Human Immunodeficiency Virus (HIV) infection is associated with a progressive deficiency of immune function (1). Lymphopenia will develop and is predominantly explained by the loss of T lymphocytes that bear the helper/inducer phenotype (also called CD4 + or, T4 + lymphocytes) from peripheral blood.
As the progressive loss of CD4 + lymphocytes is the hallmark of HIV infection and its deadly complication the Acquired ImmunoDeficiency Syndrome (AIDS), the accurate determination of this lymphocyte subset and its appropriate interpretation are essential for studying the epidemiology of the disease, for managing HIV-infected patients, and more recently, has been recognized as an essential criteria to study the efficacy of new antiretroviral treatments. This article will briefly review the physiology of the CD4 + lymphocyte, issues concerning the technology used for its peripheral blood determination, and the epidemiological and clinical significance of this marker. It will emphasize the current practical utility of CD4 + lymphocyte determination for the development of new anti-HIV compounds.
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