The document discusses the three lines of defense in the human body against pathogens. The first line of defense is barriers at body surfaces like the skin and mucous membranes. The second line of defense is nonspecific internal responses mediated by phagocytic cells, inflammation, fever, and antimicrobial proteins. The third and most specific line of defense is adaptive immunity involving cell-mediated and antibody-mediated specific immune responses. Innate immunity is nonspecific and present at birth, while adaptive immunity involves acquired responses that develop after exposure to specific pathogens.

1. 16.1 General Concepts in Immunity
Explain the basic aspects of innate (nonspecific)
and adap?ve (specific or acquired) immunity.
• What are the first lines of defense against
pathogens?
• What are the second lines of defense?
• What is the third line of defense in the body?

2. Three Lines of Defense in the Human
Body
• Innate immunity
1st: Barriers at body surfaces – 2nd: Nonspecific responses –
external internal
• Integument & mucous • Phagocy?c cells
membranes
• Inflamma?on & fever
• Chemical secre?ons
• microflora • An?microbial proteins
• 3rd: Adap?ve immunity: specific immune responses
– Cell‐mediated
– An?body‐mediated

3. Innate vs Adap?ve
• Innate – Nonspecific
– ATributes we have at birth
– Defend us from all pathogens
• Adap?ve – Acquired – Specific
– Not present at birth
– Immune responses that develop aWer exposure
• Vaccine, subclinical infec?on, clinical infec?on
– Unique cells for each specific pathogen