Proteinuria and activated T-lymphocytes in diabetic nephropathy.

The reasons for the presence of activated T-lymphocytes (ATL) in some long-standing insulin-dependent diabetic (IDDM) patients are unknown. These cells have been implicated in the genesis of proteinuria in some forms of immune-mediated renal disease. We measured ATL in 18 IDDM patients with diabetic nephropathy, 10 with nonnephrotic proteinuria (total urinary protein excretion rate greater than 0.5 and less than 3.5 g/24 h) and 8 with nephrotic proteinuria (total urinary protein excretion rate greater than 3.5 g/24 h), and in 17 age-, sex-, and duration-of-diabetes-matched diabetic control subjects without clinical proteinuria (total urinary protein less than 0.5 g/24 h). T-lymphocytes purified from peripheral blood were stained by direct immunofluorescence with the fluorescein-labeled monoclonal antibody anti-HLA-DR. Absolute number and percent of DR-positive T-lymphocytes were significantly higher in patients with nonnephrotic proteinuria (median and range 162 x 10(6)/ml, 40-320 x 10(6)/ml; 13.9%, 8.1-19.4%) compared with nonproteinuric control subjects (81 x 10(6)/ml, 2-240 x 10(6)/ml, P less than .05; 6.2%, 0-13.1%, P less than .01). In 8 patients with nephrotic proteinuria, absolute and percent DR-positive T-lymphocytes tended to be lower (36 x 10(6)/ml, 14-56 x 10(6)/ml; 3.4%, 1.1-5.4%) than in nonproteinuric control subjects. An increased number of activated T-lymphocytes may be part of an immune-mediated process associated with the development of proteinuria in diabetic nephropathy. In advanced renal disease with nephrotic proteinuria, this immune process may become exhausted.