Serum Interleukin 2 and Soluble Interleukin 2 Receptor in Patients With Multiple Sclerosis Who Are Experiencing Severe Fatigue

To the Editor.  —Elevated levels of serum interleukin 2 (Il-2) and soluble interleukin 2 receptor (sIl-2r) have been related to active sarcoidosis.¹ It has been suggested that this may reflect disease activity, since Il-2 is secreted by activated T lymphocytes and sIl-2r is shed by activated T lymphocytes during the course of a cell-mediated immune response.² Boutin and associates³ reported that serum levels of sIl-2r were markedly increased in patients with acute encephalitis, suggesting that the intrathecal immune response was reflected by elevated systemic levels of sIl-2r. Elevated systemic levels of Il-2 and sIl-2r have been reported in patients with multiple sclerosis,^4-6 stimulating questions about whether these parameters can be used to measure disease activity, to estimate prognosis, or to explain certain clinical manifestations of the disease.We measured Il-2 and sIl-2r in eight patients with multiple sclerosis who each experienced persisting and debilitating fatigue. All