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Immunology > Immunoglobulins And T-cell Receptors > Flashcards

Immunoglobulins And T-cell Receptors Flashcards

1
Q

What type of receptors are located on cells of the innate immune system?

A

PRRs that recognize PAMPs on the microbes

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2
Q

What do receptors on B and T cells recognize?

A

Unique characteristics of pathogens that they can see if the initial response and recall response

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3
Q

What can Ig or Ab bind to?

A

Pathogenic components like proteins, peptides, lipids, carbs, lipoproteins DNA, RNA

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4
Q

What can TCR bind to?

A

small peptides or glycolipids derived from pathogens (NOT full length proteins)

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5
Q

What is the possible number of receptors for lymphocytes to have?

A

10^10-10^16 (a HUGE number so they can respond to any antigen)

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6
Q

After activation of a B cell, what happens to the BCR?

A

It is secreted as an Ab or Ig into the serum from the secondary lymphoid organ

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7
Q

What are the five Ig isotopes?

A

IgG, IgA, IgM, IgD, IgE

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8
Q

What does altered levels of Igs mean?

A

It could be indicative of multiple myeloma because normally the levels of Igs is stable

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9
Q

What causes multiple myeloma?

A

Overproduction of one Ig due to a B cell tumor (plasma cell tumor)

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10
Q

What are the three diagnostic tools used to check for multiple myeloma?

A
  1. Check for Bence Jones proteins (dimers of light chain molecules) excreted in the urine in large numbers
  2. X-ray the skull because bone lesions are associated with myeloma
  3. Electrophoretic mobility- If you see an M-spike (narrow spike of homogenous Ig) then the person may have myeloma
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11
Q

What is the most common antibody type?

A

IgG

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12
Q

How are light chains bound to heavy chains?

A

Disulfide bonds

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13
Q

How are the heavy chains of Ig bound together? In what region?

A

Disulfide bonds in the hinge region

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14
Q

What two domains do both the heavy and light chain consist of? How many AA are in each domain?
How does the domain stay “pinned together”?

A

Constant and variable domains that each consist of about 110 AA pinned together by disulfide bonds (cysteine linkage)

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15
Q

Where does an antigen bind the antibody?

A

to the N-terminal ends of the Vh and Vl domains where they are joined creating a pocket for the antigenic epitope.

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16
Q

What does it mean that the IgG molecule is divalent?

A

Both antigen binding sites are identical.

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17
Q

If the Ig is cleaved by the enzyme papain, where is the molecule cleaved?

A

It is cleaved at the hinge region so it breaks the Ig into 2 Fab fragments and 1 Fc fragment

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18
Q

What is the Fab fragment?

What does Fab stand for?

A

The entire light chain, attached by a sulfide bond the Vh-Ch1 of the heavy chain

Fragments antigen binding

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19
Q

What does Fc stand for?

What components of the Ig make up the Fc domain?

A

Fragment crystallizable

It consists of the remainder of the heavy chain constant regions (not CH1 which is on the Fab)

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20
Q

What action can the Fab fragment perform even when separate from the Fc region?

What action can the Fc region perform?

A

Fab can bind antigens

Fc can participate in complement fixation, and antibody-dependent cell-mediated cytotoxicity

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21
Q

Where is the antibody cleaved if it is treated with pepsin?

A

It cleaves the Ig below the disulfide bond at the hinge (closer to the C terminal) so it generates a F(ab’)2 fragment and the rest of the Fc chain is broken into fragments.

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22
Q

What components make up the F(ab’)2 region?

A

2 light chains disulfide bound to VH and CH1 of the heavy chain.
Vh and CH1 of both heavy chains are disulfide bound together

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23
Q

When an AA variability plot was made for the 115 AA segment of the Vh domain of an antibody, what did they discover?

A

even within the variable region, there were portions that remained relatively constant (same AA) called framework regions and other regions that were highly variable (different AA) called hypervariable regions

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24
Q

What is a framework region of an Ig?

A

The AAs of the Vh that remain relatively constant

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25
Q

What is the HV region of the Ig?

How many are there on the Vh and Vl regions?

A

The region of Vh or Vl that have hypervariable AAs. There are three

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26
Q

What is the other name for hypervariable regions?

A

Complementarity Determining REgions (1-3)

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27
Q

What part of the variable region is responsible for determining the fit of antigenic epitopes?

A

Hypervariable regions

28
Q

How do antigens and antibodies bind?

A

by non-covalent forces like:

  1. hydrogen bonds
  2. ionic bonds
  3. van der Wals
  4. hydrophobic effect
29
Q

What determines the isotype of the Ig?

A 
The constant region of the heavy(mu, gamma, delta, alpha, epsilon)  and light chains (kappa, lambda). 
This is what determines the class of Ig (IgM, G,D,E,A)
30
Q

What is the allotype of the antibody?

A

allelic forms of the same protein which can vary among members of the same species (polymorphic variation)

Differences involve changes in the constant region

31
Q

What is the idiotype of the antibody?

A

Present in the variable regions of the heavy and light chain and serve as a clonal marker for the Ig molecule and the B cell that made it

32
Q

What two Ig lack the hinge region?

