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SFM - Biochem - Quiz 2 > (DSA8) Antigens and Antibodies > Flashcards

(DSA8) Antigens and Antibodies Flashcards

1
Q

Differentaite between antigens, immunogens, and tolerogens.

DSA8(Ag) S4

A

Antigen:

-a molecule or protion of a molecule that is recognized by the immune system

Immunogen:

-Ag that generates and immune response

Tolerogen:

-Ag that induces immunologic tolerance

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2
Q

Differentiate between endogenous and exogenous Ags.

DSA8(Ag) S5

A

Endogenous:

-antigens generated by the body or intracellular pathogens

Exogenous:

-outside antigens that have entered the the body

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3
Q

What are epitopes and what are the types of determinents?

DSA8(Ag) S6

A

Portion of an Ag that binds with Abs, BCRs, or TCRs

Conformational determinant:

  • epitope found only on antigen when in native conformation
  • denaturing results in loss of epitope

Liner determinant:

  • epitope consists of continuous portion of Ag
  • epitope may or may not be exposed in native conformation

Neoantigenic determinant:

-epitope generated only following selective proteolysis

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4
Q

What is the difference between T-dependent Ags and T-independent Ags?

DSA8 (Ag) S7

A

T-dependent:

  • requires Th2 costimulation to illicit Ab prodution and isotype switching
  • protein Ag
  • produces IgG, IgA, and IgE

T-independent:

  • does not require Th2 constimulation to illict Ab produciton; no isotype switching
  • multivalent lipid, polysaccharide, and nucleic acid Ags
  • produces IgM
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5
Q

What types of epitopes are recognized by T lymphocytes?

DSA8(Ag) S8

A

The linear epitope of proteins are the m Ags recognized by TCRs.

Ags must be presented by APCs as TCRs do not bind free peptides.

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6
Q

What is special about γδ T cells when compared to αβ T cells?

DSA8(Ag) S9

A

Located in epithelial/mucosal compartments (oral, respiratory, vaginal, anal, etc.)

Can bind non-protein Ags and DAMPs

Do not require MHC presentation

Comprise 5-10% of T cell population

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7
Q

What are haptens and why are they significant?

DSA8 (Ag) S11

A

Haptens are too small to be to illict an immune response on their own.

They must be coupled with a carrier protein to create a response.

Most drug allergies occur via this mechanism and vaccines are designed this way.

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8
Q

What are super antigens and what is their mechanism?

DSA8(Ag) S13

A

Binds outside of MHC groove and to certain β chains of TCRs. This overly activates the affected T cells and affects more T cells as it does so regardless of the specificity of the T cell.

Super antigens are responsibel for:

  • food poisoning (enterotoxins)
  • toxic shock syndrome (toxic shock toxin)
  • scalded skin syndrome (exfoliating toxin)
  • shock (pyrogenic exotoxins)
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9
Q

Differentiate between antibodies and BCRs.

DSA8(Ab) S5

A

Antibody:

  • soluble
  • effector mechanisms through Fc portion of tail which binds Fc receptors (opsonization, NK cell activation, mast cell activation, complement activation)
  • effector mechanisms also through Ag binding (neutralization)

BCR:

  • membrane bound to B cells
  • intracellular signaling domain (ITAMs)
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10
Q

What is the structure of an antibody and what is the function of each region?

DSA8(Ab) S6

A

Heavy chain:
-variable, Ag binding region (VH)

-constant, biologically active region (CH and hinge)

Light chain:

  • variable, Ag binding region (VL)
  • constant region (CL)
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11
Q

What is the results of digestion of an antibody with papain or pepsin?

DSA8(Ab) S7

A

Papain:

-digested into two seperate Fab regions and an intact Fc region

Pepsin:

-digested into two connected Fab regions and degraded Fc region

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12
Q

What is the hypervariable region of an antibody and what is its funciton?

DSA8(Ab) S8

A

Three regions found in the V domain surrounded by framework regions.

The hypervariable regions create a charge and shape complimentarity to the antigen they are specific for.

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13
Q

What is the difference between allotypes and idiotypes?

