Two types of signals are required to induce T cell activation and proliferation: one is a specific antigen-stimulating signal generated by the binding of TCR/CD3 complex to the specific MHC II antigen-peptide complex on the surface of antigen-presenting cells (APCs); the other is a non-specific co-stimulatory signal generated by the interaction of co-stimulatory molecules on the surface of APCs with the corresponding receptors on the T cells, of which CD28 is one of the co-stimulatory molecule.The Human CD3/CD28 T Cell Activation Beads is used for activation and expansion of sorted human T cells or T cells in PBMCs.