Vβ repertoire stimulated with superantigens in healthy controls. (▪) Healthy donors as the control; (□) stimulated with a superantigen. Peripheral T cells were isolated from the blood of 2 donors and analyzed before or after in vitro stimulation with a bacterial superantigen (1 μg/mL) for 3 days. All of the toxins preferentially stimulated T cells expressing particular Vβs.27