Download Immune System - Uplift Education

April 5-6th 2015
The specific defense system (aka immune system)
recognizes and attacks specific pathogens.
The immune system has 3 important characteristics:
What is an antigen?
» Antigen specific
Antigens are molecules (usually
sugars or proteins on cell surfaces)
that incite an immune response
The specific defense system (aka immune system)
recognizes and attacks specific pathogens.
The immune system has 3 important characteristics:
» Antigen specific What does systemic mean?
Systemic means ‘whole body’. The specific
» Systemic
immune system mounts an attack that
circulates throughout the body, not just at the
initial site of infection.
The specific defense system (aka immune system)
recognizes and attacks specific pathogens.
The immune system has 3 important characteristics:
» Antigen specific
The body ‘remembers’ antigens
that it has previously fought, and
» Systemic
mounts an even stronger & faster
» Has memory
attack if it encounters them again.
» Lymphocytes
• Natural killer cells function in non-specific defense* to kill virus
infected or cancerous body cells
• B-lymphocytes mature in bone marrow. They become activated
by binding to specific antigens then divide to form:
• Plasma cells which release antibodies
• Memory cells which ‘remember’ specific antigens
• T – lymphocytes mature in the thymus. They become activated by
binding to specific antigens then divide to form:
• Cytotoxic (killer) T cells kill virus infected or cancerous body cells
• Helper T cells stimulate the production of immune cells and release
chemicals which help destroy pathogens
• Suppressor T cells stop activity of immune cells after infection is over
• Memory T cells ‘remember’ specific antigens
» Lymphocyte quick review
• What do the B and T refer to?
The place where the
lymphocyte matures – the
bone marrow or thymus.
• Which cell has a similar function to
NK cells? How are these two cells
different?
Cytotoxic T and NK cells both
attack and kill virus-infected or
cancerous body cells. They differ
in that NK cells attack any
abnormal cell, whereas cytotoxic
Ts only attack cells displaying
specific antigens.
Fill out the visual!
» Lymphocyte quick review
• Which cells directly attack
pathogens?
None of these!
• The NK and cytotoxic T cells
attack virus –filled cells.
• The B cells produce
antibodies (which do
directly attack pathogens)
• The helper Ts produce
chemicals which will kill
pathogens
Fill out the visual!
» Macrophages
• Play a role in non-specific AND specific defense system
• Engulf foreign particles (non-specific system)
• Act as antigen presenters (specific system) by displaying
fragments of these particles on their surface and activating T
lymphocytes.
» Antibodies
• Proteins produced by plasma cells (B cells) that bind to specific antigens
• Binding of antibodies to pathogen causes their destruction / inactivation
in one of a few ways
• Complementation: Encourages other chemicals (complements) to
punch holes in the surface of the pathogen, destroying it.
• Neutralization: Binding prevents viruses or toxins from entering
healthy body cells
• Agglutination / Precipitation: clumping of antibody-bound particles,
which makes them unable to enter healthy cells and more likely to
be eaten by phagocytes
• Increased phagocytosis – the presence of antibodies ‘flags’ a
pathogen, increasing the chance that it will be eaten by a phagocyte.
» Other important chemicals
• Complements – proteins in blood that bind to pathogens; activity
increased by presence of antibodies
• Interferons – proteins that bind to virus-infected cells and reduce
the ability of viruses to multiply; also work with T cells to increase
recognition of virus infected or cancerous cells.
• Histamines and kinins – cause inflammatory response
• Lymphokines and monokines – released by T cells, increase
immune response and directly destroy pathogens
Fun Fact
Interferon therapy is used in
combination with other
treatments to fight many cancers
and Hepatitis B and C.
Fun Fact
Histamines are
involved in allergic
response
You are responsible for
knowing: complements,
interferons, and
histamines
There are two branches of the immune system:
» The humoral immune response which involves
the production of antibodies that fight
extracellular pathogens (pathogens including
viruses and bacteria that are among our cells, but
not inside them).
» The cell-mediated immune response which
involves the activation of cytotoxic T cells that
destroy virus-infected body cells and cancer cells.
But, before we talk about these,
I need to tell you about …
The body naturally produces a HUGE array of
B- and T- lymphocytes, with widely diverging
receptors. *
Each receptor is capable of binding with only one
type of antigen.
These mature, but inactive, lymphocytes take
up residence in lymphatic organs and wait to
meet their antigen.
Most never will.
