Transcript Set 6 Immune System and Vaccines

Emerging Diseases
Lecture 6:
Your Immune System
6.1 Overview
6.2 The Immune System-Anatomy
and Cells
6.3 Immune Memory
6.4 Vaccines
6.5 Types of Protection
6.1: Overview: 3 Levels of
Protection
You have three levels of protection
against infectious disease
• Physical and chemical barriers (hair, skin)
• Innate immune system: non-specific such as
inflammation
• Adaptive immune system-most important,
flexible and strong
6.2 Cells and Anatomy of the
Adaptive Immune System
It keeps you from being sick all the time
Provides protection against germs and invading substances
Distinguishes self from non-self
Can “learn” new diseases-aka adaptive
Has two important parts (aka branches, arms)
“cellular” works through intact living cells
“humoral” works through proteins dissolved in blood
Disambiguation: Two types of
Immune System Disorders
Immunodeficiency: for some reason the
adaptive immune system does not work
Autoimmune diseases: the immune system
cannot distinguish self and non-self
This is for disambiguation and clarification-AIDS
(Module 4) is an example of an
immunodeficiency disease
6.3: Anatomy of the Immune
System
Many organs and
tissues are involved
Dispersed throughout
body
Involves circulation of
blood and lymph to
distribute protection
Cells Found in the Immune System
Many different types of
cells
Each specialized for a
task
Activities must be
coordinated
Derived from
unspecialized stem cells.
They keep dividing and
their descendants
become the worker cells
of the immune system.
A second key point is that the
immune system relies on stem cells
to keep dividing-thus producing
more immune system cells for
continued protection.
The adaptive immune system
works by detecting foreign
substances (“invaders”) and
eliminating them. Foreign
substances that react with the
immune system are called
“antigens”.
Antigens are foreign substances
that enter your body and are
perceived as a threat by your
adaptive immune system.
One way that it responds is to
produce defence proteins called
“antibodies”.
Antigens are foreign substances
Antibodies are your own defense
proteins
Ag = antigen
Ab = antibody
Antigen and antibody are two
important terms that define two
completely different substancesbut the substances “go together”.
How the Immune System Works
The body detects an antigen
when a macrophage
becomes an APC
This signals an invader is
present
Pre-existing Helper T cells
respond by activating the rest
of the immune system
B cells (bone marrow) and
more T cells (thymus) are
produced
They in turn attack and
destroy the invader
Helper T calls are the “generals” in
the fight against invaders.
They trigger the main response.
The “soldier” cells are B calls and
other T cells.
They fight the battle, but they only
attack the invader that was
originally detected by the
macrophage (scouts).
This immune response is highly
specific for each invader.
And the immune system
remembers invaders from the past.
It does so by holding back some of
the B cells and T cells in reserve.
They are called “memory” cells.
The memory cells are a prepositioned defense system.
If the invader comes back a second
time, memory cells permit a rapid
and powerful response.
The second attack by the invader
does not stand a chance.
The following cartoon illustrates
the production of memory B calls,
ready to fight off the invader’s
second attack.
The following graph shows how
memory cells allow the immune
system to respond more rapidly
and more powerfully to the second
attack.
6.4: How Immune Memory Works
Faster Response When There Are
Memory Cells Around
Your immune system learns by building up many different memory cells.
They wait around until the next time the antigen shows up.
Then they cause a very fast response-too fast for the germ to take hold.
6.5: Vaccines
Artificially stimulate immune system to build
memory.
They stimulate a protective response without
the disease symptoms or dangers.
6.5: Vaccines-definitions
Inactivated vaccine: uses killed or inactivated
antigen
Subunit vaccine: uses only part of antigen
Attenuated vaccine: uses weakened antigen
Adjuvants: a substance included in vaccine to
boost the immune response-not a part of
antigen
6.6: Types of Protection
Active Immunity: your own body provides the
protection
Example: DPT vaccine protects against
diphtheria.
Passive Immunity: you are given antibodies that
you did not produce in order to save your life.
Examples: Antibodies from horses used to treat
diptheria, or-blood from Ebola survivors
transfused into patients in emergencies.