lecture 12

Question 1

define immunisation

Answer 1

a harmless molecule typically of one protein is injected into an individual in the form of a suspension containing atrovent
the adjuvant comprises sets of immunological stimulants such as inactivated mycobacterial proteins and irritants. these activate innate immunity responses
these innate immune responses also recognises the foreign antigen witches then used to train the adaptive immune response

Question 2

define herd immunity

Answer 2

it is vaccinating a small population of affected people

Question 3

who is Andrew Wakefield

Answer 3

he published a paper in 1998 falsely linking MMR Vaccines with autism

Question 4

where are lymphocytes made?

Answer 4

lymphocytes develop in central or primary lymphoid organs like the bone marrow or the thymus
they’ve been migrated to the peripheral or secondary lymphoid organs like the tonsils, lymph nodes, spleen, appendix, skin or respiratory tract

Question 5

where are lymphocytes concentrated and what is lymph?

Answer 5

lymphocytes occur in large numbers in the blood and the lymph
they are also concentrated in the lymphoid organs like the thymus, lymph nodes, spleen and appendix

lymph is the liquid in the lymphatic vessels which link the lymph nodes together

Question 6

experiment 1 from the 1950s on lymphocytes (establishing what is responsible for adaptive immune responses)

Answer 6

experiments established that lymphocytes were responsible for adaptive immune responses (aka making T cells and antibodies)

a mouse was injected with antigens and gave normal adaptive immune responses
another mouse was irradiated before injecting it with antigens and so was unable to mount an adaptive immune response but could still react via some innate responses

the assumption from this experiment was that the radiation treatment had destroyed the cells of the adaptive system

then various types of cells were transferred into these animals

Question 7

experiment 2 from the 1950s on lymphocytes (transferring lymphocytes into rodents)

Answer 7

mouse was injected with the antigen and gave a normal adaptive immune response
mouse was injected with the antigen and irradiated and did not give any adaptive immune response
mouse was injected with antigen and irradiated and given lymphocytes from normal animal and skaven normal adaptive immune response
mouse was injected with antigen and irradiated and given other cells from a normal animal and did not give any adaptive immune responses

Question 8

how do the dentritic cells link the innate system to the adaptive system?

Answer 8

dendritic cells are widely distributed in tissues and organs
they display a wide variety of tlrs and other pattern receptors
they are activated by binding of pathogen to any of these receptors. activated dendritic cells phagocytose and degrade invading microorganisms
peptides from the degraded organism are displayed on the cell surface of these dendritic cells

the dendritic cells then migrate and travel to a nearby lymphoid organ where they activate the adaptive immune response, training them to recognise the peptide fragments that are carried

(TLRs are receptors for PAMPs)

Question 9

First Contact is the dendrites with t cells

Answer 9

(an antigen capturing dendritic cell matures into antigen presenting cell)

the innate immunity responses activate the dendritic cells which engulf their prey and digest the pathogens to peptides
DC migrate to a lymphoid organ and mature during this process to an antigen presenting cell
these peptides are presented to T cells

Question 10

define and describe T cells

Answer 10

they develop in the thymus tissue from thymocytes
t cells will divide into the blood cell types (red white platelets)
the hematopoietic stem cells in the case of T cells will develop into a common lymphoid precursor in the bone marrow
then they migrate from bone marrow to the thymus where they mature into thymocytes
they are trained to not react to self antigens
they migrate to the nearest lymphoid organ where there are now activated

Question 11

how do dendritic cells activate T cells?

Answer 11

first the DC present peptides to T cells, and 1 of 3 will happen:
the t cell TCR recognises self antigen and so no action is taken
t cell TCR recognises no antigen and no action is Taken
t cell TCR recognises non self antigen and is activated, mitosis takes place and clonal expansion of specific t cells occurs

Question 12

how do antigen presenting cells present only to T cells and not other cells?

Answer 12

costimulatory molecules on antigen-presenting cells dock with t cell-specific costimulatory molecules
peptide is held in the groove of an APC presenting protein and is scanned by the TCR
both APC and T cell produce costimulatory molecules that attract each other. then the t cell can scan the display groups on the APC
no recognition = no action, cells undock / recognition = t cell activated

Question 13

how can we can get inbuilt specificaty with this system? and why do we need the innate immune system?

Answer 13

for every different pathogen in encountered, different clones of effector t cells are made

this activation and clonal expansion takes time which is why we need the innate immune system to protect us over the first few critical hours after encountering pathogens

Question 14

what are the three classes of T cells?

Answer 14

T helper cells - help other immune cells to do their job
T cytotoxic - is the killer cell
T regulatory/suppressor - is the regulation of the immune system and slow it down

Question 15

how do Tc Th and Treg migrate to the site of migration

Answer 15

activated t cells migrated to the site of infection
maturation from antigen capturing dendritic cells to mature antigen presenting cells occurs while the T cells move from the infection site to the lymphoid organ

they follow a chemical trail to get to the inflammatory region and then act locally to regulate and kill infected cells

Question 16

how do Th Tc and Treg act locally?

Answer 16

TH
they activate macrophages, dendritic cells, b cells and maintain cytotoxic t-cell activity by secreting a variety of cytokines

TREG
regulatory cells inhibit the function of helper t cells, cytotoxic t cells and dendritic cells

TC
they kill infected host cells by persuading them to commit suicide apoptotically

Question 17

how do cytotoxic T cells kill?

Answer 17

the Tc cell recognises the antigens that were used to activate it on the target cell membrane and so bind specifically to a target cell
the contact points form an immunological synapse and enclose a space

natural killer cells and T cells or closely related so the t regulatory cells can borrow the natural killer cells mechanisms

Question 18

what are the two strategies that these cytotoxic t cells use? (and natural killer cells)

Answer 18

1. the TC cell secrets perforins which assemble and form a channel in the target cell wall
   the t-cell then secretes specific proteases which enter the target cell and activate caspase (the effector proteins of apoptosis)
2. the TC cells binds receptors on the target cell that send a signal that activates caspase (the effector proteins of apoptosis)
   the second mechanism is through signalling and results in the activation of the caspase

the end result is the same where caspases induce apoptosis

Question 19

end result of apoptosis

Answer 19

the apoptotic bodies are phagocytosed by antigen presenting cells and can therefore be used to retrain T cells
this is an amplifying process and that’s why T reg suppressor t cells are needed

Question 20

advantages of apoptosis

Answer 20

it doesn’t stimulate inflammation because none of the contents of the target cell are released systematically, they are eaten by other cells

however dentritic cells are professionals at phagocytosis so the process is in amplifying process itself because more than dendritic cells are activated. this leads to more training of T cells and of new generations that are better at recognising targets

Question 21

REVISE SUMMARY GRAPH

Answer 21

of innate immune response and adaptive immune response and the links between them