Peripheral blood mononuclear cells from patients with mild-to-moderate psoriasis and healthy individuals were used to investigate the CD8 T cell immune phenotype and mediator release upon in vitro TCR-independent (phorbol 12-myristate 13-acetate (PMA) plus ionomycin (ION)) or TCR-dependent (anti-CD3/CD28) activation by flow cytometry. Here, CD28 is linked to psoriasis.