Immunity

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Key Components

Before we begin, here are some terms which you should familiarise yourself with.

  • IgE Antibodies: stimulates the release of histamine and other chemicals that cause allergies
  • Anaphylaxis: a person who has become hypersensitive and has a severe and rapid allergic reaction

Active Immunity

Active immunity is where antibodies are made by the immune system of the immune system and thus retains memory and can respond rapidly on second exposure. However, this can also cause adverse effects from the infection

  • Natural: this is when immunity is acquired naturally after an infection without any artificial intervention
  • Induced: this is the deliberate and artificial introduction of a disabled pathogen or toxin to the body

Passive Immunity

Passive immunity is where antibodies produced in one person are introduced into another person to provide immunity and thus provides immediate protection but has no memory and doesn’t provide lasting protection

  • Natural: this is where antibodies enter a person naturally like via a mother’s placenta or breast-feeding
  • Induced: this is antibodies are injected into another person after exposure to a pathogen e.g. snake antivenom

Vaccination

Vaccines are used to activate the immune system to produce antibodies against specific disease-causing organisms without causing the disease. This is because the pathogens can be killed or weakened so they cannot cause harm

Herd Immunity

Herd Immunity is the indirect protection of populations from infection where that protection is created by the presence of immune individuals as it decreases the possibility for a contagious infection to be present. This protects vulnerable members of society e.g. elderly people who are unable to access the vaccine

Monoclonal Antibodies

Monoclonal antibodies are specially artificially designed antibodies to target one specific antigen

  • Bind to growth factors to prevent new blood supply to tumour
  • Bind to cell surface markers and flag cancer cells to immune system
  • Bind to over-expressed growth factor receptors on cancer cells, blocking stimulation
  • Conjugated with cytotoxic drugs or radio-isotopes to deliver treatment direct to cancer cells

Autoimmune Disease

Autoimmune diseases occur when the immune system fails to recognise ‘self’ and produces antibodies against the body’s own cells. These antibodies are called autoantibodies

Multiple sclerosis is an autoimmune disease that results from autoantibodies attacking the myelin that forms an insulating sheath around nerve fibres in the brain and spinal cord. When the myelin is destroyed, nerve fibres are exposed, and the transmission of nerve impulses is slowed or blocked which can lead to numbness, lack of coordination and vision impairment

Immune Deficiency Diseases

Acquired immunodeficiency syndrome is a disease that results from an uncontrolled and untreated infection by the human immunodeficiency virus. HIV is a retrovirus that carries its genetic information in two fragments of single stranded RNA. The HIV targets the T helper cells of the immune system, thus crippling it, as the gradual depletion of T helper cells means that the immune system ceases to protect against pathogens

The immune system of those with untreated AIDS are suppressed and these people are at risk of opportunistic infections which are pathogens that take advantage of the weakened immune system

Allergies

An allergic reaction is an abnormal reaction of the immune system to an allergen. Allergens such as pollen, dust, peanuts react with IgE antibodies attached to mast cells – primed mast cells. They develop via sensitisation

  • The mast cells (fixed cells around blood vessels, connective tissue, lungs) release histamines
  • The histamines cause inflammation and constrict the muscle around airways