Apoptosis of CD57+ and CD57− lymphocytes in the lung and blood of HIV-infected subjects

Patients infected with HIV frequently have a CD8+ lymphocytic alveolitis consisting of HIV-specific CD8+CD57− cytotoxic T lymphocytes. However, in late stage disease, there is expansion of a CD8+CD57+ population with suppressive properties. We examined role of lymphocyte apoptosis in the expansion of the CD8+CD57+ lymphocytes in late stage HIV in the lung and blood compartment in human subjects. Fas was expressed on virtually all lung lymphocytes from HIV-infected and normal subjects. Fas ligand expression was increased in HIV infection in both CD8+CD57+ and CD8+CD57− lymphocytes, though a significantly greater percentage of CD8+CD57+ cells expressed this marker. CD8+CD57+ lymphocytes in normal and HIV-infected subjects underwent more apoptosis than CD8+CD57− cells. However, in late stage HIV infection, the percentage of CD8+CD57+ cells undergoing apoptosis declined. These data demonstrate that under normal conditions CD8+CD57+ cells appear destined to undergo programmed cell death. Expansion of suppressive CD8+CD57+ cells in the lungs of HIV-infected subjects with advanced disease may be due to the failure of this normal regulatory process.