Antigens are molecules(usually proteins) that can generate an immune response when detected in the body.
What are Pathogens?
These are organisms that cause disease, e.g bacteria, viruses and fungi.
Antigens that aren't normally found in the body are referred to as foreign antigens
Antigens allow the body to identify pathogens, abnormal body cells, toxins and cells from other individuals of the same species.
What are pathogens destroyed by?
Immune system cells
What are abnormal body cells?
They are cells that have cancerous or pathogen-infected cells which have abnormal antigens on their surface, which trigger an immune response.
What are toxins?
These are poisons. They're also molecules, not cells
Some toxins are produced by bacteria
The immune system can respond to toxins, as well as the pathogens that release them.
Toxin itself is an antigen. It has no antigens on its surface
Cells from other individuals of the same species (1)
When you receive cells from another person, such as in an organ transplant or blood transfusion, those cells will have some antigens on that are different to your own( unless the owner is genetically identical to you). The foreign antigen triggers to an immune response.
Cells from other individuals of the same species (2)
The immune response leads to the rejection of transplanted organs if drugs aren't taken to suppress the recipient'simmune system.
