Natural and innate immunity Flashcards
The skin
Physical barrier
Chemical barrier:
- free fatty acids from sebaceous glands and skin flora
- lactic acid in sweat
- relatively dry
- low pH
Mucociliary clearance
Respiratory tract lined with ciliated columnar epithelium.
200 cilia per cell. Beat at 1000 times per minute. Move mucus up towards oropharynx where it is swallowed.
Smaller particles are phagocytosed by macrophages + transported from air spaces to mucociliar escalator
Nasal secretions
Moved towards oropharynx + swallowed
Contain antibodies, lysosomes and interferon
Factors impairing mucociliary clearance
Pollutants e.g. cigarette smoke
Pathogens e.g. rhinovirus - bind to receptors on epithelial cells and damage them resulting in impaired cilia motility
Secreted antimicrobial compounds
Hydrochloric acid
Lysosomes
Lactoperoxidase
Lactic acid
Free fatty acids
Hydrochloric acid
Found in the stomach
Creates acidic environment
Lactoperoxidase
Found in saliva and breast milk
Inactivates microorganisms
Lactic acid
Found on the skin and in the vagina
Creates an acidic environment
Lysosomes
Found in saliva, tears and mucus
Enzymes degrade peptidoglycans in bacterial cell walls
Free fatty acids
Found on the skin
Create an acidic environment
The urinary tract
Passing urine flushes microorganisms from urinary tract
Relatively acidic environment maintains unfavourable conditions for bacterial growth
Normal bacterial flora
Well established and prevent colonisation by pathogenic organisms. When wiped out by antibiotic therapy, pathogenic organisms are allowed to proliferate - C. Diff + candia albicans
Produce natural antibiotics and bacteriocins to prevent proliferation of pathogens
Stimulate IgA production to prevent invasion of deeper tissues by pathogens and flora
