Transcript The Immune System

The Immune System
Nonspecific Body Defenses

Responds immediately




Intact skin
Mucous membranes
Inflammatory Response
Cellular Chemicals
Surface Protectors

Skin, Mucous membranes


Physical barrier
Chemical barrier




pH of skin; pH of vagina; sebum
Stomach acid/enzymes
Saliva/lacrimal fluids (lysozyme)
Sticky mucus to trap invaders in digestive/respiratory
passages
Cells and Chemicals

Phagocytes

Macrophages and Neutrophils


Engulf foreign invaders
Natural Killer Cells (NK) to “police” body


Kill cancer cells, virus-infected cells
NOT phagocytes (think chemical warfare)
Inflammatory Response


Nonspecific response
Cardinal Signs




Redness
Heat (inflamm… “set on fire”)
Swelling
Pain
Inflammatory Response

Chemical “alarm”

Damaged cells release histamine, kinins



Causes blood vessels to dilate, leaky capillaries
Activates pain receptors
Attracts phagocytes (WBC’s) to injured area

Called Chemotaxis (cells follow chemical signal)
Redness/heat from increased blood flow

Also causes edema (swelling)
Inflammatory Response



Prevents spread of damaging agents to other
areas
Disposes of cell debris and pathogens
Begins repair process
Chemicals

Complement

Group of plasma proteins that circulate (inactive)

Attach to foreign cells and puts holes in the cells


Amplifies inflammatory response


Foreign cells die
Calls more phagocytes to area
Cause CM’s of foreign cells to stick together
Chemicals

Interferon

Small proteins secreted by infected cells


Attach to non-infected cells
Slows down virus multiplication
Fever


Abnormally high body temperature
Pyrogens increase “thermostat”


Chemicals secreted by WBC’s that have been
exposed to foreign cells
Mild-moderate fever helpful in speeding up
repair processes in tissues
Immune Response


Recognizes antigens and acts to inactivate or
destroy them
Antigen specific


Systemic


Acts against particular pathogens
Not restricted to infection site
Has a “memory”

Recognizes and mounts stronger attacks on
previously encountered pathogens
Antigens


Substance that excites the immune system and
provokes an immune response
Foreign intruders are “non-self”




Proteins
Carbs; some lipids
Nucleic acids
Self-antigens don’t trigger immune response but do
in other people

Explains rejection of transplanted organs
Haptens

An incomplete antigen


A small (non-antigenic molecule)
When it links up with the body’s proteins, body
thinks it’s foreign

These are what cause allergies!
Lymphocytes


B and T cells
B cells
 Mature in bone marrow
 Produce antibodies (Y-shaped)
 Oversee humoral immunity



Antibody-mediated immunity
T cells
 Mature in Thymus gland
 Help with cell-mediated response (don’t make antibodies)
Immunocompetent
 When cells can respond to a specific antigen by binding to it
Lymphocytes, cont.

Immunocompetent cells only recognize one antigen




All receptors on the cell are the same
Our genes determine what ‘germs’ we can
recognize and resist
When cells are immunocompetent, they travel to
lymph nodes/spleen to mature
Mature cells circulate the body in search of antigens
Macrophages


“Big Eaters”
Antigen presenters




They engulf foreign particles and ‘present’ them
like flags so T cells can recognize the antigens
Secretes proteins called monokines
Become “Killer Macrophages” in response to
T-cell activation
Stay in lymph organs
Humoral (Antibody-Mediated)
Immunity


Immature B cell is stimulated to mature when
an antigen binds to its surface receptors
Clonal selection begins


B cell grows, multiplies to form an army of cloned
cells
Most of these become plasma cells

Antibody-producing factories (produce 2,000 per
second)
Humoral (Antibody-Mediated)
Immunity

B cell clones that don’t become plasma cells
become memory cells


Can respond to the antigen later
Provide secondary response

Faster and more effective, because attack plans have
already been made
Active vs. Passive Humoral
Immunity

Active



When B cells encounter antigens and produce
antibodies against them
Naturally acquired during infections
Artificially acquired through vaccines




Most vaccines contain dead or weakened viruses
Vaccines keep you from getting most symptoms
Vaccines still stimulate antibody production and
memory of antigens
Booster shots can intensify immunity later
Active vs. Passive Humoral
Immunity

Passive






Antibodies are obtained from serum of immune human or
animal
B cells NOT challenged
Memory does NOT occur
Protection is temporary (ends when antibodies degrade in
body)
Natural Passive immunity
 When mom’s antibodies cross placenta into fetal circulation
Artifical Passive immunity
 When someone receives immune serum/gamma globulin
 (Hepatitis, snake bites, botulism, rabies, tetanus)
Monoclonal Antibodies




