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Flashcards in Adaptive immune system Deck (52)
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1
Q

what triggers naiive B cells to proliferate?

A

APCs in lymph nodes present antigens to the B cells

2
Q

what are the cellular and soluble components of adaptive immunity?

A
cellular = B cells and T cells
soluble = immunoglobulins and cytokines
3
Q

what is the role of B cells?

A

antibody production, activation of T cells, activation of complement system

4
Q

what is the role of T cells?

A

boost the immune response

kills cells directly

5
Q

how do B cells bind to cells?

A

produce antibodies –> bind to antigens on cells –> opsonise them

6
Q

how do T cells bind to cells?

A

T cell receptors bind to protein antigens presented by cells

7
Q

where are b cells found?

A

blood and interstitial tissue NOT in cells

8
Q

what is the role of antibodies?

A

to opsonise bacteria and viruses to be phagocytosed

9
Q

what are the 2 regions of antibodies and what do they do?

A
Fc = constant region --> binds to cells surfaces such as macrophages
Fab = variable region --> at end antigen binds
10
Q

what is the mechanism by which B cells proliferate?

A

exposed to antigen in lymph nodes, antigen-antibody complex forms –> Th cells release cytokines –> proliferation + class switching + somatic hypermutation –> plasma cells –> antibodies

11
Q

what is the role of Th cells in B cell proliferation?

A

drives proliferation by releasing cytokines IL-4, IL-10, IL-13

12
Q

what is the 1st antibody released by B cells?

A

IgM (low affinity) = role in activating complement cascade

13
Q

what is class switching and where does it occur?

A

makes the antibody more specific to the antigen by changing the Fc region. Occurs in germinal centres of primary follicles in lymph nodes

14
Q

what are IgG antibodies specific for?

A

bacteria and viruses

15
Q

what are IgA antibodies specific for?

A

2 types
defence at muscosal surfaces e.g. lips lungs GI tract
protects entrance of pathogens (saliva, tears, GIT, respiratory tract)

16
Q

what are IgE antibodies specific for?

A

parasites and allergic reactions

17
Q

what are IgD antibodies?

A

found in B cell membrane, help B cell division, initial B cell receptor

18
Q

what do IgM antibodies do?

A

mainly in bloodstream, target bacteria

19
Q

overall how many different types of antibody are there?

A

5

20
Q

what are the 2 main immunoglobulins released in response to an antigen?

A

early phase = IgM (low affinity) –> activate complement cascade (bloodstream)
late phase = IgG (high affinity) –> bloodstream and interstitial tissues

21
Q

which antigen does the hepatitis B vaccination use?

A

only the surface antigen so only those antibodies found in the bloodstream

22
Q

what would the presence of antibodies against the core antigen indicate in hep B?

A

previous or chronic infection

23
Q

what is somatic hypermutation?

A
mutation of the V, D, J gene segments (Vijay is a DJ)
after class switching
24
Q

what is the role of somatic hypermutation

A

fine tunes Fab region –> more specific
3 possible results: more specific, less specific, no difference
if more specific –> more antigen-antibody complexes –> more proliferation and more antibodies produced

25
Q

what occurs in B cells overaction?

A

antibodies mimic TSH and bind to TSH receptor on thyroid

autoimmune, uncontrolled hyperthyroidism

26
Q

which Th cells are involved in activating B cells?

A

Th-2 cells

27
Q

what is the mechanism behind vaccination?

A

memory B cells remember the antigen so when exposed on the 2nd occasion they can respond more quickly which more specific antibodies so the infection is controlled more quickly

28
Q

what are the 3 types of T cells and what do they do?

A

Th cells –> cytokines –> direct action
Tk cells –> kill virus infected cells
T-reg cells –> help keep T cells under control

29
Q

what is the T cells receptor composed of?

A

TCR + CD3

30
Q

How do antigen presenting cells process antigens?

A

phagocytosis –> phagosome + lysosome –> phagolysosome –> ER releases MHC II –> MHC II + antigen expressed on cell surface

31
Q

what are the 1st and 2nd signals that activate T cells?

A

1st = CD4/CD8 bind to MHC II/ MHC I
2nd = CD28/ CD80
(CD28 on T cell, CD80 on APC)

32
Q

How are Th cells activated?

A

APC presents antigen and MHC II which binds to CD3/TCR
CD4 on T cell binds to MHCII
Th cell releases cytokines that auto-activate it

33
Q

What are the 3 types of Th cell?

A

Th-1, Th-2, Th-17

34
Q

what are the 3 types of APCs?

A

dendritic cells, macrophages, experienced B cells

35
Q

where are dendritic cells found and how do they activate Th cells?

A

reside in tissues
activated by cytokines
migrate to lymph nodes
present antigen to Th cells

36
Q

where are macrophages found and how do they activate Th cells?

A

stay in peripheral tissues and keep stimulating Th cells to keep them activating in the tissues

37
Q

how do experienced B cells activate Th cells?

A

found in blood or interstitial tissue
antigen-antibody complex –> engulf antigen –> present on surface to Th cells
rapidly activate Th cells when encounter antigen again

38
Q

what do Th 1 cells activate and which cytokines do they release?

A

cell-mediated immunity (activate Tk cells)

IL-2, IL-15

39
Q

what do Th2 cells activate and which cytokines do they release?

A

humoral response - antibody production from B cells

IL-4, IL-10, IL-13

40
Q

what are monokines and what do they do?

A

a type of cytokine that activates macrophages

41
Q

what is the clinical significance of Th1/Th2 balance?

A

determines the disease presentation or the clinical course of the disease
changes symptoms of leprosy
MS = Th1 disease
Grave’s = Th2 disease

42
Q

which cells can be infected by viruses and how is the antigen presented?

A

all cells!
virus infects –> proteosome digests viral peptides –> ER: viral peptides + MHC I –> golgi –> exocytosis –> cell membrane

43
Q

which 2 signals activate Tk cells to kill infected cells?

A

MHC I + viral peptides –> TCR/CD3

CD8 from Tk cell

44
Q

what prevents host cells from activating T cells?

A

CD80 on infected cells binds to CD28 on T cell (‘t’ and ‘two’)
second signal!

45
Q

where do T cells develop central tolerance?

A

in the thymus gland

46
Q

what is positive T cell selection and where does it occur?

A

T cells that recognise MHC molecules are positively selected for
occurs in the cortex

47
Q

what is negative T cell selection and where does it occur?

A

T cells that recognise self antigens undergo anergy

occurs in the medulla

48
Q

where does B cell tolerance develop?

A

in the bone marrow

49
Q

how do B cells develop tolerance?

A

if recognise self-antigen with help from Th cell –> anergy
don’t recognise self-antigen –> live
daily encounter with the antigen –> receptor tolerance

50
Q

what role do T-reg cells play in peripheral tolerance?

A

they eliminate immune cells directed against self-antigens

51
Q

If there is no second signal from CD80 what occurs?

A

T cell anergy (if encounter self antigen not presented by APC with CD80)

52
Q

What is an example of an immune privileged area in the body?

A

eyes - no immune cells so injury to one can lead to destruction of the other