Antigen Recognition and Receptor Diversification Flashcards
_____ cells differentiate into plasma cells to produce antibodies
B cells
Specificity for individual pathogens is achieved through _____ on lymphocyte surfaces
- Antigen receptors
- Antibody (BCR)
- T cell receptor (TCR)
Heavy and light chains of antibodies are held together by interchain ______ bonds
Dilsulfide
What is the funciton of the hinge region of antibodies?
Allows antibody to bind with both arms to many different arrangements of antigens on the surfaces of pathogens
What is the difference between the Fab and Fc regions of antibodies?
- Fab: fragment antigen binding; 2 identical fragments that bind antigen
- Fc: fragment crystallizable; 1 fragment responsible for destroying or clearing antigens from our bodies (effector functions)
What protease digests antibodies into Fab and Fc fragments?
Papain
How many complementary determining regions (CDRs) are there on an antibody?
3 on each heavy and light chain
Class of antibody is determined by the constant region of the _____ chain.
Heavy
What is the difference between kappa and lambda light chains?
Unknown functional difference
What is the difference between an antigen and an epitope?
- Antigen: a substance that serves as a target for antibodies
- Epitope: the region on an antigen to which the antibody binds
Antigenic determinants (epitopes) are usually _____ amino acids long
7-15
What is the difference between affinity and avidity?
- Affinity: the ability of an antibody to bind an antigen
- Avidity: sum of individual affinity
Diversity of antibodies is concentrated in what gene?
CDR3
________ of gene segments creates enormous diversity in the antigen-binding sites of immunoglobulins
Random recombination
B-cell receptors (BCRs) present on naive B-cells are composed of _____
Membrane-bound IgM and IgD
______ trigger signal transduction on B-cells to start differentiating into plasma cells.
Igα and Igβ
What is somatic hypermutation?
Targeted introduciton of point mutations into V regions of the H and L chains, leadinging to increased antibody affinity
What enzyme carries out somatic hypermutation? What is its function?
Activation-induced Cytidine Deaminase (AID)
Deaminates C → U
What is isotype switching?
Immunoglobulins changing class via changes in the constant region
Which classes of antibodies are always made first and together? Which are made downstream?
- IgM and IgD made first
- IgE, IgG, and IgA made downstream
- Monomer on B-cell (BCR)
- Pentamer in serum
- Neutralization of pathogen/toxic
IgM
- Monomer in serum, dimer in secretions
- More of this Ig than any other in the body
- Major form of immunity at mucosal surfaces
IgA
- 4 subclasses
- Longest ½ of any Ig (passive immunization)
- Neutralization and opsonization
- Can cross lacenta
IgG
- Monomer
- Binds to basophil via Fc region
- Participates in immunity in the respiratory tract
IgD
- Monomer
- Binds to mast cells via the Fc region
- Provides immunity against parasitic infections
- Least abundant in serum
IgE
