PROBLEM TO BE SOLVED: To provide a method that enables objective and accurate diagnosis of development of systemic lupus erythematosus (SLE), and a use thereof.SOLUTION: T-cells present in peripheral blood or lymph tissues are examined to determine the presence/absence of DOCK8-positive CD4 T-cells in the peripheral blood or lymph tissues, which enables easier identification of cells causing the development of SLE.SELECTED DRAWING: None