Immunodeficiency is a state in which the immune system’s capacity to fight infection is compromised or absent entirely

• These disorders may be inherited (e.g. SCIDs), pathogenic in origin (e.g. AIDS) or caused by drug treatments (e.g. immunosuppression)
  

HIV

The Human Immunodeficiency Virus (HIV) is a retrovirus that infects lymphocytes and consequently disables the body’s adaptive immune system

• The variety of symptoms and infections caused by the virus are collectively classed as Acquired Immuno-Deficiency Syndrome (AIDS)
  

HIV specifically targets the helper T lymphocytes, which are responsible for the activation of B cells

• Following infection, the virus undergoes a period of inactivity (clinical latency) during which infected helper T cells reproduce
  

• Eventually, the virus becomes active again and begins to spread, destroying all infected T lymphocytes in the process (lysogenic cycle)
  

• With a reduction in the number of helper T cells, antibodies are unable to be produced, resulting in a lowered immunity
  

• The body becomes susceptible to opportunistic infections, eventually resulting in death if the condition is not managed
  

HIV and TH Cells

Transmission of HIV

• HIV is transmitted through the exchange of body fluids (via unprotected sex, blood transfusions or during pregnancy)
  

• The risk of exposure to HIV through sexual contact can be minimised by using latex protection (i.e. condoms)
  

• A small minority of people are immune to HIV infection (they lack the CD4+ receptor on TH cells that HIV requires for docking)
  

• HIV is a global issue, but is particularly prevalent in poorer nations with limited access to quality education and health systems
  

Body Fluid Transmission