Cells have specific molecules on their surface that identify it. These include proteins e.g. antigens.
They help the immune system to identify:
Pathogens
Cells from other organisms of the same species
Abnormal body cells
Toxins
Definition: An antigen is a molecule, usually protein that stimulates an immune response resulting in theproduction of specific antibodies.
Antigens have the ability to mutate and change shape. When this occurs, the pathogen will notbe recognised by the receptors on memory cells from the previous infection.
This change in the antigen is known as antigenic variability (drift) and makes itdifficult to develop vaccines against these pathogens
4.) Fusion with Lysosome containing lysozymesfuses with vesicle forming a phagolysosome
5.) Digestion – lysozymes hydrolyse the pathogen
6.) Discharge - waste released (but rememberantigens get presented)
Specific Immune responses
The cellular response
This is the response produced by T lymphocytes to a foreign antigen.
T cells bind to the antigens on thesurface of pathogens or AnitgenPresenting cells and are activated.
T helper cells activate B cells andcytotoxic T cells.
Cytotoxic T cells release perforin thatputs holes in the cell membrane ofthe pathogen or they release nitricoxide which is directly toxic to thepathogen
The humoral response – The action of B cells
Helper T cell / TH cell binds to the antigen on the antigen-presenting cell
This helper T / TH cell stimulates a specific B cell and the B cell clones
divides by mitosis to form plasma cells that release antibodies and memory cells.
Structure of an antibody
Oops! This image does not follow our content guidelines. To continue publishing, please remove it or upload a different image.
An antibody is a protein specific to an antigen produced by B cells
An antibodies variable region has specific amino acid sequence (primary structure). Thetertiary structure of the binding site is complementary to / fits / binds with these antigen to forma complex between antigen and the antibody