The lucky few lymphocytes that do bind to their
antigen will undergo clonal selection so that
they, and their multitude of offspring, can fulfill
their destiny by participating in the humoral
or cell-mediated immune response.
1. B-lymphocytes bind to specific, freefloating antigens and become
activated.
2. The activated B-lymphocyte divides
many many times, forming identical
clones, also capable of binding to the
antigen.
3. Most of these clones will become
plasma cells that specialize in
producing antibodies that bind only
with that specific antigen.
4. A few will become long-lived
memory cells that will persist for
years, waiting in case the same
antigen is encountered again.
Fun fact: A plasma cell can produce 200 antibodies each second!
» The primary humoral immune response occurs the
first time the immune system encounters a specific
Why?
antigen.
It takes time because the matching B
lymphocyte must find the antigen, and be
activated before the clones can be made.
» The secondary humoral immune response occurs any
time after the immune system first defeats an antigen.
This response is much faster and produces more
antibodies. Why?
Because the body already has many matching B
memory cells, and these will divide to produce
even more plasma cells than in the 1st response.
Secondary response
is why you become
‘immune’ to diseases
How does this graph
explain the function of
vaccines?
Why are boosters
necessary?
The least common method is artificial passive immunity.
Used for exposures / disorders that are likely to be fatal
before the body can mount its own immune defense.
Includes: antivenom, botulism, rabies, & tetanus
Will passive immunity protect a person in case of secondary
exposure? Why or why not?
No, because the person will not have memory cells.
The humoral immune response involves the production
of antibodies and memory B lymphocytes.
What does the cell-mediated immune response involve?
The production of cytotoxic T lymphocytes
and memory T lymphocytes.
» T-cell activation
• Like B-cells, T-cells must bind to their one, specific antigen
before they are activated.
• Unlike B-cells, T-cells cannot bind to free-floating antigens and
must bind to an antigen-presenting cell, like a macrophage.
» Activated T cells will clone (multiply)
» T cells will do their
specific jobs
» Types of T cells
• Cytotoxic Ts… do what?
» Types of T cells
• Cytotoxic Ts kill virus infected or cancerous body cells by
shooting them with chemicals that destroy their cell membrane
• Helper Ts have many jobs
• Encourage division of activated B cells and cytotoxic Ts
• Encourage production of antibodies from plasma cells
• Release chemicals (lymphokines) which attract white blood
cells and enhance activity of phagocytes
• Suppressor Ts
• Release chemicals that inhibit B and T cells, to slow immune
response once antigen is destroyed
• Memory Ts
• Long-lived cells that remain for quick response upon
subsequent infection
Why might helper Ts be thought of as the bridge between
cell-mediated immunity and humoral immunity?
» What were our objectives, and what did you
learn?
» How does this relate to our unit question?
» What learner profile trait did we demonstrate,
and how did we show it?
1. The cells that produce antibodies are called
a. Macrophages
c. Plasma cells
b. Memory cells
d. Cytotoxic cells
2. The cells that stimulate the production of immune cells are
a. B-lymphocytes
c. Cytotoxic Ts
b. Helper Ts
d. Macrophages
3. Which of the following is not part of the specific defense
system?
a. Macrophages
b. Antibodies
c. Natural killer cells
d. Plasma cells
4. Which bind directly to antigens, causing their destruction or
inactivation?
a. Antibodies
b. Natural killer cells
c. Helper Ts
d. Cytotoxic Ts
5. Antibodies that pass from mother to infant through breast milk are
an example of which type of immunity?
a.
c.
Passive natural
Passive artificial
b. Active natural
d. Active artifical
6. Vaccines are an example of which type of immunity?
a.
c.
Passive natural
Passive artificial
b. Active natural
d. Active artifical
7. Which of the following does not bind to specific antigens?
a. Antibodies
b. Macrophages
c. Memory cells
d. T cells
8. Which type of immunity does not protect against future
exposure to the same antigen?
a. Active immunity
b. artificial immunity
c. Natural immunity
d. Passive immunity
9. The repeated division of a specific immune cell and its
progeny is called
a. Activation
c. Neutralization
b. Cloning
d. Agglutination
10. Which type of cell frequently serves as an antigen presenting
cell?
a. Antibody
c. Cytotoxic T
b. macrophage
d. Plasma cell
Extra Credit 1 (2 pts):
What is the primary difference between humoral and cellmediated immunity?
Extra Credit 2 (2 pts)
Compared to primary humoral immunity, secondary humoral
immunity occurs more ___________ and produces more
________________.