anatomy and surveillance

Question 1

what T cells are removed during clonal deletion ?

Answer 1

the ones that bind too tightly to self MHC peptide complex

Question 2

the large number of lymphocytes that are produced from a single progenitor , do they all have the same specificity?

Answer 2

no they all have a different specificity

Question 3

how does the T cell precursor produce diversity and where does this occur ?

Answer 3

in the thymus it rearranges it’s T cell genes through somatic recombination.The TCR are diverse

Question 4

what happens in the thymus if the immature T cell recognises self MHC and binds moderately ?

Answer 4

it receives a signal for survival

Question 5

what happens to the T cells that interact with self antigens ?

Answer 5

they are removed by apoptosis

Question 6

what happens to the mature T cell after selection has occured ?

Answer 6

move to the periphery lymphoid organs from the thymus and it is here that they encounter foreign antigens and become activated and matured fully.

Question 7

what happens once the T cells become activated ?

Answer 7

they acquire effector functions. The activated T cells then proliferate and migrate to the site of infection to eliminate it.

Question 8

name the primary lymphoid organs ?

Answer 8

thymus and bone marrow

Question 9

what are lymph nodes ?

Answer 9

small glands that filter lymph that circulates the lymphatic system.

Question 10

what are the lymph nodes ideal for ?

Answer 10

ideal environment for communication of immune cells

Question 11

where do the lymphocytes encounter and respond to antigens ?

Answer 11

in the peripheral lymphoid organs

Question 12

what is the Peyers patch ?

Answer 12

this is the lymphoid organ that is near the intestine

Question 13

what is situated in the inner paracortical area ?

Answer 13

this is where the T cell are

Question 14

what is situated in the outer area called primary lymphoid organ ?

Answer 14

this is where the B cells are

Question 15

do the B and T cells have seperate areas or are they in the same section ?

Answer 15

separate areas

Question 16

what occurs in the germinal centre ?

Answer 16

the B and T cells meet and they can activate each other

Question 17

what does the naive T cells do ?

Answer 17

migrate through the secondary lymphoid tissues

Question 18

what does the dendritic cells act as in the lymphoid organ ?

Answer 18

act as APC in the T cell area of the lymph node so that they can initially activate the naive T cell.

Question 19

what happens if the naive T cell does not become activated by the dendritic APC in the lymph node ?

Answer 19

it exits the lymph node via the cortical sinuses

Question 20

how do naive lymphocytes enter the lymph nodes ?

Answer 20

via the blood

Question 21

how are peptides presented to the TCR in context of the MHC ?

Answer 21

in two forms
– MHC-I - CD8+ T cells – killer cells
– MHC-II - CD4+ T cells – helper T cell

Question 22

how is the adaptive immune response initiated?

Answer 22

by the antigen and antigen presenting cells in the secondary lymphoid organs.

Question 23

what occurs if the T cell recognises the antigen/MHC ?

Answer 23

T cell and APC have an interaction and the TCR transmits a signal and the T cell becomes activated

Question 24

what happens once the T cell becomes active ?

Answer 24

proliferates it can no longer exit the lymph node and it is here that it differentiates into the effector cell of either Cd4+ or Cd8+ and then exits the lymph node.

Question 25

what do cytokines do in the role of adaptive immune ?

Answer 25

they influence the effector functions

Question 26

how are most pathogens kept outside the body ?

Answer 26

by the epidermis layer which acts as a barrier

Question 27

when will the pathogen enter the dermis layer by crossing the epidermis layer ?

Answer 27

when there’s been a breach to the barrier for example an injury.

Question 28

what do T cells in turn activate ?

Answer 28

B cells and this results in production of antibody after plasma cell has been differentiated.

Question 29

give example of how CD4+ cells are helpers ?

Answer 29

activate macrophages to become more cytotoxic while the antibodies recruit complement to lyse the pathogen directly by causing opsonisation so that phagocytes can be recruited to kill them.

Question 30

what is activated first to try and control the infection ?

Answer 30

the innate immune systems

Question 31

what happens if the innate cannot control the infection ?

Answer 31

the threshold is reached and the adaptive is induced. This is called the inductive phase

Question 32

what happens after the inductive phase ?

Answer 32

T cells are activated the effector phase occurs in the peripheral where the Cd4+ and Cd8+ are induced.

Question 33

what occurs when someone has been vaccinated ?

Answer 33

time of the effector phase has been shortened and the threshold is lower.