Innate immunity

Innate immunity is present from birth and is a non-specific first line of defence. Innate immunity includes:

• Physical barriers such as intact skin and mucous membranes
  
• Chemical barriers such as saliva and gastric acid
  
• Phagocytic cells such as macrophages in the mucosa.

Acquired immunity

Acquired immunity is specific to a single organism or group of closely related organisms and is acquired through an active or a passive mechanism. Acquired immunity can be active or passive.

Active immunity is usually long-lasting and can be acquired through exposure to the natural disease or by vaccination. The body responds by producing antibodies and T lymphocytes to act against the infection. Vaccination provides immunity without the risk from the disease and its complications.

Passive immunity provides temporary protection to an individual by the transfer of antibodies. For example:

• Across the placenta from mother to child
  
• Transfusion of blood or blood products containing immunoglobulins.