CD28 and Sepsis: As such, T cell stimulator (anti-CD3 and anti-CD28 dyna-bead) was incubated in the PBMC and isolated CD3 + T cells from patients with sepsis and healthy control for 4 days, and T cell proliferation was evaluated using carboxyfluorescein succinimidyl ester (CFSE) staining (Fig. 4A).