Elevated soluble interleukin-2 receptor and interleukin-2 receptor positive cells in carcinomatous pleural effusions

Soluble interleukin-2 receptor (IL-2R) level and IL-2R positive (IL-2R+) cells were studied in twenty patients with carcinomatous pleural effusions. The mean value of soluble IL-2R level in carcinomatous pleural effusions was 2930 +/- 1722 U/ml and that in sera was 965 +/- 610 U/ml. Soluble IL-2R level in carcinomatous pleural effusions was found to be significantly higher (p less than 0.001) than that in sera of patients with carcinomatous pleural effusions and that in transudates. Serum soluble IL-2R level in patients with carcinomatous pleural effusions was found, to be significantly higher (p less than 0.001) than that in normal controls (264 +/- 70 U/ml). We also studied IL-2R+ cells in pleural fluids and peripheral blood of patients with carcinomatous pleural effusions. The mean percentage of IL-2R+ cells in carcinomatous pleural fluid lymphocytes was 22.8 +/- 17.8%, as compared with 3.0 +/- 2.2% in peripheral blood lymphocytes of normal controls (p less than 0.001). No significant differences were observed among the cell types of lung cancer examined (adenocarcinoma, squamous, small cell and large cell carcinoma) and no correlation among levels of soluble IL-2R and IL-2R+ cell in either pleural fluid or blood. Our results suggest that in patients with carcinomatous pleural effusions, T cell-mediated active immune mechanisms (IL-2/IL-2R system) against cancer cells are more active in pleural fluid than in peripheral blood.