Biochemical characterization of interleukin 1 from a human monocytic cell line

A protein with interleukin 1 (IL-1) activity was obtained from the human acute monocytic leukemia cell line (THP-1) and purified by ultrafiltration, Ultrogel AcA54 chromatography, isoelectric focusing, and discontinuous polyacrylamide gel electrophoresis. Like the pI 6.8 species of IL-1 from human peripheral blood monocytes (PBM), the cell line IL-1 has a molecular weight (MW) of 14,000, a pI of 6.8, is heat labile, and does not bind to concanavalin A-Sepharose. Chemical modification of arginine residues by phenylglyoxal or sulfhydryl groups by N-ethyl maleimide and iodoacetamide completely destroys the activity of IL-1 from THP-1 cells as well as that of the pI 6.8 component from PBM. In contrast, the pI 5.1 component of PBM IL-1 is resistant to heat denaturation and sulfhydryl reagents, although it is totally inactivated by phenylglyoxal. IL-1 from THP-1 cells enhanced the proliferative response of the same subpopulations of PNA- thymocytes as IL-1 from PBM. These observations suggest that IL-1 derived from this cell line is similar to the IL-1 pI 6.8 species produced by human monocytes, and distinct from the pI 5.1 species.