Produced by descendants of a single cell
Are antibodies that are specific for one
antigen
Used to deliver cancer-fighting drugs
Also used to diagnose Hepatitis, Pregnancy,
Rabies, as well as for early cancer detection
Antibodies

AKA Immunoglobulins (Ig’s)




Blood proteins
Proteins secrected by activated B cells or
plasma-cell offspring in response to an
antigen
Capable of binding with that antigen
Formed in response to antgens
Antibodies



Made of 4 Amino Acid
chains linked by disulfide
bonds
Two heavy chains and two
light chains (1/2 the size of
heavy chains)
The chains combine to form
the antigen-binding site that
fits its specific antigen
Antibodies

5 classes (Remember “MADGE”)



IgD is virtually always attached to B cells
IgG is only one that can cross placenta




IgM; IgA; IgD; IgG; IgE
Also the most abundant
IgA is found in mucus and other secretions
IgM, IgG can fix complement
IgE are “trouble-makers” in allergies
Antibody Function

Inactivate antigens




Complement fixation (activation)
 Triggers events that cause lysis of foreign cells
Neutralization
 When antibodies bind to sites on foreign cells to cause cell
injury
 Blocks harmful effects of toxins produced by bacteria/virus
Agglutination
 Causes clumping of foreign cells (think Blood Transfusion
reactions)
Precipitation
 When antigen-antibody complexes are so big that they can’t
stay dissolved in solution (makes them easily captured)
Cell-Mediated Immune
Response



T cells can’t bind with free antigens like B
cells
They must recognize an antigen presented
by a macrophage AND “self” by binding to the
macrophage
The macrophage “feeds” antigens to the T
cell (kind of like a double handshake)
Classes of T cell Clones

Cytotoxic (Killer) T Cells


Specialize in killing virus-infected, cancer cells, or foreign
graft cells (inject toxic poison into CM)
Helper T Cells


“Directors/Managers” of Immune System
Circulate and recruit other cells to fight
 Stimulate B cells to divide
 Signal for antibody production
 Release chemicals that rid body of antigens



Stimulate B and T cells to grow/divide
Attract more WBC’s to area
Enhance macrophage’s ability to destroy microbes (cause
insatiable appetite for them)
Classes of T Cell Clones, cont.

Suppressor T Cells



Delayed hypersensitivity T Cells


Release chemicals that suppress activity of T and B cells
Help wind down/stop immune response after the antigen
is destroyed
Play a role in allergies and long-term inflammations
Memory Cells

Provide memory for each antigen encountered to allow
the body to respond quickly next time
Organ Transplants

4 Types of Grafts
 Autografts


Isografts


Taken from unrelated person; Blood Typing/antigen matching must
happen (at least 75% match)
Xenografts


Tissue grafts donated by identical twin; IDEAL
Allografts


Transplanted from one place to another in same person; IDEAL
Harvested from another species; NEVER SUCCESSFUL
Immunosuppressive Therapy
 Drugs, radiation (severe side effects)
 Body can’t protect itself against foreign antigens
 Most frequent cause of death is by bacterial/viral infection
Allergies

AKA Hypersensitivities



Immediate (acute) Hypersensitivity


Abnormal vigorous immune response to a perceived
“threat” that is harmless
Allergen is a type of antigen that causes this response
Runny nose, watery eyes, itching, hives, restricted air flow
(inhaled allergen)
Anaphalactic Shock


When allergen directly enters bloodstream and travels
through body
Reaction involves the whole body
Allergies, cont.

Delayed Hypersensitivity



Take days to appear (1-3)
Allergic contact dermatitis (poison ivy, contact with
heavy metals, cosmetics, deodorant)
Skin tests for TB depend on this type of reaction
Immunodeficiencies

SCID (Severe Combined Immunodeficiency
Disease)




Congenital
Not enough B and T cells
Minor infections are lethal
AIDS (Acquired Immunodeficiency
Syndrome)

Interferes with Helper T cell activity
Autoimmune Diseases


Occurs when the body produces antibodies and T
cells that attack and damage its own tissues
Triggers



Inefficient lymphocyte programming (self-reactive immune
cells aren’t eliminated)
“Hidden” antigens or “new self-antigens” caused by
mutation or damage to cell
Reaction of antibodies produced against foreign antigens
with self-antigens (Strep antibodies can react with heart
antigens and cause rheumatic fever)