title: The specific IL-1 inhibitor from the human M20 cell line is distinct from the IL-1 receptor antagonist.
abstract: Several inhibitors of IL-1 have been described. Four appear to be the same: one purified from urine of patients with monocytic leukemia, another from IgG-stimulated monocytes, a third from PMA-induced U937 cels, and a fourth from keratinocytes. Because these IL-1 inhibitors compete with bona fide IL-1 for occupancy of IL-1 receptors, they are now called the IL-1 receptor antagonist (IL-1ra) or IL-1 receptor antagonist protein (IRAP). We have described another IL-1-specific inhibitor produced by the human myelomonocytic leukemia cell line, M20. This inhibitor specifically blocks IL-1-induced effects both in vitro and in vivo. In the present study, we compared the M20 IL-1 inhibitor with IL-1ra using neutralization in an IL-1 bioassay and immunoblotting with an anti-IL-1ra antibody that recognizes natural IL-1ra. Neutralization experiments, immunoblotting, and western blotting obtained after transfer from SDS-PAGE revealed that anti-IL-1ra does not recognize the M20 IL-1 inhibitor. In addition, the isoelectric point and molecular weight of the M20 IL-1 inhibitor were different from those of the IL-1ra. From these data, we conclude that the M20 IL-1 inhibitor is antigenically unrelated to the IL-1ra but is a distinct and specific IL-1 inhibitor.
authors.affiliation: Department of Oncology, Hadassah Hospital, Ein Kerem, Jerusalem, Israel.
authors.forename: V
authors.initials: V
authors.lastname: Barak
authors.forename: D
authors.initials: D
authors.lastname: Peritt
authors.forename: I
authors.initials: I
authors.lastname: Flechner
authors.forename: P
authors.initials: P
authors.lastname: Yanai
authors.forename: T
authors.initials: T
authors.lastname: Halperin
authors.forename: A J
authors.initials: AJ
authors.lastname: Treves
authors.forename: C A
authors.initials: CA
authors.lastname: Dinarello
mesh_terms: D001681:Biological Assay; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007074:Immunoglobulin G; D007375:Interleukin-1 / Q000037:antagonists & inhibitors*; D007457:Iodine Radioisotopes; D007525:Isoelectric Focusing / Q000379:methods; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors*; D017472:Receptors, Interleukin-1
chemical_list: D007074:Immunoglobulin G; D007375:Interleukin-1; D007457:Iodine Radioisotopes; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1