Immune system

Question 1

Antigen:

Answer 1

Is a substance that is foreign to the body and

stimulates an immune response.

Question 2

Antibody:

Answer 2

Is a glycoprotein made by plasma cells derived from B-lymphocytes, secreted in response to an antigen.

Question 3

Immune response:

Answer 3

Series of responses of the body to the entry of a foreign antigen, it involves the activity of lymphocytes and phagocytes.

Question 4

Non-self:

Answer 4

Refers to any substance or cell that is recognised by the immune system as being foreign and will stimulate an immune response.

Question 5

Self:

Answer 5

Refers to substances produced by the body that the
immune system does not recognise as foreign, so they
do not stimulate an immune response.

Question 6

Active immunity:

Answer 6

Is immunity gained when an antigen
enters the body, an immune response occurs and
antibodies are produced by plasma cells.

Question 7

Passive immunity:

Answer 7

Is immunity gained without an
immune response; antibodies are injected (artificial)
or pass from mother to child across the placenta or in
breast milk (natural).

Question 8

Natural immunity:

Answer 8

Is immunity gained by being infected
(active) or by receiving antibodies from the mother
across the placenta or in breast milk (passive).

Question 9

Artificial immunity:

Answer 9

Is immunity gained either by

vaccination (active) or by injecting antibodies (passive).

Question 10

Vaccination:

Answer 10

Is giving a vaccine containing antigens for
a disease, either by injection or by mouth; vaccination
confers artificial active immunity.

Question 11

Immunity:

Answer 11

Protection against disease provided by the body’s internal defence or I.S.

Question 12

Pathogens:

Answer 12

Diseases causing organisms.

Question 13

Defence system, 3 defences:

Answer 13

Physical, chemical and cellular defences protect p.g. from entering.

• E.g. epithelial - covers airways, h.c. Acid in stomach kills bacteria, blood clotting stops loss of blood.

Question 14

Cells of I.S.:

Answer 14

• Originate from bone marrow.
• 2 groups are involved in defence, phagocytes & lymphocytes.
• Visible among r.b.c.

Question 15

Phagocytes:

Answer 15

• Neutophils and Macrophages.
• Produced in bone marrow. Stored there before distributed in blood.
• Scavangers, removes dead cells & invasive micro-organisms.

Question 16

Neutrophils:

Answer 16

• Form about 60% of W.b.c. in blood.
• Travel all over body, leaving blood by squeezing out of capillaries to “patrol” the tissues.
• Sent out in large numbers during infection, but they are short lived cells.

Question 17

Macrophages:

Answer 17

• Larger than n.p. & found in organs rather than remaining in blood.
• After made in bone marrow, they traven in blood as monocytes, which develop into m.p. once they leave the blood and settle in organs removing any foreign matter found there.
• Long-loves cells, important in initiating responses.

Question 18

Phagocytosis:

Answer 18

The ingestion of bacteria or other material by phagocytes.

Question 19

Lymphocytes:

Answer 19

• Second type of W.b.c.
• Smaller than p.c.
• Have large nucleus that fills most of the cell.
• Two types of l.c., both produced before birth in bone marrow. B-& T -cells.

Question 20

B- l.c., (B-cells):

Answer 20

• Remains in b.m. until maturity and is then spread throughout the body, concentrating in lymph nodes and the spleen.

Question 21

T- l.c., (T- cells):

Answer 21

• Leave b.m. and collect in thymus, where they mature.

- 2 types, Helper and killers.

Question 22

2 types of W.b.c.:

Answer 22

• P.c. and l.c.

Question 23

What happens if p.g. enters the body?

Answer 23

• W.b.c. Recognises them as forgein and destroy them.

Question 24

C. S. Antigens:

Answer 24

• Only stimulate production of a.b. If they enter someone else.
• Certain glycolipids on r.b.c. in g. A that B don’t have.
• b. from A to person with B, during transduction the person recognise b.c. as forgein & start to produce a.b.’s.
  -Their I.S. recognises antigens as non-self.
  ( other way around, no a.b.’s and self).

Question 25

Basic m. common to all a.b.’s:

Answer 25

- 4 polyp. chains, 2 long (heavy) and 2 short (light). - Each m. has 2 identical antigen-binding sites. - A.a. Seq. in these regions make specific 3D shape which binds to 1 type of antigen. - These sites form the variable region, is diff. on each type of a.b. m. produced.

Question 26

Hinge region:

Answer 26

- Gives flexibility for the a.b. m. to bind around the antigen.

Question 27

Immunoglobulin (lgG):

Answer 27

- A.b. m. with four p.p.

Question 28

Antitoxins:

Answer 28

- Special group of a.b.’s. | - Block toxins released by bacteria such as those that cause diphtheria and tetanus.

Question 29

T.c. receptors:

Answer 29

- Similar structure to a.b.’s. | - Specific to ons antigen.

Question 30

Autoimmune disease:

Answer 30

- When the body recognises it’s own tissue as forgein, attacking its own antigens, usually proteins.

Question 31

What happens when A.I. occurs?:

Answer 31

- When T.c. mature, many cells gets destroyed because they have T.c.r. that are complementary to self-antigens. - Not all cells destruct and are activated to stimulate an I.r. against the body’s own proteins. - This starts an attack often involving a.b.’s and killer t.c.

Question 32

Myasthenia gravis (MG):

Answer 32

- Serious muscle weakness. | - A.i. disease that targets neuromuscular junctions between motor neurone sand skeletal muscle cells.

Question 33

Ppl with MG:

Answer 33

- Have helped t.c. specific for c.s. receptors for acetylcholine. - These cells can stimulate a clone of B cells to differentiate into plasma cells and secrete a.b.’s. that bind to receptor and blocking transmission of impulses from motor neurones. - Receptors are destroyed and without them, muscle cells don’t receive any stimulation. Muscles that aren’t stimulated starts to break down.

Question 34

Symptoms of MG:

Answer 34

- Gets worse with activity and improves with rest. | - Affected muscles become fatigued very easily.

Question 35

Treatments for MG:

Answer 35

- Drug that inhibits enz. in synapses that break down acetylcholine. The drug increases conc. of acetylcholine in synapses so it’s action in stimulating muscle fibres to contract lasts for longer. - Surgical removal of thymus gland.