Fig. 2.

Dual costimulation by CD28 and CD81 increases the number of activated T cells. Isolated T cells were cultured in the presence of anti-CD3, anti-CD81 (5A6 or 1D6) and anti-CD28 mAbs, as indicated. (A) Cells stimulated for 22 h were stained for the surface expression of CD4 and CD69. (B) Cells stimulated for 48 h were stained for surface expression of CD8 and analyzed by flow cytometry for intracellular INFγ production. (C) Cell proliferation was measured by intracellular staining for Ki67 after 4 d. Data are representative of three independent experiments.