The impact of age on T cell subset profiles in patients on chronic hemodialysis awaiting renal transplantation

Age has been considered a significant risk factor in renal transplation; increasing age is associated with a higher morbidity and mortality, primarily as a consequence of infectious and cardiovascular complications. The increased incidence of potentially lethal infections in this patient population may be due to the impact of immunosuppression on a naturally declining immune system. In search for possible characteristic T cell subsets profile in aging patients, subsets of such cells were analyzed in 270 patients on chronic hemodialysis awaiting renal transplantation. Using two-color flow cytometry and murine monoclonal antibodies recognizing specific T cell subset markers, the following cell subsets were analyzed in patients < 40 yr of age (n = 229) and in patients > 55 (n = 41) years of age: total T cells (CD3); activated T cells (CD3DR); B cells (CD3-DR+); T helper/inducer (h/i) cells (CD4); T suppressor/inducer (s/i) cells (CD4+CD45+), T cytotoxic/suppressor (CD8), the activated CD4 and CD8 subsets (CD4DR and CD8DR); T cytotoxic cells (Leu2+7-); cells of the Leu-7 phenotype (Leu7+ and Leu2+7+); interleukin 2 receptor (IL-2-R) expressing CD3 and CD8 subsets (CD3IL-2-R+ and CD81L2-R+); and transferrin receptor (TR+) expressing CD3 (CD3TR+). The ratio CD4: CD8 was derived from the respective subset data. Significantly higher levels of CD3 (P < 0.005), B (P < 0.05), CD8 (P < 0.001), CD4DR (P < 0.05) and Leu2+7- (P < 0.0045) and CD8-IL-2-R+ (P < 0.005) cell subset were observed in the younger (age < 40), compared to the older (age > 55) group. In contrast, the CD4 : CD8 ratio, the s/i (CD4+CD45+), the Leu7+2- and Leu2+7+ cell subsets were found to be present at a higher level in the older group (P < 0.001, P < 0.005, P < 0.05 and P < 0.01 respectively). These data demonstrate a significant effect of aging on certain T cell subsets levels in the peripheral blood. Although this study does not provide data regarding the functional status of the immune competent cells, it highlights the actual changes in the distribution of cell subsets in the older potential organ recipients. Such changes may be responsible for the increased risk of infectious complications seen in older renal allograft recipients.