Adaptive immune system

Question 1

what triggers naiive B cells to proliferate?

Answer 1

APCs in lymph nodes present antigens to the B cells

Question 2

what are the cellular and soluble components of adaptive immunity?

Answer 2

cellular = B cells and T cells
soluble = immunoglobulins and cytokines

Question 3

what is the role of B cells?

Answer 3

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

Question 4

what is the role of T cells?

Answer 4

boost the immune response

kills cells directly

Question 5

how do B cells bind to cells?

Answer 5

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

Question 6

how do T cells bind to cells?

Answer 6

T cell receptors bind to protein antigens presented by cells

Question 7

where are b cells found?

Answer 7

blood and interstitial tissue NOT in cells

Question 8

what is the role of antibodies?

Answer 8

to opsonise bacteria and viruses to be phagocytosed

Question 9

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

Answer 9

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

Question 10

what is the mechanism by which B cells proliferate?

Answer 10

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

Question 11

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

Answer 11

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

Question 12

what is the 1st antibody released by B cells?

Answer 12

IgM (low affinity) = role in activating complement cascade

Question 13

what is class switching and where does it occur?

Answer 13

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

Question 14

what are IgG antibodies specific for?

Answer 14

bacteria and viruses

Question 15

what are IgA antibodies specific for?

Answer 15

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

Question 16

what are IgE antibodies specific for?

Answer 16

parasites and allergic reactions

Question 17

what are IgD antibodies?

Answer 17

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

Question 18

what do IgM antibodies do?

Answer 18

mainly in bloodstream, target bacteria

Question 19

overall how many different types of antibody are there?

Answer 19

5

Question 20

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

Answer 20

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

Question 21

which antigen does the hepatitis B vaccination use?

Answer 21

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

Question 22

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

Answer 22

previous or chronic infection

Question 23

what is somatic hypermutation?

Answer 23

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

Question 24

what is the role of somatic hypermutation

Answer 24

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

Question 25

what occurs in B cells overaction?

Answer 25

antibodies mimic TSH and bind to TSH receptor on thyroid | autoimmune, uncontrolled hyperthyroidism

Question 26

which Th cells are involved in activating B cells?

Answer 26

Th-2 cells

Question 27

what is the mechanism behind vaccination?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

what is the T cells receptor composed of?

Answer 29

TCR + CD3

Question 30

How do antigen presenting cells process antigens?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

How are Th cells activated?

Answer 32

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

Question 33

What are the 3 types of Th cell?

Answer 33

Th-1, Th-2, Th-17

Question 34

what are the 3 types of APCs?

Answer 34

dendritic cells, macrophages, experienced B cells

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

how do experienced B cells activate Th cells?

Answer 37

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

Question 38

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

Answer 38

cell-mediated immunity (activate Tk cells) | IL-2, IL-15

Question 39

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

Answer 39

humoral response - antibody production from B cells | IL-4, IL-10, IL-13

Question 40

what are monokines and what do they do?

Answer 40

a type of cytokine that activates macrophages

Question 41

what is the clinical significance of Th1/Th2 balance?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

which 2 signals activate Tk cells to kill infected cells?

Answer 43

MHC I + viral peptides --> TCR/CD3 | CD8 from Tk cell

Question 44

what prevents host cells from activating T cells?

Answer 44

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

Question 45

where do T cells develop central tolerance?

Answer 45

in the thymus gland

Question 46

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

Answer 46

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

Question 47

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

Answer 47

T cells that recognise self antigens undergo anergy | occurs in the medulla

Question 48

where does B cell tolerance develop?

Answer 48

in the bone marrow

Question 49

how do B cells develop tolerance?

Answer 49

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

Question 50

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

Answer 50

they eliminate immune cells directed against self-antigens

Question 51

If there is no second signal from CD80 what occurs?

Answer 51

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

Question 52

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

Answer 52

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