Interleukin-1 decreases the level of thymocytes forming rosettes with autologous erythrocytes: a new method of determination of interleukin-1 activity.

It was demonstrated that human, recombinant Il-1 significantly inhibited formation of autologous rosettes by thymocytes. In addition, Il-1 increased the percentage of thymocytes resistant to hydrocortisone. Il-2 was not active in both tests. A new method of determination of Il-1 activity, based on the inhibition of the autologous rosette formation by Il-1 is described. The activity of Il-1 in the supernatant from macrophage cultures, stimulated with carbonyl iron powder, was calculated. The lack of Il-2 interference and no necessity to handle radioactive materials, are the advantages of the new method.