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Term 3: Immunology/Pathology > B Cells & Antibodies > Flashcards

B Cells & Antibodies Flashcards

1
Q

Which chromosome has the gene for the heavy chain of B cell receptors?

A

Chromosome 14

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2
Q

What happens if both genes (on respective Chromosome 14s) fail to produce full-length Heavy Chain proteins for the BCR?

A

-the cell undergoes apoptosis

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3
Q

What happens if the B cell produces light chains that don’t match the heavy chain on its BCR’s?

A

the cell undergoes apoptosis

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4
Q

Which portion of the B cell receptor signals thenucleus when the receptor recognizes an antigen?

A
  • Ig-alpha

- Ig-beta

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5
Q

What must happen to B cell receptors before they can signal B cell activation?

A
  • bind antigen
  • clustering of BCR’s
  • Crosslinking of B cell receptors**
  • a signal from a helper T cell if necessary **
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6
Q

When does a naive/virgin B cell become experienced?

A

-when it is activated after they meet their respective cognate antigens

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7
Q

How are B cells activated independent of helper T cells?

A
  • only needs 1 signal
  • in response to certain antigens, enough BCR’s will cross-link to activate the cell

***T cells only recognize protein antigens, so this system allows us to respond to carbs and fats

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8
Q

What is the “unnatural” way in which B-cells can be activated?

A
  • a mitogen binds to molecules on the B cell’s surface, which are not BCR’s
  • molecules cluster together
  • this allows clustering of BCR’s

**does not depend on cognate antigen. parasites use mitogens to distract the immune system (irrelevant antibodies are produced) e.x. Shistoooooo

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9
Q

What are the three steps of B cell maturation?

A
  • class switching
  • somatic hypermutation
  • career decision

**order of the steps can vary and be skipped

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10
Q

What is the class switching maturation step in B cells?

A
  • switching of class of antibody produced

* i.e. IgA–>IgE

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11
Q

What is the result of class switching?

A
  • part of the antibody that binds to antigen (Fab) remains the same
  • Fc region is changed
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12
Q

Which class of antibodies are first produced by naive B cells?

A

IgM

-also IgD, but we don’t know what it does

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13
Q

What do IgM antibodies do to complement?

A
  • activates complement cascade
  • brings together C1 complexes, which then act as a C3 convertase (much C3b, wow)

**C1 has inhibitor attached, bring 2 together and inhibitors fall off

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14
Q

What is the significance of IgM binding to foreign antigens before activating complement?

A
  • some bacteria have walls that are resistant to complement binding
  • IgM allows for complement activation in these cases
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15
Q

Where does C1 bind to IgM?

A

the Fc region

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16
Q

Can IgG activate complement?

A

Yes, but it can only bind one copy of C1 a piece

-two IgG molecules must bind an invader close together to activate complement

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17
Q

Which IgG class is best at activating complement and serves as a bridge for Natural Killer cells?

A

IgG3

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18
Q

Which IgG class is good at opsonizing invaders for macrophage ingestion?

A

IgG1

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19
Q

Which antibody can cross the placental barrier, and provides the fetus protection until production of its own antibodies?

A

-IgG

**IgG is very good at fighting viruses

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20
Q

What is the most abundant antibody class in the human body?

A

IgA

***IgG is most abundant in blood

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21
Q

What do IgA antibodies do?

A

-guard the mucosal surfaces of the body

  • can coat pathogens in the intestine
  • has 4 Fab regions, so good at collecting pathogens into clumps large enough to be cleared with feces
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22
Q

Can IgA antibodies fix complement?

A

-No

**this is good, elsewise our mucosal surfaces would be in a state of constant inflammation, which is not fun

23
Q

What causes anaphylactic shock?

A

-mast cell degranulation

  • when people are exposed to allergens they make lots of IgE to that allergen, and mast cells have IgE receptors
  • triggers mast cell degranulation

-on second exposure to allergen, IgE abs already bound to mast cells bind to the allergen, clustering receptors, triggering degranulation

24
Q

Why do B cells switch classes?

A
  • with a common cold we don’t want to depend on IgM, but need IgA
  • with a parasitic infection we want IgE
25
Q

What class of antibody do B cells switch to in an area rich in IL-4 & 5? What kind of invader are they fighting?

A

IgE

Good for parasites

26
Q

What class of antibody do B cells switch to in an area rich in IFN-alpha? What kind of invader are they fighting?

