Cytokine-mediated interactions among blood cells, especially T-lymphoctes, may be impor-tant in the regulation of airway inflammation in asthma. To investigate whether T-lymphocytes are related to disease activity in asthma, serum soluble interleukin-2 receptor (sIL-2R) levels were measured in 77 bronchial asthmatics and 19 healthy volunteers. The serum sIL-2R level was higher in asthmatics than in healthy controls (mean±SD ；449.8±225.5 vs. 323.2±123.9 U/ml ; p<0.01). However, sIL-2R levels were similar between atopic and non-atopic asthmatics (451.9±235.9 vs. 416.7±147.2 U/ml), and were also similar between severe and mild to moderate asthmatics (437.4±209.9 vs. 469.8±276.1 U.ml). Steroid-dependent intractable asthmatics treated with prednisolone st doses of 5-10 mg/day showd higher sIL-2R levels (470.1±257.9 U/ml) than asthmatics treated with the drug at doses below 5 mg/day (357.2±102.6 U/ml) and intractable asthmatics treated with the drug at doses above 10 mg/day (282.5±194.5 U/ml). There was a strong correlation (r=0.915 ; p<0.01) between percentage at IL-2R-positive helper T cells among peripheral white blood cells and the serum concentration of sIL-2R.
The type Ⅳ cell-mediated immune response is considered to be related to the pathogenesis of asthman. Serum sIL-2R levels are thought to reflect the extent of T-lymphocyte activation in non-malignant disease, but the level is aiso influenced by steroid therapy.