1. Active and Passive Immunity
• Active immunity – immunity
gained when an antigen enters
the body (occurs during the
course of an infection)
– Natural active immunity:
lymphocytes activated by
antigens on the surface of
pathogens that have invaded
the body
– Artificial active immunity
(vaccination): immune
response activated artificially
by injecting antigens into the
body or taking them by mouth
ALBIO9700/2006JK

2. • Passive immunity – immunity
gained without an immune
response
– Artificial passive
immunity: antibodies
come from another person
who has encountered the
antigen (e.g. tetanus)
– Natural passive
immunity: antibodies
come from mother across
placenta or in breast milk
ALBIO9700/2006JK

3. Vaccination
• A preparation containing antigenic
material - a whole live
microorganism/dead one/a harmless
version (attenuated organism)/a
harmless form of a toxin
(toxoid)/preparation of surface antigens)
• Given either by injection into vein or
muscle, or taken orally
ALBIO9700/2006JK

4. Problems with vaccines
• Poor response
– Herd immunity
• Antigenic variation
– Antigenic drift: minor changes in the viral
antigen
– Antigenic shift: major changes in antigen
structure
• Antigenic concealment
ALBIO9700/2006JK