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Principles > Immunology: Initiation of Acquired Immune Responses - B Cells > Flashcards

Immunology: Initiation of Acquired Immune Responses - B Cells Flashcards

1
Q

where do
- B cells
- T cells
mature

A
  • bone marrow

- thymus

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2
Q

what immune response are
- B cells
- T cells
responsible for

A
  • humoral

- cellular

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3
Q

what is the role of B cells

A
  • produce antibodies to attack pathogens in circulation

- defend against both EC and IC pathogens

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4
Q

what is the role of T cells

A
  • defend against IC pathogens
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5
Q

what do CD4+ T cells do

A
  • T helper cells

- regulate immune system

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6
Q

what do CD8+ T cells do

A
  • cytotoxic T cells

- kill virally infected host cells

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7
Q

give a general description of antibodies

A
  • bind to a specific antigen
  • complex of 4 polypeptide chains
  • unique variable region that binds to antigens (Fc)
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8
Q

how do B cells use antibodies

A

membrane bound antibodies - receptor to reg=cognise and bind to antigens

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9
Q

why is the B and T cell response more specific to antigens

A

they express 1 antigen receptors that binds to a specific antigen epitope

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10
Q

where are mature T and B cells usually

A

circulating between blood, lymph and 2* lymphoid tissue

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11
Q

how to T and B cells enter lymph nodes

A

via high endothelial venules (HEV)

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12
Q

what is the function of lymph nodes

A
  • key site of pathogen detection

- faciliate T and B cell activation

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13
Q

what happens once
- B cells
- T cells
enter lymph nodes

A
  • go to lymphoid follicle

- go to T cell area and interact with dendritic cells

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14
Q

how do denritic cells enter lymph nodes

A

via lymph

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15
Q

how do lymph and lymphocytes leave the lymph nodes and where to they go after

A
  • leave through the medullary sinus then into lymph vessels

- eventually drains into a subclavian vein

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16
Q

what 2 types of cells do B cells differentiate into once activated

A
  • plamsa B cells

- memory B cells

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17
Q

what is the role of plasma B cells

A

produce and secrete soluble antibodies

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18
Q

what is the role of memory B cells

A

long-lived and continually circulate after infection

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19
Q

what antibodies do B cells use to respond to specific antigens

A

membrane-bound Igd/IgG

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20
Q

describe how B cells encounter antigens

A
  • soluble antigens are released into tissues as debris after phagocytosis
  • they then travel to lymph nodes and are trapped by cells expressing opsonin receptors
  • B cells encounter them and activate
21
Q

what are opsonised antigens

A

antigens released into tissues after phagocytosis

22
Q

what do B cells need to activate

A
  • antigen

- ‘helping’ signal

23
Q

what are the 2 signals B cells need to activate in

  • protein antigens
  • other antigens
  • repetitive epitopes
A
  • BCR binding and Th cell help
  • BCR + antigen and PRRs + PAMPs
  • multiple BCRs + antigens engaged
24
Q

after actviation what happens to B cells

A

clonally proliferate forming a germinal centre, can then differentiate

25
Q

what do plasma cells initially secrete

A

IgM

26
Q

B cells start producing ‘better’ antibodies (i.e. IgG, IgA, etc) with help from what

A

T helper cells presenting antigens to B cells

27
Q

what is the recognition function of Igs in killing pathogens

A

bind to antigen mediated by variable region sites

28
Q

what is the effector function of Igs in killing pathogens

A

clearance mechanisms that are mediated by the interaction of the heavy chain constant region with effector molecules (Fc receptors, complement proteins)

29
Q

what is the functin of IgM in its membrane bound form and what form is it in

A
  • activates B cells

- monomer

30
Q

what is the functin of IgM in its secreted form and what form is it in

A
  • agglutination and complement activation

- pentamer

31
Q

what is agglutination and what mediates it

A
  • antibody cross-links multiple antigens produing antigen clumps
  • IgM/IgG
32
Q

what is the function of agglutination and why

A
  • enhances phagocytosis

- many antigens phagocytosed at once

33
Q

what region of IgM/IgG activated the complement system and how does this work

A
  • Fc region (when bound to antigens)
  • Fc binds to antigen and a conformational change occurs, this exposes multiple binding site for the first intermediate of the classical pathway
34
Q

which antibody is the most abundant

A

IgG

35
Q

which antibody is the most dominant in the 2* immune response

A

IgG

36
Q

what form is IgG in and what is its functions

A
  • monomeric

- agglutination, NK activation, opsonisation, complement activation, neutralisation, foetal immune protection

37
Q

what is IgG’s role in foetal immune protection

A
  • transported across then placenta into foetal circulation

- protects neonates against pathogens until it develops its own immune system

38
Q

what can lead to low levels if IgG in neonates

A

IgG levels from the mother wanes over time and therefore without its own production leading to low levels

39
Q

what is neutralisation and what mediates it

A
  • prevents viruses infecting host cells and microbial toxins disrupting normal cell functions
  • IgG and secretory IgA
40
Q

how does neutralisation perform its functions

A
  • block entry of toxins/viruses into cell
  • cause agglutination of viral particles
  • stop uncoating of viral genomes
  • interfere with viruses binding to receptors
41
Q

what antibody is a good opsonin and why

A
  • IgG

- phagocytes possess and Fc receptor that IgG binds to, enhancing phagocytosis

42
Q

how are NK cells activated in the innate immune system

A
  • pathogens recognised by PAMPs
  • interferons secreted
  • NK cells activated
43
Q

how are NK cells activated in the adaptive immune system

A
  • IgG secreted

- NK cells activated

44
Q

how do NK cells kill virally-infected host cells

A

via pro-inflammatory mediators

45
Q

what is the function of IgD and what form is it in

A
  • B cell activation, membrane bound B cell receptor

- monomer

46
Q

what antibody is the second most abundant

A

IgA

47
Q

what 2 forms does IgA come in and what are each of their functions

A
  • monomer in serum, neutralisation

- dimer in secretory fluids (SIgA), neonatal defence and neutralisation

48
Q

how does IgA provide neonatal defence

A

transported into colostum and breast milks to protect neonatal GI tract

49
Q

what does IgE trigger

A

allergic responses

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