Identification of human ST2 protein in the sera of patients with autoimmune diseases

Soluble human ST2 protein (IL1RL1-a) in the sera of patients with various a utoimmune diseases was identified by a newly developed procedure using spec ific monoclonal antibodies. After immunoprecipitation and subsequent immuno blotting, a glycosylated protein of about 60 kDa was detected in the sera o f SLE patients, but not in the sera of healthy controls. The experiments us ing gel filtration and SDS-PAG;E under a nonreducing condition indicated th e existence of the ST2 multimer in serum. The mobility of the natural prote in was slower than that of the recombinant human ST2 protein produced by CO S7 cells in SDS-PAGE, suggesting a difference of glycosylation between huma ns and monkeys. The identification of the natural human ST2 protein should be important both to fundamental researches and the further clarification o f the clinical implications of the ST2 protein. (C) 2001 Academic Press.