Vaccination And HIV Flashcards
What is a vaccine
An injection of antigens from attenuated (dead or weakened) pathogens
What does a vaccine stimulate
It stimulates the formation of memory cells
Explain how vaccines provide protection to individuals against disease
Specific B lymphocytes with complementary receptors bind to antigens
Specific T helper cells bind to APCs and stimulate B cells
B lymphocytes divide by mitosis to form clones
Some B lymphocytes differentiate into B plasma cells which release antibodies and some differentiate into memory cells
On secondary exposure to the antigen B memory cells rapidly divide by mitosis to produce B plasma cells, these release antibodies faster and at a higher concentration
Define herd immunity
When the majority of a population is vaccinated against a pathogen, the spread is reduced as the chain of infection is reduced
How do vaccines provide protection for populations against disease
When lots of people are vaccinated, herd immunity can occur. This means the majority of the population is protected from being infected by the pathogen so its chain of infection is prevented. This means vaccinated people do not become ill and unvaccinated people are unlikely are come in to contact with people with the disease
Describe the process of active immunity
In order for active immunity to occur contact with the antigen/pathogen is needed
Once in contact, lymphocytes are selected, cloned and differentiated
Complementary antibodies can then be made and secreted by plasma B cells
B memory cells are made, so immunity is long term
Does active immunity take a long time upon first infection or not? Why?
It takes a long time as the correct antibodies have to be selected to bind to the complementary antigen
It is faster upon secondary infections as memory cells are left behind
What is natural active immunity
A normal response to infection
What is artificial active immunity
A response triggered by infection of foreign antigens (vaccination)
Describe the process of passive immunity
No contact is needed with an antigen
Lymphocytes are not involved
No antibodies are made, but are introduced from another organism
No memory cells are made
The response has an immediate effect
What is an example of natural passive immunity
During and after pregnancy antibodies pass across the placenta and in breast milk
What is an example of artificial passive immunity
Injection of antibodies or antitoxins from someone else, which gives immediate protection
What are the differences between active and passive immunity
In active initial exposure to the antigen is needed, in passive no exposure to the antigen is needed
In active memory cells are involved, in passive no memory cells are involved
In active antibodies are produced and secreted by B plasma cells, in passive antibodies are introduced from another organism (eg breast milk)
In active the process in slower as it takes longer to develop, in passive the process is faster acting
In passive immunity is long term and can be produced in response to the specific antigen again, in passive immunity is short term as the antibody is hydrolysed
How is HIV spread
When an infected persons body fluids mix with another persons
Eg during sexual intercourse, during a blood transfusion from an infected person, through sharing needles, across the placenta of an infected mother
Describe the action of HIV and how it affects the body
Attachment proteins attach to receptors on a T cell
Nucleic acid/RNA enters the T cell
Reverse transcriptase converts RNA to DNA
Viral proteins/capsids/enzymes are produced
Virus particles are assembled in the T cells and are released to go on and infect more cells
