Purpose: Examined the immunologic behaviors of (staphylococcal enterotoxin A, SEA) SEA-reactive two distinct T cell populations (Vβ3 CD4, Vβ3 CD8 T cells) in vivo and in vitro restimulated with SEA. Study the responsiveness of CD4 and CD8 T cell subsets reactive with superantigen SEA. Methods: Examined the proliferation and the IL-2 activity of the two purified murine SEA-reactive Vβ3 CD4 and Vβ3 CD8 T cell subsets that were restimulated with SEA. Results: Vβ3 CD4, Vβ3 CD8 T cells subsets showed significantly difference in proliferation and IL-2 activity restimulated with SEA (P<0.01). Conclusions: It did not changed the responsiveness of Vβ3 CD4 and Vβ3 CD8 T cell subsets in single SEA stimulation, but the responsiveness of Vβ3 CD4 and Vβ3 CD8 T cell subsets were changed in SEA restimulation.