Innate Immunity

• • barrier defense

  • 1st line of defense

  • Protects against any outside invaders

  • Cellular innate defense

  • 2nd line of defense

  • Immune cells which detect, devour, &

  destroy pathogens

  
• Barrier Defenses of the Human Body

  • Blocks entry of pathogens

  • Expels pathogens & foreign agents

  • Provides unsuitable environment for pathogen

  growth

  • Includes:

  1. Skin

  2. Respiratory tract structures

  3. Urethra

  4. Body secretions

  5. Organ pH

  6. Friendly microflora of some organs
• Skin

  • Internal surface of organs are made up of mucous membrane (1st line of defense of organs)
• Respiratory tract structures

  • Lining has

  • nasal hairs (nose/nasal cavity)

  • cilia (trachea to bronchioles)

  • Protective mechanisms

  • Sneeze

  • Cough reflex

  • Muco-ciliary apparatus
• Urethra

  • Long urethra in males – 1st line of defense: hard & slower for bacteria to travel

  • Females have shorter urethra --> more common UTI
• Bodily gland secretions

  • Earwax – traps dirt & germs
  • Tears – protect eyes from entry of dirt &

  pathogens

  • Lysozymes – break down bacterial cell walls

  • Phagocytes – engulf pathogens

  • IgA antibodies

  • Saliva – with lysozymes & antibody IgA
  • Mucus in the gastrointestinal & respiratory tract

  • protects cells against acid

  • Traps germs
• Organ pH

  • Acidic environment in some organs/secretions

  • Unfavorable for bacterial growth

  • Stomach – pH 2

  • Vagina – pH 3-4

  • Skin – pH 3-5

  • Urine – pH 6-7
• Friendly microflora of some organs

  • Prevent overgrowth of harmful bacteria

  • Lactobacillus – in vagina & large intestine
• Cellular Innate Defenses of the Human Body

  • Detects, devours, & destroys pathogens which breached barrier defense
  • Rely on toll-like receptors (TLRs)

  • Recognition proteins

  - viral genetic material

  - bacterial surface molecule

  • Can be classified as:

  1. Phagocytic cells
  2. Natural killer cells
  3. Anti-microbial peptides & proteins
• 1. Types of phagocytic cells:

  • Neutrophils & macrophages

  Macrophages

  • Large-eaters
  • Phagocytosis --> lysosome breakdown of pathogen
• 1. Types of phagocytic cells:

  • Neutrophils & macrophages

  - Respond immediately to infections by small pathogens (bacteria, virus, fungus)

  Neutrophils

  • Ingest marked pathogens & kill them
  • Attracted by signals released by infected cells
• Types of phagocytic cells:

  1. Eosinophils

  • immediately respond to big pathogens (ex. Worms)

  • Kills parasitic worms by releasing destructive enzymes

  2. Dendritic cells

  • Often in tissues in direct contact with environment (ex. skin)

  • Mark pathogen & presents pathogen for destruction by acquired/adaptive immunity
• 1. Types of phagocytic cells

  Inflammatory response

  • Basophil/mast cells release histamine --> dilation of blood vessels

  • macrophages release signaling molecules --> attract neutrophils

  • pus build-up (immune cells + cell debris + dead pathogens)
• Natural killer cells

  • Against virus-stricken & cancerous cells

  • Release chemicals --> cell death

  
• 3. Anti-microbial peptides & proteins

  • Directly kill pathogens & impede their reproduction

  • Interferons

  • Complement system
• 3. Anti-microbial peptides & proteins:

  Interferons

  • proteins which interfere with viral infections
• 3. Anti-microbial peptides & proteins:

  Complement system

  • Actions:

  • Eliminates dead cell wastes

  • Promote inflammation

  • Attack pathogen’s cell membrane

  • Augments adaptive immunity
• Lymphatic System

  • Distribute lymph

  • Carries leaked liquid & pathogens from interstitial fluid of cells & the blood

  • Contained in lymph nodes - where response cells involved in cellular innate defenses reside & act against pathogen