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Post Midterm - Immuno > Humoral Immune Response 1 > Flashcards

Humoral Immune Response 1 Flashcards

1
Q

Humoral Adaptive Immune Responses-

A
  • extracellular
  • meditated by antibodies
  • produced by B lymphocytes
  • Principal defense mechanism against microbes with capsules rich in polysaccharides and lipids
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2
Q

Thymus-independent antigens (TI): Non- protein antigens

A

• Noisotype-switching
• No affinity maturation
-mainly IgM
-responders-marginal zone B cells and and B-1 cells
-These antigens activate B cells by pattern recognition receptors

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3
Q

Thymus-dependent antigens (TD): Protein antigens processed in APCs

A 
-recognized by helper T cells
• help B cell activation
• heavy chain isotope switching
• affinity maturation
• Protein antigens with no helper T cell:
weak or no antibody response
-• B cell required direct contact with
TH cell
• Majority responders: follicular B- cells (B2 cells)
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4
Q

pattern recognition receptors

A

✓Type I (TI-1) – lipopolysaccharide

✓Type 2 (TI-2) – highly repetitious molecules (bacterial flagella)

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5
Q

Immunoglobulins with Thymus independent antigens

A

IgM

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6
Q

Thymus dependent immunoglobulins

A

IgM ,IgA,IgE,IgG

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7
Q

Role of the innate immune system in B cell activation (TI)

A

-Microbes become coated with C3d

▪ B-cell have C3d receptor CR2 or CD21
▪ Engagement enhances antigen-dependent activation of B cells
▪ B cells also express Toll- like receptors

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8
Q

B cell Activation (TD): signal 1

A

Membrane bound antibody have short cytoplasmic tails
▪ Membrane Ig must be associated with B-cell receptor
• Ig-α/Ig-β

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9
Q

▪ B cell co-receptor

A
  • CD19: cytoplasmic tail for signal transduction • CR2: receptor for C3d (from complement)
  • TAPA-1: transmembrane molecule
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10
Q

▪ Inhibitory co-receptor

A
  • CD22: cytoplasmic tail for signal transduction

* Contains ITIM (Immunoreceptor tyrosine-based inhibitory motif)

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11
Q

ITIM (immunoreceptor tyrosine inhibitory motif)

A
  • Associated with CD22
  • Functionsto deactivate B cells – negative regulation
  • Importantin preventing autoimmunity
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12
Q

TD-B cell activation: Tfh cells

A
  • depend on costimulatory ICOS
  • ▪ Secrete IL-21

In germinal center: class switching and affinity maturation

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13
Q

IL-21

A

antibody production

proliferation

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14
Q

ICOS-L (CD275)

A
  • Activation

- follicular helper T cells in antibiotic responses

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15
Q

• 3 events in germinal centers

A

-arise within 7-10 days after initial exposure to thymus-dependent antigen in lymph node

❖Affinity maturation
✓Result of somatic hypermutation ❖Class switching
❖Formation of plasma and memory B cells

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16
Q

Affinity Maturation

A
  • increases with prolonged or repeated exposure
  • Result of somatic hypermutation of Ig genes
  • Enzyme activation-induced cytidine deaminase (AID) is required
17
Q

Class Switching (TD)

A 
▪ Enzyme AID is required
▪ Dependent on cytokines to switch
from IgM to other isotypes
• Thymus-dependentantigens • Interaction of CD40 on B cell
and CD40L on T cell
18
Q

▪ X-linked hyper-M syndrome:

A

• TH cells don’t express CD40L, patients only produce IgM

✓No memory cell populations, no germinal centers

19
Q

Humoral response primary

A
  • lasts 5-10 days
  • smaller response peak
  • IgM > IgG
  • lower avg affinity , more variable
  • TD or TI antigen
20
Q

Humoral response - secondary

A

-1-3 days long lag after immunization
-larger peak response
-increase in IgG
-Affinity maturation
TD antigen only

21
Q

Humoral regulation

A

▪ Antibody feedback
▪ Antigen-antibody complex forms
▪ Fc tail binds to FcgRIIB receptors on B cells

22
Q

Follicular B cells (B-2 cell) -

A
  • Most common type of B cell. Found mainly in the lymphoid follicles of secondary lymphoid organs (SLOs) and circulating in blood. They are responsible for generating the majority of high-affinity antibodies during an infection
23
Q

Marginal zone B cells

A

Found mainly in the marginal zone of the spleen and serves as a first line of defense against blood-borne pathogens. They undergo mainly T cell- independent activation

24
Q

B-1 cells

A

Predominantly populate the peritoneal and pleural cavities. Generate natural antibodies (produced without infection) against mucosal pathogens. T cell- independent activation.

25
Q

Plasmablast

A

A short-lived, proliferating antibody-secreting cell. Result from T cell- independent or -dependent activation of B cells

26
Q

Regulatory B cells

A

An immunosuppressive cell type that stops the expansion of pathogenic, pro-inflammatory lymphocytes through the secretion of IL-10, IL-35, and TGF-b

Post Midterm - Immuno (5 decks)

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