Serum Levels of Soluble Interleukin-2 Receptor in Pulmonary Tuberculosis

It is well known that the activation of cell mediated immunity has an important role in the pathogenesis of pulmonary tuberculosis and the production of the protective immunity against Mycobacterium tuberculosis. During the activation of T-cell by Interleukin-1 released from the macrophage, not only Interleukin-2 but also the soluble Interleukin-2 receptor (sIL-2R) molecule is released into the extracellular fluid. In vitro study reveals that the level of this sIL-2R is well correlated with the degree of activation of the T-cell. We therefore carried out this study to evaluate the significance of the serum IL-2R level in determining the disease activity of pulmonary tuberculosis. The level of SIL-2R was measured by sandwich ELISA method. The level of sIL-2R in 42 patients with bacteriologically -proven active pulmonary tuberculosis (29 far and moderately advanced pulmonary tuberculosis, age: 30.3 ±10.3 yrs; 13 minimal pulmonary tuberculosis, age: 34.4 ± 15.3 yrs) was 1111 ± 424 u/ml, which was significantly higher than the normal control group (age: 31.0±9.9 yrs) (365±143 u/ml) and inactive pulmonary tuberculosis group (age: 37.3 ± 16.9 yrs) (465 ± 131 u/ml). But there was no significant difference between 29 patients with advanced pulmonary tuberculosis (1138 ± 405 u/ml) and 13 patients with minimal pulmonary tuberculosis (1051 ± 474 u/ml). More than three months after the initiation of antituberculosis chemotherapy, the follow-up level of serum sIL-2R in 21 patients with active pulmonary tuberculosis (advanced pulmonary tuberculosis 15, minimal pulmonary tuberculosis six) was 533 ± 182 u/ml, which was markedly lower than the pretreatment level (1020 ± 323 u/ml). In conclusion, the high level of sIL-2R (especially over 1000 u/ml) can be used as a marker of disease activity in pulmonary tuberculosis even though not diagnostic.