Lymphocytes

Question 1

What do lymphocytes stem from?

Answer 1

Common lymphoid progenitor cell

Question 2

What types of immune response are there and which lymphocytes correspond?

Answer 2

Humoral - B Cells, use antibodies

Cell-Mediated - T Cells, use cytokines

Question 3

What are antigens?

Answer 3

Proteins on cell surface membranes used to identify cells, and to know if they are self cells or foreign

Question 4

What is an epitope?

Answer 4

The part of an antigen which an antibody binds to

Question 5

What is the problem with antigen diversity?

Answer 5

To respond to all of the different antigens our bodies would require a large pool of cells with specific receptors but as specificity increases, diversity decreases

Question 6

How is antigen receptor diversity generated?

Answer 6

Immunglobulin gene rearrangement:

• Each BCR chain is encoded by separate multigene families on different chromosomes
• When B Cells mature the gene segments arrange is a random order

Question 7

What is the structure of a T cell receptor?

Answer 7

A part of a complex of proteins on the cell surface membrane

Question 8

What do T cell receptors detect?

Answer 8

Linear epitopes(fragments of proteins made by other cells)

Question 9

What do MHCs do?

Answer 9

They present antigens to T cells

Question 10

What gene encodes MHCs?

Answer 10

HLA genes

Question 11

Where are MHC class 1 found?

Answer 11

On all nucleated cells

Question 12

Where are MHC class 2 found?

Answer 12

On antigen presenting cells

Question 13

How do MHC class 1 work?

Answer 13

They are on the surface of cells and are constantly presented with proteins produced from inside the cell so the body knows what antigens are self
Viruses cause the cell to produce viral proteins and this it detected by MHC1 receptors

Question 14

How do MHC type 2 work?

Answer 14

They are present on dendritic cells and travel around the body
If they come into contact with infectious material they engulf it, break it down and present the antigen on the MHC2

Question 15

What cells do MHC1 interact with?

Answer 15

CD8 killer T cells

Question 16

What cells do MHC2 interact with?

Answer 16

CD4 T cells

Question 17

What are CD4 cells?

Answer 17

T-helper cells

Question 18

What are CD8 cells?

Answer 18

Cytotoxic T-killer cells

Question 19

How do CD8 cells work?

Answer 19

They contain perforin which punctures a hole in the membrane of a bad cell and then granzymes are injected to stimulate apoptosis of the cell

Question 20

What do CD4 cells do?

Answer 20

They contain cytokines which stimulate other immune cells in the body to react to the infection

Question 21

What is the function of B cells?

Answer 21

They make antibodies is response to soluble antigens detected
Require help from other cells to produce antibodies

Question 22

What is the structure of antibodies?

Answer 22

They have a main heavy chain and a light chain

These chains are both made up of variable and constant regions

Question 23

What are the classes of antibody?

Answer 23

IgG, IgA, IgE, IgD and IgM

Question 24

What is the function of antibodies?

Answer 24

Nerutralisation:
Bind to pathogens and prevent them from communicating to and entering cells
Opsonisation:
Surround pathogen which promotes phagocytosis
Complement activation:
Enzymatic cascade leading to cell death

Question 25

What is the structure of BCRs?

Answer 25

They are antibodies on the cells surface

Question 26

What signals can a B cell receive to produce antibodies?

Answer 26

• Signals directly from microbial constituents

- Signals from a T helper cell (CD4)

Question 27

What are thymus independent antigens?

Answer 27

Antigens that directly activate B cells without the help of T cells
They have a repeating structure, cause B cell to clump together
Second signal is provided by microbial constituent or an accessory cell
It isnt very strong

Question 28

How do T cells activate B cells?

Answer 28

• Dendritic cells and B cells both detect and engulf pathogens
• They present the antigen on their MHC2 recptors
• The dendritic cell then activates the T helper(CD4) cell
• The active CD4 cell then goes and activates the B cell
• The B cell matures into a plasma cell and produces antibodies