Immune System II

Question 1

Describe B cells and their antibodies

Answer 1

Develop in bone marrow, become plasma/memory cells, each B cell is specific for one epitope, each with unique specificity

Question 2

What do plasma cells secrete and why are plasma cells different to B cells/memory cells?

Answer 2

Antibodies of one class/specificity of the original epitope
Plasma cells are terminally differentiated - Don’t become anything else unlike B-cells (plasma/memory cells) and memory cells (further memory/plasma cells)

Question 3

Describe lymph nodes

Answer 3

A reticular network, made up of lymphocytes/macrophages/dendritic cells, interact with/respond to antigens

Question 4

Where are lymph nodes concentrated?

Answer 4

Sites with lots of lymphocytes/receive fluid from peripheral tissues

Question 5

What do T-cell receptors do (TCR)?

Answer 5

Recognise antigen fragments presented by another cell

Question 6

Where are antigen fragments presented?

Answer 6

On MHC molecule

Question 7

How do T cells produce protein IgG?

Answer 7

B cells/macrophages break down to form antigen presenting cells

Question 8

What do T cells only recognise?

Answer 8

Peptides

Question 9

Define an antigen

Answer 9

Any substance that binds specifically to an antibody/T cell receptor

Question 10

What does MHC stand for and what does it do?

Answer 10

Major histocompatibility complex (also HLA)

Present antigens on the membrane/presentation of peptide fragments to T cells

Question 11

What are the 2 classes of MHC and where can they be found?

Answer 11

Class I - On most cells (CD8+)

Class II - On immune cells/antigen presenting cells eg dendritic cells (CD4+)

Question 12

Describe the role of MHC class I

Answer 12

Endogenous path - Peptide fragments bind to MHC C1 broken down to proteasome/AA sequences, transported/bind to ER at MHC C1 molecules to display on CSM, source can be intracellular infection

Question 13

Describe the role of MHC class II

Answer 13

Exogenous - Pathogens phagocytosed into vesicles broken into peptide frags, enzymes have effect on ingested peptides to AA, associate with MHC C2 molecules for display on CSM

Question 14

Describe the response of CD8+ T cells

Answer 14

Recognise antigen presented by MHC class I
Respond to recognition by initiating cell death
Cytotoxic T cells (TC cells)

Question 15

Describe the response of CD4+ T cells

Answer 15

Recognise antigen presented by MHC class II
Respond to recognition by becoming activated and releasing cytokines
T helper cells (TH cells)

Question 16

Describe NK cells

Answer 16

Many different receptors - Activator/Inhibitor
Interact with host cell
Secrete cytokines after activation and activate macrophages

Question 17

What happens if the activation receptors are stimulated more than the inhibitory receptors (NK cells)?

Answer 17

Causes NK cells to kill the host cell

Question 18

Describe what happens outside a cell when a pathogen binds to a B cells’s membrane bound antibody

Answer 18

Pathogen is engulfed by B cell and broken down to fragments which is attached to MHC II complex
This will bind to cell membrane to present itself (APC)
A Th Cell can bind to it with its own antigen to activate B cells

Question 19

Describe what happens inside a cell if cancer cells begin to grow

Answer 19

MHC I complex binds to parts of the cancer cell pathogens and forms an antigen presenting cell
Tc Cells can bind to this using its antigen receptor and either activate memory Tc cells or Effector Tc Cells which can release perforins to kill the cancerous cells

Question 20

What do MHC I complexes bind to?

Answer 20

All cells with a nucleus (except RBCs) to bind to the cells and the foreign pathogens within he cell to present it onto the cell surface

Question 21

Describe the role of CD4+ cells (using Khan’s Academy video notes)

Answer 21

CD4+ is the alarm, only binds to MHC II complexes, dendritic cell (prof APC) will bind with the CD$+ antigen receptor
APC can become effector cells which either activate B cells or release cytokines to increase proliferation

Question 22

Describe the role of CD8+ cells (using Khan’s Academy video notes)

Answer 22

CD8+ Th cells kill, only bind to MHC I complexes, a cancerous cell can bind to its antigen receptor to present itself
Cancerous APC can become an effector or memory cell (Tc cytotoxic killer cell) to kill the cancerous cells