Activation of human lymphocytes in vitro by membrane-damaging toxins from Staphylococcus aureus

Purified staphylococcal alpha-, gamma-, and delta-toxin were shown to cause activation of lymphoid cells from adult human donors and of cord cells in vitro as measured by [14C]thymidine incorporation after 7 days of incubation. T cell-enriched and T cell-depleted lymphocyte suspensions were activated in a similar fashion. Beta-toxin, on the other hand, exerted no valid stimulation of the various lymphocyte preparations. The lymphocyte-activating properties of alpha- and gamma-toxin were shown to be independent of their hemolytic capacity. The results probably reflect unspecific mitogen effects, but a component of specific reactivity cannot be excluded. We suggest that the unspecific triggering of lymphocytes in vitro is caused by surface-active properties of the toxins.