L7 Immunogenetics - Hudig Flashcards
When stimulated with IL2, which B cells divide?
only the ones specific for the stimulating ag
Do TCRs and Ig chains follow the one gene one protein rule>?
no
How are TCR and Ab receptors encoded?
variable cassette regions
Where does the Ag bind on the TCR?
variable region, made of variable light (VL) and variable heavy (VH)
What holds the chains together?
disulfide bonds
What loci contain the D minigene? (3)
Ig H, TCR beta/delta
What are the only two regions of the minigenes that undergo somatic mutation?
IgL and H variable regions
How many cassettes of minigenes does each locus have?
2-3
What are the 7 variable region genes?
V (insert below letter) alpha beta delta gamma lambda kappa Heavy
which V genes encode B cells?
Vheavy
V lambda Ig L
V kappa Ig L
Which V genese encode T cells
Valpha
Vbeta
Vdelta
Vgamma
What two enzymes are essential for T and B cell receptor formation?
RAG1 and RAG2
Complete loss of RAG1/2 results in complete loss of T and B cells resulting in (blank)
SCID
Tumors that express RAG1/2 are derived from early developmental stages of (blank)
lymphocytes
Tumors that express TdT are derived from early developmental stages of (blank)
lymphocytes
In T and B cells, is the somatic DNA for Ag receptors the same as the germline DNA?
no
Does germline rearrangement involve somatic mutation?
No, the DNA is rearranged/spliced WITHOUT mutation
What is the result of germline rearrangement?
The various mature B cells have different DNAs for Ig, different receptors and will make different antibodies.
What enzymes are necessary for DNA breaking and rejoining within the minicassettes?
RAG1/2
(blank) fills in a “wild card” nucleotide at the rejoining sections between minicassette selections
TdT (terminal deoxynucleotide tranferase)
What are the 4 subunits that make up a heavy Ig chain and what enzyme fills in the gaps?
Vh Dh Jh Ch filled in by TdT
Describe the process of germline rearrangement?
- Splice D and J together
- Splice V and DJ together
- VDJ used as primary RNA transcript
- RNA processing removes extra intron AND EXON sequences to form mRNA
What are the extra exon sequences removed in germline rearrangement?
alternate forms of V/D/J
How many cassettes does the light chain use?
2; VJ
How many cassettes does the heavy chain use?
3; VDJ
Does TdT cause mutations of the original DNA sequence?
No technically, it is creating NEW sequences by filling in the gaps around the original sequence
Are the RAGs and TdT needed at each splicing step?
yes
How many splicing steps are there in the rearrangement>?
2
Do TCRs have hypermutation regions?
no, only Ig
When does hypermutation occurr?
After minigene rearrangement
In what gene region does hypermutation occur?
CDR region
Somatic mutation occurs (the first/each) time an antigen is encountered.
Each time
Explain how Ag reexposure causes B cell evolution?
Ag selects for B cells with highest affinity; so Ag boosters increase Ag affinity
“Cold spots” for DNA mutation likely encode what gene?
constant regions
Is Ab specificity retained after isotype switching of B cells?
yes
What cell type is needed to aid in the switching of B celsl?
T helper
Is the VDJ region changed during an isotype switch?
nope
Th2 releases what cytokine and induces what Ig isotype?
IL4, IgE, inhibits IgG3
TH1 releases what cytokine and induces what Ig isotype?
IgG3, inhibits IgE
TGF-beta induces what Isotype?
IgG2 and IgA
IL5 induces what isotype?
IgA
What DNA region is deleted to result in class switching?
Heavy chain constant regions
A preparation of identical antibodies, all with the same L and same H chains, derived from one (blank).
initial immune B cell
Can monoclonal abs be cross-reactive>?
yes, when epitopes are similar, such as in the case in conserved regions of viruses
hybridomas contain the chromosomes of what two cells?
tumor cell and immune B cell
Explain the process of creating a humanized Ab?
- Make mouse anti-human antibody
- Splice out the CDR region from the mouse Ig and plug it onto the end of a human Ig
- Replace the intervening sequences between the CDR regions on the mouse bit you stuck onto the human Ig with human intervening sequences, so EVERYTHING except the specific CDR regions is totally human—no more reactivity and totally safe!
what is the name for a chimeric mouse anti-human Ab?
ximab
what is the name for a fully humanized Mab?
zumab
Are human Mabs the same as humanIZED Mabs?
no!
