The stimulation of lymphocyte motility by cultured high endothelial cells and its inhibition by pertussis toxin.

Incubation of rat lymph node lymphocytes with cultured high endothelial cells caused a high proportion of the lymphocytes to lose their round shape and adopt a polar morphology. This shape change was rapid; a substantial increase in the number of polar cells occurred within 15 min. Between 30 and 60% of the lymphocytes became polar. The change was not dependent on protein synthesis. Both lymphocytes which adhered to the cultured high endothelial cells and those which were non-adherent changed shape. Evidence is presented for two pathways for the induction of polarity in non-adherent lymphocytes: (i) transient or weak binding to the high endothelial cells may induce a shape change which persists after lymphocyte detachment and (ii) the high endothelial cells shed or secrete high molecular weight material into the medium which induces the shape change. The rapid change in lymphocyte morphology induced by cultured high endothelial cells was inhibited by pre-incubation of the lymphocytes with low concentrations (4-100 ng/ml) of pertussis toxin. Upon prolonged (2 h) incubation of toxin-treated lymphocytes with cultured endothelial cells a significant proportion of the lymphocytes adhering to the endothelial cells changed shape while the non-adherent lymphocytes remained spherical. This implies that cultured high endothelial cells may stimulate lymphocyte motility by two mechanisms: one which is rapid and pertussis toxin sensitive and one which is slower, pertussis toxin insensitive and dependent on lymphocyte adhesion to the high endothelial cells.