Antigens & Antibodies

Question 1

What are the human body’s physical barriers to disease?

Answer 1

• Skin
• Blood clots
• Hair and mucus in the nose
• Mucus secreting cells in the trachea
• Cilia

Question 2

What are the human body’s chemical barriers to disease?

Answer 2

• Hydrocloric acid in the stomach
• Lysozymes in tears

Question 3

What happens if a pathogen breaches the physical and chemical defences of the human body?

Answer 3

The person will become infected, the pathogen will then multiply and damage body cells by secreting toxins.

Question 4

What is the immune system?

Answer 4

The immune system is made up of specialised cells that respond specifically to foreign objects and protect an individual from harm.

Question 5

How does the immune system protect against pathogens?

Answer 5

If a pathogen evades a barrier, the immune system attacks it with white blood cells, one of which being b-lymphocytes (a type of white blood cell that works against specific pathogens).

Question 6

What is a b-lymphocyte and how do they work?

Answer 6

A type of white blood cell that works against specific pathogens.

When they come across specific antigens , they initiate an immune response, producing antibodies that bind to the antigens and destroy them. The antibodies then produce rapidly to find other pathogens.

Question 7

What is an antigen?

Answer 7

Proteins or glycoproteins, which are chemical markers on the surface of pathogens or body cells.

These lead to the initiation of an immune response.

Question 8

What is an antibody?

Answer 8

Proteins produced by your immune system that protect you when an unwanted substance enters your body. Antibodies bind to these unwanted substances in order to eliminate them from your system.

Question 9

What does an antibody look like?

Answer 9

Variable Antigen binding site
constant |———-|
\ \ \ \ | / / / /
\ \ \ \ | / / / /
—– —- —- —-
\ \ \ \ / / / /
\ \ \ \ / / / / —> Light chain
| | | |
| | | |
| | | | —> Heavy chain

Question 10

What is a key aspect of the variable region of an antibody?

Answer 10

It changes.

Question 11

What is the purpose of the antigen binding site on an antibody?

Answer 11

It allows it to bind to a pathogen and destroy it.

Question 12

What are monoclonal antibodies?

Answer 12

These are artificially made antibodies.

They’re made in a lab to test for pregnancy, find blood clots, target disease and diagnose.

Question 13

How are monoclonal antibodies made?

Answer 13

• A mouse is injected with a chosen antigen.
• B-lymphocytes are taken from the mouse and fused with myeloma cells.
• A hybridoma is made.
• This divides quickly to produce lots of clones which produce monoclonal antibodies.

Question 14

What is a myeloma?

Answer 14

A cancer that forms in a type of white blood cell called a plasma cell.

Question 15

What is a hybridoma?

Answer 15

Fusing antibody producing B lymphocytes with myeloma cells to create a never ending supply of a specific monoclonal antibody.

Question 16

How do white blood cells recognise pathogens?

Answer 16

Pathogens are covered in antigens, which are proteins, that identify the cell as foreign.

Antigens are uniquely shaped depending on the exact strain of protein , allowing white blood cells to detect pathogens and attack them.

Question 17

What are antigens called in viruses?

Answer 17

Spike proteins.

Question 18

What microorganism does not have an antigen?

Answer 18

Prions.

Question 19

What is antigenic drift?

Answer 19

This is where the pathogen changes over time, so pathogens a host was previously immune to can overrun the body’s defences.

Question 20

How do pregnancy tests work?

Answer 20

In pregnant urine, there is a hormone called ‘human chronic gonadotropin’, which is detected by the test.

Where you urinate has antibodies connected to blue beads and, then the test strip also has antibodies specific to it.

If you are pregnant the ‘HCG’ hormone will bind to the antibodies connected to the blue beads. The urine moves up the stick, carrying the hormone and beads to the test strip. The beads and hormone then bind to the antibodies on the strip, turning it blue.

If you’re not pregnant nothing will stick to the beads on the strip , so it wont turn blue.

Question 21

How can you diagnose and treat cancer cells using monoclonal antibodies?

Answer 21

Cancer cells have proteins on their cell membranes called tumour markers. You can make monoclonal antibodies that will bind to these tumour markers to help diagnose and treat cancer.

Question 22

How can you find blood clots using antibodies?

Answer 22

When blood clots, proteins in the blood join to form a solid mesh.

Antibodies with radioactive markers have been developed to bind to these joined proteins. Therefore, blood clots can be imaged via radioactive markers.