Immune System

Question 1

What are the functions of the immune system?

Answer 1

Constantly defends the body against:

• bacteria
• viruses
• abnormal/cancerous cells

It can distinguish between self and non-self
Between harmful and non-harmful

It remembers past encounters

Question 2

What are the components of the immune system?

Answer 2

• Lymphatic system
  
  • lymphatic vessels
  • lymphatic tissues and organs
• Immune cells
  
  • lymphocytes
  • granulocytes
  • accessory cells (antigen-presenting cells)

Question 3

How does the lymphatic system work?

Answer 3

• Blood leaves the capillaries into the tissues.
• Tissue fluid (aka ECF or interstitial fluid) collects outside the cells
• This fluid enters the lymphatic system via flaps in the lymphatic capillaries
• Lymphatic vessels work similar to blood veins - skeletal muscle movement moves the lymphatic fluid towards the great veins in the neck, and there are valves along the way to prevent backflow.
• Lymph fluid is filtered of toxins and cancer cells as it is transported along the lymphatic vessels.
• Lymph fluid drains back into the circulatory system via the subclavian veins.

Question 4

The three palpable lymphatic nodes are:

Answer 4

• the cervical nodes
• the axillary nodes
• the inguinal nodes

Question 5

What are the lymphoid organs?

Answer 5

• Thymus gland (primary - where T cells mature)
• tonsils and adenoids
• lymph nodes and vessels
• bone marrow (primary - where lymphocytes are synthesised and B cells mature)
• spleen
• appendix
• Peyer patches in the intestinal wall

Question 6

What are the two types of immune defences?

Answer 6

Innate (born with, non-specific) and adaptive (develop, specific).

Innate

• skin barriers (skin, mucous membranes)
• internal defences (phagocytes, fever, natural killer cells, antimicrobial proteins, inflammation

Adaptive

• humoral immunity (B cells, lymphocytes, mature in the bone marrow)
• cellular immunity (T cells, lymphocytes, mature in the Thymus gland)

Question 7

What are interferons?

Answer 7

proteins that interfere with viral replication

Question 8

What are complement proteins?

Answer 8

• proteins that work with other immune responses
• attaches to and break down cell walls of pathogens
• attracts phagocytes
• stimulates inflammation

Question 9

What is the inflammatory response?

Answer 9

- mast cells contain histamine which sets off the immune response
1- blood flow increases
2- phagocytes are activated
3- capillary permeability increases
4- complement proteins are activated
5- clotting reaction walls off region
6- regional temperature increased
7- specific defences activated

Question 10

What is fever?

Answer 10

• occurs in response to infection and inflammation
• raised body temperature
• mild fevers are good - they reduce bacterial growth and aid tissue repair
• high fevers (over 40) are dangerous

Question 11

What is inflammation?

Answer 11

• occurs in response to trauma or infection
• signs - redness, heat, swelling, pain
• increased blood flow = redness and heat
• histamine makes capillaries more permeable and fluid leaks into the tissue = swelling and pain

Benefits:

• disposes of cell debris and pathogens
• alerts the adaptive immune system
• sets the stage for repair
• prevents the spread of damage to surrounding tissues

Question 12

What is the difference between humoral immunity and cellular immunity?

Answer 12

• B cells (humoral) produce antibodies that attach the pathogens. Antibodies immobilise antigens. They are also ‘memory’ cells - they remember previous antigens so they can respond faster to a second attack
• T Cells (cellular) directly attach pathogens, foreign and cancerous cells. T cells manage the immune response

Question 13

What are antigens?

Answer 13

• substances recognised as foreign, which activate the immune response.
• they are proteins and polysaccharides that are present on the surface of pollens, cells, bacteria and viruses

Question 14

What is humoral immunity?

Answer 14

B Cells
Some become memory cells
some become plasma cells
Activated B cells create immunoglobulins (Ig)
Ig is produced in response to specific antigens, and bonds to that specific antigen
Ig is grouped into 5 classes:
- IgM, IgG (main Ig, produced in response to infection), IgA, IgD, IgE

Question 15

How do primary and secondary immune responses differ?

Answer 15

The secondary response is quicker and more reactive because B cells are memory cells - they remember the pathogen and respond faster and more effectively (secondary response is often unnoticeable)
- this is why immunisations are important

Question 16

What are vaccines?

Answer 16

• dead / attenuated antigens
• humoral response is the same as if it were a live virus
• antibodies are produced
• causes the secondary response to be larger and more effective

Question 17

What is cellular immunity?

Answer 17

T-cells
some become memory cells
some become cytotoxic cells, which directly attact foreign or virus filled cells
some become helper t-cells, which boost (manage) general immune responses (these cells are destroyed by HIV, which is catastrophic to their immunity)

Question 18

What is acquired immunity?

Answer 18

• adaptive immune responses
• acquired naturally - actively, if you contract the pathogen, fight if off and have the antibodies
• acquired naturally - passively, from mother to fetus
• acquired artificially - actively through immunisation
• acquired actificially - passively through injection of immune serum (gamma globulin, IgG)

Question 19

What are the two main phagocytes?

Answer 19

Neutrophils - most common phagocyte and the fastest acting. When infection occurs, their number quadruple.

Macrophages - begin as monocytes in the bloodstream - become large, phagocytic macrophages when entering tissues to fight infection. Can be either free (freely roaming) or fixed.

Question 20

What are the five types of Immunoglobins (Ig)?

Answer 20

Think MADGE

• IgM - the first Ig class secreted by plasma cells during primary response
• IgA
• IgD
• IgG - most prolific
• IgE