Immunity

Question 1

What is immunity?

Answer 1

way of protecting the body against an infectious disease. Types of immunity are innate and adaptive.
Innate have a non-specific resistance.
Adaptive have a specific resistance.

Question 2

Explain the innate defences

Answer 2

First line of defence:
- Mechanical barriers e.g., skin, mucous membranes
- Chemical barriers e.g., stomach acid, lysozyme
Second line of defence:
- Antimicrobial proteins e.g., stomach interferon, complement (enhances immune response), transferrins (inhibit bacterial growth)
- Natural killer cells, destroy cells by perforating the plasma membrane (making them leaking)
- Phagocytes, engulf cells (may be fixed or wandering macrophages)
- Inflammation , causes redness, pain, heat and swelling
- Fever, bodas thermostat in the hypothalamus to a higher level, the increase temperature enhances interferon, inhibits some microbial growth & speeds up repair.

Question 3

What is phagocytosis?

Answer 3

surround any pathogens in the blood and engulf them. Enzymes in the phagocyte break down the pathogen and destroy it.
1. Phagocyte adheres to pathogen or debris
2. Phagocyte forms pseudopods that eventually engulf the particles, forming a phagosome
3. Lysosme fuses with the phagocytic vasicle, forming a phagolysosome
4. Toxic compounds and lysosomal enzymes destroy pathogens
5. Sometimes exocytosis of the vesicle removes indigestible and residual material

Question 4

Adaptive defences

Answer 4

Is the body’s defence against specific invading agents such as bacteria, viruses, toxins or foreign tissues.
Characterised by:
- specificity
- memory
The invading agents are recognised as being ‘non-self’.
The specific resistance is carried out by lymphocytes that originate in the bone marrow.
Once mature, the lymphocytes acquire specific antigen receptors that allow them to recognise a specific invading agent.
* Immunocompetence & self-tolerance

Question 5

What are the two types of lymphocytes?

Answer 5

• B cells (B lymphocytes)
• T cells (T lymphocytes)

Question 6

How are B cells developed/ link to the antibody mediated response?

Answer 6

• develop in the red bone marrow
• once stimulates by an antigen, B cells clone and then become plasma cells
• plasma cells produce antibodies also known as immunoglobulins
• this is known as an antibody mediates or humeral response
• antibodies ‘neutralise’ antigens

Question 7

Explain the production of antibodies

Answer 7

• a specific antigen is identified by B lymphocyte
• B cells form a clone and become plasma cells
• plasma cells secrete antibodies
  Antibodies are protective proteins produced by your immune system. They attach to antigens (foreign substances) and remove them from your body.

Question 8

What are the five classes of antibodies?

Answer 8

1. IgG- main antibody and able to cross placenta
2. IgA- secretory antibody
3. IgM- released into plasma, indicates current infection
4. IgE- associated with allergies and parasitic infections
5. IgD- attached to B cell and acts as an antigen receptor

Question 9

What is the role of T cells?

Answer 9

• leave the bone marrow and migrate to the thymus to complete their development.
• T cells are involved in cell mediated immune responses
• cell mediated immune responses are directed against intracellular pathogens such as viruses, cancer cells and tissue transplants
• T cells become killer T cells that directly attack the invading antigen
• or help become helper T cells that help both antibody mediated and cell mediated responses

Question 10

Memory in B and T cells

Answer 10

• Immunological memory is the ability of the immune system to respond more rapidly and effectively to pathogens that have been encountered previously.
• both B and T cell responses produce memory cells
• memory cells have memory of the invading antigen
• this memory allows for the second or subsequent response to be much quicker and much greater
• end result: the signs and symptoms of the disease are not seen

Question 11

Primary and secondary responses to disease

Answer 11

• Primary response is slow and ineffective. Signs and symptoms of the disease are seen.
  Thanks the memory…
• Secondary response is much faster and greater. Signs and symptoms of the disease are not seen- immune.

Question 12

Autoimmune responses=

Answer 12

• the body does not stack its own tissues because it recognises them as ‘self’
  i.e., the body tolerates its own molecules= immunological tolerance
• when the body fails to recognise self from non self, the immune system will attack its own tissues
• when your own tissues are attacked, this is termed autoimmune response

Question 13

Give some examples of autoimmune diseases

Answer 13

• Multiple sclerosis (MS): destroys the myelin (white matter) of the nervous system
• Rheumatoid arthiritis: destroys the cartilage of joints
• Type 1 (insulin-dependant) diabetes mellitus: destroys insulin producing cells of pancreas
• Glomerulonephritis: destroys the functional units (nephrons) of the kidney
• Myasthenia Gravis: impairs communication between nerves and skeletal muscle by destroying receptor sites

Question 14

Hypersensitivity/ allergy=

Answer 14

Allergy occurs when a person reacts to a substance normally tolerated by most other people. Examples:
- Pollen
- Dust mites
- Dairy products
- Sea food
The antigens that cause allergies are known as allergens.

Question 15

Explain the hypersensitivity reaction

Answer 15

1. Anaphylactic reactions= involve the breakdown of mast cells (& basophils) and may result in anaphylactic shock
2. Cytotoxic reactions= are typical of incompatible blood transfusions resulting in destruction of cells
3. Immune complex reactions= which result in the destruction of tissue such as rheumatoid arthritis, glomurelonephritis, etc.
4. Delayed hypersensitivity reactions= appear 12- 72 hours after exposure, such as the Mantoux skin text for TB.