Antigens & Antibodies
- All cells have proteins and other substances projecting (sticking out) from their cell membrane
- These are known as antigens and are specific to that type of cell
- Lymphocytes have the ability to ‘read’ the antigens on the surfaces of cells and recognise any that are foreign
- They then make antibodies which are a complementary shape to the antigens on the surface of the pathogenic cell
- Antibodies can bind to antigens because of their complementary shapes
- Like jigsaw puzzle pieces fitting together
Antigens and Antibodies Diagram
Antigens and antibodies
- The antibodies attach to the antigens and cause agglutination (clumping together)
- This means the pathogenic cells cannot move very easily
- At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed
Agglutination of Pathogens Diagram
Agglutinated pathogens cannot move easily
- The initial response of a lymphocyte encountering a pathogen for the first time and making specific antibodies for its antigens can take a few days, during which time an individual may become ill
- Lymphocytes that have made antibodies for a specific pathogen for the first time will then make ‘memory cells’ that retain the instructions for making those specific antibodies for that type of pathogen
- This means that in the case of reinfection by the same type of pathogen, antibodies can be made very quickly, in greater quantities
- The pathogens get destroyed before they are able to multiply and cause illness
- This is how people can become immune to certain diseases after only having them once
- It does not work with all disease-causing microorganisms as some of them mutate fairly quickly and change the antigens on their cell surfaces
- Therefore, if they invade the body for a second time, the memory cells made in the first infection will not recall them as they now have slightly different antigens on their surfaces (e.g. the cold virus)
