Changes in the expression of surface receptors on lymphocyte subsets in the elderly: Quantitative flow cytometric analysis

The immunophenotype of circulating lymphocytes, including the intensity exp ression of surface receptors, changes with ageing. Until now, no results of systematic studies on age-dependent changes with respect to the expression of the major lymphocyte surface receptors in healthy elderly subjects have been reported. In order to identify age-related changes in both representa tion and immunophenotype of lymphocyte populations, we investigated, by mea ns of triple-color whole-blood immunostaining and quantitative flow cytomet ry, the percent values and the absolute numbers, as well as the levels of s urface antigen expression or antigen molecules per cell (ABC values x 10(3) ), of different peripheral blood lymphocyte subsets from 23 healthy elderly subjects and 13 young donors. Naive (CD45RA(+)CD3(+)) T cells, total B cel ls, and CD5(+) B lymphocytes are decreased (22%, 6%, 0.8% vs. 30%, 12%, 1.4 %, respectively), whereas activated (HLA-DR(+)CD3(+)) and memory (CD45RO(+) CD3(+))T cells, CD3(+)CD7(-) T lymphocytes, and lymphocytes expressing the NK marker CD56 are expanded in the elderly (2%, 53%, 13%, 6% vs. 0.8%, 45%, 8%, 8%, respectively). Moreover, T lymphocytes from elderly individuals ex press lower CD3 (61 +/- 10) compared to young (69 +/- 10). Considering the different T-cell populations, CD3 antigen is respectively decreased on CD45 RO(+) T cells (55 +/- 14 vs. 66 +/- 14) and upregulated on CD56(+) T lympho cytes (62 +/- 21 vs. 45 +/- 20). Increased CD8 expression characterizes CD3 (+)CD7(-) lymphocytes (70 +/- 34 vs. 44 +/- 17) while HLA-DR on activated T cells is lower in old (39 +/- 7) than young (46 +/- 9) donors. CD7 is down -regulated both in T (22 +/- 3 vs. 28 +/- 3) and NK (48 +/- 18 vs. 71 +/- 1 8) cells, whereas CD2 expression, unchanged on NK cells, is up-regulated on T lymphocytes (54 +/- 10 vs. 41 +/- 8). Age-related changes in B-cell anti gen expressions were also found: CD20 is increased (124 +/- 23 vs. 105 +/- 16) whereas, despite the unchanged CD5 expression of T cells, CD5 intensity on the B-cell subset co-expressing this antigen is higher in old (49 +/- 3 7) than in young (22 +/- 4) people. The observed changes in the expression of functionally important cellular receptors can contribute to the remodeli ng of immune function characteristic of the elderly. Moreover, since quanti tative flow cytometry is becoming widely employed in clinical practice, our results also contribute to the assessment of specific age-dependent antige n expression changes to be considered for diagnostic approaches in the elde rly. Am. J. Hematol. 67:63-72, 2001. (C) 2001 Wiley-Liss, Inc.