The human immune response to an invading pathogen can consist of one, two, or three
phases, depending upon the severity of the infection.
PHASE 1: The immediate innate immune response begins as soon as a pathogen invades.
This is sufficient to terminate most infections.
PHASE 2: If after 4 hours of infection, the action of the immediate innate immune response has not been sufficient to subdue the infection, the induced innate immune response is brought into play.
PHASE 3: If after 4 days of infection, the combined actions of the immediate and induced innate immune responses have not been sufficient to subdue the infection, the immune system commits to make an adaptive immune response.
This response, which is made-to-order specificially for the infection at hand, is more powerful than the forces of innate immunity alone, and efficiently terminates almost all infections that get to this third phase. It is also more damaging to the tissues in which it is working.
If adaptive immunity fails to suppress the pathogen, the infected human host will either:
- Die of the acute infection, as frequently occurs for Ebola virus infections; or
- Develop chronic infection, as occurs with human immunodeficiency virus (HIV), associated with debilitating disease and premature death
Special thanks to Dr. Ananda Goldrath for sharing this video!
