Biology 120
The Immune System
R. Irwin
The immune system: various leukocytes, immunoglobulins (antibodies)
Proteins involved in the immune response: immunoglobulins (antibodies)
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immunoglobulins (antibodies): proteins that recognize and bind to
specific foreign substance
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antigens: foreign substances to which antibodies bind
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structure of an immunoglobulin (antibody) molecule:
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2 light chains and 2 heavy chains
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variable and constant regions of both kinds of chain produced by genetic
"splicing"
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the binding sites between variable regions of heavy, light chains
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result: we produce a wide diversity of immunglobulins (antibodies); each
could bind a specific disease, so they can be defenses against a wide diversity
of diseases
Some of the cells that fight pathogens during the immune reponse:
| Cell type |
Structure, function |
| macrophage |
|
| b-lymphocyte |
|
| cytotoxic t-lymphocyte |
|
| helper t-lymphocyte |
|
Memory:
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b, t-lymphocytes that fight a disease retained in body after disease; if
re-infected, kill off disease before it causes any harm
Application of understanding of the immune system:
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immune function of breastfeeding (SEE NEWMAN PAPER)
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vaccines
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AIDS (HIV infection)
Understanding, preventing, and treating AIDS:
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immunosupression
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helper t-cells: killed by HIV
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macrophages: can be infected with HIV, not killed; reservoir of HIV
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resulting vulnerability to other diseases: example: Pneumocystis
pneumonia
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transmission: contact with body fluids (sexual contact, contact with blood)
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prevention: precautions by health-care workers to avoid contact with blood;
sexual abstinence; latex condoms
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treatment: drugs to slow HIV replication
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HIV: a retrovirus; requires functions not normally found in our cells:
reverse transcription, some protein processing
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treatments: "cocktail" of different drugs that affect different functions
of HIV
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rapid mutation: traditional vaccines donít work; rapid evolution
of resistance to treatments
QUESTIONS
1. Name four major cell types of the immune system. State
what each does.
2. Where (in what part of an antibody) do antibodies bind antigens?
3. Where (in what part of an antibody) would an antibody against
rabies and an antibody against measles be similar? Where would they
differ?
4. What process, unique to immune system cells, results in the
diversity of antibodies?
5. What is meant by a humoral immune response? What is
meant by a cell-mediated immune response? Why is it necessary for
us to have both kinds of response? Which kinds of white blood cell are
involved in both? Which kind are involved specifically in the response
to pathogens in body fluids (outside of cells)? Which kind are involved
specifically in the cell-mediated response?
6. State the type of white blood cell (leukocyte) that performs
each of the following function: (a) destroy virus-infected cells
(b) produce antibodies that circulate in the blood stream (c) become
"memory" cells, resulting in future immunity to a disease after it is cured
(d) present pieces of pathogens to other immune cells for possible recognition
(e) increase production of b- and cytotoxic t-cells that can attack a specific
disease
7. A molecule of non-self that causes an immune response to occur
is called a(n) ___________.
8. Which cells of the immune system are infected by HIV?
Which of these cells are killed by HIV? Which are not killed by HIV?
What are the functions of the cells killed by HIV, and how does the fact
that they are killed affect the immune system?
9. HIV is known to mutate rapidly. As a result,
a. it is hard to develop vaccines against HIV
b. vaccine development should be easy, so it is not clear why
people have been unable to do it yet
c. HIV is likely to evolve resistance to treatments quickly
d. both a and c
e. both b and c
10. Does HIV, directly, kill people? If so, how? If not,
what kills people with AIDS?
11. Pneumocystis pneumonia
a. is common in people with AIDS and without AIDS, but is treatable
in people without AIDS
b. is rare in people without AIDS but is a main cause of death
in people with AIDS
c. is common in people without AIDS, but rare in people with
AIDS
12. How is HIV transmitted from person to person?
13. What can you do to prevent becoming infected with HIV?
14. Some combination treatments of AIDS have resulted in no detectable
HIV in treated people. Does this mean these people are cured?
Why is it unlikely for a complete cure to result from such treatments?
What is another major problem with these treatments?
15. Suppose your body has mounted a successful immune response
against the flu. Do the same individual cells and proteins that got
rid of the flu also fight off the common cold that your roommate has and
is exposing you to? Why/why not? Do the same individual cells
and proteins that got rid of your flu help you avoid getting the flu of
the same strain? Why/why not?
HOMEWORK QUESTIONS ON NEWMAN PAPER
1. Secretory IgA molecules from breast milk bind microorganisms and
keep them away from the baby's tissues. What are three ways in which
secretory IgA molecules are particularly helpful to the infant that go
beyond their ability to bind microorganisms? Make it clear how each
of these is beneficial to the infant.
2. Breast milk has other factors, in addition to immunoglobulins (antibodies,)
that help babies fight off infection. Two of these are lactoferrin
and bifidus factor. Explain what lactoferrin and bifidus factor are
by stating what each does, and why the action of each helps a baby fight
infection.