The innate immunity
- Epithelial surfaces form a physical barrier against infection.
- Low pH of skin and fatty acids in sebum inhibit microbial growth.
- The gut has gastric acid, pancreatic enzymes, mucosal immunoglobulin A (IgA), and normal colonic flora which act to prevent establishment of infection.
- The respiratory tract secretes mucus to trap organisms, and beating cilia transport them to the throat where they are swallowed.
- Continuous flushing of urine through the urinary tract prevents microbes from adhering to the urothelium.