Immunology (29/01)

Question 1

Lo’s

Answer 1

1. Describe the differences between active and passive immunity
2. Describe the major organs and tissues that are components of the immune system
3. Describe the origin of cells involved in the immune system
4. Describe the function of neutrophils
5. Describe the function of eosinophils
6. Describe the function of mast cells
7. Describe the function of basophils
8. Describe the function of natural killer cells
9. Describe the function of monocytes and macrophages
10. Describe the function of dendritic cells
11. Describe the function and variety of T lymphocytes
12. Describe the function and variety of B lymphocytes
13. Describe major differences between B and T cells.

Question 2

What is the function of the immune system?

Answer 2

The function of our immune system is to combat the ever-present threat of infection and to promote healing and restoration to normal function in the event of injury.

Question 3

Organs of the lymph system?

Answer 3

• Tonsils
• Adenoids
• Lymph nodes: contain lymphocytes and filter the lymph fluid, before it is draines back into the heart from the subclavian veins. The lymph nodes swell, when they are replicating lymphocytes to fight infection.
• Lymph vessels
• Thymus
• Spleen
• Payer’s patches
• Appendix
• Bone marrow
• B and T cells/ lymphocytes hang out in the lymph fluid.

Question 4

What is the difference between the innate and adaptive immune response?

Answer 4

• The innate immune response is activated immediately after infection and injury. It is relatively non-specific, that is it reacts the same way to all sorts of different pathogens. The cells of the innate response will then alert the acquired immune response.
• The acquired (adaptive) immune response is specific, that is it comprises of a range of exquisitely pathogen-specific responses, as well as boosting actions of the cells and mediators of the innate response. It is this response that involves B lymphocytes (which produce antibodies) and T lymphocytes. So there is memory and lasting immunity.

Question 5

Define Antigen

Answer 5

• Anti-body Gen-erating
• Any foreign material that generates antibodies
• Antigens are substances on the surface of cells, viruses, fungi or bacteria.
• Non-living substances such as toxins, chemicals, drugs, and foreign particles (e.g. splinter) can also be antigens.
• Your own body has some antigens (HLA antigens) but our immune system learns to recognise these as normal and does not react to them.

Question 6

Define epitope

Answer 6

• Tip of the antigen.
• Epitope is the small part of the antigen to which the antigen-binding sites of an antibody or the T cell receptor actually bind.

Question 7

Define immunogen?

Answer 7

• An antigen that can cause an immune response.
• Despite the fact that all antigens are recognised by a specific lymphocyte or by antibodies, not every antigen can evoke an immune response.

Question 8

What are the four steps in the immune response?

Answer 8

1. Recognition: Identify antigen as different to ‘self’.
2. Effector Functions: Containing and eliminating the foreign body.
3. Regulation: Keeping th immune response under control.
4. Memory: Long lasting immunity.

Question 9

How do we get immunity naturally and artificially?

Answer 9

• Natural
  
  • Active: foreign body invades, activates innate, then adaptive response. Get long-lasting immunity.
  • Passive: antibodies pass from the mother to the fetus via the placenta/ breast milk. Get short-lasting immunity only.
• Artificial
  
  • Active: antigens enter via vaccination. Cause innate and adaptive response. Get long-lasting immunity.
  • Passive: Antibodies from immune individuals injected into your body. Only get short term protection.

Question 10

What are the cells of the immune sytem?

Answer 10

• Leukocytes AKA white blood cells.
• Lymphocytes are T or B cells, and are a type of leukocyte.
• Develop from Pluripotent Heamatopoietic Stem Cells, found in the bone marrow.
• The PHSC can become lymphoid progenitors, or myeloid progenitor in the bone marrow.
• The myeloid progenitors can differentiate into granulocytes in the blood. Or it can become a mast cell precursor, monocyte or immature dendritic cell.
• In the tissue, the mast cell precursors become mast cells. Monocyte becomes macrophage. Immature dendritic cell stays the same in the tissue, but only matures in the lymph if they come into contact with a pathogen.

Question 11

What do neutrophils do and look like?

Answer 11

• Most common.
• Important in bactericidal mechanism and inflammation.
• Phagocytosis.

Question 12

What do basophils do and look like?

Answer 12

• 2nd most common granulocyte in blood.
• Unknown role.
• Possibly allergy/ inflammation.

Question 13

What do eosinophil do and look like?

Answer 13

• Least common granulocyte.
• Lots of them in airways in asthma for some reason.
• Kill antibody coated parasites.

Question 14

What do macrophages do and look like?

Answer 14

• Phagocytosis and activation of bactericidal mechanisms.
• Antigen presentation (neutrophils don’t do that).

Question 15

What do mast cells do and look like?

Answer 15

• Release of granules containing histamine and active agents.
• Have IgE on their surface.
• Major role in allergic responses

Question 16

What do dendritic cells do and look like?

Answer 16

• Antigen uptake and antigen presentation at peripheral sites (takes it to the lymph nodes).

Question 17

Are myeloid cells part of the innate or adaptive response?

Answer 17

• Don’t produce T or B cells.
• So innate response.

Question 18

What does the lymphoid progenitor produce?

Answer 18

• Lymphoid progenitor produced in bone marrow from PHSC.
• Differentiates in blood:
  
  • B-cells: are antigen specific, antigen binds to it, causing the b cell to proliferate and diffrentiate into a plasma cell that secretes antibodies.
  • T-cells: are antigen specific, but they need another cell to present the antigen, they don’t recognise the foreign body itself. When T cells encounter an antibody they can become cytotoxic T cells, helper T cells and regulatory T cells. They do not produce antibodies.
  • NK cells: Are not antigen specific, kill own cells they recognise as abnormal, e.g. tumours infected cells.

Question 19

Describe the granulocytes

Answer 19

1. The neutrohils are the most common granulocyte. They are involved in phagocytosis and activating the bactericidal mechanism. Have dark blue blobs in histology.
2. Basophils are the second most common granulocyte. We do not know what basophils do, they may be involved in allergy and inflammation. Have nucluei with tiny blue blobs scattered around.
3. Eosinophils are the least common granulocyte they are involved in killing antibody coated parasites. Get stained slightly pink.

Question 20

What do the myeloid cells (apart from the granulocytes) do?

Answer 20

• Mast Cells: have a major role in allergic responses. They have IgE receptors on their cell membrane and release histamine and active agents. Have a paler nulceus, and dark prurple surrounding.
• Dendritic Cells: antigen uptake and presentation at peripheral sites. Star shaped.
• Macrophages: do the same thing as neutrophils (phagocytosis and bactericidal mechanisms) and also antigen presentation. Nucleus with blue bodies surrounding it.