TCR/CD3 receptor complex plays a central role in antigen recognition and T cell activation. Therefore, the present study investigates TCR alpha/beta (TCR-1) and CD3 receptor density (RD, number of receptors per cell) on uremic CD4 T lymphocytes in relation to T cell proliferative response induced by anti-CD3 monoclonal antibodies (mAb). The influence of uremic serum on TCR/CD3 receptor expression of normal and uremic CD4 T lymphocytes was evaluated as well. We found, that: a) percentage of TCR-1 and CD3 positive cells of freshly isolated CD4 T lymphocytes is the same in controls and ESRD-patients, but the TCR/CD3 RD is lower on uremic CD4 T lymphocytes, b) Incubation for 24 h with uremic serum lowers TCR/CD3 RD on normal and uremic CD4 T cells, c) There is positive correlation between TCR/CD3 RD and anti-CD3 induced lymphocyte proliferation. These data might also support the hypothesis that blunted T-cell response to antigen in uremia is due to down-regulation of the TCR/CD3 receptor complex by uremic milieu.