Lecture 7: Generation of lymphocyte antigen receptor repertoire Flashcards
The TCR is composed of an ____ and ____ chain and its effector function is ____
alpha, beta
T Cell
What is the approximate immuglobin repertoire in humans?
10^11-10^15
What is the repertoire limited by at any one time?
B-cell population size and an individual’s exposure history
Antibody genes are made up of _____
segments
In mature lymphocytes, gene segments are brought together by ________, which means _______
somatic recombination; at random
The variable region of light chain is composed of 95-101 aa ___ segment and about 13 aa ___ segment
V (variable); J (joining)
The heavy chain has ___ segment in addition to V and J
D (diversity)
What is recombination signal sequence? (RSS)
unique sequences that guide the process of choosing V and J (and D) domains,
heptamer, 23 aa, nonamer
nonamer, 12 aa, heptamer
in accordance with major/minor grooves of DNA
RSS in lambda chain
V, 23RSS - - 12RSS, J
RSS in kappa chain
V, 12 RSS - - 23 RSS, J
RSS in heavy chain
V, 23 RSS – 12RSS, D, 12RSS - - 23 RSS, J
RSS binds to ____ and _____ that will ____ dsRNA
RAG1 and RAG2; cut
dsDNA breaks caused by RAG1 and 2 can be repaired by _____
NHEJ
RAG1 binds to RSS by recognizing ______ sequence
nonamer
_____ has endonuclease activity to make 2 ssDNA breaks on the ___ side of RSS
RAG2; 5’
ssDNA break repaired by ________ with complementary strand
hairpin formation
Flush dsDNA break formed at ________
the ends of the heptamers
Proteins involved in NHEJ
Ku70/Ku80/DNA/PKcs
_____ makes functional gene
DNA ligation
_______ complex opens hairpin
DNA-PK:Artemis
____ modifies hairpin by randomly adding/removing nucleotides
TdT
____ ligates DNA together
DNA ligase IV and XRCC4
What are the 4 ways to generate diversity in B cells?
Combinatorial diversity
Junctional diversity (TdT)
Random pairing of heavy/light chains
Somatic hypermutation
Combinatorial diversity is responsible for ____ combinations in B cells/antibodies and is _____ in T cells
3x10^6
higher
CDR 1 and 2 regions are encoded by ___ domain
V
CDR3 diversity results from _____ and falls at the ____ boundary
random insertions/deletions of nucleotides;
V-J (or V-D)
_____ diversity is produced at a considerable cost, as 2/3 recombinations will result in nonfunctional proteins
Junctional
What are the two classes of nucleotides incorporated?
Palindromic and non-templated (P and N)
DNA-PK and Artemis complex generate _______ by opening up hairpins
P nucleotides
TdT adds _____
N nucleotides
After the addition of about 20 N nucleotides, ____ can occur
complementary base pairing
SHM occurs via ______ of an optimal _______ with enhanced antigen binding capability
selection;
structure
SHM can produce two ______ sequences with ___ affinity for the ________ epitope
different;
high;
same
____ will force presence of nicks and repair of DNA so that different nucleotides are inserted
AID
_______ occurs via AID
SHM
AID is only present in ______
B cells
AID works by deaminating __ to ___
C -> U
What removes uracil and ribose from DNA after AID deaminates it from cytidine?
UNG (Uracil-DNA glycosylase)
APE1 (apurinic/apyrimidinic endonuclease)
alpha chain in T cell receptor
Valpha, J alpha, C alpha
Beta chain in TCR
Vbeta, Dbeta, Jbeta, Cbeta
TCR recognizes a sequence of ____ aa
9
The ____ of TCR makes contact with bound peptide and is responsible for the ____ variability
CDR3;
most
What cells does SHM occur in?
B cells only NOT T cells
In T cells CDR3 variability comes from ______
P and N nucleotides
In T cells, CDR1 and 2 variability comes from _____
germline (combinatorial)
___ variability is unique to Igs due to their effector function
Constant region
Isotype switching is guided by _______
switch regions mu
