Expression of the human T cell antigen receptor complex in advanced age

Several studies of T cell-associated surface marker expression in older subjects "with no evidence of diseases known to affect immune function" have suggested that diminished expression of the constant portion (CD3) of the human T cell antigen-receptor complex (CD3/Ti) may be associated with aging. To determine if there is a decrease with age in expression of this complex, we determined the percent of cells positive for WT31, an antibody that recognizes a constant epitope on Ti alpha-beta heterodimers, CD3, CD4 and CD8 by immunofluorescence on peripheral blood lymphocytes from young controls (19-31 years), and 2 well characterized populations of older donors (greater than 69 years). The first group of older donors had no history of chronic or recent acute illness and saw a physician only for routine medical care. The second group was selected from patients seen in a geriatrics clinic for diagnoses that included osteoarthritis and cardiopulmonary disorders. There were no significant differences in the percent of cells positive with WT31, or with antibodies to CD4 and CD8 between young adults and the 2 groups of older donors. The clinic subjects showed a consistent decrease in percent of CD3+ lymphocytes in peripheral blood mononuclear cells compared to young adults (5-10% reduction) with less difference between the healthy older subjects and young adults. In the clinic subjects this reduction appears to be due to a decrease in CD3+, WT31-lymphocytes. These cells represent about 5-6% of the total T cell population in the young and healthy older group and are known to express CD3 in combination with Ti gamma-delta dimers. We show here that these cells are about equally distributed in high and low density lymphocytes after Percoll fractionation. We conclude that significant quantitative reduction in expression of the CD3/Ti antigen-receptor complex on human T cells is not a feature of the primary aging process and cannot account for diminished in vitro proliferative response of healthy subjects with age. However, diminished abundance of T cells expressing products of the Ti gamma-chain in less healthy older subjects may predispose to or result from diseases not usually associated with altered immune function.