Evidence for expansion of a population of lymphocytes with reduced or absent T3 expression in aged human donors

In a previous report, we described an unusual pattern of T cell associated surface marker expression in unfractionated mononuclear cells from aged donors; an excess of T4 and T8 positive cells relative to T3 positive cells. This study further characterizes these cells on the basis of density, adherence to nylon wool and quantitative expression of cell surface markers. We find that the population of lymphocytes responsible for the unusual surface marker expression is of low density, adheres to nylon wool, and is present in small numbers in young donors. The adherent cells have a reduced quantitative expression of the T3 antigen, no change in the antigen density of T4 and T8, and have increased expression of the T10 antigen. These cells do not have the characteristics of large granular lymphocytes, monocytes, B cells with unusual marker expression, or thymocytes poised for export to peripheral blood. We suggest that these cells, found in increased numbers in aged humans, may represent an expansion of a population of T lymphocytes with absent or reduced T3 antigen expression found normally in smaller numbers in young adults. T lymphocyte antigen receptor density has been quantitatively linked to expression of the T3 antigen. Thus, our results imply that aging may lead to decreased T cell surface antigen density, which may account in part for decline in T cell function with age.