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Immunology > B cells > Flashcards

B cells Flashcards

1
Q

What components of the innate immune system recruit the adaptive system?

A
  • dendritic cells

- complement cascade -macrophages

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2
Q

What do B cells do?

A
  • make Abs that mark pathogens for destruction

- recruit other cells and molecules that destroy pathogens

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3
Q

Abs circulate as a component of _____ in blood and lymph.

A

plasma

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4
Q

Name 4 functions of Abs:

A
  • neutralization of toxins/viruses/bacteria
  • opsonization of bacteria
  • activation of compliment cascade (classical pathway)
  • help activate specialized cells in response to antigen
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5
Q

Describe IgG:

A
  • major serum Ig (75%)
  • small size i.e. diffuses easily from blood to tissues
  • subclasses of IgG have diff roles: 1. opsonization 2. activation of compliment
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6
Q

Describe IgM:

A
  • first Ab produced in immune response
  • pentameric (binds strongly)
  • BIG; doesn’t diffuse from blood (stays in circulation)
  • no receptor for IgM Fc on phagocytes/leukocytes (doesn’t directly recruit these)
  • IgM Fc can bind and activate compliment
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7
Q

Describe IgA:

A
  • predominates in secretions
  • dimeric; protects the surface of respiratory + intestinal tracts
  • poor opsonin
  • weak compliment activator
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8
Q

Describe IgE:

A
  • trace amounts in serum
  • mostly bound to surface of mast cells via Fc (beneath skin mucosa)
  • binds Ag–> release of mast cell granules: inflammatory mediators–> trigger cough, sneezing, vomiting (all to expell pathogen)
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9
Q

The molecular process through which B cells are able to detect infinite, specific antigens and create specific antibodies is called _______.

A

somatic recombination

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10
Q

What order do the following happen?

immature B cell, heavy chain rearrangement, first checkpoint, second checkpoint, early pro-B cell, light chain gene rearrangement

which of these makes functional IgM??

A

order:

  • early pro-B cell (committed)
  • heavy chain gene rearrangement
  • first checkpoint (selects functional heavy chains)
  • light chain gene rearrangement
  • second checkpoint (selects functional light chains)
  • immature B cell (makes IgM)
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11
Q

What immunoglobulin serves as the receptor on new B cells?

A

IgM

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12
Q

Only B cells that do not recognize self-antigen are allowed to leave the bone marrow for the peripheral circulation. What regulatory process allows for this?

A

Tolerance (death by apoptosis, inactivation)

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13
Q

Where do B cells encounter antigen?

A

Secondary lymphoid tissue. Here they complete development/differentiation to plasma cells.

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14
Q

What is secondary lymphoid tissue?

A
  • lymph nodes
  • spleen
  • gut-associated lymphoid tissue
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15
Q

What part of the lymph node is the ‘B cell area’ located?

The T cell area?

A

Cortex

Cortico-medullary area

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16
Q

What 3 things are necessary for B cell activation?

A
  1. cross-linking of surface Ig w specific Ag
  2. association of B cell receptor w B cell co-receptor (CDx)
  3. additional signals provided by CD4 helper T cells (Th); Th expresses CD40 ligand detected by B cell….Th secretes cytokines that activate B cell (plasma cells that secrete Ab)
17
Q

What happens to B cells in the T cell zone?

A
  • interact with Ag
  • interact with Th cells of same Ag-specificity
  • conjugate pairs form
  • activation of B cells to plasma cells
18
Q

Where is the primary focus for clonal expansion of Ah-activated B cells?

A

Medullary cords

19
Q

Do all B cells require Th to differentiate into Ab-producing plasma cells?

A

No.

20
Q

Where is the secondary focus for clonal expansion of Ag-activated B cells?

A

The germinal centre (cortex)

21
Q

What is in the germinal centre?

A
  • activated B cells
  • Th cells
  • Ag (carried by follicular dendritic cells- FDC)
22
Q

What is the difference bw the roles of the primary focus and secondary focus?

A

Primary: leads to early secretion of specific Ab and provides early protection against infx.

Secondary (germinal centre): provides more effective, later response for persistent infx and re-infx. Dependent on Th cells to refine Ab response.

23
Q

Mutations occurring in the B cell receptor gene during proliferation in the germinal centre can increase their affinity for Ag. What is this process called? What is allowing for rapid division?

A

Somatic hypermutation.

Cytokine microenvironment of the germinal centre.

24
Q

Only B cells that have the highest affinity for Ag are given survival signals in the germinal centre. What is this called?

A

Affinity maturation.

25
Q

When do germinal centres present in lymph nodes? What happens to the lymph nodes (seen clinically)?

A

~ 1 week post-infx

swelling of lymph nodes

26
Q

What determines isotype switching (from IgM to other Igs: IgE, IgA, IgG)?

What region undergoes recombination during isotype switching?

A
  • T cell interaction with B cell
  • microenvironment

-C genes recombine (V regions stay the same)

27
Q

What compounds result in centrocytes becoming 1. plasma cells versus 2. memory B cells?

A

IL-10 : plasma cells (make Ab, fight current infx)

IL-4: memory B cells (future)

28
Q

List differences bw resting B cells and plasma cells.

A

B cell: has surface Ig, surface MHC II, lower rate Ig secretion, growth inducible, somatic hypermutation possible, isotype switching possible.

29
Q

Name 2 types of B cell malignancies:

A
  • multiple myeloma (arises from plasma cells in BM)

- leukemia (CLL-chronic lymphocytic leukemia)

30
Q

List 2 B cell activation and survival factors.

A
  • BAFF (excess in SLE, high Ab)

- APRIL

31
Q

Name a Rx for lupus that relates to B cell survival factors:

A

Anti-BAFF antibody

32
Q

APRIL, BAFF + TACI=

APRIL + BCMA=

BAFF + BR3 =

A

B cell activation

Bone marrow plasma cell survival

Naive B cell survival

33
Q

Where is IgA secreted by plasma cells?

How does it get from the basal end of epithelial cells to the apical surface?

A

Just under the epithelial BM.

By binding to poly-Ig receptors.

34
Q

What receptor on erythrocytes do C3b-Ab-Ag complexes bind to for clearance from circulation?

Where are the complexes taken>

A

CR1 receptor on erythrocytes.

Taken to; liver + spleen where pahgocytotic cells remove the immune complexes.

35
Q

Immune complex mediated disease, due to circulating immune complexes that activate compliment in tissues/vessels, include

A
  • vasculitis
  • arthritis
  • glomerulonephritis in the kidney
36
Q

Low levels of C3 and C4 in serum indicates _________

A

compliment consumption (immune complex mediated disease)

37
Q

What are the most effective Abs at activating compliment?

A

IgM and IgG3

Immunology (32 decks)

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