In particular, HIV attacks a type of white blood cell known as the T-helper cell, also known as the CD4 cell. HIV also infects other types of cell, including blood cells and cells of the central nervous system. AIDS stands for Acquired Immune Deficiency Syndrome. AIDS is a condition in which progressive damage to the immune system has left the body unguarded against the development of certain illnesses, known as opportunistic infections. HIV is a virus.
Antibodies are part of the body's natural defences which fight infections and viruses.
Such people have what is known as symptomatic HIV infection. A diagnosis of AIDS varies from country to country. In the UK there is a diagnosis of AIDS if someone who is HIV positive develops one of the opportunistic infections in the presence of underlying immune deficiency, and has a low CD4 count. The HIV test is a test to detect the presence of HIV antibodies. This period is known as the Window Period, or Seroconversion.