Anchorage and lymphocyte function. Contact-induced augmentation of T-cell activation.

Beads of polyacrylamide, latex or DEAE-Sephadex markedly augmented the stimulation of unfractionated or T-enriched lymphocytes by concanavalin A (Con A) or phytohaemagglutinin (PHA). The beads were not mitogenic in the absence of Con A or PHA. A prerequisite for the bead-induced augmentation was that the stimulated lymphocytes had been depleted of phagocytic and/or adherent accessory cells. The enhancing effect of beads was most pronounced during the initial 12 h after the beginning of lymphocyte stimulation, but not limited to this early phase of the growth period. The stimulation of lymphocytes in petri dishes of adhesive tissue culture plastic and non-adhesive bacterial plastic were compared. The magnitude of the stimulation on the non-adhesive surface was 10--50% lower than on the adhesive one, this difference being most pronounced at hyperoptimal mitogen concentrations. These results indicate that contact between some cell type and a solid surface can improve lymphocyte stimulation under experimental conditions when the number of phagocytic and adherent accessory cells is a limiting factor. The fact that cultivation on bacterial plastic, where adhesion and spreading were abolished, produced substantial stimulation (albeit reduced) demonstrates that substrate contact may be important, but is not a prerequisite, for lymphocyte activation.