B lymphocytes and humoral immunity

Question 1

What is involved in humoral immunity?

Answer 1

B-cells that produce specific antibodies for a specific antigen.

Question 2

How does B-cells stimulate a response to pathogens?

Answer 2

1) When a pathogen enters the blood or tissue fluid, there’ll be one B-cell that is complementary to the proteins of the pathogen, therefore, it will attach onto ut.
2) The antigen will then enter the B-cell by endocytosis and gets presented on its surface.
This will allow T helper cells to bind and stimulate this B cell to divide by mitosis to form a clone of identical B-cells.
3) Those clones will produce the antibody that is specific to this foreign antigen. This is called clonal selection and it’s the ability for the body to respond rapidly to any number of antigens.
4) The antibodies will attach onto the antigens and destroy the pathogens.
5) Some B-cells will develop into memory cells and can respond rapidly to future infections of the same pathogen, this is the secondary immune response.

Question 3

What are monoclonal antibodies?

Answer 3

A pathogen would have many different types of proteins and maybe toxins that will acts as antigens so there will be many different types of B-cells making clones. As each clone produces one specific antibody, these antibodies are referred to as monoclonal antibodies.

Question 4

What type of cells will the clones develop into?

Answer 4

• Plasma cells
• Secrete antibodies usually into the blood plasma.
• These cells only survive for a few days, but each can make around 2000 antibodies every second.
• They cause the destruction of the antigen.
• So plasma cells are responsible for the immediate defence of the body against infection.
• The production of antibodies and memory cell production are the primary immune response.
• Memory cells
• Responsible for the secondary immune response.
• Memory cells live longer than plasma cells.
• They do not produce antibodies directly but circulates in the blood and tissue fluid.
• When they encounter the same pathogen in the future, they divide rapidly and develop into plasma cells and more memory cells.
• Plasma cells produce antibodies to kill off the pathogens while new memory cells circulate for future infection.
• This way, memory cells provide long-term immunity.
• The antibodies secreted this time would increase in number and faster.