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SFM Immunology > Adaptive Antigen Recognition > Flashcards

Adaptive Antigen Recognition Flashcards

1
Q

___ selects clones with the appropriate receptor

A

Antigen

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2
Q

How many chains does the B cell receptor have?

A

4

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3
Q

How many chains does the T cell receptor have?

A

2

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4
Q

How many antigen binding sites does a B cell have?

A

Two (Bivalent)

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5
Q

How many antigen binding sites does a T cell have?

A

One (Monovalent)

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6
Q

What antigen type(s) can bind to a B cell receptor?

A
  • Carbohydrate
  • DNA
  • Lipid
  • Protein 3D conformation
  • Macromolecule antigens
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7
Q

What antigen type(s) can bind to a T cell receptor?

A

Protein Peptides

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8
Q

What are the four chains that make-up B cell receptors?

A

IgM (x2) and IgD (x2)

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9
Q

Name of the B cell heterodimer that ensures surface expression of immunoglobulin during development and functions in signal transduction

A

Igα/Igβ

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10
Q

What is located in cytosolic signaling motifs?

A

ITAM

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11
Q

What are the two chains that make-up T cell receptors?

A

α/β chain heterodimer

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12
Q

What is the role of the CD3 complex in T cells?

A
  • Ensures the cell surface expression of the TCR
  • Where signaling occurs
  • Involved in signal transduction
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13
Q

What is CD3?

A

Complex of invariant proteins

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14
Q

What invariant protein in the CD3 complex is the major source of signal transduction?

A

CDζ (zeta)

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15
Q

___ contains many ITAMS

A

CDζ (zeta)

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16
Q

What is the first mechanism of lymphocyte receptor diversity generation?

A

Combinatorial Diversification

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17
Q

What happens during combinatorial diversification?

A

V-J or V-D-J somatic recombinations (cell chooses at random VDJ and puts it together)

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18
Q

What is the second mechanism of lymphocyte receptor diversity generation?

A

Junctional Diversity

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19
Q

What happens during junction diversity?

A

Addition of nucleotides during process of D-J or V to DJ joining

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20
Q

What cell types undergo somatic hypermutation?

A

B cells only!

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21
Q

Immunoglobulin ___ chain in B cells contains constant regions for all Ab isotopes

A

Heavy

22
Q

___ is the first isotype expressed as BCR because it is the first constant region on the gene.

A

μ (Cm), which is the isotope for IgM

23
Q

Which light chain is preferentially expressed in BCRs?

A

κ (kappa) light chain

24
Q

What are the steps in μ heavy chain production?

A

(1) Germline DNA undergoes D-J joining (somatic recombination)
(2) Rearranged DNA undergoes V-D-J joining (somatic recombination)
(3) Primary RNA transcript formed
(4) Transcription of RNA to mRNA
(5) Translation of mRNA
(6) Processing of glycosylation of protein
(7) Formation of mature polypeptide
(8) Assembly of Ig molecule

25
Q

What are the two roles of recombination signal sequences (RSS)?

A

(1) provide recognition sites for recognition enzymes that cut and rejoin DNA
(2) ensure gene segments are joined in the correct order

26
Q

What enzyme is responsible for recombing V, D, and J segments during Junction Diversity?

A

RAG-1 and RAG-2

Recombination Activating Genes

27
Q

RAG genes only made by ___

A

Lymphocytes

28
Q

What is the function of TdT (terminal deoxyribonucleotidyl transferase) in Junctional Diversity?

A

Catalyzes the random polymerization of nucleotides into DNA without the need for a template; creates random unique sequences between the coding joints and is major source of generation of diversity

29
Q

N (Non-template) Nucleotides

A

added in a non-template random manner between coding joints

30
Q

P (Palindromic) Nucleotides

A

Added to asymmetrically cleaved hairpins in a templated manner to complete unpaired nucleotides - repair enzymes

31
Q

What are the steps in μ heavy chain production?

A

(1) V-J joining of germline DNA to form rearranged DNA
(2) Transcription of rearranged DNA
(3) Processing of primary RNA transcript
(4) Translation of mRNA
(5) Processing of polypeptide
(6) Mature polypeptide assembled into Ig molecule

32
Q

What is the name of the heavy chain in TCR?

A

β Chain

33
Q

What is the name of the light chain in TCR?

A

α Chain

34
Q

What type of mutation can occur during Junctional Diversity?

