Disease And Immunity: Immunity
12.3 Immunity
Active Immunity
- Defence against pathogen by antibody production inside body.
- Specific: each antibody matches a pathogen’s antigen.
- Gained by:
- Natural infection.
- Vaccination.
Vaccination Process
- Weakened/dead pathogen or antigen introduced.
- Lymphocytes produce antibodies.
- Memory cells remain.
- Long-term immunity on re-exposure.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
Passive Immunity
- Short-term defence by antibodies from another source.
- Examples:
- From mother → across placenta or in breast milk.
- Injection of antibodies (e.g., tetanus antiserum).
- No memory cells produced.
Antibodies And Antigens
- Antigen: protein on pathogen surface → unique shape.
- Antibody: protein that binds to antigen → destroys pathogen or marks for phagocytosis.
HIV And Immunity
- HIV infects lymphocytes → reduces ability to produce antibodies.
- Leads to AIDS (weakened immune system, vulnerable to infections).
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course