module 03 section 02 (innate immune system) Flashcards
(79 cards)
what did Susumu Tonegawa discover?
he eludicated the mechanism for making millions of different antibody molecules with different specificities without requiring an unreasonably large number of genes
when do Igs ungergo “somatic recombination” ?
what part of the Ig does this refer to?
heavy and light chains undergo somatic recombination of genetic material during the early stages of B- and T-cell maturation
what does somatic recombination allow for?
a high degree of diversity among Igs and T-cell receptors
in addition to somatic recombination, what contributes to the diversity of Igs?
the fact that each class of Ig has a separate pool of gene segments from which the final Ig in synthesized
what are the 4 classifications of genes contained in the light chains?
- leader sequences
- variable gene segments
- joining gene segments
- constant gene segments
light chains can be classified into two groups, what are they? and what are these groups based on?
kappa, lambda - based on small differences in polypeptide sequence
the lambda light chain locus is found on what chromosome?
22
describe the lambda light chain
there are several J and C segments, each interacting with only its corresponding segment (e.g. J lambda1, 2, 3, or 4 and C lambda1, 2, 3 or 4)
the kappa light chain is found on what chromosome?
2
describe the kappa light chain
each Jk can join with the same Ck (as there is only one Ck)
describe the process of kappa light chain rearragement (5 steps)
(1) DNA rearrangement -somatic recombination: V-J joining (regulated by RAG)
(2) transcription and rna processing (splicing)
(3) mulitple adeinin nucelotides (poly-A-tails) are added to polyadenylation sites at 3’ of Ck
- mRNA exists the nucelus to bind ribosomes in the rough ER - translation
(4) L sequence pulls growing polypeptide into lumen of ER and is then cleaved off
(5) processing and glycosylation of the protein
if there wass a mutation in the RAG genes (recombinase enzymes that act on the variable regions of Ig) would Igs be made? would B-cells be made?
niether would be made
the heavy chain locus is found on what chromosome?
14
describe formation of the heavy chain
one D segment joins with a J segment, then a V segment joins with the D-J segment
describe the process of heavy chain rearrangement (6 steps)
(1) first rearrangement - somatic recombination: D-J joining (regulated by RAG)
(2) second rearrangement - somatic recombination: V-DJ joining (regulated by RAG)
(3) transcription and rna processing (splicing)
(4) mulitple adeinin nucelotides (poly-A-tails) are added to polyadenylation sites at 3’ of Cu (mu)
- mRNA exists the nucelus to bind ribosomes in the rough ER - translatio
(5) L sequence pulls growing polypeptide into lumen of ER and is then cleaved of
(6) processing and glycosylation of the protein
each unique heavy chain associates with a light chain to create a unique Ig, true or false?
true
the variable regions are the:
exons
how many variable heavy chain regions have we idenitifed?
100-200
how many diversity (D) heavy chain regions have we identified?
50
how many joining heavy chain regions have we identified?
6
recap: how many constant gene segments are there in the kappa light chain ?
1
recap: what is unique about the J lambda 4 gene?
it is a pseudogene, or a non-functional gene
recap: what gives rise to antibody specificity (peritope)?
the V-DJ (heavy) and the V-J (light) regions
how do we make different classes of antibodies with the same antigenic specificity?
class switch recombination - type of gene rearrangement where the constant gene regions in the Ig heavy chain switch from being one class to another (e.g. go from IgM to IgG)
