Impaired urinary excretion of soluble IL-2 receptors in patients with systemic lupus erythematosus and rheumatoid arthritis.

Several previous studies have demonstrated increased in vivo release of soluble interleukin-2 receptors (sIL-2R) in patients with disorders associated with cellular activation. In this study attempting to understand better the role of sIL-2R released in vivo, we investigated the sIL-2R levels in paired serum and urine samples from 25 patients with systemic lupus erythematosus (SLE), 41 patients with rheumatoid arthritis (RA) and 20 healthy subjects. Using an ELISA for sIL-2R, we detected significantly increased urinary sIL-2R levels in normal individuals (868 +/- 114 units/ml) compared to the corresponding serum samples (209 +/- 25, P < 0.001, mean urine/serum sIL-2R ratio: 4.5 +/- 0.6), which suggests that the clearance of sIL-2R from circulation is largely kidney-dependent. The patients with SLE and RA exhibited significantly increased serum sIL-2R levels compared to normals (682 +/- 115 and 734 +/- 101 units/ml, respectively, P < 0.001) and these levels correlated with disease activity. However, urinary excretion of sIL-2R in these patients (SLE: 620 +/- 154 units/ml; RA: 1084 +/- 148 units/ml) was found to be significantly decreased (mean urine/serum sIL-2R ratio in SLE: 0.9 +/- 0.2; in RA: 1.9 +/- 0.2; P < 0.001) compared to normals, possibly contributing to the accumulation of these soluble receptors in the serum of autoimmune patients after their release from cells. Our findings can be attributed either to the binding of the sIL-2R to serum protein(s) or to distinct structural features of serum sIL-2R in SLE and RA patients, interfering with the urinary excretion of these molecules.

Serum-soluble interleukin-2 receptors in B-cell lymphoproliferative malignancies.

The levels of soluble interleukin-2 receptors (sIL-2R) were determined in the serum of 53 patients with B-cell lymphoproliferative malignancies, including 31 patients with non-Hodgkin lymphomas (NHL), 16 with chronic lymphocytic leukemia (CLL), and 6 with multiple myeloma. In addition, serum samples from 40 patients with various solid tumors as well as from 53 healthy individuals were used as controls. It was found that the mean serum levels of sIL-2R were significantly increased (P less than 0.001) in NHL (mean +/- standard error of the mean 2,327 +/- 320 units/ml) and CLL patients (2517 +/- 451 units/ml) as compared to normal controls (207 +/- 17 units/ml). No such difference was observed when the serum sIL-2R levels of patients with multiple myeloma or solid tumors were analyzed. Serum sIL-2R levels were closely related to the clinical stage, the presence of B-symptoms, and the disease activity of patients with NHL and CLL. In fact, response to chemotherapy was followed by marked decrease or normalization of sIL-2R levels, while in a number of patients sIL-2R values were even able to predict disease relapse. Finally, no association with histologic grade in NHL patients, could be demonstrated. We conclude that serum sIL-2R (1) are increased only in B-NHL and B-CLL but not in myeloma patients, (2) are related to the tumor burden, and (3) can serve as a valuable tumor marker for the monitoring of patients treatment.

Soluble interleukin-2 receptors and autoantibodies in the serum of healthy elderly individuals.

Recently, we reported an increased incidence of various autoantibodies in a healthy elderly population (Group A, 64 subjects). Presently we examined whether there is variability in the expression of the age-associated immunological aberrations between different geriatric populations by extending our observations in another healthy elderly population (Group B, 119 subjects). We also determined the serum levels of soluble IL-2 receptors (sIL-2R) attempting to define the activation status of the immune system during senescence. Compared to non-elderly controls, healthy elderly individuals exhibited a significantly higher incidence of autoantibodies as well as significantly higher levels of sIL-2R in serum (p less than 0.001), the latter possibly suggesting the occurrence of lymphocytic activation during the ageing process. The overall prevalence of autoantibodies was statistically associated with the presence of raised sIL-2R levels in serum (p less than 0.005). These aberrant immunological phenomena were more frequent among the elderly of group A, compared to group B (p less than 0.005). In contrast to the uniform expression of various autoantibodies previously observed in group A, the autoantibody profile of group B consisted mainly of rheumatoid factor and antibodies to single-stranded DNA. Finally, no association could be demonstrated between the presence of autoantibodies and HLA antigens in 42 elderly studied.