FK506 and pertussis toxin distinguish growth-induced locomotor activation from attractant-stimulated locomotion in human blood lymphocytes.

The locomotor capacity of human lymphocytes is cell cycle-related. Many small blood lymphocytes are non-motile but acquire locomotor capacity in G1 on appropriate activation with e.g. anti-CD3 antibody (aCD3) for T cells, or interleukin-4 (IL-4) for B cells. Once this capacity is acquired, the cells can then respond by polarization and locomotor to chemoattractants such as IL-8 or foetal calf serum (FCS). These two stages in the locomotor process were distinguished by the use of two inhibitors, FK506 and pertussis toxin. FK506 caused a dose-dependent inhibition of cell cycle-related induction of locomotor capacity both of anti-CD3-cultured T cells and IL-4-cultured B cells, with an ID50 of less than 1 ng per ml. This was measured in assays both of morphological polarization and of locomotion into collagen gels. FK506 has no effect on chemoattractant-induced polarization. Conversely, pertussis toxin has little inhibitory effect on growth-induced locomotor capacity, but is an effective inhibitor of the immediate polarization response following addition of FCS or IL-8 to lymphocytes either direct from blood or after overnight culture. These results suggest that different signalling pathways are involved in the two stages. Growth-related locomotor activation does not involve a pertussis toxin-sensitive G protein and may be signalled in the same way as other mitogen-induced events which are sensitive to FK506 and cyclosporin. On the other hand, the locomotor response to attractants, on this and earlier evidence, is transduced via a pertussis toxin-sensitive G protein. However, after prolonged (24-48 hr) culture in the presence of pertussis toxin, lymphocyte locomotor responses to attractants become insensitive to pertussis toxin.