Quiz 3 Flashcards
What 4 things make adaptive immunity different than innate?
- antigen specificity
- diversity
- memory
- non-self recognition
____ cells are involved in Humoral immunity while ___ are involved in Cell-mediated immunity
B cells – humoral
T cells – cell mediated
B cell receptors are also called ___________
immunoglobulins
What is a way B and T cells increase their diversity to antigens?
DNA chromosomal rearrangment
B and T cell receptor genes are spliced/rearranged BEFORE or AFTER transcription?
rearranged before
What is the germline configuration?
gene segment region BEFORE DNA rearrangement
What are the 4 segments for B and T cell receptor rearrangment?
- variable (V)
- diversity (D)
- joining (J)
- constant (C)
What genes go through V(D)J somatic recombination?
B and T cell receptor genes
The __________ of the enzymes involved in VDJ recombination increases diversity
imprecision
What are the 2 domains on T cell receptors?
constant
variable
What holds the alpha and beta chain together on T cell receptors?
disulfide bond
Describe the look of T cell receptors?
typically an alpha and beta chain
can be gamma and delta instead
What segments are rearranged in T cell receptors with alpha or gamma?
V
J
What segments are rearranged in T cell receptors with beta or delta?
V
D
J
_________ begin as receptors on B cells but after activation they become plasma cells and are secreted
antibodies
Describe the look of B cell receptors (antibodies)
2 heavy chains
2 light chains
The light chain on antibodies links _____ and ______ segments
V
J
The heavy chain on antibodies links _____ then ______ segments
DJ
V
each “arm” on B and T cell receptors that contain VDJ segments rearrange __________
independently of one another
What does RSS do in VDJ recombination?
recognition site for RAG to bind to DNA
What does RSS ensure?
recombination only occurs in gene segements encoding for B and T cell receptors
What are RSSs made of?
heptamer
nonamer
23 or 12 spacer
Where is RSS located relative to V segments?
downstream end
Where is RSS located relative to D segments?
flanks it
Where is RSS located relative to J segments?
upstream end
What is the 12/23 rule?
only 12RSS can combine with 23 RSS to prevent joining of incorrect segments
Where does RAG1/2 bind to RSS?
randomly
What does RAG1/2 do?
cleaves DNA at heptamer sequences of 12 RSS and 23RSS
What is a signal joint?
trashed circular DNA excised during VDJ recombination
What is a coding joint?
functional portion of DNA
What is the coding joint made of?
alpha or gamma chain and light chain
What does NHEJ do?
repair that produces the coding and signal joint
What does Artemis do?
cleaves DNA hair pin to create overhangs
What are P nucleotides?
nucleotides associated with the overhangs
What are DNA overhangs filled with and by what?
P nucleotides
NHEJ
What is a variable segemnt?
DNA formed when overhangs are filled and repaired
What does Tdt do?
removes P nucleotides and replaces them with N nucleotides (increases diversity)
What is the final resulting strand named after recombination?
coding strand
VDJ recombination involves which chains?
beta or gamma
and heavy chain
VJ recombination involves which chains?
alpha or gamma
and light chain
In VDJ recombination what is the order that segments link?
D links to J then V links to DJ
What are the 2 diversity mechanisms of VDJ recombination?
- joining of segments
- junctional flexability (splicing isnt the same every time)
What 2 mechanisms all B cells to have additional diversity?
class switching
hyper mutation
What is AID in B cells?
converts cytosine into uracil causing mutations that have to be repaired = increasing diversity
What Ig’s don’t require class switching to occur?
IgM and IgD
What B cell mechanism changes antigen binding affinity?
somatic hypermutation
What is class switching?
When B cells change from IgD or M to a different class
class switching produces an antibody with the _______ antigen specificity
same
T/F: class switching and somatic hypermutation uses AID
true
What is CDRs (complementary determining regions) in B cell affinity maturation?
location where mutations are introduced to increase diversity
What are 3 possible mechanisms of somatic hypermutation?
- DNA replication (point mutation)
- base excision repair
- mismatch repair (point mutation)
What is the cause of most antigen diversity?
VDJ recombination
HLA class I is expressed on what cells?
nucleated
HLA class II is expressed on what cells?
antigen presenting cells (B cells, macrophages, DCs)
What does HLA class I present to?
cytotoxic T cells
What does HLA class II present to?
helper T cells
What type of pathogen does HLA class I deal with?
intracellular
What type of pathogen does HLA class II deal with?
extracellular
What are the 4 domains of HLA class I
alpha 1
alpha 2
alpha 3
beta 2
Where is the binding cleft in HLA class I?
alpha 1 and 2
What chromosome is HLA genes on?
6
What is the structure of HLA class II?
heterodimer (alpha 1, alpha 2 and beta 1 and beta 2)
Where is the binding cleft located on HLA class II?
alpha 1 and beta 1
What class of HLA is more specific in what it will bind to?
class II
What is the most diverse gene cluster?
HLA
For HLA, gene variation is at the __________ level
population
______ facilitate organ transplant rejection
HLA
Loading of peptides for HLA class II occurs where?
vesicle fused with phagolysosome
Loading of peptides for HLA class I occurs where?
ER
