PRODUCTION OF BOTH INTERLEUKIN-1-ALPHA AND INTERLEUKIN-1-BETA BY NEWBORN MOUSE CALVARIAL CULTURES

The conditioned medium (CM) from 4–6 day newborn mouse calvarial cultures was found to contain thymocyte comitogen proliferation activity. This activity was blocked by an antiserum to murine interleukin‐1α (IL‐1α) but not by an antiserum to murine interleukin‐1ß. The release of thymocyte comitogen proliferation activity from the cultures did not appear dependent on endotoxin and was not associated with detectable interleukin‐2 activity in the CM. Activity in the CM eluted from a gel filtration column with a peak Mr of 16–18 kD (the Mr of mature murine IL‐1α and ß is 17 kD). Western immunoblots of 100‐fold concentrated CM demonstrated only a single 33 kD band with an antiserum to murine IL‐1ß and no bands with an antiserum to murine IL‐1α. However, this assay was relatively insensitive (limit of detection 1–10 ng compared with 1–10 pg for the thymocyte comitogen proliferation assay). Immunoprecipitation of [35S]methionine‐labeled CM with three different anti‐IL‐1α antisera, a more sensitive assay, demonstrated 15–17 kD bands in all cases. These results demonstrate that 4–6 day newborn mouse calvarial cultures spontaneously release 17 kD IL‐1α and 33 kD IL‐1ß into their conditioned medium. It appears that although 17 kD IL‐1α is the major bioactive form in the CM, 33 kD IL‐1ß is present in greater amounts. These results also suggest that local production of IL‐1 can regulate bone cell function and may play a role in bone growth and remodeling Copyright © 1990 ASBMR