2. antigen is recognized by helper T-cells that have a receptor that fits the
particular antigen and is activated
a. activated helper T-cell produces interleukin-2
i. interleukin-2 causes proliferation of certain cytotoxic T cells and B
cells
a. cytotoxic T-cells bind to and produce chemicals that destroy
cells that present the particular antigen
Here is an animation:
b. activated helper T-cell binds to B cells that recognize the same antigen
i. there are many parts of the antigen that can be recognized by a T
cell, called epitopes
ii. therefore, many different B cells can be activated, each
producing different antibodies against the same pathogen
a. Therefore, against the same pathogen, a number of different
antibodies can be made
b. since many different B cells produce plasma cells, each capable
of cloning itself, this is a polyclonal response
ii. B cells divide into many plasma cells
a. plasma cell produces antibody that is specific to the antigen
b. the antibodies and most of the B cells are gradually lost from
the body when they are no longer required
c. A small number of B cells remain in the body but are inactive
until the same antigen is detected
i. called memory B cells
ii. Allow a very rapid response upon infection by the same
antigen known as the secondary immune response
iii. The reason for vaccination
III. Active versus Passive Immunity
A. active immunity: immunity that results from the body producing its own
antibodies after exposure to a particular antigen
1. can be induced by vaccination with a microbe that has been treated so
that it still has antigen but is not able to cause disease
B. Passive immunity: immunity that results from antibodies that are not self-
produced but were administered to the individual
1. is short-lived protection against disease
2. newborns often have some level of passive immunity because antibodies
can cross the placenta from the mother and enter the baby's blood
3. breast-feeding prolongs passive immunity in the baby because some
antibodies from the mother can be found in her breast milk
4. can be induced by giving vaccine with antibodies
IV. Vaccination
Here is an animation about constructing vaccines:
A. goal of vaccination is to produce an immune response without disease
1. vaccine may contain pathogen that has been treated so that it is less
virulent, i.e. Less able to cause disease
a. often referred to as the attenuated pathogen
2. vaccine can also contain inactivated toxins
3. goal is to initiate “challenge and response”
a. the immune system is challenged by a pathogen and responds by
producing antibodies
i. since there are many B cells involved in producing the antibodies,
this is a polyclonal response
B. vaccine introduced into the body most commonly by injection (the dreaded
“shot”)
C. Vaccination stimulates the primary immune response, hopefully leading to the
development of the appropriate memory B cells
D. exposure to the pathogen should stimulate the secondary immune response
which is faster, stronger and more specific than the primary response
1. the pathogen should be inactivated or destroyed before the onset of
disease
Figure 1: Speed of primary versus secondary response.
E. Benefits of vaccination
1. total elimination of certain diseases
2. preventing epidemics/pandemics
3. decreased health care costs
4. preventing harmful side effects of disease
F. Possible dangers of vaccination
1. Side effects such as soreness near the injection site, low-grade fever
2. allergic reactions to some of the vaccine's ingredients
a. e.g. Some vaccines contain egg proteins, yeast proteins, antibiotics,
(leftover from the production process), human serum albumin (help
stabilize live virus), formaldehyde (eliminates the effects of bacterial
toxins and makes viruses unable to replicate), aluminum salts (help
the vaccine work better), or gelatin that may cause an allergic
reaction
3. a preservative called thimerosol contains mercury and there have been
concerns about its safety (in the US it “has been removed from or reduced
to trace amounts in vaccines for children 6 years of age and younger with
the exception of the inactivated influenza vaccine” (Iannelli, 2008))
4. possible overload of the immune system
5. IB lists possible links to autism but...
For a comprehensive list of side effects for many vaccines, try this website:
G. So...should you use vaccines?
1. Personal choice of informed individuals is the key
V. Antibiotics
A. antibiotic: a chemical that inhibits the growth of microorganisms, particularly
bacteria
1. typically work by inhibiting some aspect of bacterial metabolism
a. inhibition of cell wall synthesis
i. most common method
ii. e.g. Penicillin, vancomycin, Bacitracin
b. inhibition of protein synthesis
i. second most common method
ii. e.g. Tetracyclines, streptomycin, erythromycin, chloramphenicol
c. Alteration of cell membranes
i. e.g. Bacitracin (topical)
d. inhibition of nucleic acid synthesis
i. e.g. Rifampin, bacitracin
e. Antimetabolite activity
i. e.g. Sulfonamides
*Note that the names of antibiotics is not required for IB but included for interest; I tried to find relatively common antibiotics
V. Monoclonal Antibody Production
Here is a video about monoclonal antibody production:
Here is another address for the same animation of monoclonal antibody production:
A. monoclonal antibodies: antibodies made by clones of the same B cell
1. since each B cell makes only a specific antibody, ensures that all the
antibodies are the same
2. allows scientist to “harvest” a substantial amount of a single antibody
3. antibodies obtained from the blood are called polyclonal antibodies
B. Production of monoclonal antibodies
*Köhler and Milstein devised this technique for mice in 1975 and won a Nobel Prize
Here is an animation of monoclonal antibody production:
1. B lymphocytes, usually from mice are exposed to a particular antigen
2. activated B lymphocytes are fused with myeloma cells/bone tumour
cells/cancerous B cells that divide indefinitely
3. fused cells are called hybridomas because they are hybrids, one of the
cells used was cancerous, thus the “-oma” part of the name
C. Uses of monoclonal antibodies
1. since they are highly specific, monoclonal antibodies can be used to select
out/find a specific molecule among many others
a. diagnose illnesses such as AIDS
b. identification of blood types and tissue typing for transplant
compatibility
c. detect substances in the blood such as HCG (human chorionic
gonadotrophin) , the hormone that women produce when pregnant
Here is an animation of the home test for pregnancy: __
d. identify infections
e. Sort out different T cells
f. Distinguish between cancerous and normal cells
i. thus can be used to carry radioactive isotopes or toxic drugs to kill
tumours
g. Treatments for various illnesses
i. emergency treatment of rabies
h. purification of industrially produced interferon
i. Detection of certain markers (cardiac isozyme) the are indicative of
heart attack
VII. HIV and AIDS
Here is an animation about HIV replication:
Here is an animation about how the HIV infection cycle works:
Here is an animation of treatment of HIV:
Figure 2: How HIV infects a cell.
