True or False: The innate immune defense operates either passively or by responding to foreign substances.

The innate immune defense indeed operates through both passive and active mechanisms in response to foreign substances. This system represents the first line of defense in the body against pathogens.

Passive mechanisms include physical barriers like the skin and mucous membranes, which serve to block the entry of pathogens. Additionally, various bodily fluids (like tears and saliva) contain antimicrobial proteins that can help prevent infections from taking hold.

On the other hand, active responses involve the detection of pathogens through pattern recognition receptors and the subsequent activation of immune cells such as macrophages, neutrophils, and natural killer cells. These cells can actively combat infections by engulfing pathogens, releasing cytokines to recruit more immune cells, and initiating inflammatory responses.

This dual approach ensures that the innate immune system functions effectively to provide immediate protection against a wide range of infectious agents. Therefore, the assertion that the innate immune defense operates either passively or in response to foreign substances is accurate.