Antibody genetics Flashcards

1
Q

VDJ recombination

A

-this is a mechanism by which lymphocytes create billions of unique antigen-specific receptors (BCR and TCR) from a relatively small set of genes

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2
Q

VDJ is mediated by

A

RAG-1 and RAG-2

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3
Q

Light chain variable regions is composed of

A

-V and J region

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4
Q

heavy chain variable region composition

A
  • composed of V,D, and J

- not all loci have D’s

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5
Q

what is the process that makes it so we can have so many combinations of V,D, and J
-this is the initial step

A
  • rearrangement of the many different genes that we have for V,D, and J regions
  • these genes are mixed and matched then set together for transcription
  • this is a RAG-1 and 2 dependent process and they are only expressed in B and T cells
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6
Q

what do naive B cells express

A
  • IgM and IgD simultaneously by alternative RNA splicing
  • both of these antibodies are specific to the same antigen
  • initially the antibody transcript has both classes of within the transcript but then one is removed via alternative splicing
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7
Q

degrees of generation of antibody diversity

  • germline
  • combinatorial
  • junctional
  • somatic hypermutation
A
  • germline: the V,D, and J genes that you inherit from your parents
  • combinatorial: the way we combine our V,D and J genes during DNA rearrangement
  • junctional: imprecise joining via TdT (terminal deoxyribonucleotidyl transferase_
  • somatic hypermutation: this is following antigen activation as increases the affinity of the anitbody to the epitope
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8
Q

somatic hypermutation

A

-this increases the affinity of antibodies to epitopes following antigen activation

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9
Q

complete deficiency in RAG 1 or 2

A

results in the absence of both B and T cells and a complete loss of adaptive immunity

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10
Q

class switch recombination

A
  • this explains how you can take a given VDJ and change its class without changing the specificity
  • after selection
  • VDJ gets cut and paste in front of one of the constant regions
  • plasma and memory B cells will be expressing different classes of Ig than naive B cells
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11
Q
class switch recombination and somatic hypermutation
-what cells and where
A

are B cell specific mechanisms that occur during clonal expansion and selection of antigen activated B cells
-both occur in the germinal centers of the secondary lymph nodes

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12
Q

activation induced cytidine deaminas

A
  • found to mediate both CSR and SHM
  • a defect in this enzyme results in high IgM levels and very limited class switching to IgG, A, and E, and limited production of high affinity antibodies
  • def represents one form of hyper IgM syndrome
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13
Q

function of class switch recombination

A
  • diversifies the anitbody effector function

- makes it so the antibody can target many different pathogens in different parts of the body

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