A. What is HIV? What is AIDS?
1. AIDS: acquired immune deficiency syndrome
2. HIV: human immunodeficiency virus
a. causes AIDS
b. a retrovirus
i. genetic material is RNA rather than DNA
c. Transmitted from human to human via blood semen, vaginal secretions
and breast milk
i. must “come in contact with a mucous membrane or damaged tissue
or be injected directly into the blood-stream (from a needle or
syringe) for transmission to possibly occur”
()
ii. HIV can also be transmitted via infected blood, infected blood
products, organs from HIV infected individuals
3. Infection by HIV
a. HIV infects host cell which is the helper T cell
i. recall: helper T cells activate B cells to become plasma cells and
also stimulate cytotoxic T cells to destroy infected cells and foreign
antigen carriers
b. HIV attaches to the helper T cell and injects its RNA and an enzyme
called reverse transcriptase into the cell
c. Reverse transcriptase uses viral RNA as a template to make DNA
d. viral DNA enters the host nucleus and attaches to the host DNA
i. host treats the viral DNA as its own and will transcribe and
translate the viral genetic material
e. Host cell will fill with viral parts which will assemble into viral particles
f. The infected cell will burst and die, releasing viral particles into the
bloodstream to infect other helper T cells
g. This is essentially the same mechanism as other viruses use however,
the important point is that the cells that are infected by this virus are
cells that would normally aid in fighting an infection
4. Consequences of HIV infection
a. eventually number of helper T cells declines
b. infected person is less able to produce antibodies
c. Immune system functioning is suppressed and opportunistic infections
such as pneumonia and Kaposi's sarcoma (a form of skin cancer) may
set in
i. individuals with normal immune systems can usually fight off these
infections
d. HIV positive: have antibodies against HIV in your blood which indicates
that the virus is in your body
e. AIDS patients are HIV positive and have a T cell count below 200 or
are HIV positive and have an opportunistic infection
f. many AIDS patients die within 2 years of the onset of symptoms but
many individuals live for years with no apparent immune complications
VIII. BLOOD CLOTTING (same as from Circulatory System package)
A. Clotting: formation of a solid mass of platelets, red blood cells and fibrin (a protein)
1. also called coagulation
2. Fibrinogen: a protein found in blood that is the precursor of fibrin
3. Prothrombin: inactive form of thrombin found in blood
a. Vitamin K is necessary for production of prothrombin
4. Serum: blood plasma without fibrinogen
B. STEPS IN BLOOD CLOTTING
1. Blood vessel is damaged
2. platelets clump at the site and partially seal the leak
3. platelets and damaged tissue release prothrombin activating factor
4. prothrombin activating factor converts prothrombin to thrombin
a. requires calcium ions (Ca2+)
5. thrombin acts as an enzyme that removes 2 short amino acid chains from each end
of a fibrinogen molecule, making them “sticky”
6. shortened fibrinogen molecules join end to end forming long threads of fibrin
7. fibrin threads tangle themselves around the platelets that are plugging the leak
8. red blood cells are trapped in the network of fibrin and give colour to the clot
9. when repair of blood vessel initiated, the enzyme plasmin destroys fibrin network
A cute video, some details are slightly different from the notes though:
C. Rewind: Thrombosis
1. thrombosis: formation of a clot in a blood vessel
a. often the result of damage to the wall of a blood vessel as in
atherosclerosis
b. other causes are outlined below:
References:
Allott and Mindorff. IB Diploma Program Biology Course Companion
Iannelli, 2008.
Mader, Sylvia. Inquiry into Life Seventh edition and Tenth edition.
This article gives detailed information on antibody structure and function including applications of monoclonal and polyclonal antibodies:
This is an interesting site as it is written for the computer sciences and outlines how the study of the immune system is relevant to computer sciences in the introduction.
Review and Practice:
1. IB Diploma Program Biology Course Companion by Allott and Mindorff: page 238 #1-7
2. A case study: Clinical Application from
Answer the six questions for homework.