physiology of immune system

1. Physiological sciences
dep.
Dr. Ramadan Saad

2. 28-2
Learning Outcomes
1 List the pathways and organs of the lymphatic system and give their locations.
2 Define lymph and tell how it is circulated in the bod
3 List and describe the nonspecific body defense mechanisms.
4 Define B cells and T cells and describe their locations and functions.
5 List the different types of T cells and describe their functions.
6 Explain how antibodies fight infection.
7 List the different types of antibodies and tell how they differ.
8 Define complement proteins and give their function.
9 Explain the difference between the primary immune response and secondary
immune response.
10 Explain the four different types of acquired immunities.
11 Describe the function of a vaccine.

3. 28-3
Introduction
• Immune system
– Protects the body against
• Bacteria
• Viruses
• Fungi
• Toxins
• Parasites
• Cancer
• Lymphatic system
– Works with immune system to
remove disease-causing agents
– Organs
• Thymus
• Spleen
• Lymph nodes

4. The Lymphatic System

5. 1. Fluid recovery:
–absorbs ECF proteins and fluid (2 to 4
L/day) from tissues and returns it to the
bloodstream
• interference with lymphatic drainage
leads to severe edema
(Fig. 21.2)
§ Functions of Lymphatic System

6. Elephantiasis
Cause- mosquito-borne roundworms
infect the lymph nodes and block the
flow of lymph
Symptoms– chronic edema,
especially extremities;
Thickening of the skin

7. 2. Immunity:
–fluids from all capillary beds are filtered
–immune cells (where are they?) stand ready to respond
to foreign cells or chemicals encountered
3. Lipid absorption:
–Lacteals (what are they?) in small intestine absorb
dietary lipids
§ Functions of Lymphatic System

8. Lymphatic Organs
Primary organs
 Red bone marrow
 Thymus gland
Secondary organs
 Lymph nodes
 Lymph nodules
 Spleen

9. Lymph Nodes
• Small, glandular structures
• Located along paths of larger
lymphatic vessels
– Afferent lymphatic vessels –
Lymph to node
– Efferent lymphatic vessels –
Lymph from node

10. 1.Cervical
2.Axillary
5.Intestinal &
mesenteric
C-Spleen
B-Thymus
A-Tonsils
• 5 lymphatic
organs– (A-E)
• Locations of
lymph nodes--
21-10
D-Red
bone
marrow
7.Popliteal
6.Inguinal
E-Lymph nodes
(7 locations):
3.Thoracic
4.Abdominal

11. 28-11
Lymph Nodes (cont.)
• More lymph enters than can leave at
one time
• Cells in nodes
– Macrophages – digest unwanted
pathogens
– Lymphocytes – start an immune
response against pathogen
• Nodes can generate some
lymphocytes

12. 28-12
Lymph Nodes (cont.)
• A lymph node’s job is to filter substances in your lymph fluid, which is a collection of
fluid that drains from your cells and tissues. Lymph fluid contains:
• Proteins.
• Minerals.
• Fats.
• Nutrients.
• White blood cells (lymphocytes).
• Damaged cells.
• Cancer cells.
• Bacteria and/or viruses (foreign invaders).
• Lymph fluid flows through the tissue that makes up lymph nodes, where the tissue
filters and recycles lymph fluid that your body needs. The cells within your lymph
nodes will attack, destroy and eliminate waste, especially foreign invaders, to help
your immune system keep you healthy.

13. How do lymph nodes help with other body
systems?
• Your lymph nodes work closely with two body systems
including your:
• Immune system: The immune system protects your body from
foreign invaders like bacteria and viruses to prevent infection,
illness or diseases. Your immune system is what keeps you
healthy.
• Lymphatic system: The lymphatic system is part of your
immune system that protects your body from foreign invaders
that cause illness, and removes waste from cells.

