Mechanisms of Innate Immunity

Jonathan Sat Dec 13, 2008 9:02 pm

Firstly, innate immunity is "the resistance to infections by virtue of his or her genetic and constitutional make-up". Therefore the following mechanisms for innate immunity can be explicated:

1. Epithelial surfaces:
- The skin protects against invading antigens
- Respiratory mucosa protects against inhaled antigens
- Acid secreted by the gastric mucosa kills consumed antigens, Alkaline nature of the small intestine and colon are permissive for good flora
- Lacrymal secretions protect the eyes (conjuntiva) from foreign contaminants
- The vaginal mucosa is acidic to protect from foriegn contaminants
- The flushing action of the urinary system protects the urethra from infection

2. The antibacterial substances in the blood and tissues:
- The complement system is important in the destruction of pathogenic bacteria in the blood and tissues
- Also the following have been flound in the blood and tissues that have antibacterial properties:
a) beta lysin
b) leukins and plakins
c) acidic substances (lactic acid)
d) lactoperoxidase
*Viral infections are protected against by interferons which are secreted by the tissues in the body

3. Microbial Antagonism:
- There is natural bacterial flora on the human skin and mucous surfaces that prevent the colonization of pathogens

4. Cellular factors:
- The presence of phagocytotic cells in the body is important for the removal of unwanted bacteria
- NK cells are activated by interferons which are activated by viral infections; these cells are important for destruction of viral infections and tumors

5. Fever:
- Important for speeding up physiological processes required to eliminate antigens
- The increase in temperature itself can eliminate the pathogen

6. Acute phase proteins:
- Infection or injury leads to increase in certain plasma concentrations of proteins; examples are:
a) C Reactive Protein
b) Mannose Binding protein
c) Alpha 1 acid glycoprotein
d) Serum Amyloid P Component
- These proteins enhance host resistance, prevent tissue injury and promote inflammatory healing