n :  a disease of the human immune system that is caused by infection with HIV, that is characterized cytologically esp. by reduction in the numbers of CD4-bearing helper T cells to 20 percent or less of normal, that in modern industrialized nations occurs esp. in homosexual and bisexual men and in intravenous users of illicit drugs, that is commonly transmitted in blood and bodily secretions (as semen), and that renders the subject highly vulnerable to life-threatening conditions (as Pneumocystis carinii pneumonia) and to some that become life-threatening (as Kaposi's sarcoma) - called also acquired immune deficiency syndrome , acquired immunodeficiency syndrome  .
 
 
 
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