MCMP 422 Exam 2 (Chapters 5-10) Flashcards
Describe the structure of TCR
Has an antigen binding site
Has both constant and variable regions
Membrane bound
Two polypeptide chains
True or False: All TCRs on a SINGLE cell are the SAME
True
Does each cell express the same TCR or are they different?
They are different
Describe the TCR binding site
6 CDR loops (CDR1) - 3 for each chain
One binding site
Two polypeptide chains
Binds to MHC peptide complex
What is the C alpha region of TCR similar to?
A light chain
What is a C beta chain similar to?
A heavy chain
Are TCRs capable of rearrangement following antigen engagement
No, because there is no somatic hypermutation or isotype switching
What are the two classes of TCR
alpha beta and gamma delta
In what ways does TCR differ from BCR?
Has a single binding site for each TCR
Doesn’t rearrange after antigen engagement
ONLY used for recognition, not an effector molecule
Where do T cells initially develop
Thymus
Do both B cells and T cells display pre-antigen diversity
Yes
Do both B cells and T cells display post-antigen diversity
No, only B cells do
Where do B cells initially develop
Bone marrow
Where does TCR rearrangement occur
In the thymus
What does the rearranged TCR gene lead to
A functional peptide chain that consists of a leader peptide region AND a correctly assembled V, C, and membrane region
What are RAG proteins?
Enzymes that perform recombination
What are RAG proteins specific to?
Adaptive immunity (i.e they utilize B and T cells)
What are transposons?
Transposons are present in viruses (typically as DNA sequence fragments) capable of undergoing transposition (an occurrence that allows viruses to integrate into the genome)
Are transposons related to RAG proteins?
Possibly… due to the fact that the have vertebrate ancestry
What is the CD3 complex
A multimeric protein complex that helps activate cytotoxic T cells and T helper cells
How many polypeptide chains does the CD3 complex have? What are their names?
4; epsilon, delta, gamma, zeta
What is the function of the zeta chain in CD3
Helps transport TCR to cell surface
Helps with signal transduction (moving signal from outside of cell to inside of cell)
What part of the TCR receptor complex is responsible for antigen recogniton
the alpha and beta chains (TCR components)
What is severe combined immunodeficiency disease (SCID)
an immunodeficiency disease caused the complete loss of RAG, which causes a disturbance in T and B cell production
Why does Omenn Syndrome occur?
RAG protein has an 80% activity reduction and has low T cell counts and NO B cells
What do alpha and beta T cells do?
Recognize MHC peptide
What do gamma and delta T cells do?
Recognize a wide variety of peptides
How does a T cell develop into an alpha beta T cell vs a gamma delta T cell
a chain locus is rearranged and only one part of the chain is made so only the alpha or the delta chain is made
What T cell variation is more common?
alpha/beta
In what area of the body do gamma/delta TCRs predominate
epithelial tissue
How does antigen processing and presentation occur?
Antigen is broken up and brought up to the surface of the MHC protein complex
What is an antigen presenting cell (APC)
cell with surface MHC peptide
What are professional APCs
super presenters that are leukocytes
After antigen recognition, what do T cells do?
Help other cells (such as CD4 T helper cells)
Kill other cells (CD8 CTL)
What does CD4 TH1 cause?
changes to a macrophage
What does CD4 TH2 cause
changes to a B cell or dendritic cell
What do CD4 and CD8 bind to and what do they act as?
MHC I and MHC II; act as co-receptors
Describe MHC I and MHC II
Proteins that play a pivotal role in presenting peptides on cell surface to be recognized by T cells
