Lymphocyte Development (Exam 2) Flashcards
Where does lymphocyte rearrangement and maturation occur?
primary lymphoid organs
B cells rearrange and mature in the _________ and T cells in the _______.
bone marrow
thymus
What are the gene segments that randomly rearrange to form unique lymphocyte receptors?
V (variable)
D (diversity)
J (joining)
C (constant)
What two chains rearrange to form T cell receptors? B cells receptors?
T cell: beta + alpha chain
B cell: heavy + light chain
Match the order of chain rearrangement for T and B cells.
T cell: first beta, then alpha chain
B cell: first heavy, then light chain
What is different between the gene segment rearrangement in T cells between the beta chain and alpha chain?
beta chain: V, D, J, C segments
alpha chain: V, J, C (no D)
Which type of cell does its receptor rearrangement have extra attempts to make appropriate receptors before programmed for cell death if it is not selected for?
B cells
Which type of T cells are the first to develop?
gamma-delta T cells
What are the two main types of T cells?
gamma-delta
alpha-beta
Where are gamma-delta T cells located?
epithelial tissue
(T/F) Ruminants have more alpha-beta T cells than gamma-delta T cells.
False - opposite
(T/F) Gamma-delta T cells receptor gene rearrangement is not a random process unlike alpha-beta T cells.
True
Explain how gamma-delta T cells rearrangement occurs since it is not randomized.
created in “waves” where same receptors develop and go to a specific type of epithelial tissue
Fill in the missing step in alpha-beta cell development:
Stem cells –> ______ –> intermediate form for gene rearrangement.
Pro-T cells
During alpha-beta T cell development, the ______ chain is rearranged randomly and then binds to a ______ of the opposite chain.
beta
surrogate
What is the purpose of a surrogate chain in alpha-beta T cell development?
these proteins bind to take place of unrearranged chain
What is the purpose of a surrogate chain in alpha-beta T cell development?
these proteins bind to take place of the unrearranged alpha chain so beta chain can go to cell surface as a “checkpoint” before continuing
Once a full lymphocyte receptor with both chains is developed and rearranged, the cell must have __________ to become mature.
weak antigen recognition
What is meant by “checkpoints” in lymphocyte development?
“stop signs” at different steps which require a cell signal to prevent cell death and continue on in development
What is called when a cell is automatically programmed for death when it does not send an appropriate signal to survive?
death by neglect
In the first step of lymphocyte development from a “pro” to a “pre” cell, signaling molecules must be present in order to prevent cell death. Which signaling molecules are required by B and T cells?
B cells: coreceptors
T cells: CD3 (marker on cell surface)
Coreceptors that prevent cell death in developing B cells are made up of _____ and _____ molecules.
Ig(alpha) + Ig(beta)
Explain the difference between strong and weak antigen recognition. Which is selected for? Which will undergo cell death?
strong: lymphocyte receptor strongly recognizes self-antigen
weak: lymphocyte receptor weakly recognizes self-antigen
weak
strong
Strong antigen recognition undergoes (positive/negative) selection and weak antigen recognition undergoes (positive/negative).
negative
positive
What is meant by double-positive T cells? Single-positive?
double-positive: CD4 + CD8 put on developing cell so it can bind to either Class I or Class II MHC
single-positive: once MHC binds, CD8 or CD4 is downregulated depending on which it binds to
What is failure of positive selection?
T cell fails to interact successfully with MHC after it has developed a receptor and it undergoes cell death
Process of lymphocytes being positively selected, and therefore not deleted, in the primary lymphoid organ due to their ability for weak antigen recognition.
central tolerance
Process of ensuring mature single-positive lymphocytes released into the circulation have weak antigen recognition.
peripheral tolerance
How can you get both IgM and IgD antibodies co-expressed on the same cell?
VDJ rearrangement randomly couples with mu (u) or delta (d) constant regions
What is the largest contribution to antigen receptor diversity?
junctional diversity
What is junctional diversity?
removal or additional of nucleotides at junctions of V/D, D/J, or V/J segments at the time these segments are joined
promotes diversity of lymphocyte receptors
Process of VDJ rearrangement that brings together multiple gene segments that combine randomly which produce different receptor.
combinatorial diversity
What two types of nucleotides are added for junctional diversity?
P + N nucleotides
Match each characteristic to either a P or N nucleotide:
- short lengths | up to 20
- added randomly | added to VDJ junctions
P: short lengths, added to VDJ
N: up to 20, added randomly
What enzyme mediates the addition of new nucleotides to gene segments in lymphocyte development?
TdT enzyme
Where are B-1 B cells from?
fetal liver
B-1 B cells only express _____ antibody and _____ molecule.
IgM
CD5
(T/F) A B-1 B cell needs to be stimulated to secrete antibody.
False - makes antibody naturally
What is the function of IgM antibodies produced by B-1 B cells?
attack commensal bacteria that get across epithelial layer
B-1 B cell receptors bind to ______ antigens with (high/low) affinity.
carbohydrate
low
Marginal zone B cells are a type of ______ cell.
B-2 cell
Where are marginal zone B cells located?
white pulp of spleen
Function of marginal zone B cells
bloodborne antigen recognition
What antibody or antibodies do marginal zone B cells express? What else do they express?
IgM
complement receptor
What kind of antigens do marginal zone B cells recognize?
protein + carbohydrate antigens
(T/F) Marginal zone B cells require T cell help to respond to antigen.
False - do not need help
What are two types of B-2 B cells?
- follicular B cells
- marginal zone B cells
Which antibody or antibodies do follicular B cells express?
IgM + IgD (co-expression)
Where are follicular B cells located?
lymph nodes
(T/F) Follicular B cells need T cell help to respond to antigen.
True
