B Lymphocytes and Humoral Immunity Flashcards
What is Humoral Immunity?
It involves antibodies, and antibodies are soluble in the blood and tissue fluid of the body.
What are B Lymphocytes (B cells)?
They mature in the bone marrow. They are associated with humoral immunity, immunity involving antibodies present in body fluid or ‘humour’ such as blood plasma.
What do B cells produce?
B cells produce specific antibodies that respond to specific antigens.
What happens when an antigen enters the blood or tissue fluid?
When an antigen, for example, a protein on the surface of a pathogen, foreign cell or toxin, enters the blood or tissue fluid, there will be one B cell that has the complimentary antibody on its own surface to the antigen. The antibody attaches to the antigen.
What happens after the complimentary B cell antibody attaches to the antigen of the invading cells?
The antigen enters the B cell by endocytosis and gets presented on its surface. T helper cells bind to these processed antigens and stimulate this B cell to divide by mitosis to form a clone of identical B cells, all of which produce this complimentary antibody specific to the foreign antigen. This is known as clonal selection.
What are monoclonal antibodies?
Different B cells make clones, each producing its own type of antibody. As each clone produces one specific antibody, these antibodies are referred to as monoclonal antibodies.
What are the two types of cells that the cells produced from each clone develop into?
Plasma cells and Memory cells.
What are plasma cells?
They secrete antibodies into blood plasma. These cells only survive for a few days but can make lots of antibodies during their lifespan, which lead to the destruction of the antigen. Plasma cells are therefore responsible for the immediate defence of the body against infection. The production of antibodies and memory cells is known as the primary immune response.
What are memory cells responsible for?
The secondary immune response
What are the memory cells role in a humoral response?
They live considerably longer than plasma cells. They do not directly produce antibodies, but circulate in the blood and tissue fluid. When they encounter the same antigen, they are able to rapidly divide and develop into plasma cells and more memory cells. The plasma cells produced, produce antibodies to destroy the pathogen, whilst new memory cells circulate in readiness for another future infection.
What nature of immunity do memory cells provide?
Long-term immunity against the original infection. They produce antibodies at a faster rate than in the primary response to ensure the infection is destroyed before it causes harm.
What is the role of B cells in immunity and their process in immune responses?
- Surface antigens of pathogen are taken up by B cell.
- B cell present antigens on their own surface.
- T helper cells attach to antigens, activating B cell.
- B cell activated to divide by mitosis and make clones.
- Cloned plasma cells produce and secrete complimentary antibodies to the antigens.
- Antibodies attach to antigens and destroy them.
- Some B cells develop into memory cells, creating secondary immune response.
