(Second Line of Defense)
Definition Activated when physical barriers are breached Non-specific response to all pathogens Immediate, present from birth
Components of Innate Immunity Phagocytes First immune cells to respond Engulf and destroy pathogens through phagocytosis Clean debris and fight infections
Types: Macrophages, neutrophils Process: Endocytosis → Lysosome releases enzymes → Pathogen destroyed → Debris expelled
Natural Killer Cells Detect and destroy abnormal cells Recognize abnormal proteins (antigens) on infected cells Release perforin to create pores in target cells Induce apoptosis (cell death) by inserting enzymes through pores
Interferons Small proteins released by virus-infected cells Signal nearby cells to produce antiviral proteins Enhance phagocytosis and activate natural killer cells Slows the spread of viral infection
Complement System Proteins that enhance the immune response Functions: Create pores in pathogens, leading to cell death Enhance phagocytosis by opsonization (coating pathogens) Trigger inflammation
Inflammation Localized tissue response to injury or infection Symptoms: Redness, swelling, heat, pain
Causes: Prostaglandins trigger inflammation Mast cells release histamine, causing vasodilation and increased blood flow Attracts white blood cells to the site, promotes healing
Fever Generalized response to infection Body temperature above 37.2°C Induced by pyrogens Benefits: Enhances immune cell activity and metabolism Inhibits growth of some pathogens Risks: Prolonged fever can damage tissues