-How can an organism that once underwent contact with an antigen be immunized against future infections by the same

Question: -How can an organism that once underwent contact with an antigen be immunized against future infections by the same antigen?
- Keywords:
  antigen,
  future,
  infection,
  organism
Asked by 454sysb37 to Carmen, Daniel, Laura, Noel, Steph on 9 Mar 2015.
- Laura Garcia Ibanez answered on 9 Mar 2015:
  
  There is a specific subset of cells in the immune system called “Memory cells” which are highly specific for the antigen they are targeted to. These can be T or B lymphocytes. When the body encounters again the same antigen, these cells are able to respond much quicker to it and help not to develop the disease again.
- Noel Carter answered on 9 Mar 2015:
  
  I can’t really add anything to laura’s answer

Question: -How can an organism that once underwent contact with an antigen be immunized against future infections by the same antigen?