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 defences 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

• cell mediated responses - T-lymphocytes (helpers (T_h) or cytotoxic (Tc)
• humoral responses - B-Lymphocytes

Question 7

How is the 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 involves the lymphocyte with the complimentary protein to undergo cell division in order to destroy the pathogen - this takes time.
• 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

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

Answer 11

Any lymphocytes that contain ‘self receptors’ are supressed or die.

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

Question 12

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

Answer 12

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

Question 13

Describe specific defences

Answer 13

Less rapid

Long lasting

Highly specific

Question 14

Identify the non-specific defences 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 (tertiary structure) can form a variety of different ‘labels’ - easily recognised.

Question 17

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

Answer 17

• They are programmed to die before they mature - apoptosis
• remaining ones = non -self and only respond to foreign material.

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.