Dexamethasone suppressed CD4⁺ T-cell proliferation and IL-2 secretion. (A) To assess whether drug treatment influences the ability of cells to proliferate in response to stimulation, healthy donor PBMCs (n = 3)were treated with lenalidomide, dexamethasone, or no drugs. The cells were then labeled with CFSE and stimulated with OKT-3 and anti-CD28/49d (as described in “Methods”). Proliferation was assessed and expressed as absolute cell numbers per division (proliferation cycles 0-6; data are pooled from 3 experiments). (B) To assess whether NK and CD4⁺ T cells could still proliferate after removal of dexamethasone, PBMCs (n = 3) were treated with dexamethasone for 3 days, followed by dexamethasone washout. The cells were cultured for a further 3 days either with no drugs or with lenalidomide, then stimulated and labeled with CFSE (data are pooled from 3 separate experiments). (C) Supernatants from sorted CD4⁺ T cells treated with either lenalidomide or dexamethasone for 3 days were collected to assess IL-2 production by cytokine bead array (n = 9).