[Demonstration of the presence during acute inflammatory reactions of a serum factor mitogenic macrophages (author's transl)].

1. The authors have searched for the existence of mitogenic factor for macrophages in the serums of rats having undergone diverse immune and non-immune inflammatory reactions. 2. The evolution of the mitogenic activity of the inflammatory serums have been studied over a 48 hour period. This study underlined that the appearance of the mitogenic factor is very rapid since it can be found as early as 30 minutes after the injection of the irritant. 3. In most cases the evolution of the mitogenic activity of serums reveals a biphasic aspect: a strong activity is observed 1 to 2 hours after the injection of the irritant followed by a decrease of this activity which becomes weak or even null towards the sixth hour. It then increases to attain, after about 24 hours, values almost equal to those seen for the first peak.