What is the first defense to react when your body attacked by a foreign substance?

When the body is attacked by a foreign substance, the first defense to react is the innate immune response. This immediate and non-specific defense mechanism is always present and does not require prior exposure to the foreign substance. It provides the body with a rapid response to defend against infections and harm caused by various pathogens and harmful substances.

Key components of the innate immune response include:

1. Physical barriers: The skin and mucous membranes act as physical barriers, preventing the entry of foreign substances into the body.

2. Phagocytes: These specialized cells, such as neutrophils and macrophages, engulf and destroy foreign particles, bacteria, and damaged cells through a process called phagocytosis.

3. Natural killer (NK) cells: NK cells recognize and eliminate virally infected cells, tumor cells, and certain immune cells without prior sensitization.

4. Inflammation: When tissues are damaged or infected, the inflammatory response is initiated. This involves increased blood flow to the affected area, leading to redness, swelling, warmth, and pain. Inflammation helps to recruit immune cells and facilitates the removal of harmful substances.

5. Antimicrobial substances: The body produces antimicrobial substances, such as interferons and defensins, which have direct antiviral and antibacterial effects.

The innate immune response is crucial in providing immediate protection against various foreign substances and harmful agents. It works in conjunction with the adaptive immune response, which is more specific and develops immunological memory for long-term protection.