ABSTRACT
We are continuously exposed to threats from organisms that could cause serious harm. The immune system has the daunting task of sensing, recognizing, and reacting to the threat so as to protect the body from harm. This is possible by a coordinated response of a diverse set of cells and molecules that orchestrate a rapid, relatively non-specific response followed by a very specific response to neutralize the threat. Both phases of the response are equally important and play distinct roles. In addition to attacking the foreign organism, the first phase, or innate response, is responsible for educating the second or adaptive phase of the response. The adaptive phase is thus able to attack the pathogen with a very precise and specific response. It also saves the antigenic characteristics of the pathogen in its memory, which can be re-activated upon future exposure to the same pathogen. Vaccines are designed to mimic the immune response by the administration of an immunogenic stimulus representing a specific pathogen, in a controlled fashion to healthy individuals. This allows the individual to mount a strong response when they encounter the same pathogen later in life.
