Despite an increase in plasma IL-7 levels, the CD4 T-cell pool decrease progressively in HIV-infected patients. Here we report on our tests to check the hypothesis that defects in the IL-7 receptor system might be involved in this phenomenon. The cell surface expression of CD127 was measured ex vivo in CD4 and CD8 T lymphocytes drawn from 3 groups of HIV patients. IL-7 function was also followed in vitro by measuring IL-7-driven T-cell proliferation, the induction of the CD25 activation marker, and overexpression of the antiapoptotic molecule Bcl-2. Untreated viremic patients showed a slight but significant decrease in CD127 expression on the surface of their CD4 lymphocytes. By contrast, CD127 expression was substantially altered on the surface of CD8 T lymphocytes taken from untreated viremic patients. IL-7-induced overexpression of the antiapoptotic molecule Bcl-2 was dramatically altered in viremic patients, whereas IL-7-dependent CD25 induction and T-cell proliferation were reduced. Highly active antiretroviral therapy partially corrected these defects in patients with an undetectable viral load and CD4 counts of more than 400 cells/μL. The effects of HAART were less pronounced in patients with undetectable VL but low CD4 counts (< 250 cells/μL). The IL-7 receptor is dysfunctional in the CD4 and CD8 lymphocytes of HIV-infected patients. This may be due to abnormal activation of the immune system in HIV-infected patients and may contribute to the reduced CD4 count and the altered function of the CD8 compartment.

From the* Unité Immunogénétique Cellulaire, Département de Médecine Moléculaire, Institut Pasteur, Paris;† Unité de Recherche et d'Expertise Epidémiologie des Maladies Emergentes, Institut Pasteur, Paris;‡ Service de Médecine Interne, Hôpital de Bicêtre, Le Kremlin Bicêtre; § Centre de Transfusion de l'Hôpital Percy, Clamart; and¶ Cytheris SA, Vanves, France.