14. The Thymus and Spleen
• Thymus
– Soft, bi-lobed organ
– Located just above the heart in the mediastinum
– Large in children, shrinks as we age
– Functions
• Same as lymph nodes
• Also produces lymphocytes
• Produces thymosin – stimulates production of lymphocytes

15. Thymus
Thymus

16. The Thymus and Spleen (cont.)
• Spleen
– Largest lymphatic organ
– Located in the upper left quadrant of abdominal cavity
– Functions
• Filters blood similarly to lymph nodes
• Removes worn-out old red cells
– If removed (splenectomy), liver takes over most of its function

17. Lymphadenopathy
• Means a disease of
the lymph nodes
• Lymph nodes become
swollen/ enlarged and
may be painful to
touch

18. Lymphomas
• Cancers originating
either from the
lymphocytes in the
lymph nodes or the
lymphatic tissue in
organs

19. Tonsillitis
• Infection of the
pharyngeal tonsils
• Tonsils are swollen,
• Fever and pain during
swallowing usually
present

20. Immune System
• Functional system
rather than organ
system
– Hematopoetic
– Vasculature
– Lymphatic
Consists of a series of defenses against intruders,
such as microorganisms

21. Immune System
• Functional system
rather than organ
system
– Hematopoetic
– Vasculature
– Lymphatic

22. Innate, Surface Defenses
• Skin
– physical barrier to microbes
– Keratin resistant to most bacterial
enzymes & toxins
– secretions are acidic pH 3-5
• Mucosa
– physical barrier & produces a variety of
protective chemicals
• Gastric mucosa
– very acidic & produces proteolytic
enzymes
• Saliva & lacrimal fluid contain
lysozyme
• Mucous
– traps bacteria & moves them away
from epithelial surface

23. Innate, Internal Defenses
• Phagocytes
– Macrophages: derived from monocytes
• Free Macrophages: roam through tissues
• Fixed Macrophages: Kupffer cells (liver) & microglia (brain)
• Ingest cellular debris, foreign material, bacteria, fungi
– Neutrophils: ingest pathogens
– Eosinophils: weakly phagocytic of pathogens. Attack parasites
(degranulation)
– Mast Cells: phagocytic of various bacteria

24. Innate, Internal Defenses
• Natural Killer Cells:
– Small population of large granular lymphocytes
– Non specific for “non-self”
– Not phagocytic: attack is by release of perforins that perforate
the target cell plasma membrane.
• Shortly after perforation the target nucleus disintegrates.
– Release chemicals that enhance the inflammatory response

25. Innate, Internal Defenses
• Antiviral proteins: interferon & complement
• Interferon: some cells produce & release interferons (IFNs) when
invaded by virus
• Released interferons stimulate nearby cells to produce proteins
(PKR) that interfere with viral replication by disrupting protein
synthesis & the ribosome
• Not virus specific.

26. Innate, Internal Defenses
• Complement – a group of plasma proteins (20) that are activated
in the presence of foreign substances
• Complement activation enhances & amplifies inflammation
• Bacteria & some other cell types are lysed by complement
activation
• Complement activation enhances both innate & adaptive
defenses

27. Acquired immune response

28. 28

29. Major Immunoglobulins
Immunogobulin G (IgG)
-effective against bacteria, viruses and toxins
Immunoglobulin A (IgA)
-common in exocrine gland secretions such as breast milk and tears
Immunoglobulin M (IgM)
-first antigen to be produced after an infection
Immunoglobulin D (IgD)
-important in B-cell activation
Immunoglobulin E (IgE)
- associated with allergic reactions
This type of immunity is provided by B lymphocytes
which converted into plasma cells
Plasma cells produce large quantities of their
specific antibody into the blood.
Memory cells lie in wait for the next infection.

