lecture 4- generation of antibody diversity Flashcards Preview

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Flashcards in lecture 4- generation of antibody diversity Deck (13)
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1
Q

___ is any molecule that enhances phagocytosis by tagging it for binding to a cell surface receptor

A

opsonins

2
Q

antibodies are also strong ___ and bind ___ on phagocytes

A

opsonins
Fc receptors

3
Q

___ is the process by which bacteria are altered by opsonins so as to become more readily and more efficiently engulfed by phagocytes

A

opsonization

4
Q

What is the difference between an antibody being able to activate complement and act as an opsonin?

A

IgG can do both -different receptors- complement receptor and Fc receptor

5
Q

the human genome has how many genes?

A

~30,000

6
Q

3 types of gene segments: ___
2 types of light chains available: ___

A

V, D, J
lambda and kappa

7
Q

generation of antibody diversity is due to: (first 3)

A

1- combinational diversity
2- junctional diversity
3- somatic hypermutation

8
Q

in all cells except for developed lymphocytes, immunoglobulin DNA exists in ___ configuration
all loci are on ___

A

germline
3 different chromosomes

9
Q

after heavy chain undergoes recombination, light chain undergoes rearrangement, what happens here?

A

allelic exclusion- only one BCR expressed by a B cell

10
Q

describe the sequence of events during VDJ recombination

A

(these steps happen over and over and are irreversible)
1- synapsis: bends linear DNA, recombination signal sequences come together (synapsed) so they can be cleaved
2- cleavage: done by RAG1 / RAG2 – generates double strand breaks in DNA, form into hairpin loops
3- hairpin processing: Artemis opens hairpins at coding ends
4- joining: non-homologous end joining done by Ku70, Ku80, and DNA ligase

11
Q

describe junctional diversity

A
  • the same VDJ segment usage can generate antibodies that have different AA sequences
  • through addition of nucleotides, diversity is further increased
  • occurs at the CDR3 region, allowing greater variability than that encoded by
    gene segments
  • mediated by TdT enzyme- adds nucleotides in junctional region between gene segments
12
Q

describe the nucleotide addition in junctional diversity

A
  • P nucleotides are put in, complementary to loose uneven ends when hairpins were cleaved
  • N nucleotides are additional nucleotides added to both strands- results in differences in length of nucleotides, could potentially change reading frame (complementary)
13
Q

name 2 reversible and regulated steps for changes in antibody genes during a B cells’ life

A

1- transcription activated with coexpression of surface IgM & IgD
2- synthesis changes from membrane Ig to secreted antibody
** both reversible because RNA splicing - not changes in genomic DNA