B lymphocytes and humoral immunity

Question 1

What does humoral immunity involve and why

Answer 1

-antibodies
-antibodies are soluble in blood and tissue fluid of the body

Question 2

Explain role of B cells in humoral immunity

Answer 2

-when antigen on surface of a foreign cell that enters blood/tissue fluid, B cell that has complementary antibody to antigen attaches to the antigen
-antigen enters B cell by endocytosis and gets presented on its surface (processed)
-T helper cells bind to these processed antigens and stimulate B cells to divide via mitosis to form clone of identical B cells
-to produce antibody specific foreign antigen (clonal selection)

Question 3

Monoclonal antibodies

Answer 3

each clone produces one specific antibody to these antibodies

Question 4

What do clones of B cells develop into

Answer 4

-plasma cells or memory cells

Question 5

Role of plasma cells and antibodies in primary immune response

Answer 5

-secrete antibodies into blood plasma
-these antibodies lead to destruction of antigen
-plasma cells are therefore responsible for immediate defence of body against infection (primary immune response)

-Produces antibodies slower and at a lower concentration because not many B cells available that can make required antibody and T helper cells need to activate B plasma cells to make antibodies (takes time) so infected individuals will express symptoms

Question 6

Role of memory cells in secondary immune response

Answer 6

-don’t produce antibodies directly but circulate in blood and tissue fluid
-when encounter same antigen at later date, they divide rapidly and develop into plasma cells and more memory cells
-plasma cells produce antibody needed to destroy pathogen
-new memory cells circulate in readiness for any future infection
-memory cells provide long-term immunity against original infection
-increased quantity of antibodies secreted at faster rate than primary immune response to ensure new infection is destroyed before it causes harm

-prodcues antibodies faster and higher conc as B and T cells are present. b memory cells undergo mitosis quicker/quicker clonal selection

Question 7

Humoral immunity

Answer 7

-surface antigens of an invading pathogen are taken up by b cells
-b cell processes antigens and present them on its surface
-t helper cells attach to the processed antigens on b cell thereby activating the b cell
-b cell now activated to divide by mitosis to give clone of plasma cells
-clones plasma cells produce and secrete specific antibody that exactly fits the antigen on pathogen’s surface
-antibody attaches to antigens on pathogen and destroys them
-some B cells develop into memory cells. these can response to future infection by same pathogen by dividing rapidly and developing into plasma cells that produce antibodies (secondary immune response)