Microbes and the immune system

• in the normal course of an infection, the infectious agent triggers an innate immune response that causes symptoms. The foreign antigens of the infectious agent, enhanced by signals from the innate immune response, induce an adaptive immune response that clears the infection and establishes a state of protective immunity. This does not always happen.

• The propagation of a pathogen depends on its ability to replicate in a host and to spread to new hosts. Common pathogens must therefore grow without activating too vigorous an immune response and, conversely, must not kill the host too quickly. The most successful pathogens persist either because they do not elicit an immune response, or because they evade the response once it has occurred.

• Until World War II, more soldiers died of microbes than of battle. The 1918 influenza epidemic killed more soldiers than World War I battles did. World War I may even have caused the 1918 influenza epidemic. Stay tuned—will the present world conflicts lead to a bird flu epidemic?

Category: Pathology Notes