Download the immune system phagocytosis antibody function

Immune System
Review
 What is an immune system?

The system in the body responsible for maintaining
homeostasis by recognizing harmful from non harmful
organisms and by producing an appropriate response
 What is immunity?
 The ability of the body to fight infection and/or foreign
invaders by producing antibodies or killing infected cells
 Different types: Natural Active, Natural Passive, Artificial
Active, Artificial Passive
How does the body fight infection/foreign
invaders?
The Body’s THREE lines of Defense
First Line of Defense – The Skin
•
Provides Physical and Chemical barriers


Physical – hard to penetrate, made of indigestible keratin
Chemical – tears, sweat, saliva and mucous (chemicals and enzymes
in body fluids)
First Lines of Defence
saliva
antibacterial
enzymes
skin
prevents
entry
stomach acid
low pH kills
harmful
microbes
tears
antibacterial
enzymes
mucus linings
traps dirt and
microbes
“good” gut
bacteria
White Blood Cells (Leukocytes)
1. Granulocytes (50-60%) (basophil, eosinophil, neutrophil)

release powerful granules that have chemicals inside that attack
an intruder
*Basophil produce histamine (high during allergic reactions)
*Eosinophil (high in parasitic invasion)
*Neutrophil (aid in phagocytosis, high during bacterial infection)
2. Monocytes (7 %)

When activated become macrophages that engulf antigens
3. Lymphocytes (30-40 %)

T- Cells and B-Cells (Viral infections)
***All WBC are produced in the bone marrow as stem cells – T-cells
migrate to the thymus – that’s where they mature
***WBC are found in lymph nodes, spleen & liver
Second Line of Defense – Nonspecific Immune
Response
These are defenses the body uses no matter what the
invader may be. These defenses include:
 Phagocytosis – done by Macrophages
 Inflammation - caused by release of Histamine
from leukocytes
 Fever – caused by histamines. The fever (high temp)
kills invaders by denaturing their proteins.
Phagocytosis

Stages in phagocytosis
1. Phagocyte detects chemicals released by a
foreign intruder (e.g. bacteria)
2. Phagocyte moves up the concentration
gradient towards the intruder
3. The phagocyte adheres to the foreign cell
and engulfs it in a vacuole by an infolding of
the cell membrane.
4. Lysosomes (organelles which are rich in
digestive enzymes & found in the
phagocytes cytoplasm) fuse with the
vacuole & release their contents into it.
Phagocytosis
5.
The bacterium is digested by the
enzymes, and the breakdown products
are absorbed by the phagocyte.
 During infection, hundreds of phagocytes
are needed.
Injury
 Chemical signals are released by the foreign invader
 Chemicals cause capillaries to dilate thus increasing blood flow
 Basophils flow through the blood stream and gather to the site of
infection and release histamine (histamine cause inflammation and
increase blood flow)
 This brings neutrophils and monocytes to the site
 Neutrophils release chemicals that engulf and kill antigens
* they have a short lifespan but are constantly supplied
* dead neutrophils form pus
 macrophages engulf and kill antigens and dead neutrophils
***Inflammation response (swelling, heat, redness & pain)
TREATMENT???
Fever
 The hypothalamus responds to a chemical signal
caused by the presence of a pathogen
 The signal makes the hypothalamus increase the
normal set point for normal temperature in the body
from 37◦C t0 ~39◦C (Optimal)
 WHY?


Some hypothesize that immune cells function more effectively
at that temperature
Invaders/pathogens are not so equipped with dealing with
heat (High temp. denatures their proteins)
Third Line of Defense – Specific Immune Response
***This is a specific response to a specific pathogen/antigen.
 The response involves lymphocytes and the creation of Antibodies.
There are 2 types of lymphocytes :
***T-cells – identify and attack foreign
substances, regulate B-cell production and stop
the immune response
***B-cells – produce antibodies and are programmed
to respond to a specific antigen
Antigens
 all cells have surface
markers called
antigens.
 body can recognize
these as self or nonself (foreign)
Specific response
 Lymphocytes detect presence of foreign
antigens
 Stimulated to produce
specific proteins called
antibodies.
How an antibody operates/works?
Deactivation of a bacterium by an antibody.
The Pathway of Specific Immune Response
Step 1
Pathogens eaten by Macrophage
Step 2
Displays portion of Pathogen
on surface
Step 3
Pathogens
Helper-T cell recognizes
Pathogen
Activates B- Cell
Activates Cytotoxic
T- Cell
Memory T-Cell
Memory B-Cell
Antibodies
Kills Infected Cells
Immune Response Explained
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Antigen infects cells.
Macrophage ingests antigen and displays portion on its surface.
Helper T- Cell recognizes antigen on the surface of the macrophage
and becomes active.
Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells.
Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T
– Cells.
Active Cytotoxic T-Cells kill infected cells.
At the same time, B-Cells divide into Plasma Cells and Memory BCells.
Plasma cells produce antibodies that deactivate pathogen.
Memory T and Memory B cells remain in the body to speed up the
response if the same antigen reappears.
Supressor T-Cells stop the immune response when all antigens have
been destroyed.
Cellular Immunity .vs. Antibody Immunity
Cellular Immunity
Antibody or Humoral Immunity
 Carried out by T-Cells
 Carried out by B-cells
 Infected cells are killed by
 Antibodies are produced and
Cytotoxic T –Cells.
dumped into blood stream.
 Antibodies bind to antigens
and deactivate them.
Immune Response Summary
Displays copy of antigen
on surface of cell
Antigen
Macrophage
Antibody Immunity
Helper T - Cell
Cellular Immunity
Active Cytotoxic T-Cell
Kills Infected Cells
Memory T- Cell
Active B - Cell
Plasma Cell
Antibodies
Deactivates Antigens
Memory B-Cell
What happens during an allergic reaction?
Anaphylaxis or anaphylactic shock:
This is the sudden and severe allergic reaction to a substance that can
cause death.
During an allergic reaction, antibodies cause histamines to be released from
certain cells. In addition blood vessels dilate which causes a decrease in
blood pressure and heart rate.
Histamines cause:
a. Swelling of tissues
b. Release of fluids (runny noses and eyes)
c. muscle spasms (some cases)
Treatments for Allergies
1.
Avoidance of material – especially food.
2.
Epinephrine – “epi – pen”
3.
Antihistamines -- benadryl