A

Frameshift

35
Q

What is the name of the heavy chain in BCR?

A

μ heavy chain

36
Q

What is the second type of combinatorial diversity that occurs just before receptor is expressed on surface of cell?

A

Mix of maternal / paternal receptor chains are combined

i.e could have maternal heavy chain and paternal light chain, could have maternal heavy and light chain, etc

37
Q

What are the stages of maturation in B and T cells?

A

(1) Stem Cell
(2) Pro-B or T
(3) Pre-B or T
(4) Immature B or T
(5) Mature B or T

38
Q

Major events at Stem Cell stage

A
  • Growth factor-mediated commitment

- Proliferation

39
Q

Major events at Pro-Lymphocyte stage

A
  • Initiation of antigen receptor gene rearrangement
40
Q

Major events at Pre-Lymphocyte stage

A
  • Selection of of cells that express pre-antigen receptors
41
Q

Major events at Immature Lymphocyte stage

A
  • Selection of repertoire
42
Q

Major events at Lymphocyte subsets

A
  • Maturation of functionally distinct T and B cell subsets
43
Q

B Stem Cell

(1) Proliferation?
(2) RAG Expression?
(3) TdT Expression?
(4) Ig DNA, RNA
(5) Ig Expression
(6) Surface markers
(7) Anatomic site
(8) Response to antigen?

A

(1) Yes
(2) No
(3) No
(4) Unrecombined germline DNA
(5) None
(6) CD43+
(7) Bone marrow
(8) None

44
Q

Pro-B Cell

(1) Proliferation?
(2) RAG Expression?
(3) TdT Expression?
(4) Ig DNA, RNA
(5) Ig Expression
(6) Surface markers
(7) Anatomic site
(8) Response to antigen?

A

(1) No
(2) Yes
(3) Yes
(4) Unrecombined germline DNA
(5) None
(6) CD43+, CD19+, CD10+
(7) Bone marrow
(8) None

45
Q

Pre-B Cell

(1) Proliferation?
(2) RAG Expression?
(3) TdT Expression?
(4) Ig DNA, RNA
(5) Ig Expression
(6) Surface markers
(7) Anatomic site
(8) Response to antigen?

A

(1) Yes
(2) Yes
(3) No
(4) Recombined H chain gene (VDJ), μ mRNA
(5) Cytoplasmic μ and pre-B receptor associated μ
(aka surrogate light chain/μ chain), ALLELIC EXCLUSION
(6) B220, CD43+
(7) Bone marrow
(8) None

46
Q

Immature B Cell

(1) Proliferation?
(2) RAG Expression?
(3) TdT Expression?
(4) Ig DNA, RNA
(5) Ig Expression
(6) Surface markers
(7) Anatomic site
(8) Response to antigen?

A

(1) No
(2) No
(3) No
(4) Recombined H chain gene (VDJ), κ or λ genes (VJ)
(5) Membrane IgM
(6) CD43-
(7) Periphery
(8) Negative selection (deletion), receptor editing

47
Q

Mature, Naive B Cell

(1) Proliferation?
(2) RAG Expression?
(3) TdT Expression?
(4) Ig DNA, RNA
(5) Ig Expression
(6) Surface markers
(7) Anatomic site
(8) Response to antigen?

A

(1) No
(2) No
(3) No
(4) Alternative splicing of VDJ-C RNA (primary transcript) to form Cμ and Cδ mRNA
(5) Membrane IgM and IgD
(6) IgM^hi
(7) Periphery
(8) Activation (proliferation and differentiation)

48
Q

Receptor Editing

A
  • Occurs in developmentally arrested, immature B cell responding to self antigen
  • Re-expression of RAG proteins for additional rearrangement of light chain genes
  • If new light chain specificity does not react with self antigen, B cell will mature
  • DOES NOT occur in T cells
49
Q

What is the role of the surrogate light chain during the Pre-BCR stage?

A
  • Invariant polypeptide that ensures the heavy chain is structurally sound, folded correctly and interacting with bone marrow stromal cells
  • Signals to irreversibly inhibit rearrangement of the Ig heavy chain locus on the other chromosome - Allelic Exclusion
50
Q

Allelic Exclusion

A
  • An individual can only express one heavy chain encoded by only one of the two inherited alleles
  • Ensures that every B cell will express a single receptor, thus maintaining clonal specificity

SFM Immunology (6 decks)

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