16 Immunology II (Acquired Immunity) Flashcards
3 lines of defense against pathogens?
- Surface entry barriers (1st line)
- Internal chemical and cellular barriers (2nd line)
- Acquired (aka specific, adaptive) immunity (3rd line)
Acquired immune sys is characterized by discrimination. What does this mean?
- It’s able to distinguish foreign from “self” molecules
2. can differentiate b/w two similar foreign molecules
Acquired immune sys is characterized by diversity. What does this mean?
It can recognize ALL possible foreign molecules
Acquired immune sys is characterized by memory. What does this mean?
It can REMEMBER a foreign molecule if it was previously encountered
Two components of acquired immunity?
- Humoral immunity
2. Cell-mediated immunity
What’s humoral immunity?
Production of antibodies by B-cells in response to antigens
What’s cell-mediated immunity?
Activation of T-cells for the ctrl of “intracellular” microbes
In humoral immunity, what is an antigen?
Any substance that stimulates the B-cells to make ANTIBODIES
In humoral immunity, what is an antibody?
Proteins made by B-cells which’re able to specifically recognize and bind to only that antigen
What occurs if an antigen is too large?
Only a small portion of the antigen (“epitope”) is able to stimulate antibody production
T or F: A single bacterial cell will contain only ONE epitope.
F
A single bacterial cell will contain many different epitopes
Structure of antibody?
- Four polypeptide chains
2. Two “ends”
What’re the two ends of an antibody?
- One end = constant end > same structure in all immunoglobulin molecules
- other end = variable > differs in structure b/w immunoglobulin molecules
What end specifically recognizes and binds a unique antigen?
The VARIABLE end
T or F: One antibody can bind two different types of antigens.
F
Both antigens must be the SAME
What is antibody specificity?
Ea. antibody specifically recognizes its own complementary antigen and shouldn’t “cross-react” w/ a diff antigen
What is antibody diversity?
A specific antibody can be made for EVERY diff antigen
What cell produces antibodies?
B-cells
How does the body make so many diff antibodies?
Humans carry a complete collection of MANY diff B-cells, ea. of which is able to recognize only one specific antigen
Outline the steps of B-cell differentiation when it encounters an antigen?
- Antigen is recognized by, and binds to, its specific B-cell
- Binding of antigen triggers the B-cell to divide and differentiate into MEMORY cells and PLASMA cells
- Plasma cells make antibodies
- Memory cells circulate in the blood and rapidly respond to the same antigen should it enter the body again
What theory describes why we don’t have B-cells that make antibodies against OUR OWN antigens?
The Clonal Deletion Theory (“Self-tolerance”)
Describe the Clonal Deletion Theory.
- During embryonic development, B-cells against our own antigens are produced
- When a developing B-cell binds to self-antigen, it gets destroyed
- Only B-cells carrying receptors for non-self antigens are RELEASED from the bone marrow and enter the blood
List the 5 types of antibodies:
- IgG
- IgA
- IgM
- IgE
- IgD
This antibody is found in secretions (breast milk, mucus, saliva, etc.)
IgA
This antibody forms large complexes with antigen which are easily cleared
IgM
This antibody is the main antibody found in circulation (80% of total antibody)
IgG
This antibody is involved in development of allergies
IgE
The fn of this antibody is unclear (may help regulate the immune sys)
IgD
This antibody blocks attachment of microbes to mucosal tissue surfaces
IgA
This antibody is able to cross the placenta and therefore protect the fetus)
IgG
Which antibodies are produced during a first-time exposure? How long does it take for them to first appear?
IgM first, the IgG.
It takes 3-6 days for igM to first appear