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SFM Immuno > B cell immunity > Flashcards

B cell immunity Flashcards

1
Q

Mature Naive B cells

A

BCR: IgM, IgD, Ig alpha & beta

Co-BCR: CD19, CD81, CR2

HLA class II (recognize CD4 helper T)

CD40 & CD 20

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2
Q

naive B2 cells

A

follicular & marginal (in spleen)

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3
Q

naive B1 cells

A

mucosa w/ limited Ag specificity

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4
Q

1st signal B cell activation

A

Ig recognizes Ag, need crosslinking of 2 Ig alpha/beta for signal transduction (via Syk) with CR2 & CD19 tails in cytoplasm (C3d protein helps BCR signaling)

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5
Q

Outcome of 1st signal

A

more IgM secretion
increase cytokine receptors
increased B7 expression
enhance survival/proliferation

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6
Q

What do B cells express after 1st signal for activation?

A

increase in CCR7 on surface (to bind CCR7 on T cells)

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7
Q

What is important in the immune synapse between B & T cells?

A

CD40 on B cell binds CD40L on T cells

B7 on B cell binds CD28 on T cells

T cell recognizes epitope on B cell & then B cell is activated & can proliferate that clone

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8
Q

What is the major outcome of T-dependent immune synapse?

A

induced expression of AID enzyme essential for class switching of B cell (IgM & IgD to IgE/IgA/etc)

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9
Q

IgM

A

complement activation

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10
Q

IgG

A

opsonization & phagocytosis, complement activation, neonatal immunity

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11
Q

IgE, IgG4

A

need IL-4, immunity v worms & leads to mast cell degranulation (immediate hypersensitivity)

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12
Q

IgA

A

need cytokines (TGF B)

mucosal immunity (transport IgA thru epithelial cells)

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13
Q

Switch Recombination

A

occurs post CD40:CD40L ligation, rearranged VDJ gene segment recombines w/ downstream C region gene & DNA in between is deleted (so not cut out during mRNA alternative splicing)

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14
Q

Somatic Hypermutation

A

intro of A TON of point mutations in switch regions of variable areas of Ig genes, VERY VERY high spontaneous mutation rate, AID converts random Cs to Us

expands Ab repertoire to generate high affinity Ag specific Abs

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15
Q

What Ig do you get w/ IL-4 in class switching?

A

IgE

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16
Q

What Ig do you get w/ TGF-B in class switching?

A

IgA

17
Q

Role of Tfh (T follicular helpers)

A

ICOS:ICOSL interaction (T to B) that provides cytokines for class switching

18
Q

Selection Checkpoint

A

selective survival of B cells w/ highest affinity Abs, occurs in germinal centers, need FDC & Tfh interaction w/ B cells for their survival, Ag comes from FDCs

19
Q

T cell independent activation

A

leads to plasma cells (B cells w/ huge ERs & produce lots of Ab/sec)

B1 to direct Ags & B2 to blood-borne polysacc

20
Q

Memory B cell

A

can live for long time w/o Ag stimulation, express lots of Bcl-2 (anti-apoptosis)

express CD27 & CD45R on surface

21
Q

Secondary Immune Response

A

mediated by memory B cells, rapid response to later exposure to same Ag, mostly by IgG

22
Q

What Ig helps in contraction of immune response?

A

IgG !!!! (high conc blocks further Ab production)

23
Q

What does humoral immunity protect against?

A

extracell pathogens

24
Q

What is the role of FcR (Fc receptors)?

A

bind the Fc region of Ag-Ab complex and tags that cell for opsonization or will activate the cell (depending on cell type)

25
Q

FcyRI

A

high affinity for IgG, on MOs/neuts/eosinophils

26
Q

FcyRIIA

A

low affinity for IgG, on MOs/neuts/eosinophils

27
Q

FcyRIIB

A

low affinity for IgG, on B cells/DCs/mast cells/neuts/MOs

decreases inflamation

28
Q

FcyRIIIA

A

low affinity for IgG, on NK cells

29
Q

FceRI

A

high affinity for IgG & IgE, on mast cells/basophils/eosinophils

activates degranulation of mast cells

30
Q

Major Functions of Abs (name all 5)

A 
activate complement
neutralization of Ag
opsonization & phagocytosis
waste management 
anti-viral state
31
Q

What Ab is passed across placenta?

A

IgG

32
Q

What Ab is passed via breast milk?

A

IgA

33
Q

Vaccination

A

mimics a natural infection, intentional delivery of an antigenic stimulus

34
Q

How do pathogens evade humoral immunity?

A

Change surface on Ags
Outer capsule prevents complement binding
Capsule prevents binding of Abs (no phagocytosis)

SFM Immuno (4 decks)

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