3.2.4.1 Cell Recognition

Question 1

Why is a fetus rarely infected by a pathogen?

Answer 1

It is protected from the outside world by the mother and the placenta

Question 2

What is immunity?

Answer 2

When the body’s defenses are able to kill a pathogen before it can cause harm

Question 3

Does the body produce specific lymphocytes (white blood cells) in response to non-self material?

Answer 3

No - there are 10 million different lymphocytes already in the body from birth.

Each one has the potential to bind to a specific antigen

The lymphocyte with the complementary receptor (clonal selection) undergoes cell division to produce many of the desired lymphocyte

Question 4

What is an antigen?

Answer 4

A protein on the surface of a cell membrane

That (in the case of a foreign antigen) will trigger an immune response

Question 5

Describe non-specific defences

Answer 5

General action

Immediate

Question 6

Identify the 2 types of white blood cell

Answer 6

• T-lymphocytes (helpers or cytotoxic)

- B lymphocytes

Question 7

How is he immune response controlled in organ transplant patients to prevent organ rejection?

Answer 7

Immunosupressant drugs

Organs donated by family members - for a close tissue match

Question 8

Why is there a time lag between infection and an immune response?

Answer 8

Clonal selection takes time i.e. the correct lymphocyte binding to the non-self antigen

Question 9

Antigens that belong to the body have ____ antigens on their cell membrane

Answer 9

Self

Question 10

When can the immune system cause problems for medical patients?

Answer 10

People who have received organ transplants

The transplanted organs have non-self antigens

The immune system will destroy the non-self material

Question 11

Foreign antigens are usually found on which 4 materials that can trigger an immune response?

Answer 11

• Pathogens
• Cells from other or the same species (organ transplants)
• Toxins from pathogens
• Cancer cells

Question 12

Why is a fetus not attacked by its own lymphocytes when in the uterus?

Answer 12

Any lymphocyte that contain “self receptors” are suppressed or die.

The only remaining lymphocytes are those that respond to non-self material

Question 13

Describe specific defences

Answer 13

Less rapid
Long lasting
Highly specific

Question 14

Identify the non-specific defenses against infection

Answer 14

• S.T.E.M.S.(Skin, Tears, Earwax, Mucus, Stomach acid)

- Phagocytosis

Question 15

Antigens can be which biological molecules?

Answer 15

Proteins (glycoproteins)

Lipids (glycolipids)

Question 16

What is it about proteins that makes them useful as antigens?

Answer 16

Their specific 3D structure can form a variety of different “laels”

Question 17

Sometimes lymphocytes develop in the bone marrow and have self receptors. Why do they not destroy the person’s cells?

Answer 17

They are programmed to die before they mature

Question 18

Antigens that do not belong to the body have ____ antigens on their cell membrane

Answer 18

Non-self

Question 19

What is a pathogen?

Answer 19

A microorganism that causes infectious disease

Question 20

Who is susceptible to pathogen infection?

Answer 20

Very old / young

People with compromised immune systems (AIDs)

Question 21

What is meant by a self antigen?

Answer 21

A glycoprotein or glycolipid found on a cell surface membrane of a cell that belongs to the organism

Question 22

What is meant by a non-self antigen?

Answer 22

A glycoprotein or glycolipid found on a cell surface membrane of a cell that does not belong to the organism