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Medical Studies 1 > 11.3 Adaptive Immunity > Flashcards

11.3 Adaptive Immunity Flashcards

1
Q

“Immunoglobulin” vs “antibody”: terminology

A
  • Immunoglobulin: Refers only to shape of protein
  • Antibody: Specific (e.g. Hep B antibodies)
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2
Q

What happens to a B cell as it moves from a Pro-B cell to a pre-IG B cell?

A

It expresses an immunoglobulin on the surface that has two “surrogate” light chains; not functional, but in the process of becoming functional.

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3
Q

What Ig isotype is expressed on the surface of an immature B cell?

A

IgM; Single, not pentameric

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4
Q

What two antibody isotypes are expressed on the surface of a mature, naive B cell?

A

M and D

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5
Q

Which Chromosome codes for the heavy chain of an immunoglobulin?

A

Chromosome 14

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6
Q

Which chromosome codes for the light chain of an immunoglobulin?

A

Chromosome 2

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7
Q

Which is the most common Ig isotype found in the body? Which two isotypes are most associated with an immune response?

A
  • IgG is the most common isotype
  • IgM and IgG are associated with an immune response
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8
Q

How long do IgG vs IgM antibodies last in the blood? Why is this significant?

A
  • IgG: 20-21 days
  • IgM: 10 days

This is significant because, the longer the antibody can last in the blood, the more likely it is to identify its antigen.

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9
Q

Which antibody classes activate the complement system?

A

IgM, IgG1, and IgG3

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10
Q

Which isotype of antibody is best transferred across the placenta?

A

IgG

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11
Q

Which parts of antigens do antibodies bind to?

A

Epitopes

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12
Q

Is AbAg bonding covalent? How does this affect reversibility?

A
  • Non-covalent
  • Therefore, reversible
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13
Q

How many complementary determining region (CDRs) are there on each variable region of an antigen (i.e. each side of the Y)?

A

Six

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14
Q

In terms of CDRs, what influences the strength of a bond between antibody and antigen?

A

The more CDRs come into contact with the antigen, the stronger the bond

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15
Q

What are the four possible outcomes of an antibody binding to an antigen?

A
  • Agglutination
  • Neutralization (cannot enter tissue)
  • Complement activation
  • Opsonisation
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16
Q

Explain how the variable portion of an antibody is altered, with reference to the different sections of chromosomes 14 and 2.

A
  • Chromosome 14 (heavy chain) has V, D, and J sections, each of which has multiple segments
  • Similarly, Chromosome 2 (light chain) has V and J sections.
  • During creation of the variable portion, one of each of these is selected, giving rise to millions of possible antibodies.
17
Q

Can a B cell ever change the variable portion of its antibody?

A

Nope

18
Q

There are 100 antibodies in my bloodstream. 69 of them bind to the antigen. What is the titre value?

A

69; it’s about the functional amount

19
Q

Why do we get a small IgG spike during the primary immune response?

A

Because, during differentiation after clonal expansion, some cells undergo isotype switching to become memory B cells. Upon meeting the antigen, these memory cells proliferate, creating more memory cells as well as IgG plasma cells. This leads to a spike in serum IgG

20
Q

Describe how somatic hypermutation drives affinity maturation in B cells

A
  • Activated B cells undergo random mutations in the CDR region during proliferation
  • This creates a wide range of antibody receptors, some of which are a better fit.
21
Q

Why are lower affinity antibodies produced during higher antigen dose?

A
  • More antigen -> more chance for lower affinity antibodies to bind to antigen
  • Therefore, wider range of antibody shapes produced
22
Q

What messengers govern which isotype a B cell releases? Which cells release them?

A

Cytokines released from helper T cells

23
Q

At a genetic level, how does B cell class switching occur?

A
  • The B cell will use the first isotype gene on the chromosome.
  • When a B cell is told to class switch, it sheds all the other genes (leaving a loop of lost DNA), until the correct gene has lined up
24
Q

What affects whether an antigen is T-dependent or T-independent?

A
  • If an antigen is complicated, it will have many different epitopes
  • As a consequence, there is little cross-linking, meaning the signal is not strong enough, and requires T cells
  • If the antigen does cross-link, it is T-independent
25
Q

Are there any memory cells or IgM antibodies produced in a T-independent B cell response?

A
  • No
  • No T cell cytokines, no class switching
26
Q

Based on genetic variability within an individual, how many different variants of MHC class 1/2 can exist in one person?

A

MHC Class 1: 6
MHC Class 2: 12

27
Q

Describe antigen processing with MHC Class I

A
  • Endogenous protein broken up into peptides by enzyme
  • Funneled into ER
  • Loaded on MHC Class 1
  • Exported via vesicle onto cell surface
28
Q

Describe antigen processing with MHC Class II

A
  • Uptake of exogenous antigen
  • Lysosomes break it down
  • MHC Class II enters endosome from ER
  • Peptide loaded onto MHC Class II
  • MHC Class II exported to cell surface in vesicle
29
Q

There is only one type of cell that can activate CD4+ T cells. What is it?

A

Dendritic cells

30
Q

What is the role of CD8 and CD4 proteins in MHC:T cell interactions?

A
  • Co-receptor
  • Binds alongside antigen/MHC complex to enhance ligand recognition
31
Q

What causes upregulation of MHC class II and B7 on a dendritic cell?

A

Recognition of an antigen via a PRR

32
Q

What 3 signals are required to activate a T cell?

A
  1. MHC:peptide synapses with CD4/8 and TCR
  2. Costimulation: B7 synapses with CD28
  3. Microenvironment cytokine production
33
Q

True or false: many kinds of T Helper cells are produced by different cytokines released from the dendritic cell during activation. This is done in equal proportion,

A
  • False
  • Many kinds are produced, but not necessarily in equal proportion; varies based on specific immune response
34
Q

Which molecule on a B cell triggers isotype switching and memory cells?

A

CD40; this is why T-independent has no memory cells

35
Q

How do helper T cells help the production of cytotoxic T cells?

A

They release cytokines that allow differentiation of CD8 -> cytotoxic T cell

36
Q
A

Medical Studies 1 (90 decks)

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