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and the immune system.
are molecules that stimulate an immune response
are protein molecules that can identify and neutralise antigens
is the communication between cells that allows effective coordination of a response
an organism that causes disease, they live by taking nutrition from their host, but also cause damage in the process
Antigens
Antibodies
Antibodies covering the pathogen binding-sites prevent the pathogen from binding to a host cell and entering the cell.
A large antibody can bind to many pathogens together. The group of pathogens is too large to enter a host cell.
The first signalling is done by the pathogen. The pathogen carries antigens on its cell surface, these act as flags that say 'I AM FOREIGN'. These are detected by our body cells.
The internal cell organelles such as lysosomes will attempt to fight the invader. Parts of the pathogen often end up attached to the host plasma membrane.
This process has been taken a step further by the macrophages in the lymph nodes. They act like phagocytes to engulf and digest the pathogen. But they do not fully digest it. They separate the antigens and link them into a cell surface molecule. This is exposed on the surface of the macrophage, which becomes known as antigen-presenting cell. It has to find the lymphocytes that can neutralise that particular antigen.
Communication using cytokines includes the following:
Pathogen engulfed by cells from the immune system
Removal of antigens from pathogen
Antigens presented on surface of engulfing cells
Production of T helper cells
Release of interleukins
Activation of B cells
Some B cell clones differentiate to make plasma cells
Plasma cells manufacture antibodies
Reproduction of B cells
Some B cell clones differentiate to make B memory cells
Memory cells circulate in body providing immunological memory
Selection of correct T killer cells and T helper cells
Production of T killer cells
T killer cells search for infected cells
T killer cells attach to infected cells
T killer cells secrete toxic substances into affected cells to kill cell and the pathogens it contains