A

IgM and IgE

33
Q

What two Ig have an extra C terminal heavy chain domain?

A

IgM and IgE

34
Q

Which antibodies are monomeric?
Dimeric?
Pentameric?

A 
Monomeric:
IgG, IgE, IgD, IgA
Dimeric:
IgA
Pentameric:
IgM
35
Q

Which antibody is in highest concentration in serum?

A

IgG (12-14mg/ml)

IgA is second, IgM is third….trace of the other two

36
Q

Which antibodies have FcR binding (to macrophages, etc)

A

IgG
IgA
IgE

37
Q

Which antibodies are transferred to newborns?

A

IgG across the plancenta

IgA in milk

38
Q

Which antibodies have high affinity for antigens?

A

IgG, IgA, IgE (same as those with FcR binding)

39
Q

Which antibody has the longest half life?

A

IgG (23 days, except IgG3 which is only 7)

40
Q

Which antibodies are able to participate in complement fixation to target antigens for destruction?

A

IgG and IgM

41
Q 
How many subclasses of IgG are there? 
Which subclass is the most prevalent?
A

There are four and IgG1 is the most prevalent

42
Q

Which IgG subunit has the shortest half-life?

A

IgG3 is only 7 days. (the rest are 23)

43
Q

Which IgG subunit binds complement the best? the worst?

A

Best - IgG3

Worst- IgG4

44
Q

Which IgG subunit is passed the worst through the placenta?

A

IgG2

45
Q

Which IgG subunits are the best at binding monocytes? Which are the worst?

A

Best- IgG1, IgG3

Worst- IgG4

46
Q

What are the three roles of antibody transport across cells?

A
  1. deliver maternal IgG across the placenta (FcRn)
  2. regulate IgG levels in the body (FcRn)
  3. deliver IgA to mucousal surface (poly-IgR)
47
Q

How are IgG levels regulated in the body?

A
  1. Pinocytosis takes IgG up into endosomes
  2. Endosomes have pH 6 and IgG binds FcRn
  3. IgG-FcRN is recycled away from lysosomal degradation which unbound IgG is taken to be degraded
  4. When the recycling compartment fuses with the plasma membrane, the near neutral pH releases IgG from FcRn
48
Q

What is the ONLY antibody to bind FcRn?

A

IgG

49
Q

How does IgA obtain its secretory component to be released into the gut?

A
  1. Plasma cells in lamina propria release IgA dimers.
  2. Poly-Ig receptors on gut epithelium bind to the Fc region of the IgA dimer
  3. Pinocytosis occurs and IgA dimer/pIgR are trafficked across the epithelial cell toward the gut
  4. As it is exocytosed, part of PIgR remains attached to the IgA dimer
50
Q

When is the J-chain added to the IgA dimer?

When is the PIgR secretory component added?

A

J-chain in the plasma cell to form the dimer (J-chain links two IgA monomers)
PIgR is added in the gut epithelial cell

51
Q

What problem is associated with hyper-IgM and what are the genetic mutations?

A

recurrent infection due to mutation in CD40/40L and AID

52
Q

What problem is associated with Hyper-IgE and what are the genetic mutations?

A

Eczema, candidiasis, infection due to STAT3, Dock8, Tyk2

53
Q

What problem is associated with hyper-IgD and what is the genetic cause?

A

Fever, elevated innate immune response caused by mevalonate kinase

54
Q

What are the problems associated with hypogammaglobulinemia?

A

recurrent infection (because these are immunodeficiencies

55
Q

What are the two types of TCRs? Are they ever expressed in the same cell?

A

TCRab (throughout the body- conventional or NKT)

TCRdg (skin, mucous, gut, iNKT)

56
Q

What structure is the extracellular domain of the TCR most like?

A

a Fab fragment (light chain, Vh and CH1 of heavy chain) but it is different because it has heterogeneous chains (alpha and beta)

57
Q

What does the variable region of the TCR bind?

A

MHC peptide complexes on APCs

58
Q

What does the TCR need to rely on a series of other molecules for signaling?

A

because it has a really short cytosolic tail that does not extend far enough to transduce signal

59
Q

What set of molecules helps the TCR alpha/beta domains to signal upon antigen binding?

A

CD3 (gamma/epsilon and delta/epsilon) and a zeta dimer which have ITAM regions that extend into the cytosol for signaling

60
Q

What is the cytosolic domain of CD3 and zeta molecules?

A

ITAM domain

61
Q

How must the antigen be presented to be recognized by the TCRab domains?

A

The antigen must be in the groove of an MHC molecule

62
Q

CD8 cytotoxic T cells bind to what?

A

8-10AA peptides in HLA1

63
Q

CD4 helper T cells bind to what?

A

12-20 peptides bound to HLA2 on APC or dendritic cells

64
Q

What T cell is the major target of HIV virus?

A

CD4

65
Q

How are the variable regions of BCR and TCR similar?

A

they both contain hypervariable regions (CDR loops) that recognize and bind antigens

66
Q

What two antibodies can be transported across cells? What receptors allow them to do so?

A

IgG- FcRn

IgA- PIgR

Immunology (25 decks)

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