Appearance of three lymphokines in culture supernatants harvested at different times

Peritoneal cells from mice with methylcholanthrene-induced tumours were reacted with the corresponding tumour extract (antigen) and supernatants were prepared after incubation times of 1, 3.5 and 24 h. All the supernatants were then tested simultaneously on the same pools of normal indicator cells for their effects on leucocyte adherence, E-rosette formation and macrophage migration. The leucocyte adherence inhibition factor (LAIF) was consistently detected only in the 1-h supernatant, E-rosette augmentation factor (E-RAF) only in the 3.5-h supernatant and migration inhibition factor (MIF) only in the 24-h supernatant. It is concluded that LAIF, E-RAF and MIF are probably distinct factors, having different stabilities to degradation or inhibition under the conditions of cell culture. A less likely interpretation is that a single factor with multiple activities is affected by a series of distinct inhibitors. In practical terms, the 3 assays correlate only if the appropriate incubation times are used.