When the body responds to a relatively harmless substance as if it were a dangerous pathogen and mounts an immune response, this response is called?

This response is known as infection. This is very common in wounds and scratches that occur on the body when not immediately treated. The body's white blood cells attack invading elements that come from the outside environment and immediately assumes that all organisms are viruses that needed to be attacked.

The asian oyster was introduced to replace depleted native fish populations - Intentional release

European brown trout were introduced to establish sport fisheries - Intentional release

European green crabs began threatening commercial fisheries - Unintentional release

Cogon grass arrived as seeds in packing material - Unintentional release