Question

Describe the various type of barriers of immunity.

Answer 1

• The human immune system includes three lines of defence against foreign invaders: 1) physical and chemical barriers, 2) nonspecific resistance, and 3) specific resistance.
  
• The first line of defence is the physical and chemical barriers, which are considered functions of innate immunity.
• Physical barriers include skin, the gastrointestinal tract, the respiratory tract, the nasopharynx, cilia, eyelashes and other body hair.
• Very few microorganisms can penetrate intact skin; instead, invaders usually enter through wounds or by being injected, such as by mosquito bites. Skin wounds heal rapidly to reestablish the protective barrier.
• A complex population of normal skin bacteria tends to exclude new invaders, while antimicrobial molecules in sweat can kill many would-be invaders.
• The defence of the intestine centers largely on the presence of the huge and immensely complex normal commensal microbiota. Potential invaders may be unable to colonize the intestine in the presence of a well-adapted population of commensal microbes. If all else fails, invaders may be rapidly removed from the GI tract by vomiting and diarrhea.
• Chemical barriers include antimicrobial proteins that harm or destroy invaders, and cells that attack foreign cells and body cells harbouring infectious agents.