11-AS-Immunity for AS Level Biology Grade 11

Use to teach grade 11 whose take AS level

1. Immunity

2. Immunity is the protection
against disease provided by the
body’s defence or immune
system.

3. Human Immunity
INNATE IMMUNITY
Recognition of traits
shared by broad ranges
of pathogens, using a
small set of receptors
Non-specific
•
•
Rapid response
•Recognition of traits
specific to particular
pathogens, using a vast
array of receptors
•Slower response
ACQUIRED IMMUNITY
Pathogens
(microorganisms
and viruses)
Barrier defenses:
Skin
Mucous membranes
Secretions
Internal defenses:
Phagocytic cells
Antimicrobial proteins
Inflammatory response
Natural killer cells
Humoral response:
Antibodies defend against
infection in body fluids.
Cell-mediated response:
Cytotoxic lymphocytes defend
against infection in body cells.

4. Immune response is about SELF AND NON-
SELF
•The key to a healthy immune system is its remarkable ability to
distinguish between the body’s own cells, recognized as “self,” and
foreign cells, or “nonself.”
•Antigen - a chemical feature (a protein) which is unique to any given
type of invading organism.
•When it wrongly identifies self as nonself it causes an
 
autoimmune
disease 
such as rheumatoid arthritis or systemic lupus
erythematosus.
•Immune system depends on the ability to distinguish between self
and non-self, and the production of antibodies.
•Antibodies are glycoprotein molecules that act against specific
antigens

5. Self and Non-Self in Blood Group

6. Immune response

8. Cellular Innate Defenses

9. Cell of the immune system

10. Cell of the immune system
•Phagocytes (neutrophils and macrophages)
•Lymphoyctes
Name cells
C:
D:
E:

11. Phagocytes
•Produced by bone marrow
•Scavengers
•Non-specific
•Two types:
•Neutrophils – small, short-lived
•Macrophages – large, long-lived

12. Phagocytes
•Neutrophils are a kind of phagocyte and form about 60% of the white
cells in the blood. They
 travel throughout the body, often leaving the
blood
 by squeezing through the walls of capillaries to ‘patrol’ the tissues.
During an infection, neutrophils are released in large numbers from their
stores, but they are short-lived cells.
•Macrophages are also phagocytes but are larger than neutrophils and
tend to be found in organs such as the lungs, liver, spleen, kidney and
lymph nodes, rather than remaining in the blood. After they are made in
the bone marrow, macrophages travel in the blood as monocytes,
•Monocytes develop into macrophages once they leave the blood and
settle in the organs, removing any foreign matter found there.
•Macrophages are long-lived cells and play a crucial role in initiating
immune responses, since they do not destroy pathogens completely, but
cut them up to display antigens that can be recognised by lymphocytes.

13. Major events in a local Inflammatory Response
Pathogen Splinter
Macrophage
Mast cell
Chemical
signals
Capillary
Phagocytic cellRed blood cells
Fluid
Phagocytosis
1. 2.
3.

14. Mode of action
•If pathogens invade the body and cause an infection, some of the
cells under attack respond by releasing chemicals such as
histamine.
•Histamine and chemical from pathogen attract passing
neutrophils to the site.
•Pathogens may covered by antibodies. The antibodies further
stimulate the neutrophils to attack the pathogens. Because
neutrophils have receptor proteins on their surfaces that
recognise antibody molecules and attach to them.
•When the neutrophil attaches to the pathogen, the neutrophil’s
cell surface membrane engulfs the pathogen, and traps it within a
phagocytic vacuole in a process called endocytosis. 
phagocytosis.
•Digestive enzymes are secreted into the phagocytic vacuole, so
destroying the pathogen.
•Macrophages collect antigens then present it to helper T-cells.
•Antigen that presented alerting the T-cells to the fact that there is
a foreign invader in the body, and triggering an further immune
response.

