T Lymphocytes and Cell-mediated Immunity Flashcards
What do antigens stimulate
An immune response as it’s recognised as foreign (non self)
What does the presence of an antigen trigger
The production of an antibody
Where are lymphocytes produced
By stem cells in the bone marrow
Why are t lymphocytes called that? What are they associated with ?
Because they mature in the thymus gland
With cell mediated immunity that is immunity involving body cells
Why are b lymphocytes called that? What are they associated with ?
Because they mature in the bone marrow
With humoral immunity, immunity involving antibodies that are present in body fluids or humour such as plasma
How can t lymphocytes distinguish these invader cells from normal cells
Because :
Phagocytes that have engulfed and hydrolysed a pathogen present some of a pathogens antigens on their own cell surface membrane
Body cells invaded by a virus present some of the viral antigens on their own cell surface membrane
Transplanted cells from individuals of the same species have different antigens on their cell surface membrane
Cancer cells are different from normal body cells and present antigens on their cell surface membrane
What is cell mediated immunity
T lymphocytes will only respond to antigens that are presented on a body cell rather than to antigens within the body fluids
How do T lymphocytes respond to infection by a pathogen
Pathogens invade body cells or are taken by phagocytes
The phagocyte places antigens from the pathogen on its cell surface membrane
Receptors on a specific helper T cell fit exactly to these antigens
This attachment activates the T cells to divide rapidly by mitosis and form a clone of genetically identical cells
The cloned T cells:
Develop into memory cells that enable a rapid response to future infections by the same pathogen
Stimulate phagocytes to engulf pathogens by phagocytosis
Stimulate B cells to divide and secrete their antibody
Activate cytotoxic T cells
What do B memory cells do
Remain in blood so if there is a second exposure to the pathogen the immune response is more rapid
How do T killer cells destroy cells ( cytotoxic)
Release perforin which punctures holes in the pathogen cell membrane causing the pathogen to die, cell contents come out and change in water potential
Why are T killer cells so effective in viruses
As viruses use living cells in which to replicate, this sacrifice of body cells prevents viruses multiplying and infecting more cells
State 2 similarities and 2 differences between B and T cells
Both are types of white blood cells
Both produced from stem cells
T cells mature in thymus gland while B cells mature in bone marrow
T cells are involved in cell mediated immunity while B cells are involved in humoral immunity
