Protamine-RNA particles of different sizes induce different immunostimulation profiles. PBMCs prepared from 3 different healthy donors were incubated overnight with protamine-RNA particles (Prot+RNA) produced by mixing 1:1 (mass ratios) protamine and RNA (RNA18 oligonucleotide) at 1 mg/mL. Protamine 5000 and RNA were diluted with water (220 nm), 25mM NaCl solution (500 nm), or Ringer lactate solution (1200 nm). Cells stimulated by R848 and dsRNA were used as positive controls. The content of interferon-α (A) or TNF-α (B) in the supernatants was then assessed by ELISA. The data show the mean content of cytokines for the 3 donors. Error bars indicate the observed deviation between donors. The data shown are representative of 12 independent experiments.