B & T lymphocytes - specific immune responses 4.1.1
active immunity
antigen presenting cells will eventually come into contact with a T & B lymphocyte
there may be only 1 B & T lymphocyte with complementary shapes to binds to the antigens on the antigen presenting cell
the antigen presenting cells therefore increase the chance of this happening much faster - as more antigens to come into contact with
once the B & T lymphocytes bind to the antigen - clonal selection has happened
specific antibodies will now be produced to combat the pathogen & memory cells will provide long term immunity
Clonal selection of T & B cells
T-Lymphocytes (T cells)
originate in bone marrow & travel to thymus gland where they mature (B cells are produced & mature in bone marrow)
each T cell has specific receptors for an antigen
when infected with a pathogen there'll be at least 1 T cell with the complementary receptors to bind to the antigen
once binding has occurred with a T cell - activation/clonal selection has occurred
1 T & 1 B cell will bind to the antigen
those chosen cells will the proliferate into identical T & B cells many times (clonal expansion)
the clones will the differentiate into useful T & B cells with specific functions
Differentiation
Clonal expansion
when a T cell manages to bind to the antigen it will then proliferate
aka clonal expansion
clonal expansion = the specific T cell makes many copies of itself by mitosis
T cells
after clonal expansion the T cells differentiate into a range of different T cell with different functions
T killer cells
attack infected host cells
T memory cells
T helper cells
T regulator cells (aka T suppresser cells)
remain in the blood
stimulate B cells to divide
shut down the immune response once pathogen has been removed
also help prevent autoimmune responses
B cells
differentiate into 2 main types;
plasma cells
B memory cells
make antibodies
remain in blood
T & B memory cells
memory cells remain in the blood - if same pathogen enter immune system again response is more rapid
existing memory cells multiply rapidly producing clones of the specific lymphocytes required to attack & destroy the pathogen before you experience symptoms
