Lecture 2 - Antibody Structure and Properties Flashcards
Which PRR on macrophages and dentridic cells recognize lipopolysaccharides (LPS)?
TLR-4. He said memorize this.
Define “polyclonal response.”
When many (100s-1000s) different B cells and antigens recognize different epitopes “shapes” on the same antigen.
What is the mechanism of multiple myeloma?
When one plasma cell becomes neoplastic (loses growth control) and makes TONS of the same antibody.
How does plasma cell neoplasticity result in monoclonal antibody (mAb)?
The neoplastic plasma cell hones in on bone marrow and crowds out normal stem cells.
How is monoclonal antibody diagnosed?
Loss of heterogeneity of the gamma-globulin region with a monoclonal spike in serum protein.
How many antigen binding sites are on one antibody?
Two
On which end of the antibody chains is the variable region located?
The N-terminus
What does the Fab consist of?
The antigen-binding fragment consists of the N-terminal end of the heavy chain and the entire light chain.
What are complimentarity-determining regions (CDRs)?
Hypervariable regions within the variable regions of antibody Fabs. These bind the epitopes.
How many different classes and subclasses of Igs are there? What determines them (Fc or Fab)?
Determined by Fc, there are 5 classes: IgM, IgD, IgG, IgA, IgE.
There are 9 subclasses: IgG1 IgG2 IgG3 IgG4 IgA1 IgA2 IgM IgD IgE
Which two Ig classes can be found as polymers?
Pentameric IgM and Dimeric IgA
What protein links the polymeric Igs together? What cells synthesize these proteins?
J chains are synthesized by plasma cells.
Can a plasma cell make both monomeric and dimeric IgA?
Yeah. Note that plasma cells that make IgM will ONLY make pentameric IgM.
What are BCRs?
B cell membrane Igs
What class of Igs are found on naive B cells?
IgM and IgD
What class of Igs are found on memory B cells?
IgG, IgA, or IgE.
Name the four antibody effector functions.
- Neutralization
- Opsonization
- Antibody-dependent cellular cytotoxicity (ADCC)
- Mast cell activation
Describe neutralization of a virus or toxin by antibody.
Free Igs attach to the invader to block its function (eg. block its ability to bind to a host cell).
Describe opsonization. Name the Ig isotype.
Free IgGs attach to invaders. Then, phagocytic cells’ (macrophages or neutrophils) IgG Fc receptors bind to the Fc fragments of the invader-bound IgGs, which signal to the phagocytes to eat.
Describe antibody-dependent cellular cytotoxicity (ADCC). Name the Ig isotype.
Free IgGs bind to tumor cells or virally infected cells. FcRs on natrual killer (NK) cells bind to the IgGs on the infected cells and induce apoptosis.
What Ig class is involved in opsonization?
IgG
Describe mast cell activation. Which Ig class is involved?
Mast cells have FcE receptors with high affinity for IgE, and bind free IgE. When the IgEs on mast cells bind to antigens (usually from parasitic worms) cross-linking of the IgE occurs, which triggers degranulation of the mast cell.
What classes of antibody are found in the blood?
Monomeric IgA
IgG
Pentameric IgM
What classes of antibody are found in the tissue fluids?
Monomeric IgA
IgG