17. Lymphocytes
•Made in bone marrow before birth
•Stored in lymphoid system
•Specific
•Secrete antibodies
•Two groups:
•T lymphocytes
•B lymphocytes

18. Acquired
Immune
Response
Humoral (antibody-mediated) immune response
B cell
Plasma cells
Cell-mediated immune response
Key
Stimulates
Gives rise to
+
+
++
+
+
+
Memory B cells
Antigen (1st exposure)
Engulfed by
Antigen-
presenting cell
Memory
Helper T cells
Helper T cell Cytotoxic T cell
Memory
Cytotoxic T cells
Active
Cytotoxic T cells
Antigen (2nd exposure)
Secreted
antibodies
Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.
Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.
+
+ +

19. Acquired
Immune
Response
Key
Stimulates
Gives rise to
+
Memory
Helper T cells
Antigen-
presenting cell
Helper T cell
Engulfed by
Antigen (1st exposure)
+
+
+
+
+
+
Defend against extracellular pathogens
Memory
B cells
Antigen (2nd exposure)
Plasma cells
B cell
Secreted
antibodies
Humoral (antibody-mediated) immune response

21. Origin and maturation of B-lymphocytes

22. Making B Memory cells and Antibody production
•

23. B Cells Action

24. B cell activation in the humoral immune response
Antigen-presenting cell
Endoplasmic
reticulum of
plasma cell
Secreted
antibody
molecules
Bacterium
B cellPeptide
antigen
Class II MHC
molecule
TCR CD4
Helper T cell
Activated
helper T cell
Cytokines
Clone of memory
B cells
Clone of plasma cells
2 µm
+

25. Antibodies
•Each antibody consists of four polypeptides– two
heavy chains and two light chains joined to form a "Y"
shaped molecule.
•The amino acid sequence in the tips of the "Y" varies
greatly among different antibodies.
•This variable region, composed of 110-130 amino
acids, give the antibody its specificity for binding to
the antigen.
•The constant region determines the mechanism used
to destroy the antigen.
 

26. Antibody

27. The action of antibody

28. Acquired
Immune
Response
Cell-mediated immune response
Defend against intracellular pathogens
Active
Cytotoxic T cells
Memory
Cytotoxic T cells
Memory
Helper T cells
Antigen-
presenting cell
Antigen (2nd exposure)
Helper T cell
Engulfed by
Antigen (1st exposure)
Cytotoxic T cell
Key
Stimulates
Gives rise to
+
+
+
+
+ +
+

29. The central role of helper T cells in humoral
and cell-mediated immune responses
Antigen-
presenting
cell
Peptide antigen
Cell-mediated
immunity
= attack on
infected cells.
Class II MHC molecule
CD4
TCR (T cell receptor)
Helper T cell
Humoral
immunity
= secretion of
antibodies by
plasma cells.
Cytotoxic T cell
Cytokines
Positive Feedback …
B cell
Bacterium
+
+ +
+

30. T lymphocytes
•Mature in thymus gland
•Specific surface receptors called T cell
receptors and glycoprotein receptors
called CD receptors.
•T Cells 
provide 
Cell Mediated Immunity

31. Origin and maturation of T lymphocytes

32. •T cells have several functions. They can be:-
•Helper T cells, which control other cells, such
as B cells or Macrophages, directing them to
carry out their task.
•Suppressor T cells, which dampen down the
immune response when it is no longer
needed.
•Cytotoxic T cells, which destroy host cells
that have become infected with the invading
organism. (Killer T)

33. The Action of T-lymphocytes

35. The killing action of cytotoxic T cells
Cytotoxic T cell
Perforin
Granzymes
TCRCD8
Class I MHC
molecule
Target
cell
Peptide
antigen
Pore
Released cytotoxic T cell
Dying target cell
1. 2.
3. lysis

36. The central role of helper T cells in humoral
and cell-mediated immune responses
Antigen-
presenting
cell
Peptide antigen
Cell-mediated
immunity
= attack on
infected cells.
Class II MHC molecule
CD4
TCR (T cell receptor)
Helper T cell
Humoral
immunity
= secretion of
antibodies by
plasma cells.
Cytotoxic T cell
Cytokines
Positive Feedback …
B cell
Bacterium
+
+ +
+

37. The killing action of cytotoxic T cells
Cytotoxic T cell
Perforin
Granzymes
TCRCD8
Class I MHC
molecule
Target
cell
Peptide
antigen
Pore
Released cytotoxic T cell
Dying target cell
1. 2.
3. lysis

38. Active Immunity
•Naturally acquired active immunity occurs when the
person is exposed to a live pathogen, develops the
disease, and becomes immune as a result of the
primary immune response.
•Artificially acquired active immunity can be induced
by a vaccine, a substance that contains the antigen.
•A vaccine stimulates a primary response against the
antigen without causing symptoms of the disease

39. Passive Immunity
•Passive memory is usually short-term, lasting between
a few days and several months.
•Newborn infants
 have had no prior exposure to
microbes and are particularly vulnerable to infection.
At birth, human babies have high levels of antibodies,
with the same range of antigens as their mother.
•This is
 passive immunity because the fetus does not
actually make any memory cells or antibodies, it only
borrows them.
•Short-term passive immunity can also be transferred
artificially from one individual to another via antibody-
rich
 serum.