30. B cells immune response
invader
(foreign antigen)
Y
Y
Y
Y
B cells
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
“reserve
s”
memory B cells
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
B cells
release
antibodies
patrol blood
forever
recognition
10 to 17 days
Y
Y
Y
Y
Y
Y
Y
Y
Y

31. B cells & antibodies
• B cells
– white blood cells that attack
invaders in blood
– mature in Bone marrow
• Patrolling B cells
– make antibodies against invader immediately
• Memory B cells
– remembers invader
– can make antibodies quickly the next time
• protects you from getting disease more than once

32. 28-32
Antibodies (cont.)
• Actions that occur when antibodies bind to antigens
– Allow phagocytes to recognize and destroy antigens
– Cause antigens to clump together, causing them to be destroyed by
macrophages
– Cover the toxic portions of antigens, making them harmless
– Activate complement
• Group of proteins in serum that attack pathogens by forming holes in them
• Attract macrophages to pathogens and can stimulate inflammation

33. 28-33
Immune Responses and Acquired Immunity
• Primary immune response occurs
with first exposure to antigen
– Slow process
– Memory cells are formed
• Secondary immune response with
next exposure to same antigen
– Quick and carried out by memory
cells
– Usually prevents person from
developing disease from the antigen

34. 34
Cell-mediated Immunity
Cell-mediated Immunity
This type of immunity is provided by the action of
the T-cells which multiply rapidly and produce
certain proteins in response to antigens.
Three Types of Specialized T-Cells (T=thymus)
B=bone marrow
•Helper cells or CD4 cells that stimulate the
immune response
•Cytotoxic cells or CD8 cells that help in the
destruction of infected cells
•Suppressor cells or T cells that suppress B-cells
and other immune cells

35. T cells
• T cells mature in Thymus
• Helper T cells
– sound the alarm for rest
of immune system
• Killer T cells
– destroy infected body cells
• Memory T cells
– remembers invader & reacts
against it again quickly
Where’s that?

36. Attack of the Killer T cells
• Killer T cells destroy infected body cells
– T cell binds to invaded cell
– secretes perforating protein
• punctures cell membrane of infected cell
• cell bursts

37. Passive Immunity
Short term, antibodies passed
on, not stimulated by antigens,
acquired naturally by placenta or
breast milk or
artificially acquired by a shot
Active Immunity
long term, conferred by actual
encounter with infection (naturally
acquired) or vaccination *(artificially
acquired)
* vaccine~ substance consisting of
weakened, dead, ,or parts of
pathogen or antigen that when
injected , stimulates the immune
system

38. 28-38
Apply Your Knowledge
Identify whether each item refers to T cells, B cells, or NK
cells:
___ Primarily target cancer cells
___ Respond to antigens by becoming plasma cells
___ Must be activated to respond to an antigen
___ Bind to antigens on cells and attack them directly
___ Kill on contact
___ Need macrophages and MHC for activation
___ Make antibodies against specific antigen
B
NK
T
T
T
B
NK
ANSWER:
Right on
Target!

39. 28-39
Apply Your Knowledge
What are the possible actions that occur when
antibodies bind to antigens?
ANSWER: Possible actions include:
 They allow phagocytes to recognize and destroy
antigens.
 They make antigens clump together, causing them to be
destroyed by macrophages.
 They cover the toxic portions of antigens to make them
harmless.
 They activate complements.
Very Good!

40. 28-40
Apply Your Knowledge
ANSWER: Immunization is an artificially acquired
immunity because a person develops this immunity
by being injected with a pathogen and then making
antibodies and memory cells against the pathogen.
After you give an immunization to a 2-year-old,
her mother asks you why this will work to
prevent her from getting a disease.

41. • I am a part of lymphatic system and protect the body
by clearing worn out red cells and foreign bodies from
the blood stream. Who am I?
A. Thymus
B. Palatine
Tonsil
C. Spleen
D. Lymph
QUESTION. 1

42. Which of these is a primary lymphoid organ ?
A. Lymph Node
B. Spleen
C. Tonsil
D. Bone Marrow
QUESTION. 2

43. Which is the correct statement about the Lymphatic
system?
A. It Reabsorbs excess interstitial fluid and
returns it to the venous circulation.
B. Transports dietary lipids through lacteals.
C. Helps in lymphocyte development, and the immune
response.
D. All of the above
QUESTION. 3

44. 28-44
End of Chapter 28
Thought is an infection.
In the case of certain
thoughts, it becomes an
epidemic.
~Wallace Stevens