Acquired Immune Deficiency Syndrome (AIDS)
AIDS is an extremely serious disease in
which the ability to mount an immune
response is disabled severely. It is
caused by human immunodeficiency
virus (HIV). The first case of
AIDS was recognized in 1981, and by
1998, over 30 million people worldwide
were infected with HIV/AIDS, of
whom 90% were in developing countries
of Asia and sub-Saharan Africa.
HIV infection virtually always progresses
to AIDS after a latent period
of some years. To the best of our current
knowledge, AIDS is a terminal disease.
AIDS patients are continuously
plagued by infections with microbes
and parasites that cause insignificant
problems in persons with normal
immune responses. HIV preferentially
invades and destroys CD4+ lymphocytes.
CD4 protein is the major surface
receptor for the virus. Normally, CD4+ cells make up 60% to 80% of the T-cell
population; in AIDS they can become
too rare to be detected. TH1 cells are
relatively more depleted than TH2
cells, which upsets the balance of
immunoregulation and results in persistent,
nonspecific B cell activation.