Humoral Response

Question 1

What are B cells/lymphocytes?

Answer 1

a white blood cell that causes a humoral response to infection by secreting antibodies

Question 2

Where a B cells produced?

Answer 2

made and mature in the bone marrow

Question 3

What is the structure of a B cell?

Answer 3

each B cell has only one type of 3D receptor protein (antibody) which are complementary to the 3D antigens on the pathogen - antibodies are soluble and transport in bodily fluids (also known as humour)

Question 4

How are B cells activated?

Answer 4

1.) antigens in the blood collide with their complementary antibody and B cell
2.) the B cell takes in the antigen by endocytosis and present it on its surface
3.) when this B cell collides with a helper T cell receptor this activates the B cell to go through clonal expansion and differentiation (clonal selection)
4.) B cells undergo mitosis to make large numbers of cells and will differentiate into plasma cells or memory B cells
- plasma cells (primary response) produce antibodies that destroy pathogens and the toxins they make
- memory cells (secondary response) remain in the blood and if the same antigen is encountered they divide rapidly into plasma cells or more memory cells = make a large number of antibodies rapidly

Question 5

What is the structure of antibodies?

Answer 5

• each antibody is composed of 4 polypeptide chains (quaternary structure protein)
• its on the variable region that the antigen binds to (antigen binding site) = only 2 variable regions so can bind 2 antigens at a time
• rest is constant region

Question 6

How do antibodies help destroy pathogens?

Answer 6

Agglutination = antibodies are flexible - pathogens can clump together which makaes sit easier for phagocytes to engulf them
Neutralisation= antibodies neutralise taxins
Opsonisation/the Complement Cascade = the binding to the surface of a pathogen can set a chain reaction with blood proteins which causes pathogen to swell up and burst
Antibodies can bind to viruses to stop them attaching to their host cells

Question 7

What are polyclonal antibodies?

Answer 7

most microbes have more that 1 antigen on their surface which stimulates more than one type of lymphocyte resulting in the producton of many different antibodies - can bring about a range of processes of destroying pathogens