IV. Innate Immunity

Barrier defense

• Nonspecific barriers to entry of body

• Physical and chemical

• Examples

Skin (integumentary system):

• not penetrable by bacteria, viruses

  • Habitat for commensal bacteria

  • Chemical barrier: oil, sweat glands, pH 5

• Mucous Lining

• Viscous, traps pathogens

• digestive , urinary, respiratory, reproductive

• Ciliated epithelial cells

• Contains lysozymes: destroy bacterial cell walls

Stomach

• Pathogens instated

• Destroyed by stomach acid

• Pathogens do get through barriers

Cellular defense

• Destroy pathogens when they get in

• Phagocytic cells: ingest pathogens via phagocytosis 

• Often found in lymphatic system

• Lymph nodes during infection

• Phagocytic cells have Toli-like receptors (tlr)

  • Bind to pathogen molecules

  • Phagocytosis

• Lipopolysaccharide

• dsRNA

• CpG DNA (methyl group makes DNA condense)

Phagocytic Cell Activity

Phagocytic cell activity

• Natural Killer Cells (NK cells)

• Recognize abnormal surface proteins: indicates virus, infection, cancer

• Release chemicals: trigger cell death

• Do not directly attack pathogens

• Antimicrobial Proteins

• Interferons: secreted by virus infected cells

  • Do not save infected cell, help other resist infection

• Complement system: 30 proteins in plasma

  • Circulated inactive, activated by surface protein of microbes

    • Lysis of invading cells

Local inflammatory response

• When tissues damage

• Specialized glucosites secrete histamines and cytokines

• When released capillaries dilate, need for white blood cells 

• Image

• Activated by tissue damage -> heat, redness, edema,

General inflammatory response

• Inflammation can involve whole body

• Fever: change in set point temp of body to facilitate immune response 

  • Also no iron or zinc released to blood, pathogens need

  • Phagocytic cells become more active

• Increase pahgocytoiss

• Interferes with pathogen growth