Lymphocytes

Question 1

Function of adaptive immunity

Answer 1

Improves efficacy of innate immune response.

Focuses a response on the site of infection and organism responsible.

Has memory but needs time to develop.

Question 2

What is immunological memory?

Answer 2

Immunological memory is the ability of the immune system to quickly and specifically recognise an antigen that the body has previously encountered and initiate a corresponding immune response.

Question 3

What are the two types of adaptive immune responses/

Answer 3

1. Humoral

2. Cell mediated

Question 4

What is an epitope?

Answer 4

The region of an antigen to which the receptor binds to.

Question 5

What is clonal selection?

Answer 5

Each lymphocyte bears a unique receptor. Interaction with an antigen and that receptor leads to activation causing differentiated effector cells of that lineage to bear the same receptor.

Question 6

What is the problem with antigen diversity?

Answer 6

We are exposed to a huge variety of antigens which the immune system must be able to respond to. However the adaptive immune system is also very specific therefore to respond to all these different antigens we need a huge pool of cells with specific receptors that can recognise this huge array of antigens.

Question 7

What is a repertoire?

Answer 7

The different receptors that can be produced through immunoglobulin gene rearrangement.

Question 8

What does MHC stand for?

Answer 8

Major histocompatibilty complex.

Question 9

What is the function of MHC?

Answer 9

Presents antigens to T cells.

Question 10

What is the difference between MHC class 1 and MHC class 2?

Answer 10

1 - present on all nucleated cells, Usually interacts with CD8 cytotoxic T cells.

2. present only on professional antigen presenting cells e.g. dendritic cells. Usually interacts with CD4 T helper cells.

Question 11

Where are intracellular and extracellular antigens processed?

Answer 11

Intracellular - cytosol

Extracellular - endosomes

Question 12

What are endosomes?

Answer 12

Membrane bound vesicles found in most animal cells.

Question 13

What is the function and mechanism of CD8 cytotoxic T cells?

Answer 13

Kills target cell by cell lysis. The cell stores perforin, granzyms and granulysin in cytotoxic granules which are released after target recognition. The perform then polymerises to form pores in the target cell allowing the enzymes to enter and also allowing fluid to enter causing cell lysis.

Question 14

What is the function of CD4 helper T cells?

Answer 14

Produces cytokines that influence the outcome of the immune response.

Question 15

What are the types of antibodies produced by a B cell?

Answer 15

IgM, IgD, IgE, IgG and IgA.

Question 16

What are the 3 main functions of antibodies?

Answer 16

1. Neutralisation
2. Opsonisation
3. Complement activation

Question 17

Can naive lymphocytes be activated by the antigen alone?

Answer 17

No - for example, B cells require accessory signals from microbial constiuent and a T helper cell.

Question 18

What are the 2 pathways by which antibody produced in B cells is achieved?
What type of antibodies can be produced by each pathway?

Answer 18

1. Thymus dependent - forms all Ig classes and memory cells.
2. Thymus independent - only forms IgM and cannot form memory cells.

Question 19

What are thymus independent antigens?

Answer 19

Antigens that can directly activate B cells without the help of T cells. The second signal required is either provided by the microbial constituent or by an accessory cell.

Question 20

What are the 5 steps by which B cells are activated by thymus dependent antigens?

Answer 20

1. The membrane bound BCR recognises antigen
2. The receptor bound antigen is internalised and degraded into peptides.
3. Peptides associate with self molecules (MHC class 2) and is expressed at the cell surface
4. This complex is recognised by matched CD4 helper T cell.
5. B cell activated