DSA8(Ab) S10

A

Allotype:

-genetic variations of the constant regions

Idiotypes:

-genetic variations of the variable regions

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14
Q

What is the structure of IgM?

What role does it play in immune response?

DSA8(Ab) S12

A

Structure:

  • pentamer with 10 Ag-binding sites
  • J-chain (required for transport into mucosa)
  • 4 heavy chain constant regions

Function:

  • predominantly produced in primary responses (first exposure)
  • coexpressed on mature B-cells with IgD
  • only Ab produced by fetus (late)
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15
Q

What is the structure of IgG?

What role does it play in immune response?

DSA8(Ab) S13

A

Structure:

  • monomer
  • 3 heavy chain constant regions

Function:

  • predominantly produced in secondary responses (any exopsure after first)
  • only Ab to cross placenta (passive immunity to fetus and neonate)
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16
Q

What is the structure of IgA?

What role does it play in immune response?

DSA8(Ab) S14

A

Structure:

  • monomer (serum) and dimer (mucosa)
  • J-chain (required for transport into mucosa)
  • secretory component (portion of receptor from transport)
  • 3 heavy chain constant regions

Function:

  • component of secondary immune response
  • predominantly found in secretions (colostrum, saliva, tears, and mucus)
  • provides passive immunity to newborns via breast milk
17
Q

What is the structure of IgE?

What role does it play in immune response?

DSA8(Ab) S15

A

Structure:

  • monomer
  • 4 heavy chain constant regions

Function:

  • component of secondary immune response
  • activates basophils and mast cells
  • protection against helminth (parasitic worms) infeciton

function in allergic/asthmatic responses

18
Q

What is the structure of IgD?

What role does it play in immune response?

DSA8(Ab) S16

A

Structure:

  • monomer
  • 3 heavy chain constant regions

Function:

  • coexpressed on mature B-cells with IgD
  • minimal serum pressence
19
Q

What is the function of FcγRI (CD64), where is it located, and what antibody is it specific for?

DSA8(Ab) S18

A

Binds IgG1 and 3 with high affinity

Located on phagocytes

Triggers phagocytosis of IgG opsonized targets

20
Q

What is the function of FcγRIIA (CD32), where is it located, and what antibody is it specific for?

DSA8(Ab) S18

A

Binds IgG with low affinity

Found on phagocytes and eosinophils

Triggers phagocytosis or degranulation

21
Q

What is the function of FcγRIIB (CD32), where is it located, and what antibody is it specific for?

DSA8(Ab) S18

A

Binds IgG with low affinity

Located on B cells, phagocytes, and mast cells

Provides feedback inhibition to B-cells and inhibits cell activity

22
Q

What is the function of FcγRIIIA (CD16), where is it located, and what antibody is it specific for?

DSA8(Ab) S18

A

Binds IgG with low affinity

Found on NK cells (CD16+ cells)

Triggers antibody dependent cellular cytotoxicity (ADCC), effector mechanism of NK cells

23
Q

What is the function of FcεRI (CD32), where is it located, and what antibody is it specific for?

DSA8(Ab) S18

A

Binds IgE with high affinity

Found on mast cells, basophils, and eosinophils

Triggers degranulation

24
Q

How do the terms affinity, valence, and avidity relate?

DSA8(Ab) S21

A

Affinity is the strength of interaction between the Ag epitope and Ab paratope (affinity of IgG is higher than affinity of IgM).

Valence refers to how many Fab regions an Ab has (valence of IgG is 2 and IgM is 10).

Avidity is the overall strength of an Ab-Ag complex and it is directly related to both affinity and valence.

25
Q

What is isotype switching?

DSA8(Ab) S22

A

DNA splicing to exchange μ-heavy chain for IgM out with α, ε, or γ-heavy chains to produce IgA, IgE, and IgG respectively.

T-dependent

26
Q

What is affinity maturation?

DSA8(Ab) S22

A

Mutations that occurs in B-cells that are activated by folicular T helper cells (T-dependent response)

Process involves somatic hypermutation and clonal selection

Does not occur to IgM as it is T-independent but does occur in IgG, IgA, and IgE as they are T-dependent

SFM - Biochem - Quiz 2 (23 decks)

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