Antigen recognized by specific B cellAntigen recognized by specific B cell

2.2. B cells produce large #B cells produce large #’’s of plasma s of plasma

and memory B cellsand memory B cells

3.3. Plasma cells release antibodiesPlasma cells release antibodies

4.4. Antibodies bind to antigenAntibodies bind to antigen

5.5. Memory cells prevent another Memory cells prevent another

infectioninfection

Antigen-

binding sites

Antigen Antibody

Structure of an Antibody

Antibodies:Proteins that recognize &

bind to specificantigens.

CellCell--Mediated ImmunityMediated Immunity

•• Once pathogen Once pathogen insideinside cellcell

1.1. Killer TKiller T cell track down pathogencell track down pathogen

2.2. Helper THelper T cell can activate killer cell can activate killer

TT’’ss

3.3.Memory TMemory T cells are produced after cells are produced after

exposureexposure

4.4. Suppressor TSuppressor T cells shut down Killer cells shut down Killer

T cells once attack under controlT cells once attack under control

Macrophage

T Cell

Helper T Cell

Killer T Cell

Infected CellAntigens are

displayed on

surface of

macrophage

T cell binds to

activated

macrophage

T cell, activated by

macrophage,

becomes a helper T

cell

Helper T cell

activates

killer T cells and B

cells

Killer T cells bind to

infected cells,

disrupting their cell

membranes and

destroying them

Section 40-2

Acquired ImmunityAcquired Immunity

•• Active ImmunityActive Immunity::

–– BodyBody’’s reaction to an antigens reaction to an antigen

––VaccinationVaccination = injection of weakened = injection of weakened

or mild form of pathogenor mild form of pathogen

•• Passive ImmunityPassive Immunity::

–– Antibodies produced by another Antibodies produced by another

organism injected into bloodstreamorganism injected into bloodstream

–– Lasts short timeLasts short time

KochKoch’’s Postulatess Postulates

The pathogen should always be found in the body of a sick organism and should not be found in a healthy one.

The pathogen must be isolated and grown in the laboratory in a pure culture.

When purified pathogens are placed in a new host, they should cause the same disease that infected the host.

The very same pathogen should

be re-isolated from the second

host. And it should be the same

as the original pathogen