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# Mechanisms of Defense The table below describes different mechanisms employed by the body to combat pathogens. | Defense Mechanism | Chemical Mediators/Examples | Site of Action | |---|---|---| | **Low pH** | Acidic pH | Stomach (hydrochloric acid) | | **Chemical Mediators** | Lysozyme (disrupts...

# Mechanisms of Defense The table below describes different mechanisms employed by the body to combat pathogens. | Defense Mechanism | Chemical Mediators/Examples | Site of Action | |---|---|---| | **Low pH** | Acidic pH | Stomach (hydrochloric acid) | | **Chemical Mediators** | Lysozyme (disrupts bacterial cell wall), Interferon (induces antiviral defenses), Complement (lyses pathogens or facilitates phagocytosis), Lysozyme and histamine (antimicrobial peptides) | Various locations (e.g., tears, saliva) | | **Phagocytic/Endocytic (Internalise)** | Macrophages, dendritic cells, neutrophils | At the site of pathogen entry/targeted sites within the body | | **Inflammatory** | Recruitment of blood leucocytes, release of cytokines | Site of damage (externally/internally) | **Explanation of Mechanisms:** * **Low pH:** The acidic environment of the stomach (hydrochloric acid) kills many undigested pathogens. * **Chemical Mediators:** These molecules, such as lysozyme, interferon, and complement proteins, directly attack pathogens or support the immune response's efficacy. * **Phagocytic/Endocytic:** Cells like macrophages and neutrophils engulf and destroy pathogens. Some immune cells break down foreign macromolecules. Other cells internalize, kill, and digest whole pathogens. * **Inflammatory Response:** Damage or infection trigger the recruitment of white blood cells and release of cytokines, initiating an inflammatory response and facilitating the influx of phagocytic cells to the affected site. **Note:** "e.g." precedes examples of specific cells or mechanisms. The "At site of..." column describes where each process primarily occurs.