Disease and Immunity Flashcards
Explain the function of Antibodies and Antigens
All cells have proteins and other substances projecting 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
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
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 get sick
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 very quickly be made in greater quantities and the pathogens 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
Explain the function of Vaccination
Vaccinations give protection against specific diseases and boost the body’s defence against infection from pathogens without the need to be exposed to dangerous diseases that can lead to death
The level of protection in a population depends on the proportion of people vaccinated
Vaccines allow a dead or altered form of the disease-causing pathogen, which contains specific antigens, to be introduced into the body
In this weakened state, the pathogen cannot cause illness but can provoke an immune response
Lymphocytes produce complementary antibodies for the antigens
The antibodies target the antigen and attach themselves to it in order to create memory cells
The memory cells remain in the blood and will quickly respond to the antigen if it is encountered again in an infection by a ‘live’ pathogen
As memory cells have been produced, this immunity is long-lasting
Explain Passive Immunity
Passive immunity is a fast-acting, short-term defence against a pathogen by antibodies acquired from another individual
Antibodies pass from mother to infant via breast milk - this is important as it helps the very young to fight off infections until they are older and stronger and their immune system is more responsive
The body does not make its own antibodies or memory cells in passive immunity, hence the name
How Chlorea leads to diarohea
Bacteria attach to the wall of the small intestine
They produce a toxin
The toxin stimulates the cells lining the intestine to release chloride ions from inside the cells into the lumen of the intestine
The chloride ions accumulate in the lumen of the small intestine and lower the water potential there
Once the water potential is lower than that of the cells lining the intestine, water starts to move out of the cells into the intestine (by osmosis)
Large quantities of water are lost from the body in watery faeces
The blood contains too little chloride ions and water
