Interleukin-18 (IL-18) is a potent cofactor for T-helper (Th-1) cell development and inducer of cytotoxic T lymphocytes (CTL), and is reported to contribute to autoimmune diseases. T-cell large granular lymphocyte (T-LGL) leukemia involves the proliferation of autoreactive CTL that is often associated with autoimmune disorders. We found increased serum IL-18 concentrations in a 55-year-old woman with systemic lupus erythematosus (SLE) and T-LGL-leukemia. Her serum IL-18 concentrations correlated with the intensity of her SLE symptoms and the number of T-LGL cells in peripheral blood. This evidence suggests that IL-18 is involved in T-LGL-related autoimmune disorders.
