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Tumor Necrosis Factor‐α Is Chemokinetic for Lymphokine‐Activated Killer Cells: Regulation by Cyclic Adenosine Monophosphate

The ability of tumor necrosis factor‐α (TNF‐α) to attract lymphokine‐activated killer (LAK) cells in vitro was examined. Utilizing modified Boyden chambers (BC), it was observed that TNF‐α is not chemoattractant for LAK cells. On the other hand, TNF‐α attracted both fresh and concanavalin A‐activated T cells. However, when TNF‐α was incubated in the upper compartments of BC and in the presence of LAK cells, it enhanced the random movement of these cells across the polycarbonate membranes. The effect of TNF‐α was inhibited by incorporating anti‐TNF‐α antibody, or a high concentration (10 ng) of TFG‐β1. The activity of TGF‐β1 was reversed by anti‐TGF‐β1 antibody. Cholera toxin (CT), which is known to activate the endogenous level of cyclic adenosine monophosphate (cAMP) also inhibited TNF‐α‐induced LAK cell chemokinesis. The effect of CT was mimicked by the cAMP analog dibutyryl cAMP or by the phosphodiesterase inhibitors isobutyl methylxanthine or aminophylline. Measurement of the intracellular level of cAMP showed that cells incubated for 1,2, or 4 hr with TNF‐α have a lower level of cAMP, whereas those incubated with a high concentration of TGF‐β1 produced significantly higher levels of this messenger. cAMP level was also increased in cells incubated with TGF‐β1 plus TNF‐α. This level was reduced to the background when anti‐TGF‐β1 antibody was added to the cultures. These results suggest that cAMP negatively regulates LAK cell chemokinesis.