A

IgG3

Bacteria and viruses

27
Q

What class of antibody do B cells switch to in an area rich in TGF-beta? What kind of invader are they fighting?

A

IgA

Enteric bacteria

28
Q

What is somatic hypermutation?

A
  • Genese for Fab region have a high mutation rate
  • When B cell switches from making IgM antibodies, mutation rate drastically increases
  • mutates the antigen binding region of Fab
29
Q

What are the three possible outcomes of somatic hypermutation?

A
  • affinity of Fab to cognate antigen is unchanged
  • affinity is increased
  • affinity is decreased
30
Q

Do B cells activated independent of T cells undergo class switching and somatic hypermutation?

A

usually not

31
Q

Through what surface receptor do Helper T cells interact with B cells to activate them?

A

CD40

32
Q

What happens to old and damaged proteins in a cell?

A

-they are cut by proteasomes then displayed by the cell’s class I MHC molecules

33
Q

What are the three main steps in class I MHC display?

A
  1. Generation of the peptide by the proteasome
  2. Transport of peptide to ER
  3. Binding of peptide to groove in MHC I molecule
34
Q

Where are class II MHC’s loaded with peptides?

A

-cytoplasmic endosomes

35
Q

What does the invariant chain do?

A

-Fills the MHC II molecule to prevent it from picking up other peptides

**important b/c ER is full of endogenous proteins, which if loaded into MHC II they would display same kinds of peptides as class I MHC

36
Q

What Does HLA-DM do to the MHC II molecule?

A

-removes the invariant chain once the MHC II reaches the endosome

37
Q

What cells read Class I and II MHC’s respectively?

A

Class I = Killer T cells

Class II = Helper T cells

38
Q

Which class of MHC is found on antigen presenting cells?

A

both class I and II

39
Q

What two things must happen for a T cell to become activated?

A
  • T cell must recognize its cognate presented by an MHC molecule
  • Must also receive a co-stimulatory signal (provided by APC’s)
40
Q

What are the three types of antigen presenting cells?

A
  • Activated Dendritic cells
  • Activated Macrophages
  • Activated B cells
41
Q

What signals activate dendritic cells?

A
  • cytokines from neutrophils and macrophages

- Cellular receptors (ex: TLR) which recognize molecular patterns of invaders

42
Q

What do dendritic cells use TLR4 to sense?

A

-LPS

=a component of (gram negative?) bacterial cell walls

43
Q

What happens to dendritic cells when they’re activated?

A
  • no longer spit fluid back into environment
  • Leave home tissue and travel via lymphatics to nearby lymph nodes

Produces B7, which along with MHC I & II, it uses to activate virgin T cells

44
Q

How do dendritic cells recruit their own replacements?

A

-once activated, they produce chemokines to cause monocytes to leave the blood and differentiate into dendritic cells

45
Q

What is the difference between dendritic cells and macrophages?

A

-Dendritic cells don’t kill

  • Macrophages don’t travel
  • macrophages not as good at antigen presenting
46
Q

If the macrophage doesn’t travel to the lymph node, what is its role in antigen presentation?

A

-Dendritic cells activate virgin T cells, Macrophages present antigens to keep the activated T cells going

47
Q

What is the advantage of B cells over other APCs?

A

-They can concentrate antigens for presentation

48
Q

Why would it be dangerous for Cytotoxic T cells to recognize antigens that aren’t presented on an MHC?

A

-if uninfected cells have some debris from a dead virus stuck on their surface, then the T cell would kill the healthy cells

49
Q

How does complement activated B cells?

A
  • C3b opsonizes enemy
  • B cell has complement receptors
  • bound complement receptors will bring BCR’s together and activate the B cell

***helps innate immune system determine if invader is dangerous

50
Q

What do IgM antibodies look like?

A

like 5 IgG antibodies stuck together by their Fc regions

51
Q

What do IgA antibodies look like?

A

Like 2 IgG antibodies held together at Fc region with a clip

52
Q

What is the utility of the structure of IgA?

A
  • allows for transport across the intestinal wall into the intestine
  • also keeps antibody safe from digestive enzymes
53
Q

What does B7 produced by dendritic cells do?

A

-serves as second signal to activate virgin T cells, along with MHC I & II

54
Q

What do CD1 molecules do?

A

Like MHC for lipids

-sample lipids from various compartments of cell, then present these molecules on surface of APC’s

**mostly on Macrophages, some on dendritic cells

Term 3: Immunology/Pathology (17 decks)

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