Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Clinical Immunology > Lecture 2 - B cells > Flashcards

Lecture 2 - B cells Flashcards

1
Q

Development and activation of B cells

A
  • The development of B-cells begins in the bone marrow and is driven by IL-7 produced by marrow stromal cells.
  • Cells are activated by encountering their cognate antigen
  • Activated B cells secrete antibodies
  • Activated B-cells develop into long-lived plasma and memory cells which persist in lymph nodes or return to the bone marrow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Precursors of B1 and B2 cells

A
  • Fetal liver–derived HSCs are the precursors of B-1 cells.
  • These respond to T-independent antigens and make natural antibodies reactive with polysaccharides.
  • Bone marrow–derived HSCs give rise to the majority of B cells (B-2).
  • These cells develop into marginal zone B cells or into follicular B cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Stem cell (development and response to antigen)

A

Anatomic site: Bone marrow

Ig DNA, RNA: Unrecombined/germline DNA

Ig expression: None

Surface markers: CD43+

Response to antigen: None

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Pro-B cell (development and response to antigen)

A

Anatomic site: Bone marrow

Ig DNA, RNA: Unrecombined/germline DNA

Ig expression: None

Surface markers: CD43+, CD19+, CD10+

Response to antigen: None

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Pre-B cell (development and response to antigen)

A

Anatomic site: Bone marrow

Ig DNA, RNA: Recombined H chain gene (VDJ); u mRNA

Ig expression: Cytoplasmic u and pre B-receptor associated u

Surface markers: B220lo, CD43+

Response to antigen: None

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Immature B cell (development and response to antigen)

A

Anatomic site: Periphery

Ig DNA, RNA: Recombined H chain gene (VDJ), k or λ chain genes, u or k or λ mRNA

Ig expression: Membrane IgM (u + k or λ light chain)

Surface markers: IgMlo, CD43-

Response to antigen: Negative selection (depletion), receptor editing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Mature B cell (development and response to antigen)

A

Anatomic site: Periphery

Ig DNA, RNA: Alternative splicing of VDJ-C RNA (primary transcript) to form Cu and Cδ mRNA

Ig expression: Membrane IgM and IgD

Surface markers: IgMhi

Response to antigen: Activation (proliferation and differentiation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Functional changes after B cell activation

A
  • Clonal expansion
  • Antibody secretion
  • Isotype switching
  • Affinity maturation
  • Memory B cells forming
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Role of heavy chains in antibodies

A
  • Regulate the formation of pentamers (IgM) and dimers (IgA)
  • Determine binding to cells via Fc receptors.
  • Determine functional properties (eg: C’ fixation )
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Role of light chains in antibodies

A
  • Important for antigen specificity and binding

- labelled as either k or λ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Weight of heavy and light chains

A

Heavy chain: 50kDa
Light chain: 25 kDa

Full Ig: 150kDa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Role of IgA

A
  • Found of mucosal surfaces and in many bodily secretions
  • Important first line of defence against antigens
  • about 13% of total serum
  • are usually monomers or dimer structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Role of IgG

A
  • Important for memory/ long term immune response
  • Binds many pathogens to control infections
  • about 80% of total serum
  • monomer structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Role of IgM

A
  • Important for initial response to a pathogen/infection (short term immune response
  • controls B cell activation
  • about 6% of total serum
  • pentamer structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Role of IgE

A
  • Important for allergic responses and responding to intestinal parasites
  • less than 0.1% of total serum
  • monomer structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Role of IgD

A
  • Important as a B cell surface receptor
  • Signals B cells to be activated and then secrete antibodies
  • about 0.2% of total serum
  • monomer structure
17
Q

Variable and constant regions

A
  • The genes encoding heavy and light chains have variable and constant regions, which are shuffled (somatic recombination) to yield multiple antigen specificities
  • This occurs in the bone marrow & is followed by a phase in which autoreactive cells are purged.
18
Q

Which immunoglobulins serve as antigen receptors on B cells?

A

Membrane IgM (u chain) and IgD (𝛿 chain)

19
Q

Isotope switching (B and T cells)

A

At the primary follicle (spleen) there is:

  • Activation and migration of T & B cells in LN
  • T-B cell interactions
  • B cell differentiation, Ig secretion, isotype switching
  • Germinal Centre reaction (contains follicular dendtritic cells), affinity maturation, memory B cells
20
Q

What happens (with regards to immunoglobulin) when B cells are activated?

A

IgM: complement activation

IgG subclasses: Fc receptor-dependent phagocyte responses; complement activation; neonatal immunity (placental transfer of IgG)

IgE: Immunity against helminths; mast cell degranulation (immediate hypersensitivity)

IgA: Musocal immunity (transfer of IgA through epithelium)

21
Q

Main enzyme needed for isotope switching

A

The key enzyme required for isotype switching and affinity maturation is activation-induced deaminase (AID) - activated mainly by CD40 signals from TFH cells

22
Q

How isotope switching works

A
  • AID converts cytosine (C) residues to uracil (U) residues.
  • Switch regions are rich in G and C bases, and switch region transcripts tend to form stable DNA-RNA
    hybrids involving the coding strand of DNA
  • this frees up the bottom or non-template strand, which forms an open single stranded DNA loop called an R-loop.
  • The double-stranded breaks in the two switch regions are joined together
  • DNA between the two switch regions is deleted,
  • the original rearranged V region becomes adjacent to a new constant region.
23
Q

How affinity maturation works

A
  • A B cell is activated by a protein antigen and helper T cells
  • The B cell migrates into the germinal centre
  • In the germinal centre there are B cells with somatically mutated Ig V genes and Igs with varing affinities for the antigen
  • Only B cells with high affinity membrane Ig bind the antigen on follicular dendritic cells
  • B cells that encounter the antigen on follicular dendritic cells are selected to survive, and other B cells die
24
Q

Cellular components of the germinal center

A
  • Mantle zone (outermost)
  • Light zone (middle)
  • Dark zone (innermost)
  • After activation by helper T cells at the edge of a primary follicle, B-cells migrate into the follicle
    and proliferate, forming the dark zone.
  • Somatic mutations of Ig V genes occur in these B cells, and they migrate into the light zone where they encounter follicular dendritic cells displaying
    antigen.
  • B-cells with the highest affinity Ig receptors are selected to survive - they differentiate
    into antibody-secreting or memory B cells.
25
Q

Histology of a secondary follicle with a germinal center in a lymph node

A

The germinal center is contained within the follicle and includes a basal dark zone and an adjacent light zone. The mantle zone is the parent follicle within which the germinal center has formed

26
Q

FDCs with immunohistochemistry

A
  • Immunohistochemical stain shows follicular dendritic cells (FDC, stained brown with a specific enzyme-labeled antibody) in a follicle of the spleen. B-cells in the follicle are stained blue.
  • FDC are HLA class II-negative and do not arise in the bone marrow.
27
Q

Role of Fc receptors

A

involved in B-cell regulation and antibody function

28
Q

Opsonisation and phagocytosis steps

A
  • Opsonistaion of the microbe by IgG
  • Binding of opsonised microbes to phagocyte Fc receptors (FcγRI)
  • Fc receptor signals activate phagocyte
  • Phagocytosis and killing of ingested microbe

Clinical Immunology (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions