Studies on the pathogenesis of interstitial pneumonia of collagen vascular diseases Part 2. Examination of interleukin 2 receptor in interstitial pneumonia of collagen vascular diseases

Abnormality of cellular immunity has been reported in the pathogenesis of collagen vascular diseases (CVD). IL-2 and IL-2 receptors play important roles as immunological regulation in CVD. In this study, the soluble forms of IL-2 receptor (sIL-2R) and IL-2 receptor positive lymphocytes (CD25) were analyzed to evaluate the role of IL-2R in the pathogenesis of interstitial pneumonia (IP) of CVD such as RA, SLE, polymyositis/dermatomyositis (PM/DM), and PSS and idiopathic interstitial pneumonia (IIP) as a disease control. High levels of sIL-2R were found in sera of patients with IP of CVD. The level of soluble IL-2R in sera of RA without IP correlated with the disease activity of the joints, while the level of sIL-2R in sera of RA with IP was higher than in that of RA without IP. Soluble IL-2R in bronchoalveolar lavage fluind (BALF) was also measured and the level was higher in IP with CVD. There were fewer IL-2R positive lymphocytes in the peripheral blood of CVD with IP than in the normal controls or IIP cases, although the serum level of sIL-2R was higher in CVD with IP and IIP than in the normal controls. These findings indicate that actibve immunological activities involving IL-2/IL-2R/sIL-2R systems play an important role in the pathogenesis of IP of CVD.