Concentrations of soluble CD95 and CD8 antigens in the plasma and levels of CD8+CD95+, CD8+CD38+, and CD4+CD95+ T cells are markers for HIV-1 infection and clinical status.

Apoptosis mediated via the CD95 (FAS/APO-1) receptor is thought to play a role in the depletion of CD4+ T cells in HIV infection. In the present study expression of the CD95 antigen on lymphocyte subsets and the plasma level of soluble CD95 (sCD95) were determined in HIV-1-infected adults. The expression of CD95 was increased on CD8 cells in all groups of HIV+ individuals, while increased expression of CD95+ cells on CD4 cells was limited to individuals with CD4 counts of < 200 mm3. The proportion of CD4+ that expressed CD95 was inversely correlated with the percentage of CD4+ PBL. The concentration of sCD95 was significantly higher in the plasma of HIV-infected individuals than in normal controls. The level of sCD95 in HIV-infected subjects showed no correlation with the percentage of PBL expressing CD95, indicating that the increased level of sCD95 did not reflect release from CD95+ PBL. The plasma sCD95 concentration was significantly correlated with the percentage of CD8+ cells and, particularly, with CD8+ CD38- cells. A striking inverse correlation was found between the sCD95 plasma concentration and the proportion of CD4+ CD95+ cells out of the total CD4+ population. There was no correlation between the serum level of sCD95 and that of soluble CD8 (sCD8), both of which were increased in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals. Unlike the level of sCD95, the level of sCD8 in the plasma of HIV+ individuals was correlated with the percentage of CD95+ and CD8+ CD38+ cells. The present study indicates that plasma sCD95 may be one of the factors that regulate apoptotic death of lymphocytes in HIV infection.