Chapter 17- Part 2: Specific Defenses of the Host Flashcards
Difference between an antigen and an epitope:
- Antigen: (antibody generator). They stimulate an immune response to produce antibodies.
- Epitope: small regions of the antigen, that are binding sites for antibodies (antigenic determinant)
How many different epitopes does a single B or T cell recognize?
Only one epitope ever
When is antigen specificity set?
Set randomly and forever during lymphocyte development.
What is a naïve lymphocyte?
Fully functional lymphocyte that has not been activated.
What is an activated B cell called, and what does an activated B cell do?
Plasma cell. Secretes antibodies in response to an antigen, or create memory cells; cell dies after a few weeks.
Explain clonal expansion:
(replication) Each newly activated lymphocyte (parent cell) will rapidly reproduce daughter cells that share specificity of the same antigen (about 1k copies of itself, this takes 18-36 hrs).
What are the major delays before the adaptive immune system is fully active?
- Epitope match
- Clonal expansion
What does a T cell use for its specific receptor?
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-TCR
What does a B cell use for its specific receptor?
Surface bound immunoglobulin (slg)
How many different B cell and T cell specificities can be generated?
-T cell: 10^18
-B cell= 10^15
How is a naïve B cell activated?
B cells bind to an antigen using Slg (surface bound antibody). Need hormonal help (cytokines) to become fully activated:
What does the B cell do with the antigen, after the antigen binds to slg Surface bound immunoglobulin?
CD4+ 2 (TH2 cells) then bind to this antigen and secrete cytokines that activate B cells.
What is the CD designation for T-independent B cells?
CD5+ intraperitoneal B cells
What type of antigens are targeted by this new subpopulation of B cells?
Repeating polysaccharide antigens. Can activate without hormonal help (CD4)
What is the full name of the protein that allows for T cell activation?
MHC l= Major Histocompatibility Complex l
What MHC type do Antigen presenting cell use to display an antigen?
MHC II
How are CD8+ T cells activated?
Are activated by an antigen being presented by MHC I
What happens to the cell that activates a CD8+ T cell?
Correct epitope match causes T cell to kill the cell displaying the proper epitope.
How are CD4+ T cells activated?
Antigen presenting cells present antigen using MHC II
What is immunological memory?
A second exposure to the same antigen results in a more rapidly and effective immune response.
What are some of the mechanisms that contribute to the development of memory?
it can “store” information about a stimulus and can mount an effective response when the stimulus is encountered again.
Exact mechanism of memory is still unknown; memory cells formed can survive for years
Know the basic structure of an individual antibody molecule
- Secreted from plasma cells
- Y-shaped protein
- Composed of 4 polypeptide chains
- Top of antibody contains two variable regions
- The bottom stem is called the constant region
What are the five different classes of antibody?
- IgA: found in body secretions as dimers.
-IgD: Found on surface of maturing and naive B cells
- IgE: Rarest. Associated w/allergies/ stimulates mast cells.
- IgG: Most common. In blood plasma.
-IgM: Common class for slg. Can class switch to IgA,E or G later.
Which antibody crossed the placenta?
- IgG: Able to cross placenta into unborn fetus.
