third line of defence (specific/adaptive immunity)

Question 1

when is the third line of defence activated?

Answer 1

when the first two are overcome

Question 2

why does the adaptive immune response have tolerance to self cells?

Answer 2

ask labrooy

Question 3

why does the adaptive immune response have immunological memory?

Answer 3

because memory T and B cells are produced.

Question 4

why is the adaptive immune response specific?

Answer 4

because cells/antibodies have receptors that are specific to each antigen

Question 5

what “test” must happen before b and T cells become naive?

Answer 5

if they don’t recognise self antigens/don’t respond to non-self antigens, they are eliminated via apoptosis; if they pass they’ll go to the lymph nodes where they’ll be activated

Question 6

cell mediated adaptive immunity involves…

Answer 6

T cells

Question 7

t cells recognise ______ pathogens

Answer 7

intracellular

Question 8

describe t cell development

Answer 8

precursor cells develop in bone marrow then migrate to thymus where they become naive t cells.

Question 9

describe t cell receptors

Answer 9

formed by 2 pp chains forming the antigen binding site

Question 10

which can antigens can t cells repsond to?

Answer 10

only those physically linked to MHC self markers on the surface of other cells

Question 11

define: antigen presenting cells

Answer 11

cells that move antigens to their surface and then display these antigens to other immune cells.

Question 12

examples of antigen presenting cells?

Answer 12

dendritic cells and some phagocyes

Question 13

wehre are dendritic cells usually found?

Answer 13

skin, lining of airways, gut

Question 14

how do dendritic cells work?

Answer 14

Engulfs pathogens via phagocytosis and degrades them; but in the cytoplasm, they retain some peptide fragments from degraded pathogens, forming anitgens.
Antigens are then linked to class II MHC molecules in cytoplasm and then transferred to the cell surface.
Then, the dendritic cells go to the nearest lymph nodes and present them to naïve helper T cells.

Question 15

what cell markers to helper t/cytotixic t cells have?

Answer 15

CD4vsCD8

Question 16

how do helper t cells work?

Answer 16

antigens of antigen presenting cells bind to naive helper T cell receptors - activates, proliferates;
releases cytokines which enables diviision of cytotoxic T cells and B cells

Question 17

how do cytotoxic t cells work?

Answer 17

when a cell is infected, its foreign antigens will be attached to MHC class I markers
Cytotoxic T cells with complementary receptors will bind to angiten, activating it, and when it receives Th cell cytokines it will divide.
THey release perforin and granzyme B, inducing apoptosis

Question 18

what is the humoral adaptive immune response?

Answer 18

B cells, and their antibodies that they produce

Question 19

humoral adaptive immune response acts on _________ pathogens

Answer 19

extracellular

Question 20

define: antibodies

Answer 20

directly identify and bind to extracellular foreign antigens, either neutralising them or tagging them for destruction.

Question 21

how are antibodies produced?

Answer 21

by B cells

Question 22

where can antibodies be present

Answer 22

in solution in blood/lymph, in secondary lymph organs or as surface receptors on B cells.

Question 23

how do antibodies work?

Answer 23

o Binding to surface antigens on pathogens, preventing them from binding to/infecting self cells
o For bacterial toxins, they bind toxin/venom, preventing them from binding to/effecting self cells.
o Binding to antigens on pathogens which tags them for destruction. Eg:
 Complement proteins are activated by antibodies on surface of pathogens which can lead to formation of MACs
 This binding opsonises them, making them more susceptible to elimination by phagocytes

Question 24

describe structure of antibodies

Answer 24

2 light and 2 heavy chains, joined by hinge region consisting of disulphide bonds which gives antibody flexibility, helping it fit with antigen
constant region and variable region, consisting of an antigen binding site

Question 25

describe IgG

Answer 25

• IgG is the main antibody in blood
• Passive natural immunity – passes placenta, in breast milk
• Activate macrophages and complement system
• Against viruses

Question 26

describe IgM

Answer 26

• First antibody to appear at infection, defends until enough IgG is formed
• IgM is made up of 5 antibodies. Activates macrophages and complement system c

Question 27

describe IgA

Answer 27

• Present in saliva, tears, sweat, mucous membranes, breast milk and bowel fluid - protects surfaces
• Against viruses

2 antibodies

Question 28

describe IgE

Answer 28

• Activate mast cells which release histamines - therefore a key factor in allergic reactions + immune reactions to parasites
• Immune reactions to parasites

Question 29

describe IgD

Answer 29

• Present on the surface of B cells and plays a role in the induction of antibody production.
• Activate basophils and mast cells

Question 30

where do B cells develop?

Answer 30

bone marrow

Question 31

deifne: clonal selection theory

Answer 31

explains how large numbers of antibodies for a specific antigen are produced at a given time when initially there are only a few B cells with these specific antibodies.

Question 32

define: clonal selection

Answer 32

in lymph nodes, when antigen meets B cell with complementary antibodies (at antigen binding sites) on surface and binds to it.

Question 33

define: clonal expansion

Answer 33

binding of antigen to its B cell. This activates it and initiates cycles of cell division, making clones of B cells.

Question 34

what happens druing clonal expansion?

Answer 34

activated by helper T cell
takes about a week for sufficient numbers to be produced
differentiated into short lived plasma cells or long lived memory B cells

Question 35

effect of memory B cells?

Answer 35

when the body encounters the pathogens again, a more rapid/strong immune response will occur – more antibodies will be produced, more quickly.
o This is the purpose of vaccinations