A) Concentration of IL-4 and IL-13 in supernatant as a function of the number of PBMC stimulated with CMV peptides (solid lines) or DMSO (peptide diluent that served as the negative control, dotted lines). The effect of freezing the supernatant before running by multiplex bead assay was also investigated (frozen supernatant, gray lines; non-frozen supernatant, black lines). B) Concentration of IL-4 and IL-13 in supernatant as a function of stimulation duration (CMV, solid lines; DMSO, dotted lines). The other analytes showed similar trends.