Cell Recognition and the immune system Flashcards
A microorganism that causes disease
Pathogen
The body’s own cells and molecules.
Self
Not your own body’s cells and molecules.
Foreign (non-self)
Antigen
A molecule that triggers an immune response by lymphocytes.
Type of white blood cell responsible for the immune response. They become activated in the presence of antigens. There are two types: B lymphocytes and T lymphocytes.
Lymphocyte
Type of white blood cell which carries out a non-specific immune response and ingests and breaks down pathogens by phagocytosis
Phagocyte
Mechanism by which phagocytes engulf particles to form a vesicle or a vacuole.
Phagocytosis
Contain enzymes called lysozymes which they release into the phagosome which hydrolyse the bacterium.
Lysosome
Phagosome
A vesicle formed as the bacterium is engulfed by the phagocyte. The lysosome release their lysozymes into the phagosome.
Antigen-presentation
When an antigen-presenting cell e.g. phagocyte displays foreign antigens on their own cell-surface membrane.
The type of response when T lymphocytes respond to antigens that are presented on a body cell.
Cell-mediated immunity
Cells which mature in the thymus and are associated with cell-mediated immunity.
T Cells
Clonal Selection
As the receptor on a helper T cell attaches to the antigen this activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells. These cloned T cells stimulate B cells to divide and form a clone of identical B cells all of which produce the antibody that is specific to the foreign antigen.
Contain receptors which respond to a single antigen. Many different types of T cell, each one responds to a different antigen.
TH cells (helper T cell)
TC cells (cytotoxic T cells)
Kill abnormal cells and body cells that are infected by pathogens by producing a protein called perforin which makes holes in the cell-surface membrane.
The type of response which involves B lymphocytes and antibodies.
Humoral Immunity
B Cells
Each type of B cell produces a specific antibody that responds to one specific antigen.
When the B cell is activated to divide by mitosis it gives a clone of plasma cells which produce and secrete the specific antibody that exactly fits the antigen on the pathogen’s surface.
Plasma B Cells
Antibody
A protein with specific binding sites produced by B cells in response to the presence of appropriate antigen.
Memory B Cells
Some B cells develop into memory cells which can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies as part of the secondary response.
Antibodies produced by a single clone of cells.
Monoclonal antibodies
Caused by initial response to the antigen which involves the production of antibodies and memory cells.
Primary Response
Secondary response
Caused by second exposure to the antigen. Memory cells are responsible for this response – they divide rapidly and develop into plasma cells (which secrete many antibodies quickly) and more memory cells.
Passive immunity
Resistance to disease that is acquired from the introduction of antibodies from another individual, rather than an individual’s own immune system e.g. across the placenta or in the mother’s milk. It is usually short lived.
