[Expression of decay-accelerating factor on CD8-positive lymphocytes as an index of aging and of host defense function].

Decay-accelerating factor (DAF) is a membrane glycoprotein that prevents complement activation on blood cells. Among CD8+ T cells, DAF-negative cells can be distinguished from DAF-positive cells. We computed the proportion of DAF-negative CD8+ T cells in the peripheral blood of 59 normal healthy subjects, 27 to 93 years old, and analyzed the differences between subjects of different ages. The proportion of CD8+ T cells that were DAF-negative correlated significantly and positively with age. We also studied these lymphocytes in patients with cerebrovascular dementia, Alzheimer's dementia, cancer, rheumatoid arthritis and systemic lupus erythematosus. The proportion of CD8+ T cells that were DAF-negative did not correlate significantly with age in patients with cerebrovascular dementia, Alzheimer's dementia or cancer, but it correlated significantly and positively with age in patients with rheumatoid arthritis and in those with systemic lupus erythematosus. Therefore, healthy subjects and patients with various diseases can be classified according to age and to the proportion of CD8+ T cells that are DAF-negative. This proportion can then be used as an index of aging and of host defense function.