lecture 4- generation of antibody diversity

Question 1

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

Answer 1

opsonins

Question 2

antibodies are also strong ___ and bind ___ on phagocytes

Answer 2

opsonins
Fc receptors

Question 3

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

Answer 3

opsonization

Question 4

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

Answer 4

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

Question 5

the human genome has how many genes?

Answer 5

~30,000

Question 6

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

Answer 6

V, D, J
lambda and kappa

Question 7

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

Answer 7

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

Question 8

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

Answer 8

germline
3 different chromosomes

Question 9

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

Answer 9

allelic exclusion- only one BCR expressed by a B cell

Question 10

describe the sequence of events during VDJ recombination

Answer 10

(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

Question 11

describe junctional diversity

Answer 11

• 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

Question 12

describe the nucleotide addition in junctional diversity

Answer 12

• 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)

Question 13

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

Answer 13

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