Transcript Human Immune System - West Linn High School

Human Immune System
Defenses Against Infection
KEY CONCEPT
 The immune system has many responses to
pathogens and foreign cells.
 The job of the immune systems is to fight off pathogens
& infections.
 Skin is a physical barrier to infection.
 Mucous Membranes trap pathogens entering the body.
Nonspecific responses
• First Line of Defense:
Skin – few pathogens can penetrate
the layers of dead skin cells
• Mucous membranes
•
Second Line of Defense:
• Inflammation - blood vessels
become leaky.
• Histamines & interferons
• Fever - body temperature
increases
• Slows growth of pathogens
• Low fevers stimulate white
blood cells to mature.
Cells of the immune system produce
SPECIFIC RESPONSES
 Specific Immune
response:
 Antigens are surface
proteins on pathogens.
 Each pathogen has a
different antigen.
antigens
Recognizing Self
 Your body’s white blood cells use antigens to
recognize “self ” versus “other”.
 Your body then works to inactivate or destroy
“other”
Attacking Invaders/Pathogens
 Phagocytes (like Pacman) consume
pathogens and present the pathogen’s
antibodies to other white blood cells.
Antibodies
 Produced by lymphocyte
 Bind to foreign antigens
 Each antibody is specific for a particular antigen
 Body can make 10B different antibodies!!!
 Tag foreign cells for destruction by other WBCs
Lymphocytes
 B – Cells
 Made in bone marrow
 Each recognizes a single antigen
 Once activated they produce
Memory B cells & plasma cells
 Memory B cells remain after
infection
 Memory B cells allow a rapid
response during re-infection
Lymphocytes
 T – Cells
 Made in bone marrow, mature in thymus
 Each recognizes a single antigen
 Helper T-cells
 Activate B-cells
 Activate killer T-cells
 Produce memory T-cells
 Vaccines
 Allow person to acquire immunity without
contracting disease
 Contain the antigen of a weakened
pathogen
 Does not cure a person who is sick
Vaccination provides immunity.
– stimulates a specific
immune response
– causes memory B & T
cells to be produced
– allows immune system
to respond quickly to
infection next time
– has such a fast
response, a person
will not get sick
Antigens in a vaccine
trigger an immune
response, and memory B
cells are made.
1
memory B cells
Memory B-cells
2
A memory B cell is
stimulated when the real
pathogen binds to it.
3
The B cell quickly
activates and makes
antibodies that fight the
pathogens before you
get sick.