Adaptive system and B cells

Question 1

What do natural killer cells act against?

Answer 1

Virally infected cells and pair with cytotoxic T cells.

Question 2

What structures are involved in the innate immunity?

Answer 2

Epithelial barriers, phagocytes, complement and NK cells.

Question 3

What structures are involved in the adaptive immunity?

Answer 3

B lymphocytes, antibodies, T lymphocytes, effector T cells.

Question 4

Why does first invasion of an antigen take weeks to build a maximal immune response?

Answer 4

Specific T and B cells need to be activated and need to track down the pathogen around the body.

Question 5

How does the immune memory work?

Answer 5

The same antigen encountered will be recognised, and memory cells will be present that have a high affinity. These can be reactivated for a quicker and stronger response.

Question 6

What do CD4 and CD8 do?

Answer 6

They have a physiological function of helping the T cell engage with antigen presented to them, but they are also used as markers for identifying populations of cells.

Question 7

What is found on the surface of B cells?

Answer 7

Immunoglobulin molecules that recognise specific structures on the surface of the antigen.

Question 8

What happens when a B cell comes into contact with an antigen?

Answer 8

The B cell becomes activated and endocytoses the antigen into a vesicle inside, breaks up the antigen and presents a fragment back onto the surface in conjunction with MHC molecules.

Question 9

How are T cells involved with B cells?

Answer 9

The T cell recognises the antigen fragment that the B cell is presenting and binds to activate the B cell further.

Question 10

What do B cells develop and mature?

Answer 10

In the bone marrow. They then migrate to the lymph nodes.

Question 11

What is the main function of B cells?

Answer 11

Antibody production, but requires T cell help.

Question 12

What happens when B cells are activated?

Answer 12

They become antibody secreting plasma cells.

Question 13

What are the physical characteristics of lymphocytes in resting state?

Answer 13

They are small and round.

Question 14

What is the B cell receptor?

Answer 14

It is an antibody - the heavy chain is synthesised before the light chains.

Question 15

What do the heavy chains of the BcR combine with?

Answer 15

The surrogate light chain to form pre-BCR.

Question 16

How is BCR formed from pre BCR?

Answer 16

There is production of gamma/kappa light chains to form the BCR.

Question 17

How are B cells activated?

Answer 17

Engagement of surface abs plus costimulatory signals from T cells.

Question 18

What is the stalk of the antibody called?

Answer 18

The Fc region - this can downregulate the B cell.

Question 19

How is enhanced signalling of B cells created?

Answer 19

A complement-binding co-receptor.

Question 20

How is B cell signalling inhibited?

Answer 20

Via Fc receptors.

Question 21

What are T cells required for?

Answer 21

Costimulatory signals.

Question 22

What do B cells present to T cells?

Answer 22

Antigenic fragment.

Question 23

What do T cells upregulate?

Answer 23

CD40L and cytokine production (IL-4).

Question 24

What happens to B cells after antigen has been eliminated?

Answer 24

Some B cells will remain as memory cells.

Question 25

What is somatic hypermutation?

Answer 25

The idea that as DNA replicates there will be mutations. Some of these mutations will provide better affinity of the antibody to the antigen and will be selected. This provides greater and greater specificity for the antibodies to the selected antigen. These higher selected antibodies will be used as memory cells and will provide a faster response.