Staphylococcal protein-A is a potent T-cell mitogen of tonsillar lymphocytes.

Optimal conditions for the stimulation of human tonsillar lymphocytes by staphylococcal protein-A (SpA) are described. By stimulating fractions enriched or depleted of E-rosette forming cells, the response was shown to be predominantly a T-cell response. A comparison of stimulation by SpA with that of phytohaemagglutinin (PHA) proved SpA to be a potent T-cell mitogen. We suggest that SpA may be another useful mitogen for studying human T-cell growth and differentiation.