Imm 4 - B Cells And Antibodies Flashcards
What are the 2 cytokines that the helper T cells produced in order to stimulate B cells?
IL-4. IL-5.
What are 8 surface markers that B cells have?
CD19. CD20. CD21. IgM. IgD. MHCII. B7 protein. CD40.
What two surface markers does NK Cells have?
CD56. CD16.
What is Antiboyd-dependent cell mediated cytotoxicity (ADCC)?
When NK cells bind to the constant region of immunoglobulins with the surface marker CD16 they have and kill the antibody-coated infected cells.
What 4 surface markers does macrophages have?
CD14. MHC II. B7 protein. CD40. All nucleated cells have MHC I.
What is the structure of an Antibody (Ab)?
It has 2 heavy chain regions and 2 light chain regions. At the very tip of each chain, it has hypervariable region on the amino portion. The Ab is held together by disulfide bonds. They have two different functional regions: the Fab region and Fc region.
What does the Fab region of an Ab do?
It is the Antigen binding fragment (which includes the variable region on the amino terminal end of the Ab) it is what determines the idiotype (the unique antigen) to which that Ab can combine.
What does the Fc region of an Ab do?
The constant region, found in the carboxyl terminal of the Ab, and only includes the heavy chains. This is the only region of the Ab that can bind to complements. This is the portion of the Ab that is recognized by the CD16 on NK cells. It is the region that determines the Isotype of the Ab (whether its IgG or IgM or IgA).
Which portion of the Ab determines the idiotype? The Isotype?
The idiotype is determined by the Fab region. The isotype is determined by the Fc region.
What are the five different types of heavy chains that determine the isotype of an Ab?
Mu (IgM). Delta (IgD). Gamma (IgG). Alpha (IgA). Epsilon (IgE).
What are the two different types of light chains in an Ab?
Lambda. Kappa. No functional difference b/w the two.
What is the normal ratio of kappa to lambda light chains in Ab?
About 2:1.
What do Antibodies do?
They bind to antigens. Can neutralize and/or opsonize pathogen. Activate complement.
What is V(D)J recombination?
Rearrangements of the DNA segments named variable (V), diversity (D), and joining (J) compose the coding region for each specific antigen receptor on B and T cells. This explains the Ab variability and the variability of antigen specificity in T cells.
Describe the process of V(D)J recombination.
The rearrangement process begins w/ breaks in the dsDNA at Recombination Signal Sequences (RSSs) that flank the V, D, and J coding regions. V(D)J recombination is initiated by the recombination activating gene complex (RAG-1 and RAG-2; these proteins recognize the RSSs).
What happens if there is a mutation in either of the RAG genes in V(D)J recombination?
Causes inability to initiate V(D)J rearrangements and an arrest of B and T cell development.
What is the main circulating immunoglobulin?
IgG, which is part of the delayed immune response.
What does IgG do?
Fixes complement. Cross the placenta. Opsonizes bacteria. Neutralizes viruses and bacterial toxins.
What is the half-life of IgG?
About 21 days.
What is the primary Ab that is secreted by the MALT?
IgA.
How is the IgA in the circulation different from secretory IgA?
IgA in circulation exists as monomer. IgA in secretions is a dimer (constant regions are linked from end to end).
How does secretory IgA goes into lumen of the gut?
Passes thru epithelium by a process called transcytosis. While passing thru the cell, it picks up a glycopeptide called secretory component, that wraps around the IgA (like a suite of armor), protecting it from gastric acid or other harsh environments.
What does IgE do?
Mediates immunity to parasites by activating eosinophils. It can also combine to specific receptors found in Mast cells and basophils leading to type I hypersensitivity reactions.
What are the four circulating Ab?
IgA. IgG. IgE. IgM.
