Lymphocyte Receptor Diversity Flashcards
What is the B cell receptor made of?
4 polypeptide chains
What are the parts of the 4 polypeptide chains in B cell receptor?
-2 shorter chains -> light chains
- 2 longer chains -> heavy chains
Where do antigens bind on B cell receptors?
areas where there are both heavy and light chains
How many antigen binding sites on B cell receptors?
2
What are the antigen binding sites referred to as?
Fab portion of receptor
What does the Fe portion of the B cell receptor contain?
only heavy chains
What does the Fe portion of the B cell receptor bind to?
- B cell membrane
- Fe receptors on other immune cells when secreted as an antibody
What does the Fe portion of B cell receptor determines?
effector function
What do light chains and heavy chains have on B cell receptors?
variable and constant regions
What does variation in antigen occur due to?
variable regions
What are constant regions of light chains on B cell receptor?
λ or κ
What are constant regions of heavy chains on B cell receptor?
one of 5 classes
What are the 5 classes of heavy chains on B cell receptor?
α, δ, ε, γ, m
What antibody is α heavy chain for?
IgA antibody (a dimer)
What antibody is δ heavy chain for?
IgD antibody
What antibody is ε heavy chain for?
IgE antibody
What antibody is γ heavy chain for?
IgG antibody
What antibody is m heavy chain for?
IgM antibody (a pentamer)
How is B cell receptor diversity generated?
- gene recombination
- gene conversion
Where does gene recombination for BCR occur?
variable regions of light and heavy chain
What genes does the variable region of light chains contain BCR?
V and J
How does gene recombination for light chains occur BCR?
1 V gene and 1 J gene are randomly selected and put together with constant region gene
What genes does the variable region of heavy chains contain BCR?
V, D, and J
How does gene recombination occur for variable regions of heavy chains BCR?
1 V gene, 1 D gene, and 1 J gene are randomly selected and put together with constant region gene
Outcome gene recombination BCR?
light chain and heavy chain are put together to form a B cell receptor specific for a unique antigen
Where does gene conversion happen BCR?
only in V gene
How does gene conversion happen BCR?
- uracil randomly inserted into V gene
- seen as an error and uracil is cut out, leave a space
- pseudogene sequences that are upstream of the V gene are inserted to fill space
- now have completely different V gene
What are the types of T cell receptors?
- α β TCRs
- γ δ TCRs
What are the majority of TCRs?
α β TCRs
What is each TCR made of?
2 polypeptide chains
What does each polypeptide chain of a TCR contain?
a variable region and a constant region
How is diversity of TCRs achieved?
gene recombination
What genes does α chain of TCR contain?
V, J, and 1 constant
How does gene recombination of α chain of TCR occur?
random selection of 1 V gene and 1 J gene, and then these genes get put with the C gene
What genes does β chain of TCR contain?
V, D, J, and 2 constant genes
How does gene recombination of β chain of TCR occur?
random selection of 1 V gene, 1 J gene, 1 D gene, and 1 constant gene, and then put together
What is unique about gene recombination of β chain TCR?
D gene is option or multiple D genes can be selected
Where does junctional diversity occur TCR?
occurs at junctions between the different genes on α and β chains
What ways does junctional diversity occur TCR?
- base insertion
- base deletion
What is base insertion TCR?
random nucleotides are inserted at junctions between V, (D), and J genes
How many nucleotides may be added between V and D genes in base insertion TCR?
5 nucleotides
How many nucleotides may be added between D and J genes in base insertion TCR?
4 nucleotides
What is base deletion TCR?
random nucleotides made be removed between genes
What does MHC stand for?
major histocompatibility complex
Where is MHC -I found?
in all nucleated cells
Where is MHC- II
professional APCs
What are the professional APCs?
- macrophages
- dendritic cells
- B cells
What does MHC-I present?
endogenous antigen
What is an endogenous antigen?
antigen comes from intracellular locations, within the cell
What can endogenous antigens be?
normal (self) or due to an infection (nonself)
What do MHC-II present?
exogenous antigen
What is an exogenous antigen?
antigen comes from extracellular locations (outside the cell)
How do MHC-I present antigen?
antigen broken into smaller pieces and these pieces can be presented on MHC-I
How do MHC-II present antigen?
antigen is phagocytized or internalized, broken into smaller pieces, and these pieces can then be presented on MHC-II