41. Vaccination
•Immunization or vaccination is the deliberate induction of an
immune response.
•Immunizations are successful because they utilize the immune
system's natural specificity as well as its inducibility.
•An antigen, derived from a disease-causing organism, is
injected and it stimulates the immune system to develop
protective immunity against that organism, but the antigen
does not
 
itself 
cause the pathogenic effects of that organism.
•Most viral
 vaccines are based on live attenuated viruses, while
many bacterial vaccines are based on avarious
 components of
microorganisms, including harmless
 chemical components.

42. Feature T-cellsB-cells
May produce antibodies  
Are classed as small lymphocytes  
Develop in the thymus  
May secrete interferon  
Give passive immunity to the organism which possesses
them
  
Give active immunity to the organisms which possesses
them
  
•The following table relates to some features of T and B cells,
If a feature is correct put tick ( 3) in the box and if it is incorrect
put a cross (7) in the box.

43. The diagram below shows the T-cell immune response when the body
is infected by a foreign antigen, such as a pathogenic bacterium.
(i) Describe the role of the
macrophage in the T-cell response.
[4]
(ii) The sensitised T-cells divide
thousands of times by mitosis to
produce a cloned population of
active Tcells. Suggest how this helps
the immune response.
[2]
b. (i) Describe the activity of the killer
T-cells in the immune response.
[3]
(ii) What is the function of the memory
T-cells in the immune response?
[1]
(iii) What is the function of the helper
T-cells in the immune response?
[1]

44. Monoclonal antibodies
Identical antibodies produced to be effective against a single,
specific antigen.
•Problem with producing them – B lymphocytes that produce
antibodies don’t divide, and B lymphocytes that divide (making
plasma cells) don’t produce antibodies!
•Plasma cells are fused with cancerous cells which go on
dividing indefinitely.
•This formed a hybridoma which divides and secretes
antibodies.

45. HAT medium is
hypoxanthine
aminopterin thymidine.
Only hybridomas
survive. Myeloma and
normal cells die.

46. Using monoclonal Antibodies
•1. Pregnancy Tests
•The monoclonal antibodies are made that bind with the human
hormone human chorionic gonadotrophin (hCG), which is
produced in pregnancy.
•The antibody is attached to a dipstick.
•The dipstick is dipped into a urine sample.
•Any hCG in the urine will bind to the antibody and will be
carried up the stick with the urine.

47. •Another antibody is made which will bind with the hCG-antibody
complex.
•This is placed further up the stick and immobilised.
•As the hCG-antibody reaches the immobilised antibody it binds
and a pink colour forms. (or blue, depending on the brand)

48. To check whether the stick is working,
another chemical is attached to it that will
change colour even if there is no hGC
present.
One band: Negative, as there was no hCG.
Two bands: Positive, as some of the mouse
antibody has hCG bound to it.

49. Monoclonal antibodies in
diagnosis and treatment
Diagnosis.
Blood clots:Fibrin (protein found in blood clots) injected into a
mouse, and monoclonal antibodies against fibrin are produced
as previously discribed.
The antibodies are labelled with a radioactive chemical so that
they can be traced.

50. The monoclonal antibodies are then
injected into the patient, and bind to the
fibrin in their blood clots.
The radiation then shows the doctors
where the blood clots are.
Cancer cells can be tracked down in a
similar way to identify the location of a
tumour.

51. Treatment:
Monoclonal antibodies are made to be
bind on to cancer cells. An anti-cancer
drug is then joined to them.
These “magic-bullets” are then injected
into a patient, and the anti-cancer drug is
taken to the cancer cell by the monoclonal
antibody, and the cancer cell is destroyed.