[Spontaneous production of mediators by mononuclear human blood cells (author's transl)]

Human mononuclear blood cells incubated in vitro without any intended stimulus produce lymphokine-like activities. Separated lymphocytes release a leukocyte migration stimulatory factor spontaneously. The spontaneous production of a leukocyte migration inhibitory factor in unstimulated cultures during the first 20 hours needs for a cooperation between lymphocytes and monocytes. As well lymphocytes as enriched monocytes elaborate leukocyte chemotactic activity. --The spontaneous activation is caused by the increasing acidity of the culture medium following metabolic processes. The dextran sedimentation and the Ficoll content of the separation solution were without importance for the stimulation.