Immune system

• The immune system is responsible for fighting off infection in the body, there are two types of immunity.
• The immune system has primary and secondary defences. The primary defence is the body's skin, mucous membranes and normal body flora. The secondary defence system is the inflammatory response, lymphocytes, protective proteins etc.
• The bodies two forms of immunity are the innate and the acquired immune system.
• The innate immune system is natural and present at birth of the individual and will include physical and bloodborne (from the mother) barriers.
• Th acquired immune system comes from exposure to diseases through childhood and life as well as from vaccines. This can further be divided into natural / artificial active and passive immunity
• Natural passive immunity comes from the mother during pregnancy and breastfeeding and will stick with baby for a given time after birth.
• Natural active immunity comes from the individual throughout life catching infections and creating antibodies
• Artificial passive immunity comes from an external source such as vaccination or injection of antibodies
• Artificial active immunity comes from vaccinations which stimulate the production of antibodies by the individuals own cells
• Antibodies are immunoglobins produced by plasma cells, they are able to recognise foreign substances of the body (typically antigens) and destroy them
• Phagocytes are white blood cells that engulf and destroy foreign agents using the process of phagocytosis
• Lymphocytes are white blood cells that produce antibodies when antigens enter the body.
• B - lymphocytes are also known as B cells lead to the production of antibodies from plasma cells
• T-lymphocytes are also known as T cells and have two main functions; cytotoxic T cells kill infected host cells and helper T cells activate other immune responses
• Cell mediated immunity refers to the direct attack activated by T cells, they react with foreign antigens on the surfaces of other host cells
• Humoral immunity is an indirect response where antibodies bind to specific antigens and neutralise or mark them for destruction
• Antibody mediated immunity involves the binding of antibodies to pathogens which can either neutralise them (inactivating their ability to cause disease) or mark them for destruction by phagocytes
• The complement system consists of proteins produced by the liver that work together to enhance the activity of antibodies against invading organisms
• Complement activation leads to inflammation, increased vascular permeability, chemotaxis and opsonisation